The synthesis of bioactive indolocarbazoles related to K-252a

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A R T I C L E

David Moffat,†^aChristopher J. Nichols,^bDean A. Riley^band Nigel S. Simpkins*^b

^aCelltech Therapeutics Ltd, 216 Bath Road, Slough, UK SL1 4EN

^bSchool of Chemistry, The University of Nottingham, University Park, Nottingham,

UK NG7 2RD

Received 9th May 2005, Accepted 3rd June 2005

First published as an Advance Article on the web 30th June 2005

A range of functionalised indolocarbazoles, related to the natural product K-252a, have been prepared, starting from

a readily available bridged cyclopentene. Sequences of transformations, involving initial hydroboration–oxidation to

give a ketone, or by dihydroxylation and cyclic sulfate formation, enable the preparation of diverse indolocarbazole

products. Issues of imide nitrogen protection for the indolocarbazole, and opportunities for asymmetric

desymmetrisation of key intermediates were also explored. A novel chiral lithium amide base mediated

transformation of a cyclic sulfate intermediate gave the anticipated ketone product in up to 87% ee. A number of

compounds, in the form of unprotected imide substituted indolocarbazoles, were screened for biological activity and

were found to be potent inhibitors of a number of kinase enzymes.

further related compounds by use of a cyclic sulfate as a key

Introduction

intermediate.¹¹The purpose of this paper is to describe this

Natural products incorporating the 1H-indolo[2,3-a]carbazole

work in full, including previously undisclosed chemistry and

ring system have emerged as an important class of compounds

preliminary biological screening data.

due to their broad range of potent biological activities.¹Key

members of this family include staurosporine 1,²K-252a 2,³

and rebeccamycin 3.⁴Staurosporine 1 was the ﬁrst member

Results and discussion

of this family to be identiﬁed and was isolated from Strepto-

myces staurosporeus (AM 2282), cultivated from a soil sample

taken in Japan in 1977.²The compound has a distinctive

indolocarbazole-bridged pyranose structure, and was shown to

possess diverse biological activities, including antimicrobial, hy-

potensive, cytotoxic and kinase inhibition.⁵K-252a 2, originally

isolated from the culture broth of Nocardiopsis sp., has a pendant

furanose, and is a highly potent inhibitor of serine/threonine

and tyrosine kinases, especially protein kinase C (PKC).⁶Rebec-

camycin 3 produced by Saccharothrix aerocolonigen possesses a

doubly chlorinated heterocyclic nucleus, has only one glycosidic

C–N linkage, and is known to induce topoisomerase I mediated

DNA cleavage.⁷

The powerful and varied biological activities of these systems

endow them with many potential therapeutic applications,

particularly as anticancer agents, and several have reached the

stage of clinical trials, including staurosporine.⁸Unsurprisingly,

these fascinating structures have attracted substantial synthetic

interest, both from the standpoint of total synthesis of the

natural products themselves, and the design of simpler analogues

for probing structure–activity relationships.⁹Some time ago

we reported the synthesis of novel carbocyclic analogues of

K-252a,¹⁰and more recently we described the synthesis of

(i) A rapid route to indolocarbazole-bridged cyclopentanes

Our initial efforts were directed towards establishing a rapid

and efﬁcient route to bridged structures resembling either K-

252a or staurosporine. A breakthrough came with the ﬁnding

that the reaction of the known indolocarbazole unit 4a with

cis-dibromocyclopentene 5 generated the bridged alkene 6a,

Scheme 1.

Most of our initial work was carried out using the readily

available N–Bn series of compounds, but two other series of

derivatives having the imide nitrogen unprotected (i.e. the N–H

series), or protected as a para-methoxybenzyl (N–PMB) were

also utilised. A key problem with the N–Bn compounds was

the extreme difﬁculty of debenzylation to give the free imide

compounds ultimately required for biological testing (see later).

As a stopgap measure we carried out some work with the free N–

H series, but this limited our synthesis options, the compounds

proved extremely insoluble in most organic solvents, and the

initial coupling to give 6b was low-yielding. Eventually, we

settled on the N–PMB series of compounds as a reasonable

compromise in terms of availability, protecting group stability,

moderate (although still less than ideal) solubility, and ease of

removal. As shown in Scheme 1 each series of compounds was

amenable to diastereoselective alkene hydroboration to give 7,

and oxidation to give bridged ketones 8.

† Present address: Chroma Therapeutics Ltd, 93 Milton Park, Abing-

don, UK, OX14 4RY.

T h i s j o u r n a l i s

T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 5 3

©

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Scheme 1 ^aOverall yield for hydroboration–oxidation without alcohol puriﬁcation.

The initial coupling process involving dibromide 5 was found

to be more convenient and higher yielding than alternatives

involving a reaction of the corresponding diacetates with

palladium catalysts. Although we have not explored the scope

of this reaction in detail, it is capable of supplying alternative

bridged structures, for example the simpler indolocarbazole 10,

Scheme 2.

directly to the corresponding hydroxyacid, by use of manganese

or ruthenium based oxidants, or by ozonolysis under basic

conditions, failed to give the desired products.

As an alternative, we prepared the cyanohydrin 14a using the

procedure described by Danishefsky,¹²which employs Me₃SiCN

in the presence of catalytic quantities of 18-crown-6 and

potassium cyanide, Scheme 3.

This process generated mixtures of diastereomers (presumably

by equilibration) if conducted at 0 ^◦C, but was completely

◦

diastereoselective at −25 C. In the case of the starting ketone

bearing the unprotected imide, the cyanohydrin product was

isolated in the form of the N–SiMe₃derivative 14b. As shown,

hydrolysis of both series of cyanohydrin under acidic conditions

resulted in the formation of the desired hydroxyester derivatives

15 in good yield.

The successful series of transformations, culminating in the

synthesis of K-252 model compound 15b provided us with the

ﬁrst compounds suitable for biological screening (see later). We

found it impossible to convert members of the N–Bn series into

the N–H series, for example using conventional hydrogenation

conditions, or by adopting oxidative cleavage conditions using

molecular oxygen and base,¹³or by hydrolysis to an intermediate

anhydride.¹⁴Therefore, in most subsequent chemistry, use of the

N–Bn series was discontinued in favour of the corresponding

N–PMB series.

Scheme 2

The next phase of our work involved further manipulation

of the ketone function present in 8a (and subsequently 8b) to

give the type of a-hydroxyester present in K-252a. The N–Bn

derivative 8a was shown to undergo highly stereoselective addi-

tion reactions with a range of nucleophilic reagents, including

borane, vinylmagnesium bromide, and a nitromethane anion,

giving products 11–13.

Alcohol 11, the product of borane reduction, is the epimer

of alkene hydroboration product 7a, and was formed with

complete stereoselectivity. It is clear that in all such reactions

the indolocarbazole bridge effectively blocks one face of the

ketone, leading to highly stereoselective addition reactions.

Cleavage of the alkene in 12 was seen as one possible route

to the required hydroxyester grouping, but efforts to proceed

(ii) Vicinally substituted products via a key cyclic sulfate

intermediate

All of the transformations of the alkenes 6 described above

rely on initial hydroboration, and so necessarily involve

2 9 5 4

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

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Scheme 3

reduction at one ring position. We were particularly interested

in alternative processes that would enable us to generate more

highly substituted systems, particularly those bearing vicinal

heteroatom substituents, somewhat akin to the staurosporine

glycone. Consequently, our attention became focused on the

stereoselective synthesis of epoxide intermediates and their ring

opening reactions. However, epoxidation of alkenes 6a and 6c

proved to be problematic, Scheme 4.

Epoxide generation using peracids was consistently low yield-

ing, with destruction of the material being evident, even in the

presence of mild base or radical scavengers.¹⁵Dimethyldioxirane

gave a borderline satisfactory yield with the N–PMB derivative

6c, but the reaction proved capricious, and was not suitable for

scale-up. Complementary approaches to epoxide intermediates

via bromohydrin formation also proved ineffective.¹⁶To further

diminish the attractiveness of epoxides 16, experiments involving

epoxide opening, using the modest supplies available from the

DMDO reaction, were also discouraging, with various forms of

azide (normally an excellent nucleophile for epoxide opening)¹⁷

giving azidoalcohol products such as 17 in only very modest

yield.

These problems led us to develop a complementary approach,

which relied on the use of a reactive cyclic sulfate as an epoxide

surrogate,¹⁸and which required initial alkene dihydroxylation.

In contrast to the problematic epoxidation process, the corre-

sponding dihydroxylation reaction proved efﬁcient and totally

stereoselective under standard conditions, Scheme 5.¹⁹

With diol 18 in hand we expected that cyclic sulfate synthesis

would be routine using the standard two step procedure

described by Sharpless.²⁰Initial transformation to the cyclic

sulﬁte 19, as a mixture of diastereomers at sulfur (ca. 2.4 : 1),

was near-quantitative using thionyl chloride, but the subsequent

oxidation to the desired sulfate 20 proved exceedingly sluggish,

at least in part due to the low solubility of sulﬁte 19 in suitable

Scheme 4

Scheme 5

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 5 5

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workers.²³Azide cycloaddition using dimethyl acetylenedicar-

boxylate as a reaction partner, one of the processes highlighted

by Sharpless in his ‘click chemistry’ approach,²⁴was also

effective, leading to triazole 27 in a very high yield.

Table 1

Since a free imide N–H function was deemed a prerequisite

for biological screening (see later), we next tackled the issue of

PMB removal from a number of the indolocarbazole derivatives.

Several protocols proved ineffective for this transformation,

including hydrogenolysis at 300 psi using palladium hydroxide

as a catalyst, and use of either DDQ or CAN. Ultimately, we

established that the use of triﬂuoroacetic acid in anisole was an

effective procedure, although removal of the imide protecting

group was usually accompanied by triﬂuoroacetylation of the

secondary alcohol of the cyclopentane, Table 2.

As indicated in the Table, somewhat disparate outcomes were

observed in these deprotection reactions. In the case of the azide

17, we obtained a mixture of the desired secondary alcohol and

the corresponding triﬂuoroacetate. The morpholine adduct 21

gave the desired product 31 in 50% yield, accompanied by the

triﬂuoroacetyl derivative of the starting N–PMB imide. In the

case of thioether 23 only the triﬂuoroacetate 29 was isolated,

whereas in the cases of thiocyanate 24 and triazole 27 we

obtained only the corresponding alcohols. In the cases of the

azide and thioether substituted systems, we conducted LiOH

mediated hydrolysis of the initially formed triﬂuoroacetates 28

and 29 to generate the required secondary alcohol products.

In addition, we exposed cyclic sulﬁte 19 to the same con-

ditions, and were able to isolate the required product 35 (as a

mixture of diastereomers at sulfur) in a very high yield, Scheme 7.

Reagent

X

Compound (yield %)

NaN₃, DMF, 80 ^◦C

Morpholine, reﬂux

N₃

17 (91)

21 (36)

22 (88)

23 (67)

24 (64)

N-Morpholino

OCOPh

SPh

PhCO₂NH₄, DMF, 70 ^◦

PhSH, NaH, THF, RT

C

NH₄SCN, DMF, 70 ^◦

C

SCN

solvents. As indicated, we found a very acceptable, and direct,

alternative synthesis of the sulfate, which involved reaction of

the diol 18 with sulfonyl diimidazole in THF, with DBU as base.

This combination appeared uniquely suitable to this system,

providing reproducibly high yields, and enabling multi-gram

synthesis.²¹

Ring opening of the cyclic sulfate 20 was then carried out

under various conditions to give a range of products 17, 21–

24 in which interesting vicinal functionality had been installed,

Table 1.

The reaction of 20 with azide attested to the excellent

activating properties of the cyclic sulfate, since the ring opening

occurred in high yield under conditions which left the corre-

sponding epoxide 16c unreacted. However, the direct installation

of amine groups still proved difﬁcult, the modest yield obtained

by reaction of 20 in neat morpholine at reﬂux being one of

the best results.²²Under these conditions we obtained substan-

tial amounts of diol 18, presumably formed by a competing

nucleophilic attack at sulfur, and also quantities of ketone 8c.

The formation of this compound as a by-product stimulated

further investigation of the base-mediated rearrangement of

cyclic sulfates, which is described later.

In contrast to the problematic amine reactions, sulfate

ring-opening with oxygen or sulfur-centred nucleophiles was

relatively straightforward, leading to benzoate, thiophenyl and

thiocyanate-substituted products 22–23.

Given the apparent importance of nitrogen functionality in

bioactive systems such as staurosporine, we were pleased to

demonstrate that the azide function present in 17 could enable

access to additional nitrogen containing products, such as 25–27

in a straightforward fashion, Scheme 6.

Thus, azide reduction to give the potentially versatile primary

amine 25, was possible under several types of typical hydrogena-

tion conditions, the imide N–PMB being unaffected. Although

amine 25 may prove useful in reductive alkylation sequences, we

also gained access to diallyl amine 26 by means of the indium

mediated Barbier type process described by Yadav and co-

Scheme 7

Although the cyclic sulfate ring-opening and imide depro-

tection sequence had been quite fruitful in delivering some

attractive indolocarbazoles for biological study, we were dis-

appointed that the chemistry did not work with carbon-

centred nucleophiles. Somewhat surprisingly, we were unable

to effect efﬁcient ring opening of sulfate 20 with cyanide, using

sodium or potassium cyanide under various conditions, or using

Et₂AlCN.²⁵A similar lack of success was seen with other carbon

nucleophiles, including metal acetylides, Grignard and cuprate

reagents, and with hydride (NaBH₄) or ﬂuoride (TBAF).

A ﬁnal transformation that was accomplished in this series

was the reduction of the azidoalcohol 30 to the corresponding

aminoalcohol 36, Scheme 8.

Scheme 6 Reagents: (25) Pd(C), H₂, DMF; (26) indium, NaI, allylbromide, DMF, 50 ^◦C; (27) MeO₂C–≡–CO₂Me, DMF, 70 ^◦C.

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 5 6

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Table 2

Product(s) from TFA/anisole

OCOCF₃

Starting material (X)

OH

Total (%) after LiOH

17 X = N₃

28 (ca. 50%)^a

ND^b

29 (56%)

ND

30 (47%)

31 (50%)

32 ND

33 (54%)

34 (52%)

30 (85)

NA

32 (45)

NA

21 X = morpholine

23 X = SPh

24 X = SCN

27 X = triazole unit

ND

NA

^aNot obtained in pure form. ^bThe triﬂuoroacetate derivative of starting PMB imide 21 was isolated in 28% yield. ND = Not detected. NA = Not

applicable

We initially considered that nitromethane adduct 13 might be

useful in this regard, since reduction to a b-aminoalcohol might

prelude ring expansion using diazotisation methods. However,

our failure to effect nitro group reduction precluded such an

investigation, and we turned instead to protocols more closely

akin to those described by Wood. After some preliminary

investigations, we established the synthetic sequence shown in

Scheme 9.

Effective ozonolysis of 12 required prior alcohol protection,

for which we installed a trimethylsilyl ether, giving 37, and

subsequently enabling access to the key aldehyde 38. Alternative

routes to this compound, either by reduction of cyanohydrin

14a, or by redox operations on the ester 15a, were not fruitful.

Pleasingly, the type of a-ketol rearrangement described by Wood

was equally effective when applied to aldehyde 38, exposure of

this compound to excess BF₃–OEt₂leading to cyclohexanone

Scheme 8

The reduction proved less facile than we anticipated, hydro-

genation using palladium on carbon giving lower yields than

Lindlar catalyst, and alternatives such as the Staudinger proce-

dure (PPh₃, THF, H₂O), or FeCl₃–NaI being unproductive.²⁶

1

39. The structure of the product was fully supported by H

NMR; the coupling patterns (from ¹H–¹H COSY experiments)

and magnitudes of J-values being distinctive for the regioisomer

shown (as opposed to the product from the migration of bond

b) with the equatorial hydroxyl stereochemistry. This outcome

derives from selective migration of bond a in 38 to the si face of

the Lewis-acid activated aldehyde, and is exactly analogous to

the result seen by Wood.

(iii) Reactions of indolocarbazole ketones: focus on

cyclopentane ring-expansion

At the outset of this project it was hoped that we would be

able to access staurosporine analogues in a similar fashion

to the approach described above for the ﬁve membered K-

252a mimics, i.e. combination of an indolocarbazole fragment 4

with a suitable 6-membered (electrophilic) partner. However,

an alternative strategy involving ring expansion of the ﬁve-

membered derivatives to give staurosporine analogues suggested

itself, since Wood and co-workers had successfully accomplished

such a process in their synthesis of the natural product itself.^9b

Although this approach to indolocarbazoles with six-

membered bridging carbocycles provided adequate access to

hydroxyketone 39, we were also interested in a more direct

route to a less functionalised cyclohexanone. In particular,

the simpler cyclohexanone corresponding to 39 without the

hydroxyl group (i.e. 40, see below) was seen as an attractive

intermediate, since chiral base desymmetrisation might then

Scheme 9

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 5 7

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Scheme 10

enable access to diverse products in enantiomerically enriched

form. We were also interested in the idea of ring expansion using

the Saegusa process, which involves regioselective ring-opening

of a silyloxycyclopropane using FeCl₃.²⁷Both of these avenues

were explored, Scheme 10.

In diazoalkane ring expansions of ketones, the regiochemical

outcome depends upon the migratory aptitude of the two groups

attached to the carbonyl in the starting ketone.²⁸From the estab-

lished examples we anticipated a mixture of 40 and 41 would be

formed, probably with the undesired isomer 41 predominating.

However, the migratory aptitudes of the groups in ketone 8a

could not be guaranteed considering the unusual features of the

system. In the event, reactions using trimethylsilyldiazomethane

and BF₃–OEt₂formed only the latter ketone 41, in rather

modest yield. Substantial experimentation with the nature of

the Lewis acid did not lead to any improvement or variation in

regiochemistry.²⁹

In the alternative approach to ring expansion that we ex-

plored, we required the enol silane 42, which we found could be

prepared in high yield from 8c under standard conditions. Un-

fortunately, despite extensive experimentation, we were unable

to ﬁnd conditions for the cyclopropanation of this compound,

which is a prerequisite for the Saegusa process.³⁰

As an adjunct to this part of the work, we brieﬂy explored

alkylations of ketone 8c. The viability of enolate chemistry was

expected to be improved in the carbocyclic analogues, compared

to the natural products, which would be expected to suffer

b-elimination problems associated with either the ring oxygen

or the carbazole nitrogen substituents. Somewhat surprisingly,

we were unable to achieve meaningful alkylation results using

LDA as a base, but on switching to NaH (one equivalent) we

observed clean, but incomplete, transformation to the doubly

alkylated products 43 and 44, using allyl bromide and methyl

iodide respectively, Scheme 11.

to force alkylation to give good yields of a dialkylated product,

for example the dibenzylketone 45, obtained in 71% yield, using

two equivalents of base.

Although we did not explore this area further, it seems

that using metal enolates derived from 8c, or enol silane

intermediates such as 42, should provide a means to additional

types of indolocarbazole, through alkylation, aldol, Mukaiyama

and related processes.

(iv) Asymmetric synthesis of key indolocarbazole alcohol 7c

and ketone 8c

Throughout this project a key consideration had been the

prospect of developing very concise routes to biologically

active indolocarbazoles, which would be amenable to asym-

metric modiﬁcation. One idea, which would generate chiral

six-membered variants, was mentioned earlier, and involved

chiral base desymmetrisation of ketone 40. Clearly, most of our

chemistry involves the ﬁve-membered variants, and it would be

preferable to effect the key asymmetric step on a readily available

(i.e. early stage) intermediate. Therefore, for the ﬁve-membered

systems we ﬁrst considered that asymmetric hydroboration or

hydrosilylation of alkene 6c would be ideal, since the alcohol

product 7c and all subsequent materials would then be available

in non-racemic form.

It was quickly established that low levels of asymmetric

induction could be obtained by hydroboration of alkene 6c using

diisopinocamphenylborane (Ipc₂BH) in THF at 0 ^◦C, to give 7c,

as shown earlier in Scheme 1.³²Although the chemical yield

for this process was good (83%) the enantiomeric excess of the

material, estimated by HPLC, was a very modest 33%. This was

surprising to us, since higher values (>80% ee) are established

for asymmetric hydroboration of norbornene systems using

this reagent.³³The low solubility of alkene 6c in appropriate

solvents necessitated the use of rather dilute solutions, which

in turn led to very slow reactions unless an excess of borane

was employed. Unfortunately, this level of asymmetric induction

proved optimal, since screening of the reaction with other

boranes, including monoisopinocamphenylborane (IpcBH₂),

dilongifolylborane (Lgf₂BH) or dicaranylborane (Icr₂BH) gave

even less satisfactory results. As a complementary approach,

we also attempted asymmetric hydrosilylation, which has given

even higher levels of asymmetric induction than hydroboration,

when applied to bridged systems like norbornene (96% ee).³⁴

Both the allylation and methylation reactions proceeded to

about 50% conversion, and we were unable to identify mono-

alkylated product from examination of the NMR spectra of

crude reaction product. The yields of 43 and 44 were about

70%, taking into consideration the recovery of about half of

the starting ketone. Over-alkylation is a well known problem

in ketone enolate chemistry, particularly for cyclopentanones,

and under these conditions it seems that enolate equilibration

leading to disubstituted products is highly favoured.³¹Although

we were unable to control mono-alkylation, it did prove possible

Scheme 11

2 9 5 8

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

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Scheme 12

Despite extensive exploration using the Hayashi palladium

catalysed process, which employs HSiCl₃and the MOP binaph-

thyl ligand, we were unable to achieve conversion of 6c into

alcohol 7c. Under all conditions that we could conceive, the

indolocarbazole system appeared incompatible with the highly

corrosive trichlorosilane reagent, and complete destruction of

the substrate was observed.

In the attempted ring-opening reaction of cyclic sulfate 20

with morpholine we had noted the formation of ketone 8c

as a by-product. A literature search revealed that this type

of overall transformation had been reported previously, for

example the conversion of cyclitol derived cyclic sulfate 46 to

give the ketone 47, described by Ferna´ndez-Mayoralas and co-

workers, Scheme 12.³⁵

These authors proposed a b-elimination process to give an in-

termediate vinyl bisulfate, which on acidiﬁcation gave the ketone

product. Unfortunately, application of these conditions to our

cyclic sulfate 20 gave only very modest yields (8%) of the desired

ketone 8c. Similarly, the use of LDA at low temperature also gave

very modest (ca. 5%) yields of the desired ketone, and recovery

of starting sulfate or the corresponding diol 18 predominated.

Our main motivation for persisting with this transformation

was the hope that an asymmetric variant might enable access to

ketone 8c in non-racemic form. Carrying out the reaction under

the vigorous, high temperature, conditions involving reﬂuxing

amine, under which we had initially observed ketone formation

(as a by-product), did not offer hope of asymmetric induction.

Since the high-yielding literature examples used metal alkoxides,

we initially probed the use of their chiral analogues, in the

form of metal salts of ephedrine derivatives—but to no effect.³⁶

Finally, we found that chiral lithium amide base 48 provided

some more encouraging preliminary results.³⁷Thus, addition of

cyclic sulfate 20 to a solution of (R,R)-lithium amide 48 and

LiCl (4 equivalents) at −78 ^◦C provided a 39% yield of ketone

8c, following acidiﬁcation.

biological screening carried out focused primarily on kinase

inhibitory activity.

The protein kinases constitute a large family of structurally

related enzymes responsible for controlling signal transduction

within the cell. Inhibition of protein kinases is a well established

approach for medicinal chemistry targets in a number of areas,

for example, protein kinase C (PKC) is implicated in a number

of key cell responses, including gene expression and cell prolif-

eration, and established PKC inhibitors display antiproliferative

activity against human tumor cell lines in vitro.⁴⁰

A major obstacle blocking the potential application of kinase

inhibitors in medicine is the problem of selectivity in inhibiting

a particular enzyme. This arises because many inhibitors work

by competing with ATP at a catalytic domain that is largely

conserved across many kinase families and isoforms.⁴¹Although

many K-252a derivatives have been prepared, the need to

further probe the ‘chemical space’ around various regions of the

molecule was identiﬁed by Wood and co-workers, who reported

a number of interesting biologically active systems, including

C-2^ꢀand C-7 (either C-7 stereochemistry) modiﬁed compounds,

such as 49 and 50.⁴²

We considered that our carbocyclic analogues would enable

us to further probe such effects (although with the limitations of

the indolocarbazole having the symmetrical imide ring, rather

than the naturally occurring lactam system).

The ﬁrst group of compounds to be screened arose from our

initial studies on the N-benzyl and N–H series of compounds

shown in Schemes 1 and 3, Table 3.

Firstly, it should be noted that the N-benzyl series of

compounds, including 6a–8a and 15a were inactive in these

screens. This was expected, since there is usually a prerequisite

for a free NH function in the indolocarbazole lactam or imide

group for signiﬁcant biological activity. Most likely this NH

engages in hydrogen bonding to the peptide backbone of the

kinase (mimicking the N-6 amino group of ATP) by analogy

with the published crystal structures of staurosporine bound

to CDK2 (cyclin-dependent kinase 2)⁴³and PKA (cyclic AMP

dependent kinase),⁴⁴and K-252a bound to the tyrosine kinase

domain of the hepatocyte growth factor receptor c-Met.⁴⁵

The enantiomeric excess of the ketone was established by

HPLC to be 87%, and the absolute conﬁguration was tentatively

assigned as shown in Scheme 1 by correlation with material

obtained from the asymmetric hydroboration reactions. Unfor-

tunately, further screening failed to uncover conditions under

which higher yields of ketone 13 can be obtained, and we have

not yet been able to test additional cyclic sulfate substrates.

