A Facile Synthetic Approach to Nonracemic Substituted Pyrrolo-allocolchicinoids Starting from Natural Colchicine

SYNTHESIS

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2018, 50, A–L

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de

E. S. Shchegravina et al.

Paper

Synthesis

A Facile Synthetic Approach to Nonracemic Substituted Pyrrolo-

allocolchicinoids Starting from Natural Colchicine

Ekaterina S. Shchegravina^a

Elena V. Svirshchevskaya^b

Hans-Günther Schmalz^c

MeO

NHAc

R'

6 steps

MeO

Alexey Yu Fedorov*^a

0

0-0

0

3-

0

4

8

9-1

8

2

7

MeO

+

O

R

NH

N

^aDepartment of Organic Chemistry, Nizhny Novgorod State

University, 23 Gagarin Avenue, 603950 Nizhny Novgorod, Rus-

sian Federation

H

OMe

via Fischer indole synthesis

R'

R

14 examples

afnn@rambler.ru

^bShemyakin-Ovchinnikov Institute of Bioorganic Chemistry

RAS, 16/10 Miklukho-Maklaya Street, 117997 Moscow,

Russian Federation

^cDepartment of Chemistry, University of Cologne, Greinstrasse

4, 50939 Cologne, Germany

Received: 28.10.2018

Accepted after revision: 05.11.2018

Published online: 13.12.2018

mitotic tubulin-binding agents with improved pharmaco-

chemical properties, potentially useful in cancer treat-

ment.²Colchicine (1) belongs to the well-known natural tu-

bulin-destabilizing agents.³It possesses a strong antimitotic

activity and suppresses cell motility. In clinical practice, it

has been approved for the treatment of Mediterranean fe-

ver, Behçet’s disease and acute gout,⁴and might also be use-

ful in the treatment of inflammatory cardiovascular diseas-

es,⁵chronic infections or allergy.⁶While colchicine itself

cannot be used in humans as an antitumor drug due to its

substantial systemic toxicity,^7a,bits unique tricyclic struc-

ture has been a basis for the preparation of numerous de-

rivatives^7c,dthat exhibit anticancer activity often exceeding

the parent compound.

DOI: 10.1055/s-0037-1610673; Art ID: ss-2018-n0283-op

Abstract A six-step semisynthetic approach towards chiral nonrace-

mic pyrrolo-allocolchicinoids starting from naturally occurring colchi-

cine was developed. The synthetic scheme includes an electrocyclic tro-

polone ring contraction to afford allocolchicinic acid followed by the

Curtius reaction, giving the corresponding aniline. The Sandmeyer reac-

tion and copper-mediated hydrazination gave hydrazine-substituted al-

locolchicine. This was introduced into the Fischer indole synthesis, af-

fording libraries of regioisomeric indole-based allocolchicine congeners.

Key words colchicine, pyrrolo-allocolchicinoids, Fischer indole syn-

thesis, tubulin, anti-tubulin agents

Recent research in the field of heterocyclic allocolchi-

cinoids has demonstrated an improved affinity of several

novel compounds to tubulin as well as their decreased sys-

temic toxicity in comparison with the parent colchicines.^8,9

A quite promising biological activity was found for pyrrolo-

allocolchicinoids 2 and 3⁸(Scheme 1).

Tubulin is an important target for anticancer therapy.¹

The disturbance of the dynamic equilibrium between the

tubulin assembly into microtubules and their depolymer-

ization leads to the arrest of cell division and, eventually, to

apoptosis of relatively quickly dividing tumor cells. This fact

has inspired intense efforts in the search for novel anti-

Br

MeO

NHAc

MeO

OMe

O

N

R

OMe

2a–c

3

(–)-(aR,7S)-colchicine (1)

N

HO

R = H, Me

or

=

N

ref. 8d,e: 9 steps from 1

ref 8a–c: 11–12 steps, total synthesis

MeO

This work

6 steps

NHAc

R¹

NHAc

MeO

+

OMe

R²

4b

4a

N

NH

R²

H

R¹

Scheme 1 Different synthetic approaches towards pyrrolo-allocolchicinoids

B

E. S. Shchegravina et al.

Paper

Synthesis

The antitumor activity of these compounds strongly de-

pends on the orientation of the pyrrole ring in the tetracy-

clic skeleton as well as the substitution pattern in the side

chain of the heterocyclic fragment. Herein, we present a

new convenient approach to nonracemic substituted pyrro-

lo-allocolchicinoids 4a and 4b (Scheme 1) with different

orientations of the pyrrole moiety via a six-step reaction

sequence, exploiting a catalytic Ullmann amination^10,11and

the Fischer indole synthesis¹²as the key steps, starting from

naturally occurring colchicine.