(v) Biological screening of indolocarbazoles

As mentioned earlier, our motivation for exploring the indolo-

carbazole area was to generate both new chemistry, especially

involving desymmetrisation reactions, and new biologically

active entities that would mimic the natural products. Both K-

252a and staurosporine are potent protein kinase inhibitors, the

latter compound having also been ascribed immunosuppressive

activity,³⁸and multidrug resistance reversal (MDR) activities.³⁹

We expected that the new indolocarbazoles would mimic K-

252a, although some of our compounds somewhat resemble

‘hybrid’ systems of these two natural products. The limited

Table 3 IC₅₀(nM) values for selected indolocarbazoles

Compound

PKC

p56lck

p60src

809

>10 000

3105

KDR FGFr-2

K-252a 2

Alkene 6b

Alcohol 7b

Ketone 8b

Ester 15b

23

108

46

66

53

440

9239

838

400

1648

521

739

78

447

>10 000

958

51

312

>10 000

94

521

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 5 9

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Table 4

Compound

MAPKAP-K2 (IC₅₀lM)

p38 MAPK (IC₅₀lM)

Akt (IC₅₀lM)

FGFr (IC₅₀lM)

30

31

32

33

34

35

63.6

17.2

24.1

13.0

45.5

41.9

14.5

14.7

15.0

12.0

15.8

10.6

0.36

1.20

9.70

0.29

>20

1.40

0.14

—

5.72

>20

The NH series of compounds shown in Table 3 showed

good PKC inhibitory activity, with alcohol 7b and hydroxyester

15b being the most potent, and having activities (as racemic

compounds) of the same order of magnitude as K-252a. As

shown, we also assayed against a number of tyrosine kinases,

including p56lck, which is a T-cell speciﬁc member of the

Src kinase family, p60src, FGFr-2, and recombinant Kinase

Domain Receptor (KDR). Again, our new compounds showed

signiﬁcant levels of activity, for example ketone 8b had an IC₅₀

of 51 nM against KDR kinase, this being substantially more

potent than K-252a itself. This suggests that our compounds are

potential inhibitors of angiogenesis via their effects on VEGF

receptor tyrosine kinases.⁴⁶

malignancies such as breast cancer and ovarian cancer.⁴⁹Thio-

cyanate 33 and azide 30 displayed the greatest level of inhibition

of Akt, by an order of magnitude, with IC₅₀values of 0.29 and

0.36 lM respectively. The levels of inhibition observed compare

well with those of known inhibitors, for example NL-71-101 53,

a selective inhibitor of PKB in ovarian cancer cell lines, has an

IC₅₀of 3.7 lM.⁵⁰

On the whole, selectivity proﬁles for these compounds are

unremarkable, although both the alcohol 7b and the ester 15b

showed enhanced selectivity for other tyrosine kinases over

p60src, compared to K-252a. In a separate screen we also

established that some of the later compounds also displayed

PKC and PKA inhibitory activities, including the aminoalcohol

36, which showed an IC₅₀of 295 nM, which appears lower than

the activities in Table 3 (although the values are not strictly

comparable).

The N–H imide series of indolocarbazoles 30–35 arising from

the cyclic sulfate ring opening phase of the study were also

submitted to screening against the mitogen activated protein

kinases MAPKAP-K2 and p38 MAPK, and against Akt and

tyrosine kinase FGFr (Table 4).

Mitogen activated protein kinases are kinase enzymes which

form part of the complex MAPK signalling pathway. In vivo

(in cells), MAPAP-K2 is predominately regulated by p38

MAPK.⁴⁷Activation of this pathway leads to the production

of inﬂammatory cytokines like IL-1 (interleukin-1) and TNF-a

(tumour necrosis factor-a). Inhibitors of either of these enzymes

are expected to be of use in the control of arthritis and COPD

(chronic obstructive pulmonary disease).

FGFr (Fibroblast Growth Factor receptor) is a receptor

tyrosine kinase. The binding of FGF to FGFr results in

activation of the kinase leading to the stimulation of a signalling

cascade, which is implicated in the formation of blood vessels

(angiogenesis). It is believed that inhibition of FGFr may cause

a reduction in blood vessel growth, which would, in turn,

slow tumour growth.⁵¹Of the three compounds tested, azide

30 displayed the greatest level of inhibition by an order of

magnitude (IC₅₀= 0.14 lM). Reports on potent and selective

inhibitors of receptors involved in neovascularisation, such as

FGFr, are less prevalent in the literature, and the discovery of

tyrosine kinase inhibitors that can inhibit angiogenesis remains

a fertile area for drug discovery. However, Parke–Davis have

shown that the selective FGFr inhibitor PD 173074 54 (IC₅₀

29 nM), currently in animal trials, is a promising candidate for

=

use in the treatment of cancer.⁵²

Micromolar inhibition was observed with all of the com-

pounds in both the MAPKAP-K2 and p38 MAPK screens,

with thiocyanate 33 being the most active against MAPKAP-K2

and sulﬁte 35 being the most active against p38 MAPK. Sulﬁte

35 and azide 30 showed a four-fold level of selectivity for p38

MAPK over MAPKAP-K2. The levels of inhibition observed

in the indolocarbazole analogues are much lower than the low

nanomolar p38 inhibitors SB 203580 51 and RWJ 67657 52.⁴⁸

Overall, the preliminary screening gave some pleasing results,

with some of our new compounds showing high levels of potency

and some interesting selectivities. Whether speciﬁc examples of

these compounds can be further reﬁned for clinical applications

remains to be seen.

Experimental

General procedures

Melting points were obtained from a Melt Temp II machine or

a Stewart Scientiﬁc SPM3 and are uncorrected. Microanalytical

data were obtained on a Perkin-Elmer 240B elemental analyser.

Infrared spectra were recorded using a Perkin Elmer 1600 series

FTIR spectrophotometer as sample solutions in chloroform, un-

less otherwise stated, and are reported in cm⁻¹. Optical rotations

were recorded using a JASCO DIP370 digital polarimeter.

Akt, also known as protein kinase B, is an anti-apoptotic

protein kinase that has strongly elevated activity in human

2 9 6 0

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

High resolution mass spectra were acquired on a VG Mi-

cromass LCT, VG Micron Autospec or AEI MS-902 mass

spectrometer, using electrospray (ES), electron impact (EI) or

fast atom bombardment (FAB), using meta-nitrobenzyl alcohol

as the matrix.

vacuo and partitioned between CHCl₃(300 mL) and H₂O

(100 mL). The organic layer was washed with H₂O (100 mL),

brine (100 mL), dried (MgSO₄) and concentrated in vacuo to

yield the crude product, which was puriﬁed by ﬂash column

chromatography using a CHCl₃solvent system, to give alkene

6a as a yellow solid (2.70 g, 89%). A portion of the solid was

recrystallised from acetone–water to give yellow needles: mp

¹H and ¹³C NMR spectra were recorded on a Bruker AM 400

or Bruker DRX 500 machine. ¹H NMR and ¹³C NMR spectra

were recorded in CDCl₃or d₆-DMSO. Chemical shifts are given

in ppm downﬁeld from tetramethylsilane, using either TMS or

a residual protic solvent as an internal standard. J values are

recorded in Hz and quoted to the nearest 0.1. Where necessary,

◦

309–312 C; (found: m/z (FAB⁺) M⁺479.1630. C₃₂H₂₁N₃O₂

requires 479.1634); m_max(CHCl₃)/cm⁻¹1752, 1697, 1573, 1459,

1383, 1346, 1306; d_H(d₆-DMSO, 500 MHz) 2.75 (1H, d, J 13.9,

1^ꢀ-H_a), 3.18 (1H, dt, J 13.9, 6.4, 1^ꢀ-H_b), 4.91 (s, 2H, CH₂Ph),

6.27 (2H, d, J 6.4, 2^ꢀ-H and 5^ꢀ-H), 6.46 (2H, s, 3^ꢀ-H and 4^ꢀ-H),

7.30 (1H, t, J 7.2, Ph), 7.37–7.45 (6H, m, 3-H, 9-H and Ph),

7.68 (2H, dd, J 8.2, 7.7, 2-H and 10-H), 8.04 (2H, d, J 8.2, 1-H

and 11-H) and 9.08 (2H, d, J 8.0, 4-H and 8-H); d_C(d₆-DMSO,

125 MHz) 40.6 (1^ꢀ-CH₂), 41.6 (CH₂Ph), 59.3 (2^ꢀ-CH and 5^ꢀ-CH),

110.8 (CH), 117.0 (C), 119.5 (C), 121.3 (CH), 121.8 (C), 125.6

(CH), 128.0 (CH), 128.2 (CH), 128.3 (CH), 129.6 (CH), 129.8

(C), 136.8 (CH), 138.4 (C), 140.9 (C), 170.2 (CO); (found: C,

79.82; H, 4.40; N, 8.68. C₃₂H₂₁N₃O₂requires C, 80.17; H, 4.38;

N, 8.77%); m/z (FAB⁺) 480 (M⁺+ H, 15%), 479 (M⁺, 58), 402

(4), 389 (3) and 149 (11).

1

proton and carbon assignments were assisted with H COSY,

DEPT or NOE sequences.

Enantiomeric excesses were determined by high performance

liquid chromatography (HPLC), using a Diacel Chiralpak AD

column, at temperatures ranging from 20–30 ^◦C as stated.

Detection was by UV at the stated frequency and data was

processed using a HP-3D Dos chemstation.

Reaction progress was monitored by thin layer chromatog-

raphy (TLC), using Polygram Sil G/UV₂₅₄plates which were

visualised using a combination of ultraviolet light, iodine and

potassium permanganate. Flash column chromatography was

performed using indicated solvent systems on Fluka silica gel 60

(220–240 mesh).

Organic solvents were dried as follows: THF and Et₂O

(sodium-benzophenone ketyl), CH₂Cl₂(DCM) (CaH₂), DMF

(calcium sulfate), PhMe (sodium), morpholine (KOH). Petrol

refers to petroleum ether (bp 40–60 ^◦C), which was distilled

before use. Brine, saturated aqueous NaHCO₃, saturated aque-

ous Na₂S₂O₃, 2N HCl and 2N NaOH were stock solutions in

distilled H₂O.

A number of the indolocarbazole substrates, in particular the

free imide series, do not have mass spectrometry data despite

exhaustive investigations with a variety of ionisation techniques.

The high melting points of the compounds, generally >250 ^◦C,

meant that CI and EI techniques were not powerful enough

to volatilise the samples. The insolubility of indolocarbazole

substrates in aqueous acetonitrile, the solvent system used

in ES, meant that molecular ion peaks corresponding to the

indolocarbazole substrates were never observed. FAB was by far

the most successful technique often resulting in observation of

molecular ion peaks, however, the solubility of indolocarbazole

substrates in meta-nitrobenzyl alcohol, the matrix in FAB,

was poor and in some cases compounds were insoluble, thus

molecular ion peaks were not observed.

12,13-(Cyclopent-3^ꢀ-ene-2^ꢀa,5^ꢀa-diyl)-5H-indolo[2,3-a]pyrrolo-

[3,4-c]carbazole-5,7(6H)-dione 6b

To a stirred solution of indolocarbazole 4b (0.33 g, 1.0 mmol)

dry DMF (30 mL), under a nitrogen atmosphere, was added

60% dispersion of NaH in mineral oil (0.126 g, 3.15 mmol),

and the resulting mixture was stirred at room temperature for

45 min. Then cis-dibromocyclopentene 5 (0.23 g, 1.00 mmol)

was added and the reaction mixture was stirred overnight

before being quenched with brine (100 mL). The organic

solvent was separated, the solvent removed in vacuo, and the

residue dissolved in EtOAc (100 mL). The organic solution was

washed with H₂O (2 × 50 mL), brine (50 mL), dried (MgSO₄),

ﬁltered and concentrated in vacuo to yield the crude product.

Puriﬁcation by ﬂash column chromatography (4 : 1 CHCl₃–

EtOAc) gave the alkene 6b as a yellow solid (0.09 g, 23%). A

portion of the solid was recrystallised from acetone–water to

give yellow needles: mp 380–381 ^◦C; (found: m/z (FAB⁺) M⁺+

H 390.1235. C₂₅H₁₅N₃O₂requires 390.1243); m_max(CHCl₃)/cm⁻¹

3696, 3438, 2927, 2871, 1754, 1718, 1602, 1460, 1348, 1319, 1062,

1000 and 914; d_H(d₆-DMSO, 400 MHz) 2.71 (1H, d, J 14.0, l^ꢀ-

H_a), 3.14 (1H, dt, J 14.0, 6.5, 1^ꢀ-H_b), 6.23 (2H, d J 6.5, 2^ꢀ-H

and 5^ꢀ-H), 6.42 (2H, s, 3^ꢀ-H and 4^ꢀ-H), 7.38 (2H, dd, J 8.0, 7.5,

3-H and 9-H), 7.63 (2H, dd, J 8.0, 7.5, 2-H and 10-H), 8.00

(2H, d, J 8.0, 1-H and 11-H), 9.07 (2H, d, J 8.0, 4-H and 8-H)

and 11.06 (1H, s, NH); d_C(d₆-DMSO, 126 MHz), 39.7 (1^ꢀ-CH₂),

58.3 (2^ꢀ- and 5^ꢀ-CH), 109.8 (1-CH and 11-CH), 115.8 (C), 119.9

(C), 120.3 (3-CH and 9-CH), 121.0 (C), 124.8 (4-CH and 8-CH),

Biological assay methods

Inhibitor activity against protein kinase C (PKC) was de-

termined using PKC obtained from either Sigma Chemical

Company or Calbiochem, and we used a commercially available

assay system available from Amersham International. PKC

catalyses the transfer of the c-phosphate (³³P) of ATP to the

threonine group on a peptide speciﬁc for PKC. Phosphorylated

peptide is bound to phosphocellulose paper and then quantiﬁed

by scintillation counting. The other kinase assays employed

kinases as GST-fusion products puriﬁed from NS0 cells.

Tyrosine kinase assays were conducted under conditions

previously described.⁵³

=

126.8 (2-CH and 10-CH), 128.9 (C), 135.9 (CH ), 139.8 (C) and

171.0 (CO); m/z (FAB+) 390 (M⁺+ H, 6%), 389 (M⁺8%), 329

(7), 307 (25) and 289 (14).

12,13-(Cyclopent-3^ꢀ-ene-2^ꢀa,5^ꢀa-diyl)-6-(4-methoxybenzyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 6c

Indolocarbazole 4c (2.00 g, 4.49 mmol) was dissolved in dry

DMF (100 mL), with stirring under N₂and NaH (0.38 g,

9.43 mmol) was added in one portion. The reaction mixture was

stirred for 0.5 h before the addition of cis-dibromocyclopentene

5 (1.52 g, 6.74 mmol) and then stirred overnight. TLC analysis

showed consumption of starting material, MeOH (1 mL) was

added to quench the reaction before concentration in vacuo to

give a brown solid which was redissolved in CHCl₃(200 mL)

and washed with H₂O (200 mL) and brine (200 mL), dried

(MgSO₄) and concentrated in vacuo to give a brown solid. The

crude product was puriﬁed by ﬂash column chromatography

using a CHCl₃solvent system to give alkene 6c as a yellow

12,13-(Cyclopent-3^ꢀ-ene-2^ꢀa,5^ꢀa-diyl)-6-(benzyl)-dihydro-5H-

indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 6a

Indolocarbazole 4a (2.63 g, 6.33 mmol) was suspended in

dry DMF (250 mL) with stirring under an N₂atmosphere.

A 60% dispersion of NaH (0.53 g, 13.30 mmol) was added

in one portion and the reaction mixture was stirred for 30

minutes, before the addition of cis-dibromocyclopentene 5

(2.15 g, 9.50 mmol). The reaction mixture was stirred overnight

before being quenched with MeOH (5 mL), concentrated in

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 6 1

View Article Online

solid (1.66 g 73%). A portion of the solid was recrystallised

from acetone–water to give 6c as yellow needles: mp 289 ^◦C

decomp; (found: m/z (EI⁺) M⁺509.1712 C₃₃H₂₃N₃O₃requires

509.1739); m_max(CHCl₃)/cm⁻¹1751, 1694, 1459, 1383, 1346, 1089,

979; d_H(d₆-DMSO, 400 MHz) 2.73 (1H, d, J 14.1, 1^ꢀ-H_a), 3.16

(1H, dt, J 14.1, 6.6, 1^ꢀ-H_b), 3.72 (3H, s, OMe), 4.79 (2H, s,

CH₂Ar), 6.24 (2H, d, J 6.6, 2^ꢀ-H and 5^ꢀ-H), 6.43 (2H, s, 3^ꢀ-H

and 4^ꢀ-H), 6.92 (2H, d, J 8.7, PMB), 7.35–7.42 (4H, m, PMB,

3-H and 9-H), 7.65 (2H, dd, J 8.3, 7.3, 2-H and 10-H), 8.02

(2H, d, J 8.3, 1-H and 11-H), 9.06 (2H, d, J 7.9, 4-H and 8-

H); d_C(d₆-DMSO, 100 MHz) 40.6 (1^ꢀ-CH₂), 41.1 (CH₂Ar), 56.0

(OMe), 59.3 (2^ꢀ-CH and 5^ꢀ-CH), 110.8 (CH), 114.9 (CH), 116.9

(C), 119.4 (C), 121.3 (CH), 121.8 (C), 125.6 (CH), 127.9 (CH),

129.8 (C), 130.0 (CH), 130.4 (C), 136.8 (CH), 140.9 (C), 159.5

(C) 170.1 (CO); (found: C, 77.33; H, 4.47; N, 8.14. C₃₃H₂₃N₃O₃

requires C, 77.80; H, 4.52; N, 8.25%); m/z (EI⁺) 510 (M⁺+ H,

36%), 509 (M⁺, 100), 389 (6), 149 (5), 121 (10).

solvent was removed in vacuo. The residue was dissolved in

ethyl acetate (50 mL) and the organic mixture washed with

water (2 × 50 mL), 2.0 M aqueous hydrochloric acid (50 mL)

and brine (50 mL). The organic extract was dried (MgSO₄),

ﬁltered and the solvent removed in vacuo, to give the crude

product. Puriﬁcation by ﬂash chromatography (2 : 1 CHCl₃–

ethyl acetate), gave the product as a yellow solid (0.153 g, 74%).

A portion was recrystallised from a mixture of acetone–water,

to give 7b as a yellow crystalline solid: mp 370–371 ^◦C; (found:

m/z (FAB⁺) M⁺407.1270. C₃₂H₁₇N₃O₃requires 407.1270);

m_max(CHCl₃)/cm^−l3438, 2927, 1754, 1720, 1602, 1352, 1317 and

680; d_H(d₆-DMSO, 400 MHz) 1.98 (1H, dd, J 15.5, 6.5, 4^ꢀ-H_a),

2.39 (1H, dd, J 15.5, 8.0, 4^ꢀ-H_b), 2.63 (1H, d, J 15.0, 1^ꢀ-H_a), 3.15

(1H, ddd, J 15.0, 7.5, 6.5, 1^ꢀ-H_b), 4.42 (1H, m, 3^ꢀ-H), 5.35 (1H,

d, J 6.5, 2^ꢀ-H), 5.63 (1H, d, J 3.0, OH), 5.90 (1H, dd, J 8.0, 7.5,

5^ꢀ-H), 7.35–7.43 (2H, m, 3-H and 9-H), 7.59–7.62 (2H, m, 2-H

and 10-H), 7.91–7.96 (2H, m, 1-H and 11-H), 9.00–9.07 (2H, m,

4-H and 8-H) and 11.05 (1H, s, NH); d_C(d₆-DMSO, 126 MHz)

37.0 (1^ꢀ-CH₂), 41.9 (4^ꢀ-CH₂), 55.3 (5^ꢀ-CH), 64.4 (2^ꢀ-CH), 75.8 (3^ꢀ-

CH), 109.8 (CH), 110.1 (CH), 115.1 (C), 115.4 (C), 119.7 (C),

119.8 (C), 120.3 (CH), 120.6 (CH), 121.1 (C), 121.4 (C), 124.6

(CH), 126.76 (CH), 126.81 (CH), 128.0 (C), 128.7 (C), 139.9 (C),

140.3 (C), 171.0 (CO) and 171.1 (CO); m/z (FAB⁺) 408 (M⁺+

H, 5%), 407 (M⁺5%), 307 (27), 289 (13), 275 (11) and 176 (11).

12,13-(3^ꢀb-Hydroxycyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(benzyl)-dihydro-

5H-indolo[2,3-a]pyrrolo [3,4-c]carbazole-5,7(6H)-dione 7a

To a stirred suspension of the alkene 6a (0.70 g, 1.46 mmol)

in THF (35 mL) under an N₂atmosphere was added a 1.0 M

solution of BH₃–THF (7.31 mL, 0.73 mmol), and the reaction

mixture was stirred at rt. After 3 h the reaction mixture had

become homogeneous and TLC analysis showed consumption

of starting material. MeOH (4.0 mL) was added cautiously and

the solution stirred for 15 min before the addition of 2 M

NaOH (11.0 mL) and 30% H₂O₂(2.89 mL). After 1 h, TLC

analysis showed the reaction had gone to completion and most

of the solvent was removed in vacuo to leave a crude residue.

The residue was dissolved in DCM (100 mL) and the organic

mixture washed with saturated aqueous NaHCO₃solution (2 ×

100 mL), brine (100 mL), dried (MgSO₄) and concentrated in

vacuo to give crude product as an orange solid. Puriﬁcation

by ﬂash column chromatography using a 4 : 1 DCM–EtOAc

solvent system afforded alcohol 7a as an orange solid (0.48 g,

69%): mp 306–308 ^◦C; m_max(CHCl₃)/cm⁻¹3696, 3606, 1751, 1696,

1602, 1573, 1384, 1351, 1315; (found: m/z (FAB⁺) M⁺497.1761.

C₃₂H₂₃N₃O₃requires 497.1739); d_H(d₆-DMSO, 500 MHz) 2.00

(1H, dd, J 15.5, 6.3, 4^ꢀ-H_a), 2.41 (1H, dd, J 15.5, 7.7, 4^ꢀ-H_b),

2.68 (1H, d, J 14.4, 1^ꢀ-H_a), 3.18 (1H, ddd, J 14.4, 7.3, 6.5, 1^ꢀ-

H_b), 4.24 (1H, m, 3^ꢀ-H), 4.79 (2H, s, CH₂Ph), 5.35 (1H, d, J 6.5,

2^ꢀ-H), 5.67 (1H, d, J 2.7, OH), 5.92 (1H, dd, J 7.7, 7.3, 5^ꢀ-H),

7.29 (1H, t, J 6.9, Ph), 7.35–7.44 (6H, m, 3-H, 9-H and Ph),

7.63 (1H, dd, J 8.2, 7.6, 10-H), 7.68 (1H, dd, J 8.2, 7.5, 2-H),

7.95 (2H, app t, J 8.2, 1-H and 11-H), 8.99 (1H, d, J 7.9, 8-H),

9.04 (1H, d, J 7.9, 4-H); d_C(d₆-DMSO, 125 MHz) 37.8 (1^ꢀ-CH₂),

41.5 (CH₂Ph), 42.8 (4^ꢀ-CH₂), 56.2 (5^ꢀ-CH), 65.3 (2^ꢀ-CH), 76.7

(3^ꢀ-CH), 110.7 (CH), 111.0 (CH), 116.2 (C), 116.6 (C), 119.2

(C), 119.3 (C), 121.2 (CH), 121.5 (CH), 121.8 (C), 122.1 (C),

125.4 (CH), 125.5 (CH), 127.9 (CH), 127.9 (CH), 128.2 (CH),

128.9 (C), 129.5 (CH), 129.6 (C), 138.4 (C), 140.9 (C), 141.4 (C),

170.1 (CO), 170.1 (CO); m/z (FAB⁺) 498 (M⁺+ H, 20%), 497

(M⁺, 25), 391 (4), 329 (5), 176 (13), 120 (11), 91 (21), 77 (22).

12,13-(3^ꢀb-Hydroxycyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo[2,3-a]pyrrolo[3,4-

c]carbazole-5,7(6H)-dione 7c

To a stirred suspension of the alkene 6c (1.50 g, 2.95 mmol) in

THF (150 mL) under an N₂atmosphere was added a 1.0 M

solution of BH₃·THF (14.7 mL, 14.73 mmol), and the reaction

mixture was stirred at rt. After 45 min the reaction mixture had

become homogeneous and TLC analysis showed consumption

of starting material. MeOH (15 mL) was added cautiously and

the solution stirred for 10 min before the dropwise addition of

2 M NaOH (23.4 mL) and 30% H₂O₂(5.9 mL). After 0.5 h

TLC analysis showed the reaction had gone to completion and

most of the solvent was removed in vacuo to leave a crude

residue. The residue was dissolved in DCM (200 mL) and the

organic mixture was washed with saturated aqueous NaHCO₃

solution (2 × 100 mL), brine (100 mL), dried (MgSO₄) and

concentrated in vacuo to give the crude product as an orange

solid. Puriﬁcation by ﬂash column chromatography using a

2% MeOH–DCM solvent system afforded the product 7c as

an orange solid (1.13 g, 73%). A portion of the solid was

recrystallised from acetone–water to give 7c as yellow needles:

mp 298–301 ^◦C; (found: m/z (FAB⁺) M⁺527.1850. C₃₃H₂₅N₃O₄

requires 527.1845); m_max(CHCl₃)/cm⁻¹3617, 1750, 1691, 1384,

1350, 1315; d_H(d₆-DMSO, 400 MHz) 2.04 (1H, dd, J 15.4, 6.0,

4^ꢀ-H_a), 2.43 (1H, dd, J 15.4, 7.9, 4^ꢀ-H_b), 2.78 (1H, d, J 14.2,

1^ꢀ-H_a), 3.21 (1H, ddd, J 14.2, 7.0, 6.5, 1^ꢀ-H_b), 3.75 (3H, s, OMe),

4.25 (1H, d, J 6.0, 3^ꢀ-H), 4.82 (2H, s, CH₂Ar), 5.37 (1H, d, J

6.5, 2^ꢀ-H), 5.56 (1H, bs, OH), 5.91 (1H, dd, J 7.9, 7.0, 5^ꢀ-H),

6.93 (2H, d, J 8.7, PMB), 7.38 (2H, d, J 8.7, PMB), 7.39 (1H,

dd, J 8.3, 7.2, 9-H), 7.44 (1H, dd, J 7.8, 7.3, 3-H), 7.64 (1H, dd,

J 8.5, 7.2, 10-H), 7.69 (1H, dd, J 8.2, 7.3, 2-H), 7.94 (1H, d, J

8.5, 11-H), 7.96 (1H, d, J 8.2, 1-H), 9.04 (1H, d, J 8.3, 8-H),

9.09 (1H, d, J 7.8, 4-H); d_C(d₆-DMSO, 100 MHz) 37.8 (1^ꢀ-CH₂),

41.0 (CH₂Ar), 42.8 (4^ꢀ-CH₂), 56.0 (OMe), 56.2 (5^ꢀ-CH), 65.3 (2^ꢀ-

CH), 76.7 (3^ꢀ-CH), 110.7 (CH), 111.0 (CH), 114.9 (CH), 116.2

(C), 116.5 (C), 119.2 (C), 119.4 (C), 121.2 (CH), 121.5 (CH),

121.8 (C), 122.1 (C), 125.5 (CH), 127.9 (CH), 127.9 (CH), 128.9

(C), 129.6 (C), 129.8 (CH), 130.4 (C), 140.9 (C), 141.4 (C), 159.4

(C), 170.1 (CO), 170.2 (CO); m/z (FAB⁺) 527 (M⁺5%), 154 (18),

133 (4), 120 (5), 74 (7).

12,13-(3^ꢀb-Hydroxycyclopentan-2^ꢀa,5^ꢀa-diyl)-5H-indolo[2,3-a]-

pyrrolo[3,4-c]carbazole-5,7(6H)-dione 7b

To a stirred suspension of the alkene 6b (0.2 g, 0.51 mmol)

in dry tetrahydrofuran (20 mL) under a nitrogen atmosphere,

was added a 1.0 M solution of borane in tetrahydrofuran

(2.54 mL, 2.54 mmol) and the resulting mixture was stirred

at room temperature. After 45 min, the mixture had become

homogeneous and TLC analysis indicated that the starting

material had been consumed. Methanol (3 mL) was added

cautiously and the solution stirred for 15 min, before the addition

of a 2 M aqueous solution of sodium hydroxide (3.82 mL,

7.34 mmol), followed by a 27% aqueous solution of hydrogen

peroxide (0.96 mL, 7.34 mmol). After 30 min, TLC analysis

indicated that the reaction was complete and so most of the

Non-racemic 7c via asymmetric hydroboration

(Ipc)₂BH (0.56 g, 1.96 mmol) was dissolved with stirring under

N₂, in freshly distilled THF (5 mL) and cooled to 0 ^◦C. A

2 9 6 2

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

THF solution (10 mL) of alkene 6c (0.10 g, 0.20 mmol) was

added dropwise and the reaction mixture was stirred for 5 h.

The reaction mixture was quenched by the careful addition

of MeOH (2 mL) and stirred for 10 min before the dropwise

addition of 2 N NaOH (3.13 mL) and 30% H₂O₂(0.8 mL). The

reaction mixture was stirred for 0.5 h before being concentrated

in vacuo, and partitioned between DCM (100 mL) and H₂O

(100 mL). The organic layer was washed with saturated aqueous

Na₂SO₃solution (2 × 100 mL), saturated aqueous NaHCO₃

solution (2 × 100 mL), brine (100 mL), dried (MgSO₄) and

concentrated to give a yellow solid which was puriﬁed by ﬂash

column chromatography using a 1 : 1 EtOAc–petrol solvent

system. The desired alcohol was obtained as a yellow solid

(86.0 mg, 83%; 33% ee, HPLC 80 : 19 : 1 hexane–ⁱPrOH–MeCN,

aqueous solution of sodium thiosulfate (20 mL) was added

and the mixture was stirred for 20 min. The organic layer was

washed with water (50 mL), brine (50 mL), dried (MgSO₄),

ﬁltered and the solvent removed in vacuo, to yield the crude

ketone. Puriﬁcation by ﬂash chromatography (4 : 1 CH₂Cl₂–

ethyl acetate), gave the ketone 8b as a yellow solid (0.333 g, 71%,

◦

2 steps): mp 376–377 C; (found: m/z (FAB⁺) M⁺405.1115.

C₂₅H₁₄N₃O₃requires 405.1113); m_max(CHCl₃)/cm⁻¹3435, 2935,

1759, 1720, 1602, 1461, 1350 and 1320; d_H(d₆-DMSO, 400 MHz)

2.47 (1H, dd, J 19.0, 2.5, 4^ꢀ-H_a), 3.04 (1H, dd, J 15.0, 2.5, l^ꢀ-H_a),

3.23 (1H, dd, J 19.0, 6.5, 4^ꢀ-H_b), 3.48 (1H, ddd, J 15.0, 8.0, 6.5,

l^ꢀ-H_b), 5.59 (1H, d, J 8.0, 2^ꢀ-H), 6.15 (1H, dd, J 6.5, 6.5, 5^ꢀ-H),

7.38–7.44 (2H, m, 3-H and 9-H), 7.62–7.68 (2H, m, 2-H and

10-H), 7.90–7.98 (2H, m, 1-H and 11-H), 9.04–9.06 (2H, m, 4-H

and 8-H) and 11.09 (1H, s, NH); d_C(d₆-DMSO, 126 MHz) 36.6

(1^ꢀ-CH₂), 44.3 (4^ꢀ-CH₂), 53.4 (5^ꢀ-CH), 59.9 (2^ꢀ-CH), 110.1 (CH),

110.2 (CH), 115.7 (C), 116.0 (C), 120.0 (C), 120.6 (CH), 120.9

(CH), 121.0 (CH), 121.4 (C), 121.4 (C), 124.8 (CH), 124.9 (CH),

127.2 (CH), 127.4 (CH), 128.2 (C), 128.5 (C), 140.2 (C), 140.4

(C), 171.0 (CO) and 214.4 (CO); m/z (FAB⁺) 405 (M⁺, 27%),

307 (16), 220 (14), 219 (55) and 176 (12).

26

AD column). [a]_D−0.70 (c 0.57, THF). The spectroscopic data

were identical to those described above.

12,13-(3^ꢀCyclopentan-2^ꢀa,5^ꢀa-diyl-one)-6-(benzyl)-dihydro-5H-

indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 8a

Alcohol 7a (0.31 g, 0.62 mmol) was suspended in DCM (30 mL)

with stirring under an N₂atmosphere. DMP (0.52 g, 1.24 mmol)

was added in one portion and the reaction mixture was stirred

overnight. TLC analysis showed consumption of the starting

material and the reaction was quenched by the addition of a

saturated aqueous solution of Na₂S₂O₃(25 mL). The resulting

solution was stirred vigorously for 0.5 h before being partitioned

between DCM (100 mL) and H₂O (100 mL). The organic layer

was washed with H₂O (2 × 100 mL), brine (2 × 100 mL), dried

(MgSO₄) and concentrated in vacuo to give an orange solid which

was puriﬁed by ﬂash column chromatography using a DCM

solvent system to give ketone 8a as a yellow solid (0.205 g, 67%):

mp 315–317 ^◦C; (found m/z (FAB⁺) M⁺495.1573. C₃₂H₂₁N₃O₃

requires 495.1583); m_max(CHCl₃)/cm⁻¹1755, 1698, 1603, 1573,

1460, 1384, 1349; d_H(d₆-DMSO, 400 MHz) 2.50 (1H, dd, J 19.3,

2.9, 4^ꢀ-H_a), 3.09 (1H, dd, J 15.0, 2.9, 1^ꢀ-H_a), 3.26 (1H, dd, J 19.3,

6.8, 4^ꢀ-H_b), 3.53 (1H, ddd, J 15.0, 8.1, 6.5, 1^ꢀ-H_b), 4.80 (2H, s,

CH₂Ph), 5.61 (1H, d, J 8.1, 2^ꢀ-H), 6.17 (1H, dd, J 6.8, 6.5, 5^ꢀ-H),

7.27–7.31 (1H, m, Ph), 7.35–7.46 (6H, m, 3-H, 9-H and Ph), 7.66

(1H, ddd, J 8.4, 7.2, 1.0, 10-H), 7.69 (1H, ddd, J 8.4, 7.2, 1.0, 2-

H), 7.91 (1H, d, J 8.4, 11-H), 7.99 (1H, d, J 8.4, 1-H), 9.02 (1H,

d, J 7.9, 8-H), 9.03 (1H, d, J 7.9, 4-H); d_C(d₆-DMSO, 126 MHz)

37.3 (1^ꢀ-CH₂), 41.5 (CH₂Ph), 45.0 (4^ꢀ-CH₂), 54.1 (5^ꢀ-CH), 58.4

(2^ꢀ-CH), 110.9 (CH), 111.0 (CH), 116.6 (C), 116.9 (C), 119.3 (C),

119.9 (C), 121.7 (CH), 121.8 (CH), 121.9 (C), 125.4 (CH), 125.5

(CH), 128.2 (CH), 129.0 (C), 129.3 (C), 129.5 (CH), 138.3 (C),

141.0 (C), 141.2 (C), 170.0 (CO), 215.0 (CO); m/z (FAB⁺) 496

(M⁺+ H, 13%), 495 (M⁺, 13), 154 (57), 107 (30), 92 (6), 91 (29),

77 (19).

12,13-(3^ꢀ-Oxocyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-methoxybenzyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 8c

Alcohol 7c (0.79 g, 1.51 mmol) was dissolved in dichloromethane

(60 mL) with stirring under an N₂atmosphere, and Dess–Martin

periodinane (0.96 g, 2.26 mmol) was then added in one portion

and the reaction mixture was stirred for 2 h. TLC analysis then

showed consumption of the starting material and the reaction

was quenched by the addition of a saturated aqueous solution

of Na₂S₂O₃(25 mL) and stirred vigorously for 30 minutes before

being partitioned between dichloromethane (100 mL) and H₂O

(100 mL). The organic layer was washed with H₂O (2 × 100 mL),

brine (2 × 100 mL), dried (MgSO₄), ﬁltered and concentrated in

vacuo to give an orange solid, which was puriﬁed by ﬂash column

chromatography (CH₂Cl₂) to yield ketone 8c as a yellow solid

(0.57 g, 72%): mp 319–321 ^◦C; (found: m/z (EI⁺) M⁺525.1663.

C₃₃H₂₃N₃O₄requires 525.1689); m_max(CHCl₃)/cm⁻¹1753, 1697,

1461, 1384 and 1349; d_H(d₆-DMSO, 400 MHz) 2.50 (1H, dd, J

19.3, 3.1, 4^ꢀ-H_a), 3.07 (1H, dd, J 15.0, 3.1, 1^ꢀ-H_a), 3.25 (1H, dd,

J 19.3, 6.5, 4^ꢀ-H_b), 3.52 (1H, ddd, J 15.0, 8.2, 6.5, 1^ꢀ-H_b), 3.74

(3H, s, OMe), 4.76 (2H, s, CH₂Ar), 5.59 (1H, d, J 8.1, 2^ꢀ-H),

6.14 (1H, app t, J 6.5, 5^ꢀ-H), 6.92 (2H, d, J 8.7, PMB), 7.35 (2H,

d, J 8.7, PMB), 7.40 (1H, dd, J 7.9, 7.0, 9-H), 7.44 (1H, dd, J

7.9, 7.0, 3-H) 7.63 (1H, dd, J 8.4, 7.0, 10-H), 7.68 (1H, dd, J

8.4, 7.0, 2-H), 7.89 (1H, d, J 8.4, 11-H), 7.97 (1H, d, J 8.4, 1-H),

9.04 (1H, d, J 7.9, 8-H), 9.05 (1H, d, J 7.9, 4-H); d_C(d₆-DMSO,

100 MHz) 37.3 (1^ꢀ-CH₂), 41.0 (CH₂Ar), 45.0 (4^ꢀ-CH₂), 54.1 (5^ꢀ-

CH), 56.0 (OMe), 58.4 (2^ꢀ-CH), 110.8 (CH), 111.0 (CH), 114.9

(CH), 116.6 (C), 116.9 (C), 119.3 (C), 119.9 (C), 121.6 (CH),

121.8 (CH), 121.9 (C), 125.4 (CH), 125.5 (CH), 128.1 (CH),

128.2 (CH), 128.9 (C), 129.2 (C), 129.9 (CH), 130.3 (C), 141.0

(C), 141.2 (C), 159.4 (C), 169.9 (CO), 215.0 (CO); (found: C,

74.89; H, 4.42; N, 7.99. C₃₃H₂₃N₃O₄requires C, 75.43; H, 4.38;

N, 8.00%); m/z (EI⁺) 526 (M⁺+ H, 11%), 525 (43), 509 (100).

12,13-(3^ꢀ-Oxocyclopentan-2^ꢀa,5^ꢀa-diyl)-5H-indolo[2,3-a]pyrrolo-

[3,4-c]carbazole-5,7(6H)-dione 8b

To a stirred suspension of the alkene 6b (0.45 g, 1.16 mmol) in

dry tetrahydrofuran (40 mL) under a nitrogen atmosphere was

added a 1.0 M solution of borane in tetrahydrofuran (5.8 mL,

5.8 mmol) and the stirring continued at room temperature. After

30 min, methanol (6 mL) was added and the mixture was stirred

for 10 min, before the addition of a 2.0 M aqueous solution

of sodium hydroxide (8.7 mL, 17.4 mmol), followed by a 27%

aqueous solution of hydrogen peroxide (2.2 mL, 17.4 mmol).

The reaction mixture was stirred for 20 min, then neutralised

by dropwise addition of concentrated hydrochloric acid. Most

of the solvent was removed in vacuo and the remaining residue

extracted with ethyl acetate (2 × 75 mL). The combined extracts

were washed with water (50 mL), brine (50 mL), dried (MgSO₄),

ﬁltered and the solvent removed in vacuo, to give the crude

orange alcohol 7b (0.477 g). This alcohol was then dissolved

in dry dichloromethane (150 mL) and in one portion was

added Dess–Martin periodinane (1.0 g, 2.32 mmol) and the

mixture was stirred for 90 min at room temperature. A saturated

Non-racemic ketone 8c by chiral base rearrangement of cyclic

sulfate 20

A mixture of chiral lithium amide 48 and LiCl was prepared

by treatment of a solution of the appropriate secondary amine–

HCl salt (88.0 mg, 0.34 mmol) in THF (1 mL) at −78 ^◦C under

N₂with ⁿBuLi (1.27 M in hexanes) (0.52 mL, 0.66 mmol). The

mixture was allowed to warm to room temperature for 0.5 h

◦

before being recooled to −78 C and then a solution of cyclic

sulfate 20 (50.0 mg, 0.08 mmol) in THF (15 mL) pre-cooled

to −78 ^◦C was added dropwise. After 4 h the reaction mixture

was quenched with H₂O (1 mL) and 20% H₂SO₄(3.3 mL) was

added. The reaction mixture was allowed to warm to room

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 6 3

View Article Online

temperature with stirring for 18 h and was then partitioned

between EtOAc (75 mL) and H₂O (75 mL). The organic layer was

washed with H₂O (75 mL), saturated aqueous NaHCO₃solution

(75 mL), brine (75 mL), dried (MgSO₄), and concentrated

in vacuo to give a yellow solid which was puriﬁed by ﬂash

column chromatography using a 2–10% MeOH–CH₂Cl₂solvent

CH), 110.2 (CH), 111.4 (CH), 116.0 (C), 116.2 (C), 118.6 (C),

118.9 (C), 120.6 (CH), 120.8 (CH), 121.5 (C), 124.7 (CH), 125.0

(CH), 127.2 (CH), 127.4 (CH), 127.8 (CH), 128.7 (C), 129.1

(CH), 130.1 (C), 138.0 (C), 140.4 (C), 143.1 (C), 169.9 (CO) and

170.0 (CO); m/z (FAB⁺) 498 (M⁺+ H, 17%), 497 (M⁺, 20%),

307 (34), 289 (18), 176 (12), 120 (12) and 91 (14).

26

system to give ﬁrstly ketone 8c (17.0 mg, 39%), [a]_D−62.9 (c

0.60, CHCl₃), mp >280 ^◦C, with spectroscopic data identical

to those described previously. The enantiomeric excess was

determined as 87% by HPLC, using a Chiralpak AD column

and a solvent of MeCN–EtOH–Et₂NH (95 : 5 : 0.1), with a ﬂow

rate of 0.5 mL/min [retention times 21 min (minor) and 29 min

(major)].

12,13-(3^ꢀa-Hydroxy-3^ꢀb-vinyl-cyclopentan-2^ꢀa,5^ꢀa-diyl)-6-

(phenylmethyl)-5H-indolo[2,3-a] pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 12

To a stirred solution of the ketone 8a (0.05 g, 0.1 mmol) in

dry tetrahydrofuran (12.5 mL) at −78 ^◦C under a nitrogen

atmosphere, was added a 1.0 M solution of vinylmagnesium

bromide in tetrahydrofuran (10.5 mL, 0.5 mmo1), and the

stirring continued at −78 ^◦C. After 4 h, a saturated aqueous

solution of NH₄Cl (1 mL) was added and reaction mixture

was allowed to warm to room temperature. Most of the

solvent was removed in vacuo and the residue was dissolved in

dichloromethane (20 mL). The organic layer was washed with

water (20 mL) and brine (20 mL), dried (MgSO₄), ﬁltered and the

solvent removed in vacuo, to give the crude product. Puriﬁcation

by ﬂash chromatography (1 : 1 ethyl acetate–petroleum ether),

gave the allylic alcohol 12 as a yellow solid (0.028 g, 54%).

A portion of the solid was recrystallised from a mixture of

chloroform–petroleum ether, to give 12 as a yellow crystalline

Diol 5 was also recovered (5.0 mg, 11%).

11,12-(Cyclopent-3^ꢀ-ene-2^ꢀa,5^ꢀa-diyl)indolo[2,3-a]carbazole 10

To a stirred solution of indolocarbazole 9 (0.3 g, 0.78 mmol) in

dry DMF (20 mL) under a nitrogen atmosphere, was added 60%

dispersion of NaH in mineral oil (0.063 g, 1.6 mmol), and the

resulting mixture was stirred at room temperature for 10 min.

Then cis-dibromocyclopentene 5 (0.265 g, 1.2 mmol) was added

and the reaction mixture was stirred for a further 3 h. The organic

solvent was removed in vacuo, and the residue dissolved in CHCl₃

(100 mL). The organic solution was washed with H₂O (2 ×

30 mL), brine (30 mL), dried (MgSO₄), ﬁltered and concentrated

in vacuo to yield the crude product. Puriﬁcation by ﬂash column

chromatography (3 : 1 petroleum ether–ethyl acetate) gave the

alkene 10 as a yellow solid (0.084 g, 33%). A portion of the solid

was recrystallised from petroleum ether–ethyl acetate to give

10 as off-white needles: mp 309–310 ^◦C; (found: m/z (EI⁺) M⁺

320.1315. C₂₃H₁₆N₂requires 320.1313); m_max(CHCl₃)/cm⁻¹3063,

2968, 1602, 1564, 1434, 1398, 1343, 1225, 1207, 1131, 1049 and

827; d_H(CDCl₃, 400 MHz) 2.68 (1H, d, J 13.5, l^ꢀ-H_a), 3.06 (1H,

dt, J 13.5, 6.5, 1^ꢀ-H_b), 5.78 (2H, d J 6.5, 2^ꢀ-H and 5^ꢀ-H), 6.18

(2H, s, 3^ꢀ-H and 4^ꢀ-H), 7.17–7.23 (2H, m, 3-H and 8-H), 7.40

(2H, ddd, J 8.0, 7.5, 1.0, 2-H and 9-H), 7.51 (2H, d, J 8.0, 1-H

and 10-H), 7.86 (2H, s, 5-H and 6-H) and 8.09 (2H, d, J 8.0, 4-H

and 7-H); d_C(d₆-acetone, 68 MHz) 40.9 (1^ꢀ-CH₂), 58.6 (2^ꢀ-CH

and 5^ꢀ-CH), 109.1 (CH), 112.0 (CH), 119.2 (CH), 120.3 (CH),

120.9 (C), 124.4 (C), 124.9 (CH), 125.1 (C), 135.9 (1^ꢀ-CH and

2^ꢀ-CH), 139.2 (C); m/z (EI⁺) 320 (M⁺, 100%), 293 (16), 255 (40)

and 160 (15).

◦

solid: mp 297–298 C; (found: m/z (FAB⁺) M⁺523.1896.

C₃₅H₂₅N₃O₃requires 523.1896); m_max(CHCl₃)/cm⁻¹3577, 3445,

2940, 1750, 1694, 1574, 1494, 1462, 1385, 1351, 1111, 1068, 1021

and 943; d_H(CDCl₃, 400 MHz) 1.53 (1H, br s, OH), 1.95 (1H, br

d, J 15.5, 4^ꢀ-H_a), 2.71 (1H, dd, J 15.0, 2.0, 1^ꢀ-H_a), 2.95–3.08 (2H,

m, 1^ꢀ-H_band 4^ꢀ-H_b), 4.78 (2H, collapsed AB, J 15.0, CHaHbPh),

5.15 (1H, d, J 6.5, 2^ꢀ-H), 5.41 (1H, d, J_cis10.5, CH ), 5.50–5.57

=

ꢀ

=

(2H, m, 5 -H and CH ), 6.37 (1H, dd, J 17.0, 10.5, CH ), 7.33

(3H, m, Ar), 7.34 (1H, m, Ar), 7.42 (1H, m, Ar), 7.48–7.54 (3H,

m, Ar), 7.55–7.62 (3H, m, Ar), 9.15 (1H, d, J 8.0, 4-H or 8-H)

and 9.26 (1H, d, J 8.0, 4-H or 8-H); d_C(CDCl₃, 68 MHz) 37.2 (1^ꢀ-

CH₂), 40.7 (CH₂Ph), 44.8 (4^ꢀ-CH₂), 54.4 (5^ꢀ-CH), 63.7 (2^ꢀ-CH),

80.7 (3 -C), 109.8 (CH), 110.9 (CH), 112.6 ( CH₂), 115.6 (C),

ꢀ

=

115.8 (C), 118.3 (C), 120.2 (CH), 120.3 (CH), 121.1 (C), 124.2

(CH), 124.5 (CH), 126.8 (CH), 127.0 (CH), 127.3 (CH), 128.5

(C), 128.6 (CH), 129.7 (C), 137.5 (C), 140.0 (C), 142.5 (C), 144.3

( CH), 169.4 (CO) and 169.5 (CO); m/z (FAB ) 524 (M + H,

25%), 523 (M⁺, 29%), 452 (2), 413 (4), 329 (5), 207 (5), 176 (23),

120 (16), 107 (29), 91 (42), 73 (53), 69 (51), 67 (24), 57 (81) and

55 (64).

+

=

12,13-(3^ꢀa-Hydroxycyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(phenylmethyl)-

5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 11

To a stirred suspension of the ketone 8a (0.05 g, 0.1 mmol) in dry

tetrahydrofuran (20 mL), at 0 ^◦C under a nitrogen atmosphere,

was added a 1.0 M solution of borane in tetrahydrofuran

(0.3 mL, 0.3 mmol) and the stirring continued at 0 ^◦C. After

2 h, the reaction appeared complete by TLC analysis and so

water (0.5 mL), was added and the mixture was stirred for

10 min. The solvent was removed in vacuo and the residue was

dissolved in dichloromethane (30 mL). The organic layer was

washed with water (30 mL), brine (30 mL), dried (MgSO₄),

ﬁltered and the solvent removed in vacuo to yield the crude

product. Puriﬁcation by ﬂash chromatography (2.5% ethyl

acetate in dichloromethane), gave the alcohol 11 as a yellow solid

(0.047 g, 94%). A portion was recrystallised from a mixture of

chloroform–dichloromethane, to give 11 as yellow needles: mp

264–265 ^◦C; (found: m/z (FAB⁺) 497.1727. C₃₂H₂₃N₃O₃requires

497.1739); m_max(CHCl₃)/cm⁻¹2928, 1750, 1697, 1574, 1462, 1385,

1351, 1097 and 908; d_H(d₆-DMSO, 400 MHz) 1.27 (1H, dd, J

14.5, 7.0, 4^ꢀ-H_a), 2.61 (1H, br d, J 15.5, 1^ꢀ-H_a), 2.89–2.95 (2H, m,

1^ꢀ-H_band 4^ꢀ-H_b), 4.66 (1H, m, 3^ꢀ-H), 4.92–4.95 (3H, m, CH₂Ph

and OH), 5.47 (1H, t, J 5.5, 2^ꢀ-H), 5.65 (1H, t, J 7.0, 5^ꢀ-H), 7.27

(1H, t, J 7.0, Ph), 7.33–7.42 (6H, m, Ar), 7.59–7.63 (2H, m, 2-H

and 10-H), 7.85–7.89 (2H, m, 1-H and 11-H) and 9.02–9.08 (2H,

m, 4-H and 8-H); d_C(d₆-DMSO, 126 MHz) 37.5 (1^ꢀ-CH₂), 40.4

(CH₂Ph), 41.1 (4^ꢀ-CH₂), 53.9 (5^ꢀ-CH), 60.0 (2^ꢀ-CH), 72.5 (3^ꢀ-

12,13-[3^ꢀa-Hydroxy-3^ꢀb-(nitromethyl)-cyclopentan-2^ꢀa,5^ꢀa-diyl]-

6-(phenylmethyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 13

To a stirred solution of the ketone 8a (0.2 g, 0.4 mmol) in a

mixture of dry tetrahydrofuran (40 mL) and dry nitromethane

(40 mL) under a nitrogen atmosphere, was added sodium

ethoxide (0.137 g, 2 mmol) and the stirring continued at room

temperature. After 75 min, TLC analysis suggested that the

reaction was complete and so a 2.0 M aqueous solution of

hydrochloric acid (1 mL) was added to neutralise the reaction

mixture. The solvent was removed in vacuo to yield a crude

residue and water (35 mL) was added. The mixture was extracted

with dichloromethane (2 × 35 mL) and the combined extracts

were washed with water (35 mL), brine (35 mL), dried (MgSO₄),

ﬁltered and the solvent removed in vacuo, to yield the crude

product. Recrystallisation from a mixture of acetone–water gave

the product 13 as orange needles (0.168 g, 75%): mp 265–

267 ^◦C; (found: C, 70.52; H, 4.87; N, 9.07. C₃₃H₂₄N₄O₅+ acetone

requires C, 70.33; H, 4.92; N, 9.12%); (found: m/z (FAB⁺) M⁺

556.1742. C₃₃H₂₄N₄O₅requires 556.1747); m_max(CHCl₃)/cm^−l

2927, 1752, 1698, 1559, 1462, 1384, 1352, 1315 and 1111; d_H(d₆-

DMSO, 400 MHz) 1.80 (1H, br d, J 15.0, 4^ꢀ-H_a), 2.73 (1H, br

d, J 15.0, 1^ꢀ-H_a), 2.91 (1H, dd, J 15.5, 7.5, 4^ꢀ-H_b), 3.20 (1H, m,

2 9 6 4

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

1^ꢀ-H_b), 4.93 (2 H, s, CH₂Ph), 4.97 (1H, d, J 12.0, CHaHbNO₂),

5.21 (1H, d, J 12.0, CHaHbNO₂), 5.47 (1H, s, OH), 5.70 (1H,

dd, J 7.5, 7.0, 5^ꢀ-H), 5.74 (1H, d, J 7.0, 2^ꢀ-H), 7.27 (1H, t, J 7.5,

Ph), 7.33–7.42 (6H, m, Ar), 7.60–7.65 (2H, m, 2-H and 10-H),

7.83 (1H, d, J 8.5, 1-H or 11-H), 7.88 (1H, d, J 8.5, 1-H or 11-H)

and 9.04–9.07 (2H, m, 4-H and 8-H); d_C(d₆-DMSO, 68 MHz)

37.2 (1^ꢀ-CH₂), 40.6 (CH₂Ph), 44.4 (4^ꢀ-CH₂), 54.3 (5^ꢀ-CH), 60.8

(2^ꢀ-CH), 80.2 (3^ꢀ-C), 82.9 (CH₂NO₂), 109.7 (CH), 110.6 (CH),

115.6 (C), 115.8 (C), 118.2 (C), 120.3 (CH), 120.4 (CH), 121.1

(C), 124.3 (CH), 124.5 (CH), 126.9 (CH), 127.0 (CH), 127.2

(CH), 128.5 (C), 128.6 (CH), 129.6 (C), 137.5 (C), 140.0 (C),

142.3 (C), 169.3 (CO) and 169.4 (CO); m/z (FAB⁺) 557 (M⁺+

H, 6%), 556 (M⁺, 5%), 460 (5), 419 (4), 176 (11), 120 (11) and 91

(14).

and the solvent removed in vacuo, to yield N-trimethylsilyl-

O-trimethylsilylcyanohydrin 14b as a yellow solid (0.247 g,

95%); (found: m/z (FAB⁺) M⁺576.2044. C₃₂H₃₂N₄O₃Si₂requires

576.2013); d_H(CDCl₃, 400 MHz) −0.30 (9H, s, SiMe₃), 0.65

(9H, s, SiMe₃), 1.85 (1H, br d, J 15.5, 4^ꢀ-H_a), 2.86 (1H, dd,

J 15.5, 2.0, l^ꢀ-H_a), 3.24–3.36 (2H, m, 1^ꢀ-H_band 4^ꢀ-H_b), 5.64–5.67

(2H, m, 2^ꢀ-H and 5^ꢀ-H), 7.41–7.46 (2H, m, Ar), 7.52–7.62 (4H,

m, Ar) and 9.24–9.28 (2H, m, 4-H and 8-H); m/z (FAB⁺) 577

(M⁺+ H, 3%), 576 (M⁺, 5%), 207 (12), 147 (26), 136 (19), 133

(7), 91 (11), 90 (11), 75 (8), 74 (8), 73 (100) and 59 (8).