The proposed method provides an easy access to librar-

ies of substituted indole-based allocolchicine congeners.

For the construction of the indolyl moiety in compounds of

type 4, we developed the strategy presented in Scheme 2.

The arylhydrazine precursor 5 could be prepared from the

substituted allocolchicine 6 (X = OTf, I or NH₂). The substit-

uent X could be transformed into the hydrazine moiety

through catalytic Buchwald amination,¹⁰Ullmann chemis-

try¹¹or via the aryldiazonium salt.¹³Compound 6 is readily

accessible from colchicine (1) via the known C-ring con-

traction¹⁴followed by the proper functionalization.

Fischer

indole

synthesis

MeO

NHAc

R'

OMe

R

4

5

NH

NHNH₂

R'

catalytic amination

or diazotization

R

Fischer

indole

synthesis

MeO

B

NHAc

A

NHAc

ring

contraction

OMe

C

O

1

6

X

X = OTf, I, NH₂

OMe

Scheme 2 Retrosynthetic scheme for the preparation of pyrrolo-allo-

colchicinoids

screened. Only in the case of the catalytic system Pd(OAc)₂

(10 mol%)/rac-BINAP (30 mol%)/K₃PO₄(2 equiv) in toluene

was the desired product 9 isolated, albeit in poor yield

(14%). In all other cases, the products of N–N hydrazone

moiety bond cleavage and/or hydrogenolysis of the triflate

group were observed.

Thus, another conventional approach toward arylhydra-

zines, using one-pot diazotization–reduction, was attempt-

ed. In the first stage, base-induced contraction of the tropo-

lone ring of colchicine (1) in wet MeOH gave allocolchicinic

acid (10) in excellent yield (Scheme 3).^8dThe subsequent

Curtius degradation proceeded smoothly when using a

combination of NaN₃with di-tert-butyl dicarbonate (Boc₂O)

as an activating agent. Boc cleavage afforded amine 11 in

72% yield for the two steps. For the next step, despite the

smooth formation of the corresponding diazonium salt

The synthesis started with the oxidative degradation of

colchicine (1) to iodocolchinol 7 using the Windaus proce-

dure (NaOH, I₂, KI in H₂O).¹⁴After reductive deiodination of

7 (Zn in AcOH)^14band subsequent reaction with Tf₂O, the

aryl triflate 8 was isolated in 76% yield over two steps. Com-

pound 8 was subjected to Buchwald-type catalytic amina-

tion

(H₂NN=CPh₂) as a hydrazine surrogate. Various sources of

palladium [Pd(OAc)₂, Pd(dppf)Cl₂, Pd(dppe)Cl₂,

conditions

using

benzophenone

hydrazone

Pd₂(dba)₃·CHCl₃], ligands (Ph₃P, BINAP, XPhos, XantPhos,

DavePhos, CyJohnPhos), and bases (AcOK, K₃PO₄, Na₂CO₃,

K₂CO₃, Cs₂CO₃, t-BuONa, t-BuOK) in toluene, 1,4-dioxane,

MeCN, DMF, EtOH, or EtOH–toluene mixtures were

MeO

H₂NN=CPh₂

NHAc

O

NHAc

a,b

MeO

Buchwald

amination

MeO

OR²

NHX

R¹

1

OMe

R¹= I, R²= H 7 (93%)

R¹= H, R²= OTf 8 (76%)

NHX = NHN=CPh₂9 (max 14%)

12 NHX = NHNH₂

c,d

e

MeO

NHAc

MeO

NHAc

h

f,g

MeO

I

NH₂

CO₂H

13 (64%)

11 (63%)

10 (98%)

Scheme 3 Synthetic route to key intermediate 13. Reagents and conditions: a) 0.1 N HCl, AcOH–H₂O, 100 °C, 3 h, 98%; b) I₂, NaI, NaOH, H₂O, 0–5 °C,

1 h, 95%; c) Zn dust, AcOH, reflux, 4 h, quant.; d) Tf₂O, Pyridine, CH₂Cl₂, 0 °C to rt, 3 h, 76%; e) NaOMe, MeOH, 65 °C, 4 h, then H₂O, 20 min, r.t., 98%;

f) NaN₃, Boc₂O, 1,4-dioxane, 90 °C, 2 d, 77%; g) HCl, CH₂Cl₂, r.t., 2 h, 94%; h) HCl, NaNO₂, H₂O, 0 to –5 °C, 30 min, then KI, 0 °C to r.t., 48 h, 64%.