12,13-[3^ꢀa-Hydroxy-3^ꢀb-(methoxycarbonyl)cyc1opentan-2^ꢀa,5^ꢀa-

diyl]-6-(phenylmethyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 15a

A stirred solution of the O-trimethylsilylcyanohydrin 14a (0.05 g,

0.1 mmol) in a mixture of tetrahydrofuran (10 mL), methanol

(5 mL) and concentrated hydrochloric acid (5 mL), was heated

to reﬂux. After 24 h, a precipitate had formed and the heating

was discontinued. After cooling, the precipitate was removed by

ﬁltration and the ﬁltrate was returned to reﬂux. The precipitate

was washed with a minimum of methanol and left to dry.

After a total time at reﬂux of 72 h, additional precipitate had

formed, and the heating was again discontinued. This second

batch of precipitate was removed by ﬁltration and washed

and dried as before. The solids were combined to give the

a-hydroxymethylester 15a, as a yellow solid (0.04 g, 87%).

A portion of the product was recrystallised from a mixture

of tetrahydrofuran–petroleum e_◦ther, to give 15a as a yellow

crystalline solid: mp 305–307 C; (found: m/z (FAB⁺) M⁺

555.1788. C₃₄H₂₅N₃O₅requires 555.1794); m_max(CHCl₃)/cm⁻¹

2930, 1749, 1697, 1575, 1463, 1385, 1352, 1155, 1110, 1068 and

945; d_H(d₆-DMSO, 400 MHz) 1.72 (1H, br d, J 15.0, 4^ꢀ-H_a),

2.78 (1H, dd, J 15.5, 2.0, 1^ꢀ-H_a), 3.06 (1H, m, 1^ꢀ-H_b), 3.15 (1H,

dd, J 15.0, 7.0, 4^ꢀ-H_b), 3.86 (3H, s, Me), 4.87 (2H, s, CH₂Ph),

5.55 (1H, s, OH), 5.73 (1H, d, J 7.0, 2^ꢀ-H), 5.81 (1H, t, J 7.0,

5^ꢀ-H), 7.26 (1H, m, Ph), 7.33–7.41 (6H, m, Ar), 7.58–7.63 (2H,

m, 2-H and 10-H), 7.77 (1H, d, J 8.5, 1-H or 11-H), 7.88 (1H,

d, J 8.0, 1-H or 11-H) and 9.02–9.04 (2H, m, 4-H and 8-H);

d_C(d₆-DMSO, 126 MHz) 39.0 (1^ꢀ-CH₂), 40.8 (CH₂Ph), 45.6 (4^ꢀ-

CH₂), 52.9 (Me), 55.5 (5^ꢀ-CH), 62.0 (2^ꢀ-CH), 81.3 (3^ꢀ-C), 110.0

(CH), 110.6 (CH), 115.8 (C), 118.4 (C), 120.5 (CH), 120.7 (CH),

121.3 (C), 121.4 (C), 124.5 (CH), 124.7 (CH), 127.0 (CH), 127.2

(CH), 127.5 (CH), 128.7 (C), 128.8 (CH), 129.9 (C), 137.6 (C),

140.3 (C), 142.3 (C), 169.5 (CO) and 175.5 (CO); m/z (FAB⁺)

556 (M⁺+ H, 8%), 555 (M⁺, 10%), 453 (3), 452 (3), 329 (3), 123

(11), 121, (13), 107 (26) and 91 (38).

12,13-[3^ꢀb-Cyano-3^ꢀa-(trimethylsiloxy)-cyclopentan-2^ꢀa,5^ꢀa-diyl]-

6-(phenylmethyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 14a

To a stirred suspension of the ketone 8a (0.2 g, 0.4 mmol) in

dry dichloromethane (40 mL) under a nitrogen atmosphere, was

added a catalytic quantity of potassium cyanide (ca. 1 mg),

followed by a catalytic quantity of 18-crown-6 (ca. 1 mg). The

mixture was cooled to −45 ^◦C, trimethylsilyl cyanide (0.12 mL,

0.9 mmol) was added dropwise and the stirring continued at

−45 ^◦C. After 1 h, TLC analysis indicated that the reaction

was complete, so the reaction mixture was allowed to warm

to 0 ^◦C, a saturated aqueous solution of NaHCO₃(20 mL)

was added and the mixture was stirred for 10 min. The organic

layer was washed with a saturated aqueous solution of NaHCO₃

(20 mL), water (2 × 20 mL) and brine (20 mL), dried (Na₂SO₄),

ﬁltered and the solvent was removed in vacuo to yield the O-

trimethylsilylcyanohydrin 14a as a yellow solid (0.231 g, 96%). A

portion of the solid was recrystallised from a mixture of acetone–

water to give 14a as yellow needles: mp 310–311 ^◦C; (found: C,

72.43; H, 4.98; N, 9.43. C₃₆H₃₀N₄O₃Si requires C, 72.7; H, 5.09;

N, 9.43%); (found: m/z (FAB⁺) M⁺594.2086. C₃₆H₃₀N₄O₃Si

requires 594.2087); m_max(CHCl₃)/cm^−l2959, 1752, 1697, 1575,

1461, 1385, 1351, 1126, 1112, 944 and 870; d_H(CDCl₃, 400 MHz)

−0.30 (9H, s, SiMe₃), 1.82 (1H, dt, J 15.5, 2.0, 4^ꢀ-H_a), 2.86 (1

H, dd, J 15.5, 2.0, 1^ꢀ-H_a), 3.23–3.34 (2H, m, 1^ꢀ-H_band 4^ꢀ-H_b),

4.99 (2H, s, CH₂Ph), 5.61–5.65 (2H, m, 2^ꢀ-H and 5^ꢀ-H), 7.25–

7.28 (1H, m, Ph), 7.33–7.37 (2H, m, Ar), 7.39–7.44 (2H, m, Ar),

7.51–7.63 (6H, m, Ar) and 9.22–9.25 (2H, m, 4-H and 8-H);

d_C(CDCl₃, 68 MHz) 0.2 (SiMe₃), 36.8 (1^ꢀ-CH₂), 41.2 (CH₂Ph),

46.8 (4^ꢀ-CH₂), 53.6 (5^ꢀ-CH), 64.4 (2^ꢀ-CH), 74.9 (3^ꢀ-C), 108.2

(CH), 109.5 (CH), 117.2 (C), 117.4 (C), 119.3 (C), 119.6 (C),

121.0 (CH), 121.2 (CH), 121.9 (C), 122.1 (C), 122.2 (C), 125.5

(CH), 125.9 (CH), 127.1 (CH), 127.5 (CH), 128.6 (CH), 128.7

(CH), 137.4 (C), 139.9 (C), 142.4 (C), 169.5 (CO) and 169.6

(CO); m/z (FAB⁺) 595 (M⁺+ H, 86%), 495 (M⁺, 100%), 517 (8),

454 (11), 452 (13), 329 (9), 207 (10), 176 (30), 120 (16), 107 (33),

91 (54), 73 (77), 69 (26), 57 (36) and 55 (36).

12,13-[3^ꢀa-Hydroxy-3^ꢀb-(methoxycarbonyl)cyclopentan-2^ꢀa,5^ꢀa-

diyl]-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 15b

A stirred solution of the N-trimethylsilyl-O-trimethylsilyl-

cyanohydrin 14b (0.05 g, 0.086 mmol) in a mixture of tetrahydro-

furan (5 mL), methanol (5 mL) and concentrated hydrochloric

acid (2.5 mL) was heated to reﬂux. After 5 d, TLC analysis

suggested that the reaction was complete, so the heating was

discontinued and the solvent removed in vacuo, furnishing

a crude product. The crude mixture was puriﬁed by ﬂash

chromatography (2 : 1 CHCl₃–ethyl acetate), to give the a-

hydroxymethylester 15b as a yellow solid (0.023 g, 57%): mp

329–330 ^◦C; (found: m/z (FAB⁺) M⁺+ H 466.1359. C₂₇H₂₀N₃₀O₅

requires 466.1403); m_max(CHCl₃)/cm^−l3437, 2930, 2867, 1754,

1720, 1572, 1462, 1352, 1320, 1112 and 1002; d_H(d₆-DMSO,

400 MHz) 1.74 (1H, d, J 15.0, 4^ꢀ-H_a), 2.76 (1H, d, J 14.0, l^ꢀ-H_a),

3.06 (1H, dt, J 14.0, 7.0, l^ꢀ-H_b), 3.15 (1H, dd, J 15.0, 7.0, 4^ꢀ-H_b),

3.86 (3H, s, Me), 5.56 (1H, s, OH), 5.74 (1H, d, J 7.0, 2^ꢀ-H), 5.83

(1H, t, J 7.0, 5^ꢀ-H), 7.37–7.42 (2H, m, 3-H and 9-H), 7.58–7.64

(2H, m, 2-H and 10-H), 7.77 (1H, d, J 8.5, 1-H or 11-H), 7.89

(1H, d, J, 8.0, 1-H or 11-H), 9.04–9.07 (2H, m, 4-H and 8-H)

and 11.05 (1H, s, NH); d_C(d₆-DMSO, 126 MHz) 39.1 (1^ꢀ-CH₂),

45.6 (4^ꢀ-CH₂), 52.9 (Me), 55.5 (5^ꢀ-CH), 62.0 (2^ꢀ-CH), 81.4 (3^ꢀ-C),

12,13-[3^ꢀb-Cyano-3^ꢀa-(trimethylsilyloxy)-cyclopentan-2^ꢀa,5^ꢀa-

diyl]-6-(trimethylsilyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 14b

To a stirred suspension of the ketone 8b (0.183 g, 0.452 mmol)

in dry dichloromethane (100 mL) under a nitrogen atmosphere,

was added a catalytic quantity of potassium cyanide (ca. 1 mg),

followed by a catalytic quantity of 18-crown-6 (ca. 1 mg).

The mixture was cooled to −40 ^◦C and trimethylsilylcyanide

(0.181 mL, 1.36 mmol) was added dropwise and the stirring

continued at −40 ^◦C. After 1.5 h, TLC analysis indicated

that the reaction was incomplete, so additional trimethylsi-

lylcyanide (0.28 mL) was added and the reaction mixture

was warmed to 0 ^◦C over 4 h. Water (50 mL) was added

and the mixture allowed to warm to room temperature, then

stirred for 10 min. The organic layer was washed with water

(4 × 50 mL) and brine (50 mL), dried (Na₂SO₄), ﬁltered

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 6 5

View Article Online

110.0 (CH), 110.6 (CH), 115.6 (C), 115.7 (C), 119.8 (C), 120.5

(CH), 120.6 (CH), 121.4 (C), 121.5 (C), 124.6 (CH), 124.9 (CH),

126.9 (CH), 127.1 (CH), 128.7 (C), 129.9 (C), 140.3 (C), 142.2

(C), 171.3 (CO) and 175.5 (CO); m/z (FAB⁺) 466 (M⁺+ H, 3%),

465 (M⁺, 3%), 329 (5), 308 (8), 307 (32), 289 (15) and 176 (11).

10-H), 8.11 (2H, d, J 8.1, 1-H and 11-H), 9.09 (2H, d, J 7.7, 4-H

and 8-H); d_C(d₆-DMSO, 100 MHz) 35.0 (1^ꢀ-CH₂), 41.1 (CH₂Ar),

54.8 (3^ꢀ-CH and 4^ꢀ-CH), 56.0 (OMe), 56.1 (2^ꢀ-CH and 5^ꢀ-CH),

111.0 (CH), 114.9 (CH), 116.9 (C), 119.6 (C), 121.7 (CH), 122.0

(C), 125.5 (CH), 128.2 (CH), 129.1 (C), 129.9 (CH), 130.3 (C),

141.4 (C), 159.5 (C), 170.1 (CO); m/z (FAB⁺) 526 (M⁺+ H, 3%),

525 (7), 447 (7), 307 (11), 176 (17), 155 (20), 154 (64), 136 (53),

121 (17).

12,13-(3^ꢀb,4^ꢀb-Epoxycyclopentane-2^ꢀa,5a^ꢀ-diyl)-6-(benzyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7 (6H)-

dione 16a

Epoxidation using DMDO

Alkene 6a (50.0 mg, 0.11 mmol), 2,6-di-tert-butyl-4-

methylphenol (2.0 mg, 0.01 mmol) and mCPBA (22.0 mg,

0.13 mmol) were dissolved in CHCl₃(7 mL) and the reaction

mixture was heated to reﬂux for 4 h. TLC analysis showed the

presence of starting material so a further portion of mCPBA

(44.0 mg) and 2,6-di-tert-butyl-4-methylphenol (4.0 mg) was

added and the reaction mixture was returned to reﬂux overnight.

Starting material was still present after the overnight reﬂux

and so further equivalents of mCPBA (44.0 mg) were added

and the mixture was heated to reﬂux for a further 5 h. The

reaction mixture was cooled and quenched by the addition of

a saturated aqueous solution of Na₂S₂O₃(10 mL), which was

stirred vigorously for 30 min before being partitioned between

CHCl₃(50 mL) and H₂O (50 mL). The organic layer was washed

with saturated aqueous NaHCO₃solution (50 mL), saturated

aqueous Na₂S₂O₃solution (50 mL), saturated aqueous NaHCO₃

solution (50 mL), brine (50 mL), dried (MgSO₄), concentrated

in vacuo and puriﬁed by ﬂash column chromatography using a

DCM solvent system to give 16a as a yellow solid (10.0 mg, 19%):

mp 297–300 ^◦C; m_max(CHCl₃)/cm⁻¹2926, 2854, 1753, 1697, 1384,

1349; d_H(d₆-DMSO, 500 MHz) 2.59 (1H, d, J 15.0, 1^ꢀ-H_a), 2.81

(1H, dt, J 15.0, 6.6, 1^ꢀ-H_b), 3.83 (2H, s, 3^ꢀ-H and 4^ꢀ-H), 4.95

(2H, s, CH₂Ph), 5.96 (2H, d, J 6.6, 2^ꢀ-H and 5^ꢀ-H), 7.31 (1H, t,

J 7.3, Ph), 7.39 (2H, dd, J 7.6, 7.3, Ph), 7.44–7.48 (4H, m, 2-H,

10-H and Ph), 7.71 (2H, dd, J 7.9, 7.5, 3-H and 9-H), 8.13 (2H,

d, J 8.4, 1-H and 11-H), 9.11 (2H, d, J 7.9, 4-H and 8-H); d_C(d₆-

DMSO, 125 MHz) 35.0 (1^ꢀ-CH₂), 41.7 (CH₂Ph), 54.8 (CH), 56.1

(CH), 111.1 (CH), 116.9 (C), 119.6 (C), 121.8 (CH), 122.0 (C),

125.5 (CH), 128.2 (CH), 129.2 (C), 129.5 (CH), 138.3 (C), 141.4

(C), 170.2 (CO).

Alkene 6c (50.0 mg, 0.10 mmol) was dissolved in DCM (5 mL)

and cooled to 0 ^◦C before the addition of freshly prepared

DMDO solution in acetone (∼0.1 M) (4.9 mL) with stirring.

The reaction mixture was stirred for 2 h at 0 ^◦C before being

allowed to warm to rt. TLC analysis showed starting material

still present so the reaction mixture was recooled to 0 ^◦C and a

further 5 mL of DMDO solution were added and the reaction

mixture was allowed to warm to rt overnight. TLC analysis

showed consumption of starting material. The reaction mixture

was concentrated in vacuo to give a brown solid and puriﬁed

using ﬂash column chromatography with a DCM solvent system

to give epoxide 16c as a yellow solid (24.0 mg 47%). The

spectroscopic data were identical to those described above.

12,13-(3^ꢀb-Hydroxy,4^ꢀa-azidocyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 17

Epoxide 16c (30.0 mg 0.06 mmol) was suspended in DCM (3 mL)

with stirring under N₂. TMSN₃(0.03 mL, 0.20 mmol) and

BF₃·OEt₂(0.03 mL, 0.20 mmol) were added and the reaction

was stirred for 18 h. TLC analysis showed consumption of

starting material, and the reaction mixture was concentrated

in vacuo to give a brown solid which was puriﬁed by ﬂash

column chromatography using a 2% MeOH–DCM solvent

system to afford 17 as a yellow solid (0.013 g, 40%); mp 267–

269 ^◦C; (found: m/z (FAB⁺) M⁺568.1836. C₃₃H₂₄N₆O₄requires

568.1859); m_max(CHCl₃)/cm⁻¹3449, 2930, 2108, 1750, 1695, 1385,

1350; d_H(d₆-DMSO, 500 MHz) 2.76 (1H, d, J 14.8, 1^ꢀ-H_a), 3.28

(1H, ddd, J 14.8, 7.5, 6.5, 1^ꢀ-H_b), 3.74 (3H, s, OMe), 3.87 (1H,

dd, J 5.3, 4.8, 3^ꢀ-H), 4.45 (1H, dd, J 5.9, 5.3, 4^ꢀ-H), 4.84 (2H, s,

CH₂Ar), 5.40 (1H, d, J 7.5, 2^ꢀ-H), 5.93 (1H, dd, J 6.5, 5.9, 5^ꢀ-H),

6.35 (1H, d, J 4.8, OH), 6.94 (2H, d, J 8.8, PMB), 7.39 (2H, d, J

8.8, PMB), 7.45 (2H, dd, J 8.4, 7.2, 3-H and 9-H), 7.70 (2H, dd,

J 8.2, 7.2, 2-H and 10-H), 7.94 (1H, d, J 8.2, 11-H), 7.95 (1H,

d, J 8.2, 1-H), 9.07 (1H, d, J 8.4, 8-H), 9.09 (1H, d, J 8.4, 4-

H); d_C(d₆-DMSO, 125 MHz) 36.3 (1^ꢀ-CH₂), 41.0 (CH₂Ar), 56.0

(OMe), 59.6 (5^ꢀ-CH), 63.1 (2^ꢀ-CH), 72.2 (4^ꢀ-CH), 83.6 (3^ꢀ-CH),

111.1 (CH), 111.2 (CH), 114.9 (CH), 116.6 (C), 116.8 (C), 119.5

(C), 119.6 (C), 121.6 (CH), 121.7 (CH), 122.0 (C), 125.4 (CH),

125.5 (CH), 128.0 (CH), 128.2 (CH), 129.3 (C), 129.6 (C), 129.9

(CH), 130.4 (C), 141.0 (C), 142.6 (C), 159.5 (C), 170.1 (CO),

170.2 (CO); m/z (FAB⁺) 569 (M⁺+ H, 8%), 568 (M⁺, 12), 419

(5), 329 (5), 289 (15), 137 (52), 108 (5), 77 (13).

12,13-(3^ꢀb,4^ꢀb-Epoxycyclopentane-2^ꢀa,5a^ꢀ-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 16c using mCPBA

Alkene 6c (50.0 mg, 0.10 mmol), 2,6-di-tert-butyl-4-

methylphenol (2.0 mg, 0.01 mmol) and mCPBA (22.0 mg,

0.13 mmol) were dissolved in CHCl₃(7 mL) and the reaction

mixture was heated to reﬂux for 4 h. TLC analysis showed the

presence of starting material so a further portion of mCPBA

(44.0 mg) and 2,6-di-tert-butyl-4-methylphenol (4.0 mg) was

added and the reaction mixture was returned to reﬂux overnight.

Starting material was still present after the overnight reﬂux and

so a further portion of mCPBA (44.0 mg) was added and the

mixture heated at reﬂux for a further 5 h. The reaction mixture

was cooled and quenched by the addition of a saturated aqueous

solution of Na₂S₂O₃(10 mL), which was stirred vigorously for

30 min before being partitioned between CHCl₃(50 mL) and

H₂O (50 mL). The organic layer was washed with saturated

aqueous NaHCO₃solution (50 mL), saturated aqueous Na₂S₂O₃

solution (50 mL), saturated aqueous NaHCO₃solution (50 mL),

brine (50 mL), dried (MgSO₄), concentrated in vacuo and

puriﬁed by ﬂash column chromatography using a DCM solvent

system to give 16c as a yellow solid (10.0 mg, 17%): mp 315–

318 ^◦C; (found: m/z (FAB⁺) M⁺525.1699. C₃₃H₂₃N₃O₄requires

525.1689); m_max(CHCl₃)/cm⁻¹1752, 1696, 1574, 1462, 1384, 1349;

d_H(d₆-DMSO, 400 MHz) 2.55 (1H, d, J 14.5, 1^ꢀ-H_a), 2.80 (1H,

dt, J 14.5, 6.8, 1^ꢀ-H_b), 3.74 (3H, s, OMe), 3.82 (2H, s, 3^ꢀ-H and

4^ꢀ-H), 4.82 (2H, s, CH₂Ar), 5.94 (2H, d, J 6.8, 2^ꢀ-H and 5^ꢀ-H),

6.93 (2H, d, J 8.6, PMB), 7.37 (2H, d, J 8.6, PMB), 7.45 (2H,

dd, J 7.7, 7.5, 3-H and 9-H), 7.70 (2H, dd, J 8.1, 7.5, 2-H and

Azide 17 via opening of cyclic sulfate 20

Cyclic sulfate 20 (0.48 g, 0.79 mmol) was dissolved in dry DMF

(50 mL) with stirring under N₂. NaN₃(0.52 g, 7.92 mmol) was

added and the reaction mixture was heated to 80 ^◦C for 5 h.

TLC showed consumption of starting material. The reaction

mixture was allowed to cool to rt and concentrated in vacuo to

give a brown solid. The brown solid was redissolved in THF

(20 mL), 20% H₂SO₄(5 mL) was added and the resulting

mixture was stirred vigorously for 18 h. The reaction mixture

was partitioned between EtOAc (200 mL) and H₂O (100 mL)

and the organic layer was washed with H₂O (200 mL), saturated

aqueous NaHCO₃solution (150 mL), brine (2 × 200 mL),

dried (MgSO₄) and concentrated in vacuo to give crude azido

alcohol. Puriﬁcation by ﬂash column chromatography using a

2 9 6 6

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

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5% MeOH–DCM solvent system yielded 17 as an orange solid

(0.41 g, 91%). The spectroscopic data were identical to those

described above.

(3H, s, OMe), 4.89 (2H, s, CH₂Ar), 5.38 (2H, d, J 1.4, 3^ꢀ-H and

4^ꢀ-H), 5.94 (2H, d, J 7.2, 2^ꢀ-H and 5^ꢀ-H), 6.94 (2H, d, J 8.8,

PMB), 7.39 (2H, d, J 8.8, PMB), 7.50 (2H, dd, J 7.9, 7.2, 3-H

and 9-H), 7.72 (2H, dd, J 8.3, 7.2, 2-H and 10-H), 8.04 (2H, d,

J 8.3, 1-H and 11-H), 9.14 (2H, d, J 7.9, 4-H and 8-H).

12,13-(3^ꢀb,4^ꢀb-Dihydroxycyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 18

12,13-((3^ꢀb,4^ꢀb)Tetrahydrocyclopenta[3^ꢀ,4^ꢀ,2]dioxathiole-2,2-

dioxide-2^ꢀa,5^ꢀa-diyl)-6-(4-methoxybenzyl)-dihydro-5H-

indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 20

Indolocarbazole 6c (0.37 g, 0.73 mmol) was suspended in THF

(20 mL) and NMMO (0.15 g, 1.10 mmol), OsO₄(^tBuOH

solution, 1 mL = 0.1 mmol) (0.10 mL) and H₂O (0.1 mL)

were added. The reaction mixture was stirred for 2 h before

the addition of saturated aqueous Na₂S₂O₃solution (15 mL)

and then stirred for a further 0.5 h. The reaction mixture

was partitioned between EtOAc (100 mL) and H₂O (100 mL)

and the organic layer was washed with H₂O (100 mL), brine

(100 mL), dried (MgSO₄) and concentrated in vacuo to give

crude product. The crude material was puriﬁed by ﬂash column

chromatography using a 2% MeOH–DCM solvent system to

afford 18 as an orange solid (0.38 g, 95%). A portion of the

solid was recrystallised_◦from acetone–water to give 18 as yellow

needles: mp 260–262 C; (found: m/z (FAB⁺) M⁺543.1802.

C₃₃H₂₅N₃O₅requires 543.1794); m_max(CHCl₃)/cm⁻¹2936, 1752,

1695, 1384, 1350, 1088; d_H(d₆-DMSO, 500 MHz) 2.57 (1H, d, J

14.5, 1^ꢀ-H_a), 3.36 (1H, dt, J 14.5, 7.3, 1^ꢀ-H_b), 3.73 (3H, s, OMe),

4.12 (2H, d, J 3.6, 3^ꢀ-H and 4^ꢀ-H), 4.76 (2H, s, CH₂Ar), 5.42

(2H, d, J 7.3, 2^ꢀ-H and 5^ꢀ-H), 5.52 (2H, d, J 3.6, OH), 6.92

(2H, d, J 8.7, PMB), 7.35 (2H, d, J 8.7, PMB), 7.42 (2H, dd,

J 7.8, 7.4, 3-H and 9-H), 7.67 (2H, dd, J 8.2, 7.4, 2-H and 10-

H), 7.86 (2H, d, J 8.2, 1-H and 11-H), 9.04 (2H, d, J 7.8, 4-H

and 8-H); d_C(d₆-DMSO, 125 MHz) 35.7 (1^ꢀ-CH₂), 41.0 (CH₂Ar),

55.9 (OMe), 64.3 (2^ꢀ-CH and 5^ꢀ-CH), 78.1 (3^ꢀ-CH and 4^ꢀ-CH),

110.7 (CH), 114.9 (CH), 116.4 (C), 119.4 (C), 121.4 (CH), 122.0

(C), 125.5 (CH), 127.9 (CH), 129.6 (C), 129.8 (CH), 130.3 (C),

141.1 (C), 159.4 (C), 170.1 (CO); (found: C, 70.80; H, 5.01; N,

6.92. C₃₃H₂₅N₃O₅·H₂O requires C, 70.58; H, 4.81; N, 7.49%);

m/z (FAB⁺) 544 (M⁺+H, 17%), 543 (34), 524 (6).

Cyclic sulﬁte 19 (1.00 g, 1.70 mmol) was dissolved in DCM

(300 mL). MeCN (100 mL), H₂O (150 mL), NaIO₄(0.726 g,

3.40 mmol) and RuCl₃(0.20 g, 0.77 mmol) were added. The

reaction mixture was stirred vigorously for 3 d before being

partitioned between DCM (200 mL) and H₂O (200 mL). The

organic layer was washed with H₂O (100 mL), saturated aqueous

NaHCO₃solution (100 mL), brine (100 mL), dried (MgSO₄)

and concentrated in vacuo to give a brown solid. The crude

material was puriﬁed by ﬂash column chromatography using a

DCM solvent system to g_◦ive cyclic sulfate 20 as a yellow solid

(0.45 g, 44%): mp 275–277 C; (found: m/z (FAB⁺) M⁺605.1257.

C₃₃H₂₃N₃O₇S requires 605.1257); m_max(CHCl₃)/cm⁻¹1754, 1698,

1384, 1350, 991; d_H(d₆-DMSO, 400 MHz) 3.09 (1H, d, J 15.6,

1^ꢀ-H_a), 3.46 (1H, dt, J 15.6, 7.3, 1^ꢀ-H_b), 3.74 (3H, s, OMe), 4.86

(2H, s, CH₂Ar), 5.73 (2H, d, J 1.5, 3^ꢀ-H and 4^ꢀ-H), 6.25 (2H, d, J

7.3, 2^ꢀ-H and 5^ꢀ-H), 6.94 (2H, d, J 8.8, PMB), 7.38 (2H, d J 8.8,

PMB), 7.50 (2H, dd, J 7.8, 7.3, 3-H and 9-H), 7.73 (2H, dd, J 8.4,

7.3, 2-H and 10-H), 8.07 (2H, d, J 8.4, 1-H and 11-H), 9.09 (2H,

d, J 7.8, 4-H and 8-H); d_C(d₆-DMSO, 100 MHz) 36.1 (1^ꢀ-CH₂),

41.0 (CH₂Ar), 55.8 (OMe), 60.5 (2^ꢀ-CH and 5^ꢀ-CH), 89.0 (3^ꢀ-CH

and 4^ꢀ-CH), 110.9 (CH), 114.8 (CH), 117.1 (C), 119.7 (C), 122.0

(CH), 122.2 (C), 125.4 (CH), 128.2 (CH), 129.1 (C), 129.6 (CH),

130.1 (C), 140.8 (C), 159.4 (C), 167.7 (CO); (found: C, 65.03; H,

3.84; N, 6.95; S, 5.29. C₃₃H₂₃N₃O₇S requires C, 65.45; H, 3.80;

N, 6.94; S, 5.29%); m/z (FAB⁺) 606 (M⁺+ H, 8%), 605 (22), 509

(4), 137 (20), 136 (49), 121 (100), 107 (15).

Cyclic sulfate 20 by reaction of diol 18 with SO₂Im₂

12,13-((3^ꢀb,4^ꢀb)Tetrahydrocyclopenta[3^ꢀ,4^ꢀ,2]dioxathiole-2-oxide-

2^ꢀa,5^ꢀa-diyl)-6-(4-methoxybenzyl)-dihydro-5H-indolo[2,3-a]-

pyrrolo[3,4-c]carbazole-5,7(6H)-dione 19

Diol 18 (0.69 g, 1.26 mmol) was dissolved in THF (75 mL) with

stirring under N₂at rt. SO₂Im₂(1.00 g, 5.05 mmol) was added

in one portion and the reaction mixture was stirred for 10 min

before the dropwise addition of DBU (0.76 mL, 5.05 mmol).

The reaction mixture was stirred for 18 h, a yellow precipitate

formed overnight and was collected by ﬁltration. The yellow

solid was washed with THF (20 mL) and dried. The organics

were combined, partitioned between EtOAc (150 mL) and H₂O

(150 mL) and washed with 2N HCl (150 mL), H₂O (150 mL),

brine (150 mL) and concentrated in vacuo to give a yellow solid.

The two batches were combined to give 20 as a yellow solid

(0.82 g, 90%). The spectroscopic data were identical to those

described above.

Diol 18 (0.67 g, 1.24 mmol) was dissolved in THF (40 mL),

SOCl₂(1.35 mL, 18.56 mmol) was added and the reaction

mixture was heated to reﬂux for 18 h. The solid yellow 19

that precipitated out of the reaction mixture was collected by

ﬁltration and washed with THF (10 mL), Et₂O (10 mL) and

petrol (10 mL). The reaction mixture was partially concentrated

in vacuo and a second crop of product was collected and washed

with THF (10 mL), Et₂O (10 mL) and petrol (10 mL). The

mother liquors were concentrated in vacuo and puriﬁed by

ﬂash column chromatography using a 2% MeOH–DCM solvent

system to give cyclic sulﬁte 19 as a yellow solid. The batches were

combined to give 19 as a 2.4 : 1 mixture of diastereoisomers

(0.72 g, 98%): major isomer mp 340 ^◦C decomp.; (found:

m/z (FAB⁺) M⁺589.1311. C₃₃H₂₃N₃O₆S requires 589.1308);

m_max(solid)/cm⁻¹1691, 1386, 1242, 1213, 979, 801, 741; d_H(d₆-

DMSO, 400 MHz) 2.90 (1H, d, J 15.6, 1^ꢀ-H_a), 3.30 (1H, dt, J

15.6, 7.4, 1^ꢀ-H_b), 3.74 (3H, s, OMe), 4.80 (2H, s, CH₂Ar), 5.52

(2H, d, J 1.6, 3^ꢀ-H and 4^ꢀ-H), 5.93 (2H, d, J 7.4, 2^ꢀ-H and 5^ꢀ-H),

6.94 (2H, d, J 8.8, PMB), 7.36 (2H, d, J 8.8, PMB), 7.47 (2H, dd,

J 7.9, 7.3, 3-H and 9-H), 7.71 (2H, dd, J 8.4, 7.3, 2-H and 10-H),

7.96 (2H, d, J 8.4, 1-H and 11-H), 9.07 (2H, d, J 7.9, 4-H and

8-H); d_C(d₆-DMSO, 100 MHz) 35.5 (CH₂), 41.2 (CH₂Ar), 56.0

(OMe), 61.2 (CH), 89.8 (CH), 111.0 (CH), 115.0 (CH), 117.1

(C), 119.7 (C), 122.1 (CH), 122.3 (C), 125.6 (CH), 128.5 (CH),

129.5 (C), 129.8 (CH), 130.3 (C), 141.0 (C), 159.5 (C), 170.1

(CO); (found: C, 66.67; H, 3.82; N, 7.08; S, 6.13. C₃₃H₂₃N₃O₆S

requires C, 67.23; H, 3.90; N, 7.13; S, 5.4%); m/z (FAB⁺) 590

(M⁺+ H, 11%), 589 (16). Minor isomer d_H(d₆-DMSO, 400 MHz)

2.89 (1H, d, J 15.1, 1^ꢀ-H_a), 3.31 (1H, dt, J 15.1, 7.2, 1^ꢀ-H_b), 3.76

12,13-(3^ꢀb-Hydroxy,4^ꢀa-morpholinylcyclopentan-2^ꢀa,5^ꢀa-diyl)-6-

(4-methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 21

Cyclic sulfate 20 (50.0 mg, 0.08 mmol) was dissolved in freshly

distilled morpholine (4 mL), with stirring under an atmosphere

of N₂and the reaction mixture was heated to reﬂux for 15 h.

TLC analysis showed the consumption of starting material and

so the reaction mixture was cooled to rt before being partitioned

between EtOAc (100 mL) and H₂O (100 mL). The organic

layer was washed with brine (100 mL). The aqueous washings

were combined and re-extracted with EtOAc (50 mL). The

organics were combined, concentrated in vacuo, redissolved in

THF (5 mL) and 20% H₂SO₄(5 mL) was added. The resulting

mixture was stirred vigorously for 15 h. The reaction mixture

was partitioned between EtOAc (150 mL) and H₂O (150 mL).

The organic layer was washed with H₂O (150 mL), saturated

aqueous NaHCO₃solution (2 × 150 mL), brine (200 mL), dried

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 6 7

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(MgSO₄), and concentrated in vacuo to give the crude product as

an orange solid. Puriﬁcation by ﬂash column chromatography

using a 10% EtOAc–DCM solvent system gave ﬁrstly ketone

8c (15.0 mg, 28%); secondly morpholine 21 as an orange solid

(R_f0.49) (18.0 mg, 36%): mp 272–275 ^◦C; m_max(CHCl₃)/cm⁻¹

3696, 3606, 2928, 2360, 1697, 1602, 1384, 1350; d_H(d₆-DMSO,

400 MHz) 2.68 (1H, d, J 15.0, 1^ꢀ-H_a), 3.27 (4H, dd, J 5.1, 4.2,

NCH₂), 3.44 (1H, ddd, J 15.0, 7.5, 7.2, 1^ꢀ-H_b), 3.61 (4H, dd, J

6.3, 4.2, OCH₂), 3.76 (3H, s, OMe), 4.51 (1H, dd, J 5.9, 5.6,

3^ꢀ-H), 4.87 (2H, s, CH₂Ar), 4.99 (1H, d, J 5.6, 4^ꢀ-H), 5.52 (1H,

d, J 7.2, 2^ꢀ-H), 5.83 (1H, d, J 7.5, 5^ꢀ-H), 5.99 (1H, d, J 5.9, OH),

6.94 (2H, d, J 8.8, PMB), 7.39 (2H, d, J 8.8, PMB), 7.45 (2H,

dd, J 8.0, 7.2, 3-H and 9-H), 7.67–7.72 (2H, m, 2-H and 10-H),

7.88 (1H, d, J 8.9, 1-H), 7.91 (1H, d, J 8.8, 11-H), 9.12 (2H, d, J

8.0, 4-H and 8-H); d_C(d₆-DMSO, 100 MHz) 36.2 (1^ꢀ-CH₂), 41.0

(CH₂Ar), 47.2 (NCH₂), 56.0 (OMe), 62.0 (CH), 63.8 (CH), 66.0

(OCH₂), 77.8 (CH), 86.0 (CH), 110.8 (CH), 110.9 (CH), 114.9

(CH), 116.7 (C), 116.8 (C), 119.4 (C), 119.7 (C), 121.6 (CH),

121.7 (CH), 121.9 (C), 122.1 (C), 125.4 (CH), 125.5 (CH), 128.1

(CH), 129.4 (C), 129.5 (C), 129.8 (2CH), 130.3 (C), 141.2 (C),

159.4 (C), 170.0 (2CO); and ﬁnally diol 18 (6.0 mg, 13%).

0.33 mmol), a gas was evolved and the reaction mixture turned

milky white. The reaction mixture was stirred for 30 min at rt

before the dropwise addition of a suspension of cyclic sulfate

20 (40.0 mg, 0.07 mmol) in THF (5 mL). After 7 h, H₂O

(0.1 mL) was added and the reaction mixture was stirred for

5 min before the dropwise addition of 20% H₂SO₄(5 mL); the

resulting solution was stirred overnight. The reaction mixture

was partitioned between EtOAc (150 mL) and H₂O (150 mL).

The organic layer was washed with H₂O (150 mL), saturated

aqueous NaHCO₃solution (2 × 150 mL), brine (200 mL), dried

(MgSO₄), and concentrated in vacuo to give the crude product as

an orange solid. Puriﬁcation by ﬂash column chromatography

using a 1 : 1 EtOAc–petrol solvent system gave ﬁrstly recovered

sulfate 20 (10.0 mg), followed by sulﬁde 23 as an orange solid

(28.0 mg, 67%; 91% based on recovered starting material): mp

273–275 ^◦C; m_max(THF)/cm⁻¹3335, 1701, 1574, 1384, 752; d_H(d₆-

DMSO, 400 MHz) 2.82 (1H, d, J 15.0, 1^ꢀ-H_a), 3.40 (1H, ddd,

J 15.0, 7.0, 6.8, 1^ꢀ-H_b), 3.76 (3H, s, OMe), 4.01 (1H, m, 3^ꢀ-H),

4.30 (1H, dd, J 6.7, 4.2, 4^ꢀ-H), 4.89 (2H, s, CH₂Ar), 5.43 (1H, d,

J 7.0, 2^ꢀ-H), 6.13 (1H, dd, J 6.8, 6.7, 5^ꢀ-H), 6.23 (1H, d, J 4.30,

OH), 6.95 (2H, d, J 8.8, PMB), 7.12–7.23 (5H, m, Ph), 7.38 (1H,

dd, J 8.0, 7.1, 9-H), 7.42 (2H, d, J 8.8, PMB), 7.46 (2H, m, 3-H,

10-H), 7.64 (1H, d, J 8.5, 11-H), 7.69 (1H, dd, J 8.5, 7.1, 2-H),

7.97 (1H, d, J 8.5, 1-H), 9.08 (1H, d, J 8.0, 8-H), 9.12 (1H, d, J

8.0, 4-H); d_C(d₆-DMSO, 100 MHz) 37.8 (1^ꢀ-CH₂), 41.1 (CH₂Ar),

56.0 (OMe), 58.2 (CH), 59.9 (CH), 64.6 (CH), 85.7 (CH), 111.2

(CH), 111.3 (CH), 114.9 (CH), 119.4 (C), 119.5 (C), 121.4 (CH),

121.6 (C), 121.7 (CH), 122.1 (C), 125.3 (CH), 125.5 (CH), 126.5

(CH), 127.7 (CH), 128.0 (CH), 128.6 (CH), 129.5 (C), 129.7 (C),

129.8 (CH), 130.0 (CH), 130.4 (C), 136.5 (C), 141.1 (C), 142.5

(C), 159.5 (C), 170.2 (2CO).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-benzoatecyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 22

To a stirred solution of cyclic sulfate 20 (50.0 mg, 0.08 mmol) in

DMF (5 mL) under an N₂atmosphere was added PhCO₂NH₄

(0.12 g, 0.83 mmol). The reaction mixture was heated to

70 ^◦C for 25 h. TLC analysis showed starting material was

still present so a further portion of PhCO₂NH₄(0.5 g) was

added and the reaction mixture was stirred overnight. TLC

analysis showed the reaction had gone to completion and so the

reaction mixture was concentrated in vacuo, redissolved in THF

(5 mL) and 20% H₂SO₄(5 mL) was added. The reaction mixture

was stirred vigorously overnight at rt before being partitioned

between EtOAc (150 mL) and H₂O (150 mL). The organic layer

was washed with H₂O (150 mL), saturated aqueous NaHCO₃

solution (2 × 150 mL), brine (200 mL), dried (MgSO₄), and

concentrated in vacuo to give the crude product as an orange

solid. Puriﬁcation by ﬂash column chromatography using a 1 :

1 EtOAc–petrol solvent system gave benzoate 22 as an orange

solid (47.0 mg, 88%): mp 291–293 ^◦C; (found: m/z (FAB⁺) M⁺

647.2069. C₄₀H₂₉N₃O₆requires 647.2056); m_max(CHCl₃)/cm⁻¹

2931, 2359, 1750, 1697, 1385, 1351, 1318, 1123; d_H(d₆-DMSO,

400 MHz) 2.92 (1H, d, J 15.0, 1^ꢀ-H_a), 3.45 (1H, ddd, J 15.0, 7.0,

6.4, 1^ꢀ-H_b), 3.73 (3H, s, OMe), 4.07 (1H, m, 3^ꢀ-H), 4.74 (2H, s,

CH₂Ar), 5.42 (1H, d, J 7.0, 2^ꢀ-H), 5.69 (1H, dd, J 6.2, 3.3, 4^ꢀ-H),

6.07 (1H, dd, J 6.4, 6.2, 5^ꢀ-H), 6.22 (1H, d, J 5.0, OH), 6.81 (2H,

d, J 7.5, 2^ꢀꢀ-H and 6^ꢀꢀ-H), 6.93 (2H, d, J 8.8, PMB), 6.98 (2H, dd,

J 7.5, 7.3, 3^ꢀꢀ-H and 5^ꢀꢀ-H), 7.23 (1H, app t, J 7.8, 9-H), 7.30 (1H,

t, J 7.3, 4^ꢀꢀ-H), 7.36 (2H, d, J 8.8, PMB), 7.44 (2H, app dd, J 7.8,

7.5, 3-H and 10-H), 7.65 (1H, d, J 8.0, 11-H), 7.69 (1H, dd, J

8.3, 7.5, 2-H), 7.95 (1H, d, J 8.3, 1-H), 8.88 (1H, d, J 7.8, 8-H),

9.05 (1H, d, J 7.8, 4-H); d_C(d₆-DMSO, 100 MHz) 36.4 (1^ꢀ-CH₂),

41.0 (CH₂Ar), 56.0 (OMe), 58.2 (CH), 62.8 (CH), 82.4 (CH),

110.9 (CH), 111.1 (CH), 114.9 (CH), 116.6 (C), 119.5 (C), 121.3

(CH), 121.6 (CH), 125.1 (CH), 125.5 (CH), 127.8 (CH), 128.0

(CH), 128.9 (CH), 129.1 (C), 129.3 (CH), 129.5 (C), 129.6 (C),

130.0 (CH), 130.1 (C), 130.2 (C), 130.4 (C), 134.0 (CH), 141.2

(C), 142.2 (C), 159.5 (C), 165.6 (CO), 170.0 (2CO); m/z (FAB⁺)

647 (M⁺, 3%), 322 (4), 203 (6), 137 (7), 121 (15), 107 (15), 91

(18), 83 (39) 77 (12).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-sulfenylcyanocyclopentan-2^ꢀa,5^ꢀa-diyl)-

6-(4-methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 24

To a stirred solution of cyclic sulfate 20 (50.0 mg, 0.08 mmol) in

DMF (5 mL) under an N₂atmosphere was added NH₄SCN

(63.0 mg, 0.83 mmol). The reaction mixture was heated to

70 ^◦C for 2 h; TLC analysis showed that the reaction had

gone to completion. The reaction mixture was concentrated in

vacuo, redissolved in THF (5 mL), and 20% H₂SO₄(5 mL) was

added. The reaction mixture was stirred vigorously overnight

before being partitioned between EtOAc (150 mL) and H₂O

(150 mL). The organic layer was washed with H₂O (150 mL),

saturated aqueous NaHCO₃solution (2 × 150 mL), brine

(200 mL), dried (MgSO₄), and concentrated in vacuo to give the

crude product as an orange solid. Puriﬁcation by ﬂash column

chromatography using a 5% MeOH–DCM solvent system gave

24 as an orange solid (28.0 mg, 64%): mp 285–288 ^◦C; (found:

m/z (FAB⁺) M⁺584.1500. C₃₄H₂₄N₄O₄S requires 584.1518);

m_max(THF)/cm⁻¹3494, 3346, 2157, 1753, 1699, 1384, 750; d_H(d₆-

DMSO, 400 MHz) 2.86 (1H, d, J 14.9, 1^ꢀ-H_a), 3.36 (1H, ddd, J

14.9, 7.7, 6.0, 1^ꢀ-H_b), 3.73 (3H, s, OMe), 4.10 (1H, dd, J 5.8, 5.2,

3^ꢀ-H), 4.20 (1H, dd, J 6.0, 5.8, 4^ꢀ-H), 4.78 (2H, s, CH₂Ar), 5.48

(1H, d, J 7.7, 2^ꢀ-H), 6.01 (1H, app t, J 6.0, 5^ꢀ-H), 6.61 (1H, d, J

5.2, OH), 6.94 (2H, d, J 8.8, PMB), 7.38 (2H, d, J 8.8, PMB),

7.45 (1H, dd, J 7.8, 7.2, 3-H or 9-H), 7.47 (1H, dd, J 7.8, 7.2,

3-H or 9-H), 7.68 (1H, dd, J 8.3, 7.2, 2-H or 10-H), 7.70 (1H,

dd, J 8.3, 7.2, 2-H or 10-H), 7.94 (2H, d, J 8.3, 1-H and 11-H),

9.07 (2H, app t, J 7.8, 4-H and 8-H); d_C(d₆-DMSO, 125 MHz)

37.6 (1^ꢀ-CH₂), 41.1 (CH₂Ar), 56.0 (OMe), 58.5 (CH), 60.7 (CH),

63.8 (CH), 84.7 (CH), 111.0 (C), 111.1 (CH), 111.3 (CH), 114.9

(CH), 116.7 (C), 117.1 (C), 119.4 (C), 119.7 (C), 121.7 (CH),

121.8 (CH), 121.9 (C), 122.0 (C), 125.5 (CH), 128.0 (CH), 128.1

(CH), 129.4 (C), 129.8 (C), 130.1 (CH, CH), 130.3 (C), 140.9

(C), 142.3 (C), 159.5 (C), 170.0 (CO), 170.1 (CO); m/z (FAB⁺)

584 (M⁺4%), 477 (3), 325 (3), 141 (2), 137 (32), 121 (18), 107

(25), 83 (43).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-phenylsulfanylcyclopentan-2^ꢀa,5^ꢀa-diyl)-

6-(4-methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 23

To a stirred solution of PhSH (0.03 mL, 0.33 mmol) in THF

(1 mL), under a N₂atmosphere was added NaH (13 mg,

2 9 6 8

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

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12,13-(3^ꢀb-Hydroxy-4^ꢀa-aminocyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-

methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 25

DMSO, 100 MHz) 35.9 (1^ꢀ-CH₂), 41.1 (CH₂Ar), 54.8 (NCH₂),

56.0 (OMe), 60.3 (5^ꢀ-CH), 63.9 (2^ꢀ-CH), 73.3 (4^ꢀ-CH), 79.2 (3^ꢀ-

CH), 111.2 (CH), 111.9 (CH), 114.9 (CH), 116.2 (C), 116.5 (C),

=

117.3 (CH₂CH), 119.2 (C), 119.3 (C), 121.2 (CH), 121.4 (CH),

Azido alcohol 17 (35.0 mg, 0.06 mmol) was dissolved in dry

DMF (3 mL) and Pd/C (15.0 mg) was added. The reaction

mixture was stirred under a H₂atmosphere (300 psi) for 18 h.

TLC analysis showed consumption of starting material and so

the reaction mixture was ﬁltered through celite to remove the

catalyst and partitioned between EtOAc (100 mL) and H₂O

(100 mL). The organic layer was washed with H₂O (100 mL),

saturated aqueous CaCl₂solution (2 × 100 mL) and brine

(100 mL). The aqueous layers were re-extracted with EtOAc

(2 × 50 mL) and all the organics were combined, dried (MgSO₄)

and concentrated in vacuo to give a brown solid. Puriﬁcation via

ﬂash column chromatography using a 5% MeOH–DCM solvent

system afforded amino alcohol 25 as a yellow solid (0.025 g,

122.0 (C), 125.2 (CH), 125.4 (CH), 127.7 (CH), 127.8 (CH),

129.4 (C), 129.7 (C), 130.1 (CH), 130.4 (C), 137.2 (CH), 140.9

(C), 142.5 (C), 159.5 (C), 170.1 (CO), 170.2 (CO); m/z (FAB⁺)

623 (M⁺+ H, 5%), 622 (M⁺, 10), 138 (31), 134 (4), 107 (44), 97

(14), 92 (5).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-(dimethyl-1H-1,2,3-triazole-4,5-

dicarboxylate)cyclopentan-2^ꢀa,5^ꢀa-diyl)-6-(4-methoxybenzyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 27

Azido alcohol 17 (44.0 mg, 0.08 mmol) was suspended in

DMF (1.5 mL) with stirring under an N₂atmosphere. Dimethyl

acetylenedicarboxylate (0.10 mL, 0.77 mmol) was added and

the reaction mixture was heated to 70 ^◦C for 15 h. TLC analysis

showed consumption of starting material and so the reaction

mixture was cooled to rt and partitioned between EtOAc (50 mL)

and H₂O (50 mL). The organic layer was washed with a saturated

aqueous CaCl₂solution (2 × 50 mL), brine (2 × 50 mL), dried

(MgSO₄) and concentrated in vacuo to give the crude product.

Puriﬁcation via ﬂash column chromatography using a 1 : 1

EtOAc–petrol solvent sys_◦tem gave triazole 27 as an orange solid

(0.052 g, 95%): mp 240 C decomp; (found: m/z (FAB⁺) M⁺

710.2141. C₃₉H₃₀N₆O₈requires 710.2125); m_max(CHCl₃)/cm⁻¹

3697, 3605, 2956, 1746, 1688, 1602, 1384, 1349, 1081; d_H(d₆-

DMSO, 400 MHz) 2.96 (1H, d, J 15.3, 1^ꢀ-H_a), 3.64 (1H, ddd,

J 15.3, 7.7, 6.1, 1^ꢀ-H_b), 3.76 (3H, s, OMe), 3.77 (3H, s, OMe),

4.16 (3H, s, OMe), 4.84 (2H, s, CH₂Ar), 4.94 (1H, dd, J 5.6,

5.0, 3^ꢀ-H), 5.57 (1H, d, J 7.7, 2^ꢀ-H), 5.74 (1H, dd, J 5.9, 5.6,

4^ꢀ-H), 6.09 (1H, dd, J 6.1, 5.9, 5^ꢀ-H), 6.35 (1H, d, J 5.0, OH),

6.95 (2H, d, J 8.8, PMB), 7.27 (2H, app dd, J 8.2, 7.0, 9-H

and 11-H), 7.38 (1H, ddd, J 8.2, 7.0, 1.3, 10-H), 7.41 (2H, d, J

8.8, PMB), 7.48 (1H, dd, J 7.8, 7.5, 3-H), 7.72 (1H, dd, J 8.5,

7.5, 2-H), 7.97 (1H, d, J 8.5, 1-H), 8.98 (1H, d, J 7.3, 8-H),

9.12 (1H, d, J 7.8, 4-H); d_C(d₆-DMSO, 100 MHz) 37.1 (1^ꢀ-CH₂),

41.0 (CH₂Ar), 53.5 (OMe), 55.2 (OMe), 56.0 (OMe), 60.4 (CH),

62.8 (CH), 71.7 (CH), 82.5 (CH), 109.0 (CH), 111.1 (CH), 114.9

(CH), 116.8 (C), 119.3 (C), 119.7 (C), 121.6 (CH), 121.7 (CH),

121.9 (C), 122.0 (C), 125.3 (CH), 125.5 (CH), 127.7 (CH), 128.1

(CH), 129.6 (C), 129.9 (CH), 130.3 (C), 132.7 (C), 138.6 (C),

141.0 (C), 141.5 (C), 159.5 (CO), 159.7 (C), 160.4 (CO), 170.0

(CO), 170.1 (CO); m/z (FAB⁺) 711 (M⁺+ H, 4%), 710 (M⁺, 6),

603 (4), 135 (7), 121 (18), 107 (22).

◦

71%): mp 292–296 C; (found: m/z (FAB⁺) M⁺542.1996.

C₃₃H₂₆N₄O₄requires 542.1954); m_max(THF)/cm⁻¹3383, 1751,

1698, 1572, 1385, 750; d_H(d₆-DMSO, 500 MHz) 2.59 (1H, d,

J 15.0, 1^ꢀ-H_a), 3.28 (1H, ddd, J 15.0, 7.3, 6.0, 1^ꢀ-H_b), 3.59 (1H,

m, 3^ꢀ-H), 3.65 (1H, dd, J 5.3, 4.6, 4^ꢀ-H), 3.74 (3H, s, OMe), 4.83

(2H, s, CH₂Ar), 5.28 (1H, d, J 7.3, 2^ꢀ-H), 5.57 (1H, dd, J 6.0,

4.6, 5^ꢀ-H), 5.79 (1H, s, OH), 6.95 (2H, d, J 8.6, PMB), 7.38 (2H,

d, J 8.6, PMB), 7.43 (2H, m, 3-H and 9-H), 7.63 (1H, dd, J 7.9,

7.7, 10-H), 7.68 (1H, dd, J 7.9, 7.5, 2-H), 7.91 (1H, d, J 7.9,

1-H), 7.96 (1H, d, J 7.9, 11-H), 9.07 (1H, d, J 8.5, 8-H), 9.09

(1H, d, J 8.9, 4-H); d_C(d₆-DMSO, 125 MHz) 36.6 (1^ꢀ-CH₂), 41.1

(CH₂Ar), 56.0 (OMe), 61.8 (CH), 63.6 (CH), 65.6 (CH), 86.9

(CH), 111.1 (CH), 111.7 (CH), 114.9 (CH), 116.3 (C), 116.6 (C),

119.2 (C), 119.4 (C), 121.2 (CH), 121.3 (CH), 121.9 (C), 122.0

(C), 125.2 (CH), 125.4 (CH), 127.8 (CH), 129.6 (C), 129.9 (CH,

CH), 130.2 (C), 130.4 (C), 140.9 (C), 143.2 (C), 159.4 (C), 170.3

(CO), 170.4 (CO); m/z (FAB⁺) 543 (M⁺+ H, 6%), 542 (M⁺, 13),

435 (9), 118 (3), 107 (37).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-diallylaminocyclopentan-2^ꢀa,5^ꢀa-diyl)-

6-(4-methoxybenzyl)-dihydro-5H-indolo [2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 26

Azido alcohol 17 (50.0 mg, 0.09 mmol) was dissolved in DMF

(1.5 mL) with stirring under an atmosphere of N₂at rt. Indium

powder (51.0 mg, 0.44 mmol), NaI (66.0 mg, 0.44 mmol) and

allyl bromide (0.08 mL, 0.88 mmol) were added and the reaction

mixture was stirred for 48 h. A yellow solid had precipitated

out of solution, TLC analysis indicated no reaction had taken

place and so further In (0.20 g), NaI (0.26 g) and allyl bromide

(0.50 mL) were added and the reaction was heated to 50 ^◦C. After

6 h, TLC analysis showed that no reaction had taken place. The

12,13-(3^ꢀb-Hydroxy-4^ꢀa-azidocyclopentan-2^ꢀa,5^ꢀa-diyl)-dihydro-

5H-indolo[2,3-a]pyrrolo [3,4-c]carbazole-5,7(6H)-dione 30

◦

reaction mixture was stirred overnight at 50 C. TLC analysis

showed the consumption of starting material and so the reaction

mixture was cooled to rt and partitioned between EtOAc

(100 mL) and H₂O (100 mL). The organic layer was washed

with H₂O (3 × 100 mL), saturated aqueous CaCl₂solution

(100 mL), brine (100 mL), dried (MgSO₄) and concentrated

in vacuo to yield an orange solid. Puriﬁcation via ﬂash column

chromatography using a 0–2% MeOH–DCM solvent system

afforded diallyl amine 26 as an orange solid (33.0 mg, 60%):

mp 291–295 ^◦C; (found: m/z (FAB⁺) M⁺622.2563. C₃₉H₃₄N₄O₄

requires 622.2580); m_max(THF)/cm⁻¹3356, 1752, 1699, 1573,

Azide 17 (0.10 g, 0.18 mmol) was suspended in anisole (2 mL)

◦

with stirring under N₂and cooled to 0 C. TFA (10 mL) was

added slowly over 10 min; once the addition was complete,

the reaction mixture was warmed to 70 ^◦C for 18 h. TLC

analysis showed the consumption of starting material and so

the reaction mixture was cooled to rt and partitioned between

EtOAc (100 mL) and saturated aqueous NaHCO₃solution

(100 mL). The organics were washed with saturated aqueous

NaHCO₃solution (3 × 100 mL), H₂O (100 mL), brine (100 mL),

dried (MgSO₄) and concentrated in vacuo to give a yellow oil.

The addition of petrol (20 mL) resulted in precipitation of a

yellow solid, which was collected by ﬁltration and puriﬁed via

ﬂash column chromatography using a 5% THF–DCM solvent

system to give ﬁrstly triﬂuoroacetate 28 (not fully pure) R_f0.52

1384, 751; d_H(d₆-DMSO, 400 MHz) 2.46 (2H, dd, J 14.6, 5.0,

ꢀ

=

NCHHCH CH₂), 2.59 (1H, d, J 14.7, 1 -H_a), 2.74 (2H, dd,

=

J 14.6, 6.4, NCHHCH CH₂), 3.19 (1H, ddd, J 14.7, 7.4, 6.0,

1^ꢀ-H_b), 3.68 (1H, dd, J 6.0, 5.7, 4^ꢀ-H), 3.72 (3H, s, OMe), 4.00

(1H, dd, J 5.7, 5.4, 3^ꢀ-H), 4.75 (2H, s, CH₂Ar), 4.79 (4H, d, J

◦

8.0, CH₂CH), 5.09–5.19 (2H, m, CH₂CH), 5.29 (1H, d, J

7.4, 2^ꢀ-H), 5.67 (1H, app t, J 6.0, 5^ꢀ-H), 5.94 (1H, d, J 5.4, OH),

6.92 (2H, d, J 8.6, PMB), 7.38 (2H, d, J 8.6, PMB), 7.41 (2H,

dd, J 8.0, 7.4, 3-H and 9-H), 7.65 (1H, dd, J 8.2, 7.4, 2-H or

10-H), 7.66 (1H, dd, J 8.2, 7.4, 2-H or 10-H), 7.92 (2H, d, J

8.2, 1-H and 11-H), 9.03 (2H, app t, J 8.0, 4-H and 8-H); d_C(d₆-

(65.0 mg): mp 321–325 C; m_max(THF)/cm⁻¹3312, 2106, 1721,

=

1572, 749; d_H(d₆-DMSO, 400 MHz) 2.92 (1H, d, J 15.4, 1^ꢀ-H_a),

3.26 (1H, ddd, J 15.4, 7.3, 6.5, 1^ꢀ-H_b), 5.06–5.09 (2H, m, 3^ꢀ-H

and 4^ꢀ-H), 6.05 (1H, d, J 7.3, 2^ꢀ-H or 5^ꢀ-H), 6.09 (1H, d, J 6.5,

2^ꢀ-H or 5^ꢀ-H), 7.47 (2H, dd, J 8.6, 6.5, 3-H and 9-H), 7.70 (1H,

dd, J 7.6, 6.5, 2-H or 10-H), 7.73 (1H, dd, J 7.6, 6.5, 2-H or

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 6 9

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10-H), 7.95 (2H, app t, J 7.6, 1-H and 11-H), 9.12 (2H, app t, J

8.6, 4-H and 8-H), 11.19 (1H, s, NH); d_C(d₆-DMSO, 100 MHz)

37.0 (1^ꢀ-CH₂), 59.4 (CH), 59.8 (CH), 68.5 (CH), 89.0 (CH),

111.9 (CH), 111.9 (CH), 114.9 (CH), 116.9 (C), 121.1 (C), 121.8

(CH), 122.1 (2C), 122.2 (2C), 125.5 (CH), 125.7 (CH), 127.9

(CH), 128.2 (CH), 129.1 (C), 129.3 (C), 141.1 (C), 142.5 (C),

171.9 (2CO) and secondly azide 30 R_f0.21 (37.0 mg): mp 333–

336 ^◦C; (found: m/z (FAB⁺) M⁺448.1272. C₂₅H₁₆N₆O₃requires

448.1284); m_max(THF)/cm⁻¹3500, 3352, 2106, 1754, 1721, 1640,

1573, 749; d_H(d₆-DMSO, 500 MHz) 2.75 (1H, d, J 14.8, 1^ꢀ-H_a),

3.29 (1H, ddd, J 14.8, 7.4, 6.3, 1^ꢀ-H_b), 3.88 (1H, dd, J 5.0, 4.8,

3^ꢀ-H), 4.46 (1H, dd, J 5.9, 5.0, 4^ꢀ-H), 5.40 (1H, d, J 7.4, 2^ꢀ-H),

5.94 (1H, dd, J 6.3, 5.9, 5^ꢀ-H), 6.36 (1H, d, J 4.8, OH), 7.46 (2H,

dd, J 8.3, 7.3, 3-H and 9-H), 7.69 (2H, dd, J 8.2, 7.3, 2-H and

10-H), 7.94 (1H, d, J 8.2, 11-H), 7.95 (1H, d, J 8.2, 1-H), 9.09

(1H, d, J 8.3, 8-H), 9.11 (1H, d, J 8.3, 4-H), 11.14 (1H, s, NH);

d_C(d₆-DMSO, 125 MHz) 36.4 (1^ꢀ-CH₂), 59.6 (CH), 63.2 (CH),

72.3 (CH), 83.7 (CH), 111.0 (CH), 111.1 (CH), 116.5 (C), 116.6

(C), 120.8 (C), 121.0 (C), 121.5 (C), 121.6 (CH), 122.2 (C), 125.5

(CH), 125.6 (CH), 127.9 (CH), 128.0 (CH), 129.3 (C), 129.6 (C),

140.9 (C), 142.5 (C), 171.9 (CO), 172.0 (CO); m/z (FAB⁺) 448

(M⁺, 2%), 109 (22), 85 (24).

159.5 (C), 170.0 (2CO); and secondly alcohol 31 (R_f0.35) as a

◦

yellow solid (16.0 mg, 50%): mp 362–365 C; m_max(THF)/cm⁻¹

3486, 1721, 1658, 1573, 1390, 750; d_H(d₆-DMSO, 400 MHz) 2.68

(1H, d, J 15.1, 1^ꢀ-H_a), 3.24 (4H, d, J 7.5, NCH₂), 3.42 (1H, ddd,

J 15.1, 7.6, 7.0, 1^ꢀ-H_b), 3.57 (4H, d, J 7.5, OCH₂), 4.50 (1H, dd,

J 6.0, 5.6, 3^ꢀ-H), 5.01 (1H, d, J 5.6, 4^ꢀ-H), 5.54 (1H, d, J 7.6,

2^ꢀ-H), 5.86 (1H, d, J 7.0, 5^ꢀ-H), 6.22 (1H, d, J 6.0, OH), 7.46

(2H, dd, J 7.6, 7.4, 3-H and 9-H), 7.70 (1H, dd, J 8.2, 7.6, 2-H or

10-H), 7.71 (1H, dd, J 8.2, 7.6, 2-H or 10-H), 7.91 (1H, d, J 8.2,

1-H or 11-H), 7.92 (1H, d, J 8.2, 1-H or 11-H), 9.10 (2H, d, J

7.4, 4-H and 8-H), 11.14 (1H, s, NH); d_C(d₆-DMSO, 100 MHz)

36.3 (1^ꢀ-CH₂), 47.2 (NCH₂), 62.0 (CH), 63.8 (CH), 66.0 (OCH₂),

77.9 (CH), 86.0 (CH), 110.8 (CH), 110.9 (CH), 116.6 (C), 116.7

(C), 120.9 (C), 121.1 (C), 121.6 (CH), 121.7 (CH), 122.1 (C),

122.3 (C), 125.7 (CH, CH), 128.0 (CH, CH), 129.5 (C), 129.6

(C), 141.1 (C), 141.2 (C), 171.9 (2CO).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-phenylsulfanylcyclopentan-2^ꢀa,5^ꢀa-diyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione

32, via triﬂuoroacetate 29

Sulﬁde 23 (55.0 mg, 0.09 mmol) was suspended in anisole

(1.0mL)withstirringunderanN₂atmosphereandTFA(4.0mL)

was added dropwise. The reaction mixture was heated to 80 ^◦C

for 15 h. TLC analysis showed consumption of the starting

material and so the reaction mixture was allowed to cool to rt

and partitioned between EtOAc (200 mL) and saturated aqueous

NaHCO₃solution (200 mL). The organic layer was washed

with saturated aqueous NaHCO₃solution (3 × 200 mL), H₂O

(100 mL), brine (150 mL), dried (MgSO₄), and concentrated in

vacuo to give a brown gum. The brown gum was triturated with

petrol (100 mL) for 1 h to give a brown solid that was collected

by ﬁltration. The resulting solid was puriﬁed via ﬂash column

chromatography using a 4–10% EtOAc–DCM solvent system to

give the triﬂuoroacetate 29 as a yellow solid (30.0 mg, 56%): mp

354–356 ^◦C; m_max(CHCl₃)/cm⁻¹3342, 1790, 1713, 1643, 1608,

1574, 746; d_H(d₆-DMSO, 500 MHz) 2.98 (1H, d, J 15.2, 1^ꢀ-H_a),

3.31 (1H, ddd, J 15.2, 7.3, 6.8, 1^ꢀ-H_b), 4.80 (1H, dd, J 6.5, 4.4,

4^ꢀ-H), 5.12 (1H, d, J 4.4, 3^ꢀ-H), 6.11 (1H, d, J 7.3, 2^ꢀ-H), 6.27

(1H, dd, J 6.8, 6.5, 5^ꢀ-H), 7.18–7.23 (5H, m, Ph), 7.44 (1H, dd,

J 7.8, 7.5, 9-H), 7.48 (1H, dd, J 7.8, 7.4, 3-H), 7.62 (1H, dd, J

8.2, 7.5, 10-H), 7.68 (1H, dd, J 8.2, 7.4, 2-H), 7.80 (1H, d, J 8.2,

11-H), 7.97 (1H, d, J 8.2, 1-H), 9.12 (1H, d, J 7.8, 8-H), 9.13

(1H, d, J 7.8, 4-H), 11.20 (1H, s, NH); d_C(d₆-DMSO, 125 MHz)

38.5 (1^ꢀ-CH₂), 56.2 (CH), 60.0 (CH), 61.1 (CH), 91.9 (CH), 111.3

(CH), 111.9 (CH), 114.9 (q, J ¹³C¹⁹F = 286.0, CF₃), 116.8 (C),

116.9 (C), 121.0 (C), 121.1 (C), 121.7 (CH), 121.8 (CH), 122.2

(C), 125.5 (CH), 125.6 (CH), 127.9 (CH), 128.3 (CH), 128.6 (C),

129.3 (C), 129.8 (C), 130.0 (CH), 131.6 (CH), 133.5 (C), 141.1

(C), 142.3 (C), 156.3 (q, J ¹³C¹⁹F = 42.3, COCF₃), 171.9 (2CO);

m/z (FAB⁺) 611 (M⁺, 2%), 515 (M⁺, 2).

Hydrolysis of triﬂuoroacetate 28 to give alcohol 30

Triﬂuoroacetate 28 (65.0 mg, 0.12 mmol) was dissolved in THF

(1 mL) with stirring, under N₂. LiOH (29.0 mg, 1.20 mmol)

was added and the reaction mixture was stirred for 0.5 h. TLC

analysis showed the consumption of starting material and so the

reaction mixture was partitioned between EtOAc (40 mL) and

H₂O (40 mL). The organic layer was washed with H₂O (50 mL),

brine (50 mL), dried (MgSO₄) and concentrated in vacuo to give

a yellow solid. Puriﬁcation via ﬂash column chromatography

using a 5% THF–DCM solvent system gave 30 as a yellow solid

(30.0 mg, total yield from 17 of 85%).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-morpholinylcyclopentan-2^ꢀa,5^ꢀa-diyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 31

Morpholine derivative 21 (47.0 mg, 0.08 mmol) was suspended

in anisole (0.75 mL), with stirring under an N₂atmosphere and

TFA (3.5 mL) was added dropwise. The reaction mixture was

heated to 80 ^◦C for 15 h. TLC analysis showed consumption of

the starting material and so the reaction mixture was allowed

to cool to rt and partitioned between EtOAc (200 mL) and

saturated aqueous NaHCO₃solution (200 mL). The organic

layer was washed with saturated aqueous NaHCO₃solution (3 ×

200 mL), H₂O (100 mL), brine (150 mL), dried (MgSO₄), and

concentrated in vacuo to give a brown gum. The brown gum

was triturated in petrol (100 mL) for 1 h to give a brown solid

that was collected by ﬁltration. Puriﬁcation via ﬂash column

chromatography using a 5% THF–DCM solvent system gave

ﬁrstly a triﬂuoroacetate derivative of the starting NPMB imide

(R_f0.85) as a yellow solid (15.0 mg, 28%): mp 292–294 ^◦C;

m_max(CHCl₃)/cm⁻¹3358, 2447, 1753, 1699, 1611, 1574, 1515,

1385, 750; d_H(d₆-DMSO, 500 MHz) 2.90 (1H, d, J 15.1, 1^ꢀ-H_a),

3.19–3.25 (4H, m, NCH₂), 3.38 (1H, m, 1^ꢀ-H_b), 3.55–3.58 (4H,

m, OCH₂), 3.73 (3H, s, OMe), 4.77 (2H, s, CH₂Ar), 5.37 (1H, d,

J 5.4, 4^ꢀ-H), 5.77 (1H, d, J 5.4, 3^ꢀ-H), 6.06 (1H, d, J 7.3, 2^ꢀ-H),

6.13 (1H, d, J 7.3, 5^ꢀ-H), 6.93 (2H, d, J 7.8, PMB), 7.35 (2H, d, J

7.8, PMB), 7.44–7.51 (2H, m, 3-H and 9-H), 7.70 (2H, dd, J 8.3,

7.8, 2-H and 10-H), 7.94 (1H, d, J 8.3, 1-H or 11-H), 7.97 (1H, d,

J 8.3, 1-H or 11-H), 9.05 (2H, app t, J 6.9, 4-H and 8-H); d_C(d₆-

DMSO, 125 MHz) 36.9 (1^ꢀ-CH₂), 41.0 (CH₂Ar), 47.2 (NCH₂),

55.8 (OMe), 60.6 (CH), 61.6 (CH), 66.0 (OCH₂), 81.2 (CH), 83.8

(CH), 111.0 (CH), 111.4 (CH), 114.9 (CH), 115.2 (q, J ¹³C¹⁹F =

285.7, CF₃), 117.1 (C), 117.2 (C), 119.6 (C), 119.7 (C), 121.8

(CH), 121.9 (CH), 122.0 (C), 122.1 (C), 125.4 (CH), 125.5 (CH),

128.2 (CH), 128.3 (CH), 129.4 (C), 129.6 (C), 129.8 (CH), 130.3

(C), 141.1 (C), 141.5 (C), 156.4 (q, J ¹³C¹⁹F = 42.3, COCF₃)

Hydrolysis of 29 using LiOH

Triﬂuroacetate 29 (28 mg, 0.05 mmol) was dissolved in THF

(1 mL) with stirring under an N₂atmosphere. LiOH (3.0 mg.

0.14 mmol) was added and the reaction mixture was stirred for

1 h. TLC analysis showed starting material remained so a further

portion of LiOH (6 mg) was added and the reaction mixture was

stirred for a further 2 h. TLC analysis showed consumption of

starting material and so the reaction mixture was partitioned

between EtOAc (100 mL) and H₂O (100 mL). The organic

layer was washed with H₂O (100 mL), brine (100 mL), dried

(MgSO₄) and concentrated in vacuo to give the crude product.

Puriﬁcation via ﬂash column chromatography using a 5% THF–

DCM solvent system yielded the desired product 32 as a yellow

solid (19.0 mg, 81%; 45% overall from 23): mp 371–373 ^◦C;

m_max(CHCl₃)/cm⁻¹3352, 2076, 1719, 1644, 1573, 746; d_H(d₆-

DMSO, 400 MHz) 2.83 (1H, d, J 14.9, 1^ꢀ-H_a), 3.39 (1H, ddd, J

14.9, 7.1, 7.0, 1^ꢀ-H_b), 4.00 (1H, m, 3^ꢀ-H), 4.30 (1H, dd, J 6.6, 4.2,

4^ꢀ-H), 5.44 (1H, d, J 7.0, 2^ꢀ-H), 6.18 (1H, dd, J 7.1, 6.6, 5^ꢀ-H),

2 9 7 0

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

6.36 (1H, d, J 4.2, OH), 7.12–7.25 (5H, m, Ph), 7.38 (1H, dd, J

7.8, 7.2, 9-H), 7.46 (1H, dd, J 8.5, 7.2, 10-H), 7.49 (1H, dd, J

8.2, 7.1, 3-H), 7.66 (1H, d, J 8.5, 11-H), 7.70 (1H, dd, J 8.3, 7.1,

2-H), 7.99 (1H, d, J 8.3, 1-H), 9.08 (1H, d, J 7.8, 8-H), 9.11 (1H,

d, J 8.2, 4-H), 11.13 (1H, s, NH); d_C(d₆-DMSO, 100 MHz) 37.9

(1^ꢀ-CH₂), 58.2 (CH), 59.9 (CH), 64.6 (CH), 85.8 (CH), 111.1

(CH), 111.3 (CH), 116.2 (C), 116.4 (C), 120.7 (C), 120.8 (C),

121.3 (CH), 121.6 (CH), 121.7 (C), 122.3 (C), 125.4 (CH), 125.6

(CH), 126.5 (CH), 127.6 (CH), 127.8 (CH), 128.7 (CH), 129.5

(C), 129.7 (C), 129.8 (CH), 136.5 (C), 141.0 (C), 142.4 (C), 172.0

(2CO).

(1^ꢀ-CH₂), 53.5 (OMe), 55.2 (OMe), 60.4 (CH), 62.8 (CH), 71.7

(CH), 82.5 (CH), 109.1 (CH), 111.1 (CH), 116.7 (C), 120.8 (C),

121.1 (C), 121.6 (CH), 121.7 (CH), 122.1 (C), 122.2 (C), 125.5

(CH), 125.7 (CH), 127.6 (CH), 128.0 (CH), 129.7 (C), 130.0 (C),

132.8 (C), 138.6 (C), 140.9 (C), 141.4 (C), 159.7 (CO), 160.4

(CO), 171.9 (CO), 172.0 (CO); m/z (ES⁺) 613 (M⁺+ Na, 8%),

434 (5), 322 (7) 154 (13), 83 (41).

12,13-((3^ꢀb,4^ꢀb)Tetrahydrocyclopenta[3^ꢀ,4^ꢀ,2]dioxathiole-2-oxide-

2^ꢀa,5^ꢀa-diyl)-dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 35

Cyclic sulﬁte 19 (predominantly the major diastereomer, ca. 12 :

1 ratio) (40.0 mg, 0.07 mmol) was suspended in anisole (1 mL)

with stirring under N₂and cooled to 0 ^◦C. TFA (5 mL) was added

dropwise over 15 min, and once the addition was complete the

reaction mixture was heated to reﬂux for 18 h. A yellow solid

formed in the reaction mixture, which was then cooled to rt

and partitioned between DCM (100 mL) and H₂O (100 mL).

The organic layer was washed with saturated aqueous NaHCO₃

solution (3 × 100 mL), H₂O (100 mL), brine (100 mL), dried

(MgSO₄) and concentrated in vacuo to give a yellow oil which was

triturated with petrol (20 mL) for 1 h. A yellow solid precipitated

out of the solution and was collected by ﬁltration, washed with

petroleum ether (3 × 20 mL) and dried to give cyclic sulﬁte 35,

an inseparable mixture of diastereoisomers (ca. 12 : 1 by NMR)

(31.0 mg, 97%): mp 364 ^◦C decomp.; m_max(THF)/cm⁻¹3494,

3188, 1754, 1722, 1643, 1573, 750; major isomer d_H(d₆-DMSO,

400 MHz) 2.90 (1H, d, J 15.2, 1^ꢀ-H_a), 3.28 (1H, dt, J 15.2, 7.3,

1^ꢀ-H_b), 5.56 (2H, d, J 1.5, 3^ꢀ-H and 4^ꢀ-H), 5.96 (2H, d, J 7.3, 2^ꢀ-H

and 5^ꢀ-H), 7.48 (2H, dd, J 7.8, 7.3, 3-H and 9-H), 7.71 (2H, dd, J

8.4, 7.3, 2-H and 10-H), 7.99 (2H, d, J 8.4, 1-H and 11-H), 9.09

(2H, d, J 7.8, 4-H and 8-H), 11.16 (1H, s, NH); d_C(d₆-DMSO,

100 MHz) 35.4 (CH₂), 61.1 (CH), 89.8 (CH), 110.8 (CH), 116.8

(C), 121.0 (C), 122.0 (CH), 122.4 (C), 125.7 (CH), 128.2 (CH),

129.4 (C), 140.8 (C), 171.7 (CO); minor isomer d_H(d₆-DMSO,

400 MHz) 2.90 (1H, d, J 15.2, 1^ꢀ-H_a), 3.28 (1H, dt, J 15.2, 7.3,

1^ꢀ-H_b), 5.40 (2H, d, J 1.5, 3^ꢀ-H and 4^ꢀ-H), 6.09 (2H, d, J 7.3, 2^ꢀ-H

and 5^ꢀ-H), 7.48 (2H, dd, J 7.8, 7.3, 3-H and 9-H), 7.71 (2H, dd,

J 8.4, 7.3, 2-H and 10-H), 8.06 (2H, d, J 8.4, 1-H and 11-H),

9.09 (2H, d, J 7.8, 4-H and 8-H), 11.16 (1H, s, NH).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-sulfenylcyanidecyclopentan-2^ꢀa,5^ꢀa-diyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 33

Thiocyanate 24 (41.0 mg, 0.07 mmol) was suspended in anisole

(1.0mL)withstirringunderanN₂atmosphereandTFA(4.0mL)

was added dropwise. The reaction mixture was heated to 80 ^◦C

for 15 h. TLC analysis showed consumption of the starting

material and so the reaction mixture was allowed to cool to rt

and partitioned between EtOAc (200 mL) and saturated aqueous

NaHCO₃solution (200 mL). The organic layer was washed

with saturated aqueous NaHCO₃solution (3 × 200 mL), H₂O

(100 mL), brine (150 mL), dried (MgSO₄), and concentrated in

vacuo to give a brown gum. The brown gum was triturated with

petrol (100 mL) for 1 h to give a brown solid that was collected

by ﬁltration. The resulting solid was puriﬁed via ﬂash column

chromatography using a 10% THF–DCM solvent system to give

the product 33 as a yellow solid (16.0 mg, 54%): mp 376–380 ^◦C;

m_max(THF)/cm⁻¹3472, 2157, 1754, 1721, 1644, 1574, 750; d_H(d₆-

DMSO, 400 MHz) 2.83 (1H, d, J 15.0, 1^ꢀ-H_a), 3.36 (1H, ddd, J

15.0, 7.6, 6.1, 1^ꢀ-H_b), 4.13 (1H, dd, J 5.8, 5.3, 3^ꢀ-H), 4.22 (1H,

dd, J 5.9, 5.8, 4^ꢀ-H), 5.50 (1H, d, J 7.6, 2^ꢀ-H), 6.04 (1H, dd, J

6.1, 5.9, 5^ꢀ-H), 6.62 (1H, d, J 5.3, OH), 7.48 (2H, dd, J 8.0, 7.3,

3-H and 9-H), 7.69–7.73 (2H, m, 2-H and 10-H), 7.98 (2H, d, J

8.4, 1-H and 11-H), 9.12 (2H, app t, J 8.0, 4-H and 8-H), 11.16

(1H, s, NH); d_C(d₆-DMSO, 100 MHz) 37.7 (1^ꢀ-CH₂), 58.6 (CH),

60.7 (CH), 63.8 (CH), 84.8 (CH), 111.1 (CH), 111.3 (CH), 116.5

(C), 116.9 (C), 120.8 (C), 121.1 (C), 121.7 (CH), 121.8 (CH),

122.1 (C), 122.1 (C), 125.6 (2CH, C), 127.9 (2CH), 129.5 (C),

129.8 (C), 140.8 (C), 142.3 (C), 171.9 (CO), 172.0 (CO).

12,13-(3^ꢀb-Hydroxy-4^ꢀa-aminocyclopentan-2^ꢀa,5^ꢀa-diyl)-

dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-

dione 36

12,13-(3^ꢀb-Hydroxy-4^ꢀa-(dimethyl-1H-1,2,3-triazole-4,5-

dicarboxylate)cyclopentan-2^ꢀa,5^ꢀa-diyl)-dihydro-5H-indolo-

[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 34

Azido alcohol 30 (111.0 mg, 0.25 mmol) was dissolved in

DMF (6 mL) and Lindlar catalyst (30.0 mg) was added. The

reaction mixture was stirred under a H₂atmosphere (150 psi)

for 5 h. The reaction mixture was ﬁltered through celite to

remove the catalyst. The celite was washed with DMF (3 ×

15 mL), the organics were combined and partitioned between

EtOAc (100 mL) and H₂O (100 mL). The organic layer was

washed with saturated aqueous CaCl₂solution (3 × 100 mL),

H₂O (100 mL) and brine (2 × 100 mL). The aqueous layer

washings were combined and re-extracted with EtOAc (2 ×

20 mL). The organics were combined and concentrated in vacuo

to give a brown solid which was puriﬁed via ﬂash column

chromatography using a 5% MeOH–DCM solvent system to

give 36 as a yellow solid (52.0 mg, 50%): mp 344–347 ^◦C;

m_max(THF)/cm⁻¹3478, 1753, 1720, 1640, 1570, 749; d_H(d₆-

DMSO, 400 MHz) 2.59 (1H, d, J 14.8, 1^ꢀ-H_a), 3.20 (1H, ddd,

J 14.8, 8.0, 5.9, 1^ꢀ-H_b), 3.60 (1H, m, 3^ꢀ-H), 3.65 (1H, dd, J 5.7,

5.4, 4^ꢀ-H), 5.29 (1H, d, J 8.0, 2^ꢀ-H), 5.58 (1H, dd, J 5.9, 5.4,

5^ꢀ-H), 5.79 (1H, d, J 3.9, OH), 7.42 (1H, dd, J 8.2, 8.1, 9-H),

7.44 (1H, dd, J 8.2, 7.5, 3-H), 7.63 (1H, dd, J 8.7, 8.1, 10-H),

7.68 (1H, dd, J 8.4, 7.5, 2-H), 7.92 (1H, d, J 8.4, 1-H), 7.97 (1H,

d, J 8.7, 11-H), 9.10 (2H, app t, J 8.2, 4-H, 8-H), 11.07 (1H, s,

NH); d_C(d₆-DMSO, 100 MHz) 39.8 (1^ꢀ-CH₂), 61.8 (CH), 63.6

(CH), 65.6 (CH), 87.0 (CH), 111.0 (CH), 111.7 (CH), 116.1 (C),

116.4 (C), 120.5 (C), 120.7 (C), 121.1 (CH), 121.3 (CH), 122.0

Triazole 27 (63.0 mg, 0.09 mmol) was suspended in anisole

(1.2 mL) with stirring under an N₂atmosphere and TFA (6 mL)

was added dropwise. The reaction mixture was heated to 80 ^◦C

for 15 h. TLC analysis showed consumption of the starting

material and so the reaction mixture was allowed to cool to rt

and partitioned between EtOAc (200 mL) and saturated aqueous

NaHCO₃solution (200 mL). The organic layer was washed

with saturated aqueous NaHCO₃solution (3 × 200 mL), H₂O

(100 mL), brine (150 mL), dried (MgSO₄), and concentrated in

vacuo to give a brown gum. The brown gum was triturated in

petrol (100 mL) for 1 h to give a brown solid that was collected

by ﬁltration. The resulting solid was puriﬁed via ﬂash column

chromatography using a 5% THF–DCM solvent system to give

the desired product 34 as a yellow solid (27 mg, 52%): mp 347–

350 ^◦C; (found: m/z (ES⁺) M⁺+ Na 613.1498. C₃₁H₂₂N₆O₇Na

requires 613.1448); m_max(CHCl₃)/cm⁻¹3344, 1720, 1573, 750;

d_H(d₆-DMSO, 400 MHz) 2.95 (1H, d, J 14.9, 1^ꢀ-H_a), 3.61 (1H,

ddd, J 14.9, 7.8, 6.0, 1^ꢀ-H_b), 3.77 (3H, s, OMe), 4.16 (3H, s,

OMe), 4.92 (1H, m, 3^ꢀ-H), 5.60 (1H, d, J 7.8, 2^ꢀ-H), 5.73 (1H,

dd, J 6.0, 5.6, 4^ꢀ-H), 6.10 (1H, dd, J 6.0, 5.6, 5^ꢀ-H), 6.48 (1H, d,

J 4.4, OH), 7.28 (2H, m, 9-H and 11-H), 7.38 (1H, dd, J 7.7, 7.5,

10-H), 7.49 (1H, dd, J 7.8, 7.5, 3-H), 7.73 (1H, dd, J 8.1, 7.5,

2-H), 8.01 (1H, d, J 8.1, 1-H), 8.97 (1H, d, J 8.0, 8-H), 9.12 (1H,

d, J 7.8, 4-H), 11.19 (1H, s, NH); d_C(d₆-DMSO, 100 MHz) 37.2

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 7 1

View Article Online

(C), 122.1 (C), 125.4 (CH), 125.5 (CH), 127.6 (2CH), 129.6 (C),

130.2 (C), 140.8 (C), 143.2 (C), 172.1 (2CO).

(C), 119.2 (C), 119.3 (C), 120.9 (CH), 122.0 (C), 122.2 (C), 125.6

(CH), 125.9 (CH), 126.9 (CH), 127.0 (CH), 127.5 (CH), 128.0

(C), 128.6 (CH), 129.3 (C), 137.5 (C), 140.0 (C), 142.5 (C), 170.0

(CO), 170.1 (CO) and 202.2 (CHO); m/z (FAB⁺) 598 (M⁺+ H,

26%), 597 (M⁺, 30%), 452 (15), 413 (8), 391 (14), 329 (9) 307

(15), 289 (10), 176 (34) and 91 (47).

12,13-[3^ꢀa-(Trimethylsilyloxy)-3^ꢀb-vinyl-cyclopentan-2^ꢀa,5^ꢀa-

diyl]-6-(phenylmethyl)5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 37

To a stirred solution of the allylic alcohol 12 (0.05 g, 0.098 mmol)

in dry dichloromethane (10 mL) under a nitrogen atmosphere,

was added triethylamine (0.04 mL, 0.3 mmol) and the mixture

was cooled to 0 ^◦C. Trimethylsilyl triﬂate (0.053 mL, 0.3 mmol)

was added dropwise and the stirring continued. After 80 min,

TLC analysis suggested that the reaction was complete, so water

(10 mL) was added and the reaction mixture was stirred for

15 min. The organic layer was then washed with water (15 mL)

and a saturated aqueous solution of NaHCO₃(2 × 15 mL),

dried (Na₂S0₄), ﬁltered and the solvent was removed in vacuo to

yield the crude product. Puriﬁcation by ﬂash chromatography

(CHCl₃) gave the allylic ether 37 as a yellow solid (0.048 g, 82%).

A portion of the product was recrystallised from a mixture

of acetone–water to give 37 as a yellow crystalline solid: mp

12,13-(3^ꢀa-Hydroxy-4-oxocyclohexan-2^ꢀa,6^ꢀa-diyl)-6-

(phenylmethyl)-5H-indolo[2,3-a] pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 39

To a stirred solution of the aldehyde 38 (0.05 g, 0.084 mmol) in

dry tetrahydrofuran (5 mL), was added boron triﬂuoroetherate

(0.052 mL, 0.42 mmol) and the mixture was left to stir overnight.

After this period, a precipitate had formed and water (0.5 mL)

was added and the mixture was stirred for 15 min. Ethyl acetate

(20 mL) was then added and the organic layer was washed

with water (20 mL), brine (20 mL), dried (MgSO₄), ﬁltered and

the solvent was removed in vacuo to yield the crude product.

Recrystallisation from a mixture of acetone–water gave 39 as a

yellow crystalline solid (0.033 g, 74%): mp 267–269 ^◦C; (found:

m/z (FAB⁺) M + H⁺526.1746. C₃₃H₂₄N₃O₄requires 526.1767);

m_max(CHCl₃)/cm^−l3696, 3604, 2929, 2862, 1752, 1720, 1697,

1602, 1462, 1384, 1352 and 1103; d_H(d₆-DMSO, 400 MHz) 2.62

(1H, br d, J 14.0, 5^ꢀ-H_a), 3.03 (1H, br d, J 16.0, 1^ꢀ-H_a), 3.45

(1H, dt, J 16.0, 5.0, 1^ꢀ-H_b), 3.53 (1H, dd, J 14.0, 5.0, 5^ꢀ-H_b), 4.87

(2H, s, CH₂Ph), 5.17 (1H, m, 3^ꢀ-H), 5.35 (1H, d, J 4.0, OH), 5.91

(1H, m, 6^ꢀ-H), 6.05 (1H, m, 2^ꢀ-H), 7.27 (1H, t, J 6.5, Ph), 7.33–

7.44 (6H, m, Ar), 7.57 (1H, dd, J 8.0, 7.0, 2-H or 10-H), 7.65

(1H, dd, J 8.0, 7.0, 2-H or 10-H), 7.80 (1H, d, J 8.0, 1-H or 11-

H), 7.88 (1H, d, J 8.0, 1-H or 11-H) and 9.03–9.10 (2H, m, 4-H

and 8H); d_C(d₆-DMSO, 126 MHz) 31.2 (1^ꢀ-CH₂), 40.7 (CH₂Ph),

47.8 (5^ꢀ-CH₂), 54.5 (6^ꢀ-CH), 59.9 (2^ꢀ-CH), 77.2 (3^ꢀ-CH), 110.0

(CH), 112.5 (CH), 115.3 (C), 116.2 (C), 118.2 (2C), 120.3 (CH),

120.7 (C), 120.9 (CH), 121.4 (C), 123.8 (CH), 124.6 (CH), 126.5

(CH), 127.3 (CH, C), 128.6 (CH), 137.4 (C), 139.5 (C), 142.8

(C), 169.2 (2CO) and 202.2 (4^ꢀ-CO); m/z (FAB⁺) 526 (M⁺+ H,

43%), 525 (M⁺, 38%), 448 (15), 391 (18), 329 (18), 307 (20), 289

(13), 242 (14), 107 (33) and 91 (37).

◦

240–241 C; (found: m/z (FAB⁺) M⁺595.2332. C₃₈H₃₃N₃₀O₃Si

requires 595.2291); m_max(CHCl₃)/cm⁻¹3068, 2959, 1750, 1695,

1573, 1424, 1350, 1316, 1243, 1126, 1038 and 842; d_H(CDCl₃,

400 MHz) 0.59 (9H, s, SiMe₃), 1.74 (1H, br d, J 15.0, 4^ꢀ-H_a),

2.57 (1H, d, J 15.0, 1^ꢀ-H_a), 2.91–2.98 (2H, m, 1^ꢀ-H_band 4^ꢀ-H_b),

4.99 (2H, s, CH₂Ph), 5.04 (1H, d, J 6.0, 2^ꢀ-H), 5.40 (1H, d, J_cis

ꢀ

=

10.5, CH₂), 5.44–5.51 (2H, m, 5 -H and CH₂), 6.32 (1H, dd,

=

J 17.0, 10.5, CH ), 7.26 (1H, m, Ar), 7.33–7.41 (4H, m, Ar),

7.53–7.60 (6H, m, Ar) and 9.22–9.25 (2H, m, 4-H and 8-H);

d_C(CDCl₃, 126 MHz) 1.1 (SiMe₃), 36.2 (1^ꢀ-CH₂), 41.4 (CH₂Ph),

43.1 (4^ꢀ-CH₂), 54.3 (5^ꢀ-CH), 65.5 (2^ꢀ-CH), 83.7 (3^ꢀ-C), 108.2

=

(CH), 110.1 (CH), 114.5 ( CH₂), 116.8 (C), 117.1 (C), 119.1

(C), 119.4 (C), 120.6 (CH), 120.6 (CH), 121.9 (C), 122.2 (C),

125.5 (CH), 125.9 (CH), 126.6 (CH), 126.7 (CH), 127.5 (CH),

128.1 (C), 128.5 (CH), 128.6 (CH), 129.4 (C), 137.5 (C), 139.9

=

(C), 143.2 (C), 143.5 ( CH), 170.0 (CO) and 170.1 (CO); m/z

(FAB⁺) 596 (M⁺+ H, 58%), 595 (M⁺, 67%), 453 (12), 307 (5),

289 (15), 176 (16), 107 (26) and 91 (31).

12,13-[3^ꢀb-Formyl-3^ꢀa-(trimethylsilyloxy)-cyclopentan-2^ꢀa,5^ꢀa-

diyl]-6-(phenylmethyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 38

12,13-(3^ꢀCyclohexan-2^ꢀa,6a^ꢀ-diyl-one)-dihydro-5H-indolo-

[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-dione 41

Ketone 8a (50.0 mg, 0.10 mmol) was dissolved in DCM (10 mL)

with stirring under an N₂atmosphere. BF₃·OEt₂(0.04 mL,

0.32 mmol) was added dropwise and the reaction mixture was

A stream of ozone in oxygen was bubbled through a stirred

solution of the allylic ether 37 (0.3 g, 0.5 mmol) in a mix-

ture of dichloromethane (45 mL) and methanol (45 mL) at

−78 ^◦C. Once the reaction appeared complete by TLC analysis,

the reaction mixture was purged with oxygen for 5 min, dimethyl

sulﬁde (5 mL) was added, and the mixture was stirred at −78 ^◦C

for 20 min before being allowed to warm to room temperature.

After 3 h, the solvent was removed in vacuo and the residue

dispersed in water (50 mL). The aqueous mixture was extracted

with dichloromethane (2 × 50 mL) and the combined organic

extracts were washed with water (2 × 50 mL), brine (50 mL),

dried (Na₂SO₄), ﬁltered and the solvent was removed in vacuo

to yield the crude product. The product was puriﬁed by ﬂash

chromatography (CH₂Cl₂) to give the aldehyde 38 as a yellow

solid (0.18 g, 60%). A portion of the solid was recrystallised from

a mixture of acetone–water to give 38 as yellow needles: mp

◦

cooled to −78 C before the dropwise addition of TMSCHN₂

(0.06 mL, 0.11 mmol). The reaction mixture was stirred for

3 h before being allowed to warm to rt overnight and was

quenched by the careful addition of AcOH (1 mL). The reaction

mixture was partitioned between DCM (25 mL) and 2N HCl

(25 mL) and the organic layer was washed with H₂O (25 mL),

saturated aqueous NaHCO₃solution (25 mL), brine (25 mL),

dried (MgSO₄), concentrated in vacuo and triturated in Et₂O

(10 mL) for 1 h. Puriﬁcation by ﬂash column chromatography,

using a 2 : 1 EtOAc–petrol solvent _◦system gave 41 as an orange

solid (0.015 g, 29%): mp 303–305 C; (found m/z (FAB⁺) M⁺

509.1737. C₃₃H₂₃N₃O₃requires 509.1739); m_max(CHCl₃)/cm⁻¹

2929, 2856, 1713, 1572, 1348, 1320; d_H(CDCl₃, 400 MHz) 2.28

(1H, d, J 13.2, 4^ꢀ-H_a), 2.44–2.59 (2H, m, 4^ꢀ-H_band 5^ꢀ-H_b), 2.66

(1H, d, J 12.8, 5^ꢀ-H_a), 3.23 (1H, ddd, J 15.8, 5.6, 5.2, 1^ꢀ-H_a), 3.43

(1H, d, J 15.8, 1^ꢀ-H_b), 4.92 (2H, s, CH₂Ph), 5.31–5.33 (1H, m, 6^ꢀ-

H), 5.36 (1 H, d, J 5.6, 2^ꢀ-H), 7.27 (1H, t, J 8.0, Bn), 7.35 (2H, dd,

J 8.0, 7.4, Bn), 7.45 (3H, app ddd, J 7.9, 7.4, 7.4, 3-H, 9-H and

11-H), 7.54 (2H, d, J 7.4, Bn), 7.62 (3H, app ddd, J 7.9, 7.4, 7.4,

2-H, 10-H and 1-H), 9.24 (1H, d, J 7.9, 8-H), 9.31 (1H, d, J 7.9,

4-H); d_C(CDCl₃, 125 MHz) 31.8 (CH₂), 34.2 (CH₂), 35.8 (CH₂),

41.5 (CH₂), 49.4 (CH), 60.9 (CH), 108.7 (CH), 109.8 (CH), 117.1

(C), 117.6 (C), 119.6 (C), 120.2 (C), 121.5 (CH), 122.0 (CH),

122.4 (C), 122.5 (C), 126.0 (CH), 126.3 (CH), 127.7 (CH, C),

127.9 (CH), 128.7 (CH), 128.9 (CH), 129.0 (CH), 130.4 (C),

◦

268–269 C; (found: m/z (FAB⁺) M⁺597.2061. C₃₇H_3lN₃O₄Si

requires 597.2084); m_max(CHCl₃)/cm⁻¹2958, 2808, 1750, 1730,

1697, 1574, 1462, 1384, 1351, 1124, 945 and 868; d_H(CDCl₃,

400 MHz) −0.69 (9H, s, SiMe₃), 1.59 (1H, d, J 15.0, 4^ꢀ-H_a), 2.74

(1H, d, J 15.0, 1^ꢀ-H_a), 2.84 (1H, dt, J 15.0, 7.0, 1^ꢀ-H_b), 3.05 (1H,

dd, J 15.0, 7.5, 4^ꢀ-H_b), 4.93 (2H, s, CH₂Ph), 5.24 (1H, d, J 7.0,

2^ꢀ-H), 5.54 (1H, dd, J 7.5, 7.0, 5^ꢀ-H), 7.27 (1H, m, Ar), 7.34–7.39

(4H, m, Ar), 7.46–7.58 (6H, m, Ar), 9.19–9.21 (2H, m, 4-H and

8-H) and 9.92 (1H, s, CHO); d_C(CDCl₃, 126 MHz) 0.7 (Me₃Si),

36.7 (1^ꢀ-CH₂), 40.4 (CH₂Ph), 41.3 (4^ꢀ-CH₂), 55.2 (5^ꢀ-CH), 60.3

(2^ꢀ-CH), 88.0 (3^ꢀ-C), 109.0 (CH), 109.1 (CH), 117.0 (C), 117.2

2 9 7 2

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

137.7 (C), 140.3 (C), 140.7 (C), 169.7 (2CO), 203.5 (CO); m/z

(FAB⁺) 510 (M⁺+ H, 4%), 509 (M⁺, 3), 91 (32).

(CH₂), 40.9 (CH₂), 56.0 (OMe), 57.2 (C), 58.9 (CH), 61.2 (CH),

111.0 (CH), 111.1 (CH), 114.9 (CH), 116.6 (C), 116.9 (C), 118.4

(CH₂), 119.6 (C), 119.9 (C), 121.5 (CH₂), 121.7 (CH), 121.8 (C),

122.0 (CH), 125.5 (CH), 125.6 (CH), 128.2 (CH), 128.4 (CH),

129.6 (C), 130.0 (CH), 130.3 (C), 132.7 (CH), 133.1 (CH), 141.1

(C), 142.1 (C), 159.5 (C), 170.0 (CO), 170.1 (CO), 217.1 (CO);

m/z (FAB⁺) 606 (M⁺+ H, 4%), 605 (M⁺, 13), 498 (11).

12,13-(3^ꢀCyclopenten-2^ꢀa,5^ꢀa-diyl-oxy)(trimethyl)silane-6-(4-

methoxybenzyl)-dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 42

Ketone 8c (0.10 g, 0.19 mmol) and ZnCl₂(0.10 g, 0.76 mmol)

were suspended in THF (5 mL) with stirring under N₂. Freshly

distilled TMSCl (0.24 mL, 1.90 mmol) and freshly distilled NEt₃

(0.05 mL, 0.38 mmol) were added and the reaction mixture was

stirred for 20 min. TLC analysis showed the consumption of

starting material and so the reaction mixture was concentrated

in vacuo to give a brown solid which was redissolved in DCM

(20 mL). The DCM solution was washed with saturated aqueous

NH₄Cl solution (10 mL), H₂O (10 mL), brine (10 mL), dried

(Na₂SO₄) and concentrated in vacuo to give the crude product.

The crude solid was dissolved in a minimum amount of DCM

and quickly ﬁltered through a silica pad, and concentrated to

give enol silane 42 was a yellow solid (0.10 g, 89%): mp 233 ^◦C

decomp.; (found: m/z (FAB⁺) M⁺597.2089. C₃₆H₃₁N₃O₄Si

requires 597.2084); m_max(CHCl₃)/cm⁻¹1750, 1694, 1638, 1572,

1513, 1347, 1035, 854; d_H(CDCl₃, 400 MHz) −0.31 (9H, s,

SiMe₃), 2.63 (1H, d, J 13.8, 1^ꢀ-H_a), 3.26 (1H, ddd, J 13.8, 6.8,

6.2, 1^ꢀ-H_b), 3.78 (3H, s, OMe), 4.93 (2H, s, CH₂Ar), 5.04 (1H, d,

J 2.5, 4^ꢀ-H), 5.44 (1H, d, J 6.8, 2^ꢀ-H), 5.90 (1H, dd, J 6.2, 2.5,

5^ꢀ-H), 6.88 (2H, d, J 8.5, PMB), 7.38–7.41 (2H, m, 3-H and 9-H),

7.53 (2H, d, J 8.5, PMB), 7.58–7.60 (3H, m, 3H, Ar), 7.65 (1H,

d, J 8.2, Ar), 9.27 (2H, app t, J 7.0, 4-H and 8-H); d_C(CDCl₃,

100 MHz) −0.7 (SiMe₃), 38.9 (1^ꢀ-CH₂), 40.9 (CH₂PMB), 55.3

(OMe), 57.4 (5^ꢀ-CH), 60.0 (2^ꢀ-CH), 104.8 (CH), 108.3 (CH),

108.7 (CH), 114.1 (CH), 117.2 (C), 117.3 (C), 119.5 (C), 119.8

(C), 120.5 (CH), 120.6 (CH), 122.0 (C), 122.1 (C), 125.9, (CH),

126.1 (CH), 126.8 (CH), 127.0 (CH), 129.0 (C), 129.1 (C), 129.9

(C), 130.1 (2CH), 140.1 (C), 141.0 (C), 159.1 (C), 160.0 (C),

170.0 (CO), 170.1 (CO); m/z (FAB⁺) 598 (M⁺+ H, 4%), 597

(M⁺, 10), 137 (8), 136 (22), 121 (13), 109 (9), 107 (15), 91 (23),

75 (17).

12,13-(4^ꢀ,4^ꢀ-Dimethyl-3^ꢀcyclopentan-2^ꢀa,5^ꢀa-diyl-one)-6-(4-

methoxybenzyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-

5,7(6H)-dione 44

Ketone 8c (30.0 mg, 0.06 mmol) was dissolved in THF (5 mL)

◦

with stirring under N₂, and was cooled to 0 C. NaH (2.3 mg,

0.06 mmol) was added and the reaction mixture _◦was allowed to

warm to rt over 1 h before being recooled to 0 C and methyl

iodide (0.10 mL, 1.61 mmol) was added dropwise. The reaction

mixture was stirred for 3 h. TLC analysis showed consumption of

the starting material and so the reaction mixture was partitioned

between EtOAc (50 mL) and H₂O (50 mL). The organic layer was

washed with H₂O (100 mL), brine (100 mL), dried (MgSO₄), and

concentrated in vacuo to give a yellow solid which was puriﬁed

via ﬂash column chromatography using a DCM solvent system

to give the dialkylated product 44 as a yellow solid (12.0 mg,

73% based on ca. 14 mg recovered starting material): mp 336–

338 ^◦C; m_max(THF)/cm⁻¹3498, 1753, 1698, 1385, 750; d_H(d₆-

DMSO, 400 MHz) 0.44 (3H, s, Me_a), 1.53 (3H, s, Me_b), 2.98

(1H, d, J 15.5, 1^ꢀ-H_a), 3.65 (1H, ddd, J 15.5, 8.3, 6.5, 1^ꢀ-H_b), 3.75

(3H, s, OMe), 4.86 (2H, s, CH₂PMB), 5.74 (1H, d, J 6.5, 5^ꢀ-H),

5.85 (1H, d, J 8.3, 5^ꢀ-H), 6.94 (2H, d, J 8.8, PMB), 7.39 (2H,

d, J 8.8, PMB), 7.45 (1H, dd, J 7.9, 7.3, 3-H), 7.47 (1H, dd, J

7.9, 7.3, 9-H), 7.68 (1H, dd, J 8.4, 7.3, 2-H), 7.71 (1H, dd, J 8.4,

7.3, 10-H), 7.97 (1H, d, J 8.4, 11-H), 8.02 (1H, d, J 8.4, 1-H),

9.09 (1H, d, J 7.9, 4-H), 9.12 (1H, d, J 7.9, 8-H); d_C(d₆-DMSO,

100 MHz) 18.7 (Me), 25.0 (Me), 33.6 (CH₂), 41.1 (CH₂), 51.1

(C), 56.0 (OMe), 58.1 (CH), 63.4 (CH), 110.9 (CH), 111.4 (CH),

114.9 (CH), 116.7 (C), 116.9 (C), 119.6 (C), 119.9 (C), 121.6 (C),

121.7 (CH), 121.9 (CH), 122.0 (CH), 125.4 (CH), 125.5 (CH),

128.3 (CH), 128.4 (CH), 128.9 (C), 129.3 (C), 129.9 (CH), 130.3

(C), 141.2 (C), 142.4 (C), 159.5 (C), 169.9 (CO), 170.0 (CO),

219.2 (CO); m/z (FAB⁺) 553 (M⁺20%), 446 (30), 432 (15).

12,13-(4^ꢀ,4^ꢀ-Diallyl-3^ꢀ-cyclopentan-2^ꢀa,5^ꢀa-diyl-one)-6-(4-

methoxybenzyl)-dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 43

Ketone 8c (30.0 mg, 0.06 mmol) was dissolved in THF (5 mL)

with stirring under N₂, and was cooled to 0 C. NaH (2.3 mg,

12,13-(4^ꢀ,4^ꢀ-Dibenzyl-3^ꢀcyclopentan-2^ꢀa,5^ꢀa-diyl-one)-6-(4-

methoxybenzyl)-dihydro-5H-indolo[2,3-a]pyrrolo[3,4-c]-

carbazole-5,7(6H)-dione 45

◦

0.06 mmol) was added and the reaction mixture was allowed

◦

to warm to rt over 1 h before being recooled to 0 C and allyl

bromide (0.10 mL, 1.16 mmol) was added dropwise. The reaction

mixture was stirred for 3 h. TLC analysis showed consumption of

the starting material and so the reaction mixture was partitioned

between EtOAc (50 mL) and H₂O (50 mL). The organic layer was

washed with H₂O (100 mL), brine (100 mL), dried (MgSO₄), and

concentrated in vacuo to give a yellow solid which was puriﬁed

via ﬂash column chromatography using a DCM solvent system

to give the dialkylated product 43 as a yellow solid (12.0 mg,

71%_◦based on ca. 15 mg recovered starting material): mp 331–

332 C; (found m/z (FAB⁺) M⁺605.2298. C₃₉H₃₁N₃O₄requires

605.2315); m_max(THF)/cm⁻¹3498, 1752, 1700, 1384, 750; d_H(d₆-

DMSO, 400 MHz) 1.65–1.73 (2H, m, CH₂allyl_a), 2.60 (1H, dd, J

14.1, 6.7, CH₂allyl_b), 2.75 (1H, dd, J 14.1, 7.8, CH₂allyl_b), 2.97

(1H, d, J 15.7, 1^ꢀ-H_a), 3.67 (1H, ddd, J 15.7, 8.0, 7.2, 1^ꢀ-H_b),

Ketone 8c (50.0 mg, 0.10 mmol) was dissolved in THF (5 mL)

with stirring under N₂, and was cooled to 0 C. NaH (8.0 mg,

◦

0.20 mmol) was added and the reaction mixture was allowed

to warm to rt over 1 h before being recooled to 0 ^◦C and

benzyl bromide (0.11 mL, 1.00 mmol) was added dropwise. The

reaction mixture was allowed to warm to rt over 18 h. TLC

analysis showed consumption of the starting material and so

the reaction mixture was partitioned between EtOAc (75 mL)

and H₂O (75 mL). The organic layer was washed with H₂O

(100 mL), brine (150 mL), dried (MgSO₄), and concentrated

in vacuo to give a yellow solid which was puriﬁed via ﬂash

column chromatography using a DCM solvent system to give the

dialkylated product 45 as a yellow solid (47.0 mg, 71%): mp 335–

337 ^◦C; (found m/z (FAB⁺) M⁺705.2607. C₄₇H₃₅N₃O₄requires

705.2628); m_max(THF)/cm⁻¹3502, 1750, 1699, 1384, 750; d_H(d₆-

DMSO, 400 MHz) 2.27 (1H, d, J 14.7, CHH–Ph_a), 2.80 (1H, d,

J 15.5, 1^ꢀ-H_a), 2.92 (1H, d, J 14.7, CHH-Ph_a), 3.13 (1H, ddd, J

15.5, 7.7, 6.7, 1^ꢀ-H_b), 3.26 (1H, d, J 13.6, CH₂Ph_b), 3.35 (1H, d,

J 13.6, CH₂Ph_b), 3.37 (3H, s, OMe), 4.85 (2H, s, CH₂Ar), 5.61

(1H, d, J 7.7, 2^ꢀ-H), 5.69 (2H, d, J 7.5, Ph_a), 5.84 (1H, d, J 6.7,

5^ꢀ-H), 6.10 (2H, dd, J 7.6, 7.5, Ph_a), 6.31 (1H, t, J 7.6, Ph_a), 6.95

(2H, d, J 8.7, PMB), 7.37 (2H, d, J 8.7, PMB), 7.39–7.60 (9H,

m, 3-H, 9-H, 10-H, 11-H and Ph_b), 7.71 (1H, dd, J 8.3, 7.2, 2-H),

=

3.76 (3H, s, OMe), 4.23 (1H, dd, J 17.0, 1.3, CH CH_2a), 4.37

=

(1H, dd, J 10.1, 1.3, CH CH_2a), 4.88 (2H, s, CH₂Ar), 5.07–

5.16 (1H, m, CH CH_2a), 5.40–5.47 (2H, m, CH CH_2b), 5.79

=

(1H, d, J 7.2, 2^ꢀ-H), 5.81 (1H, d, J 8.0, 5^ꢀ-H), 6.02–6.11 (1H, m,

CH CH_2b), 6.94 (2H, d, J 8.6, PMB), 7.40 (2H, d, J 8.6, PMB),

7.46 (1H, dd, J 8.1, 7.0, 3-H or 9-H), 7.48 (1H, dd, J 8.1, 7.0,

3-H or 9-H), 7.72 (2H, dd, J 8.3, 7.0, 2-H and 10-H), 7.90 (1H,

d, J 8.3, 1-H), 7.98 (1H, d, J 8.3, 11-H), 9.12 (2H, 2 d, J 8.1, 4-H

and 8-H); d_C(d₆-DMSO, 100 MHz) 33.9 (CH₂), 34.8 (CH₂), 39.1

=

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 7 3

View Article Online

8.01 (1H, d, J 8.3, 1-H), 8.96 (1H, d, J 7.9, 8-H), 9.06 (1H, d, J

7.9, 4-H); d_C(d₆-DMSO, 125 MHz) 34.1 (CH₂), 38.8 (CH₂), 41.0

(CH₂), 44.6 (CH₂), 56.0 (OMe), 60.0 (CH), 60.7 (CH), 68.0 (C),

110.1 (CH), 111.2 (CH), 114.9 (CH), 116.4 (C), 116.8 (C), 119.1

(C), 119.8 (C), 121.6 (CH), 122.0 (CH), 122.2 (C), 122.5 (C),

125.4 (CH), 125.5 (CH), 125.7 (CH), 127.1 (CH), 127.9 (CH),

128.2 (CH), 128.5 (CH), 128.9 (C), 129.6 (CH), 129.7 (CH),

130.1 (C), 130.4 (C), 131.9 (2CH), 136.0 (C), 136.9 (C), 140.8

(C), 141.9 (C), 159.5 (C), 169.9 (CO), 170.1 (CO), 216.8 (CO);

m/z (FAB⁺) 706 (M⁺+ H, 6%), 705 (M⁺, 11), 598 (6), 121 (27),

107 (26).

18 For an excellent review of cyclic sulfate chemistry, see: H.-S. Byun,

L. He and R. Bittman, Tetrahedron, 2000, 56, 7051.

19 This dihydroxylation appears in a patent, see: H. Roder, T. B.

Lowinger, D. R. Brittelli and M. C. VanZandt, US Pat. 6,013,646,

Jan 11, 2000.

20 Y. Gao and K. B. Sharpless, J. Am. Chem. Soc., 1988, 110, 7538.

21 The use of NaH as base seems more usual, but was ineffective in

our system, see for example: (a) T. J. Tewson and M. Soderlind,

J. Carbohydr. Chem., 1985, 4, 529; (b) S. Hanessian and J.-M. Vatele,

Tetrahedron Lett., 1981, 22, 3579.

22 Cyclic sulfate ring opening by heating in neat amine has been used

previously, see for example: R. Hirsenkorn, Tetrahedron Lett., 1990,

31, 7591.

23 J. S. Yadav, C. Madhuri, B. V. S. Reddy, G. S. K. K. Reddy and G.

Sabitha, Synth. Commun., 2002, 32, 2771.

24 H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem., Int. Ed.,

2001, 40, 2004.

25 K. Makino and Y. Ichikawa, Tetrahedron Lett., 1998, 39, 8245.

26 A. Kamal, K. V. Ramana, H. B. Ankati and A. V. Ramana,

Tetrahedron Lett., 2002, 43, 6861.

Acknowledgements

We gratefully acknowledge support for this work from The

University of Nottingham, Eli Lilly and Company, Indianapolis,

and NADAG, Munich.

27 Y. Ito, S. Fujii and T. Saegusa, J. Org. Chem., 1976, 41, 2073.

28 (a) H. O. House, E. J. Grubbs and W. F. Gannon, J. Am. Chem.

Soc., 1960, 82, 4099; (b) J. Furukawa, N. Kawabata and J. Nishimura,

Tetrahedron, 1968, 24, 53; (c) Y. Mori, K. Yaegashi and H. Furukawa,

Tetrahedron, 1997, 53, 12917; (d) G. R. Krow, Tetrahedron, 1987, 43,

3.

References

1 For chemically-orientated reviews of the indolocarbazole area, see:

(a) H.-J. Kno¨lker and K. R. Reddy, Chem. Rev., 2002, 102, 4303; (b) J.

Bergman, T. Janosik and N. Wahlstro¨m, Adv. Heterocycl. Chem.,

2001, 80, 1. For more recent contributions, and leading references

to biological areas, see:; (c) T. L. Schneider, R. S. Mathew, K. P.

Price, K. Tamaki, J. L. Wood and A. Schepartz, Org. Lett., 2005, 7,

1695; (d) M. M. Faul, T. A. Engler, K. A. Sullivan, J. L. Grutsch,

M. T. Clayton, M. J. Martinelli, J. M. Pawlak, M. LeTourneau, D. S.

Coffey, S. W. Pederson, S. P. Kolis, K. Furness, S. Malhotra, R. S.

Al-awar and J. E. Ray, J. Org. Chem., 2004, 69, 2967; (e) G. Zhu, S. E.

Conner, X. Zhou, H.-K. Chan, C. Shih, T. A. Engler, R. S. Al-awar,

H. B. Brooks, S. A. Watkins, C. D. Spencer, R. M. Schultz, J. A.

Dempsey, E. L. Considine, B. R. Patel, C. A. Ogg, V. Vasudevan and

M. L. Lytle, Bioorg. Med. Chem. Lett., 2004, 14, 3057; (f) L. Zhang,

P. Carroll and E. Meggers, Org. Lett., 2004, 6, 521; (g) S. Messaoudi,

F. Anizon, B. Pfeiffer, R. Golsteyn and M. Prudhomme, Tetrahedron

Lett., 2004, 45, 4643.

29 K. Muruoka, A. Concepcion and A. Yamamoto, Synthesis, 1994,

1283.

30 (a) J. Nishimura, J. Furukawa, N. Kawabata and M. Kitayama,

Tetrahedron, 1971, 27, 1799; (b) S. E. Denmark and J. P. Edwards,

J. Org. Chem., 1991, 56, 6974.

31 A. Streitwieser, Y.-J. Kim and D. Z.-R. Wang, Org. Lett., 2001, 3,

2599.

32 (a) H. C. Brown, P. K. Jadhav and A. K. Mandal, Tetrahedron, 1981,

37, 3547; (b) H. C. Brown and P. V. Ramachandran, J. Organomet.

Chem., 1995, 500, 1.

33 H. C. Brown, M. C. Desai and P. K. Jadhav, J. Org. Chem., 1982, 47,

5065.

34 T. Hayashi, Acc. Chem. Res., 2000, 33, 354.

35 (a) M. Carpintero, C. Jaramillo and A. Ferna´ndez-Mayoralas,

Eur. J. Org. Chem., 2000, 1285; (b) see also: T. Gourlain, A.

Wadouachi and D. Beaupere, Tetrahedron Lett., 2000, 41, 659.

36 For asymmetric reactions using chiral alkoxides, see for example:

(a) M. Amadji, J. Vadecard, J. C. Plaquevent, L. Duhamel and P.

Duhamel, J. Am. Chem. Soc., 1996, 118, 12483; (b) C. D. Jones and

N. S. Simpkins, Tetrahedron Lett., 1998, 39, 1023.

2 S. Omura, Y. Iwai, A. Hirano, A. Nakagawa, J. Awaya, H. Tsuchiya,

Y. Takahashi and R. Masuma, J. Antibiot., 1977, 30, 275.

3 (a) M. Sezaki, T. Sasaki, T. Nakazawa, U. Takeda, M. Iwata,

T. Watanabe, M. Koyama, F. Kai, T. Shomura and M. Kojima,

J. Antibiot., 1985, 38, 1437; (b) H. Kase, K. Iwahashi and Y. Matuda,

J. Antibiot., 1986, 39, 1059.

4 (a) D. E. Nettleton, T. W. Doyle, B. Krishnan, G. K. Matsumoto

and J. Clardy, Tetrahedron Lett., 1985, 26, 4011; (b) Y. Yamashita,

N. Fujii, C. Murkata, T. Ashizawa, M. Okabe and H. Nakano,

Biochemistry, 1992, 31, 12069.

37 For a review of chiral lithium amide base chemistry, see: (a) P.

O’Brien, J. Chem. Soc., Perkin Trans. 1, 1998, 1439; (b) For a special

journal edition dedicated to chiral lithium amide base chemistry, see:

P. O’Brien (Symposium in Print guest editor), Tetrahedron, 2002,

58(23), 4567–4733; (c) For our most recent chiral lithium amide

chemistry, see: J. D. Bennett, P. L. Pickering and N. S. Simpkins,

Chem. Commun., 2004, 1392.

38 J. B. McAlpine, J. P. Karwowski, M. Jackson, M. M. Mullaly, J. E.

Hochlowski, U. Premachandran and J. Burres, J. Antibiot., 1994, 47,

281.

39 S. Wakusawa, K. Inoko, K. Miyamoto, S. Kajita, T. Hasegawa, K.

Hariyama and M. Koyama, J. Antibiot., 1993, 46, 353.

40 (a) H. J. Mackay and C. J. Twelves, Endocr.–Relat. Cancer, 2003, 10,

389; (b) A. J. Bridges, Chem. Rev., 2001, 101, 2541. See also ref. 8.

41 (a) D. R. Knighton, J. Zheng, L. F. Teneyck, V. A. Ashford, N. G.

Xuong, S. S. Taylor and J. M. Sowadski, Science, 1991, 253, 407;

(b) W. T. Miller, Nat. Struct. Biol., 2001, 8, 16.

42 (a) K. Tamaki, J. B. Shotwell, R. D. White, I. Drutu, D. T. Petsch, T. V.

Nheu, Y. HiroKawa, H. Murata and J. L. Wood, Org. Lett., 2001,

3, 1689; (b) J. L. Wood, D. J. Petsch, B. M. Stoltz, E. M. Hawkins,

D. Elbaum and D. R. Stover, Synthesis, 1999, 1529; (c) K. Tamaki,

E. W. D. Huntsman, D. T. Petsch and J. L. Wood, Tetrahedron Lett.,

2002, 43, 379. See also:; (d) T. L. Underiner, J. P. Mallamo and J.

Singh, J. Org. Chem., 2002, 67, 3235; (e) C. Murakata, M. Kaneko, G.

Gessner, T. S. Angeles, M. A. Ator, T. M. O’Kane, B. A. W. McKenna,

B. A. Thomas, J. R. Mathiasen, M. S. Saporito, D. Bozyczko-Coyne

and R. L. Hudkins, Bioorg. Med. Chem. Lett., 2002, 12, 147; (f) D. E.

Gringrich and R. L. Hudkins, Bioorg. Med. Chem. Lett., 2002, 12,

2829.

5 M. Prudhomme, Curr. Pharm. Des., 1997, 3, 265.

6 (a) S. Nakanishi, Y. Matsuda, K. Iwahashi and H. Kase, J. Antibiot.,

1986, 39, 1066; (b) T. Yasuzawa, T. Iida, M. Yoshida, N. Hirayama,

M. Takahashi, K. Shirahata and H. Sano, J. Antibiot., 1986, 39, 1072.

7 (a) M. Prudhomme, Eur. J. Med. Chem., 2003, 38, 123; (b) M.

Prudhomme, Curr. Med. Chem., 2000, 7, 1189.

8 P. Cohen, Nat. Rev. Drug Discovery, 2002, 1, 309.

9 For key synthetic contributions in the K-252a area, see: (a) J. L.

Wood, B. M. Stoltz, H.-J. Dietrich, D. A. Pﬂum and D. T. Petsch,

J. Am. Chem. Soc., 1997, 119, 9641; (b) J. L. Wood, B. M. Stoltz,

S. N. Goodman and K. Onwueme, J. Am. Chem. Soc., 1997, 119,

9652; (c) T. B. Lowinger, J. Chu and P. L. Spence, Tetrahedron Lett.,

1995, 36, 8383; (d) Y. Kobayashi, T. Fujimoto and T. Fukuyama,

J. Am. Chem. Soc., 1999, 121, 6501.

10 D. A. Riley, N. S. Simpkins and D. Moffat, Tetrahedron Lett., 1999,

40, 3929.

11 C. J. Nichols and N. S. Simpkins, Tetrahedron Lett., 2004, 45, 7469.

12 S. J. Danishefsky, J. J. Masters, W. Byoung, J. T. Link, L. B. Snyder,

T. U. Magee, D. K. Jung, R. C. A. Isaacs, W. G. Bornmann, C. A.

Alaimo, C. A. Coburn and M. J. DiGrandi, J. Am. Chem. Soc., 1996,

118, 2849.

13 R. Gigg and R. Conant, J. Chem. Soc., Chem. Commun., 1983, 465.

14 M. Brenner, H. Rexhausen, B. Steffan and W. Steglich, Tetrahedron,

1988, 44, 2887.

15 (a) W. K. Anderson and T. Veysoglu, J. Org. Chem., 1973, 38, 2267;

(b) P. A. Bartlett and L. A. McQuaid, J. Am. Chem. Soc., 1984, 106,

7854.

43 A. M. Lawrie, M. E. M. Noble, P. Tunnah, N. R. Brown, L. N.

Johnson and J. A. Endicott, Nat. Struct. Biol., 1997, 4, 796.

44 L. Prade, R. A. Engh, A. Girod, V. Kinzel, R. Huber and D.

Bossenmeyer, Structure, 1997, 5, 1627.

16 D. R. Dalton, V. P. Dutta and D. C. Jones, J. Am. Chem. Soc., 1968,

90, 5498.

17 For a recent example with leading references, see: J. Boruwa, J. C.

Borah, B. Kalita and N. C. Barua, Tetrahedron Lett., 2004, 45, 7355.

45 N. Scheiring, S. Knapp, M. Marconi, M. M. Flocco, J. Cui, R. Perego,

L. Rusconi and C. Cristiani, Proc. Natl. Acad. Sci. USA, 2003, 12654.

2 9 7 4

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

View Article Online

46 (a) L. M. Strawn and L. K. Shawver, Expert Opin. Invest. Drugs,

1998, 7, 553; (b) D. Fabbro, E. Buchdunger, J. Wood, J. Mestan, F.

Hofmann, S. Ferrari, H. Mett, T. O’Reilly and T. Meyer, Pharmacol.

Ther., 1999, 82, 293.

47 L. C. Platanias and R. H. Lurie, Pharmacol. Ther., 2003, 98, 129.

48 R. L. Thurmond, S. A. Wadsworth, P. H. Schafer, R. A. Zivin and

J. J. Siekierka, Eur. J. Biochem., 2001, 268, 5747.

50 H. Reuveni, N. Livnah, T. Geiger, S. Klien, O. Ohne, I. Cohen, M.

Benhar, G. Gellerman and A. Levitzki, Biochemistry, 2002, 41, 10304.

51 W. D. Klohs, D. W. Fry and A. Kraker, Curr. Opin. Oncol., 1997, 9,

562.

52 M. Mohammadi, S. Froum, J. M. Hamby, M. C. Schroeder, R. L.

Panek, G. H. Lu, A. V. Eliseenkova, D. Green, J. Schlessinger and

S. R. Hubbard, EMBO J., 1998, 17, 5896.

49 K. M. Nicholson and N. G. Anderson, Cell Signalling, 2002, 14,

381.

53 P. D. Davis, J. D. Davis, D. F. C. Moffat and M. C. Hutchings,

International Patent Speciﬁcation, no. WO97/19605.

O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 9 5 3 – 2 9 7 5

2 9 7 5

Article Doi

The synthesis of bioactive indolocarbazoles related to K-252a

DOI: 10.1039/b506444a

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