C

E. S. Shchegravina et al.

Paper

Synthesis

MeO

NHAc

NH₂

NHAc

a

+

MeO

NHBoc

N

I

N

13

14a

14b

Boc

H

b

14a + 14b (70%, 7:3)

MeO

NHAc

R¹

MeO

+

MeO

R²

NH

R²

N

15a–22a

15b–20b

H

R¹

Scheme 4 Synthesis of the target pyrrolo-allocolchicinoids. Reagents and conditions: a) NH₂NHBoc (1.3 equiv), CuI (5 mol%), o-phenanthroline

(20 mol%), Cs₂CO₃(2 equiv), DMF, 80 °C, 70%; b) ketone (3 equiv), p-TsOH·H₂O (2.5 equiv), EtOH, 100 °C.

(NaNO₂/HCl or t-BuONO/HBF₄systems), we were not able

to reduce this salt to arylhydrazine 12 (SnCl₂, Zn/NiCl₂,

NaBH₄/NiCl₂, Ph₃P/HCl) in an acceptable yield.

actions proceeded exclusively with the formation of pyrro-

lo-allocolchicinoids corresponding to thermodynamic con-

trol (Scheme 5).

However, when a solution of the diazonium salt from

aniline 11 was treated with KI, iodide 13 was isolated in

64% yield (Scheme 3). The latter was subjected to an

Ullmann-type reaction with NH₂NHBoc in the presence of

CuI (5 mol%)/o-phenanthroline (20 mol%)/Cs₂CO₃(2 equiv)

in DMF at 80 °C^15athat gave regioisomeric hydrazines 14a

and 14b in 70% yield (7:3 ratio), which could be easily sepa-

rated on silica gel (Scheme 4).

The Boc-protected arylhydrazine 14a smoothly reacted

with aliphatic ketones in the presence of p-TsOH to yield

the regioisomeric pyrrolo-allocolchicines 15a–22a and

15b–20b (Scheme 4, Table 1).^15bIsomeric 14b remains com-

pletely inert under these conditions (Scheme 4). The mix-

ture of regioisomeric indoles can be effectively separated

using silica gel column chromatography with petroleum

ether–AcOEt–EtOH (9:1:1) as eluent. The indoles of type ‘b’

were eluted first in all cases.

14a

MeO

NHAc

MeO

OMe

NH

H

NH

23

23'

H

N

H

[3,3']-shift

NHAc

[3,3']-shift

NHAc

NH

NH₂

NH

NH₂

NH

Reaction of 14a with acetophenone and with cyclohexa-

none led to the formation of pyrrolo-allocolchicines 21a

and 22a, respectively, as single regioisomers, but only in

traces. β-Cyano ketones, β-nitro ketones and β-diketones

did not yield the desired indoles.

NH₂

NHAc

Regioselectivity in indolization reactions depends on a

number of factors.^15cAmong others, quite important is the

acidity of the reaction medium: strong acids favor forma-

tion of the least-substituted ene-hydrazine, while weakly

acidic conditions favor the more substituted one.^15dp-TsOH

is a strong acid in aqueous media, but EtOH as a solvent re-

duces its acidity by 3–4 orders of magnitude.^15eDecreased

medium acidity leads to the preferential formation of the

most-substituted ene-hydrazine intermediate in the reac-

tion. Indeed, in our cases of nonsymmetric ketones, the re-

N

NH

N

H

NH

H

17b

17a

17c

17d

Kinetically controlled

product formation

not observed

Scheme 5 Formation of indoles corresponding to thermodynamic

reaction control

D

E. S. Shchegravina et al.

Paper

Synthesis

Table 1 Indoles Synthesized via the Fischer Reaction

Entry

1

Ketone substrate

Product(s)

Overall yield (%)

73

Ratio of products

15a/15b = 1:2.3

O

15a

NH

15b

N

H

2

63

16a/16b = 1:3.2

O

NH

16a

16b

N

H

3

4

5

64

57

17a/17b = 1:1.6

18a/18b = 1:2

19a/19b = 1:2

O

NH

17a

17b

N

H

O

3

NH

N

18a

18b

H

O

2

N

NH

H

19a

19b

6

7

52

20a/20b = 1:2

O

8

9

N

NH

20a

20b

H

8

traces

O

Ph

21a

NH

Ph

8

traces

O

NH

22a

E

E. S. Shchegravina et al.

Paper

Synthesis

MeO

NHAc

proton transfer,

NHAc

MeO

OMe

[3,3']-shift

cyclization

H

R¹

NH

R²

NH

– NH₂H

R¹

H

NH₂

N

H

R²

25

R²

Intermediate 1

series "a"

O

MeO

R¹

R²

NHAc

14a

H

N

H

OMe

24

N

R¹

H

R²

MeO

NHAc

MeO

[3,3']-shift

R¹

NHAc

R¹

NH

O

proton transfer,

cyclization

OMe

R¹

H

R²

NH₂

OMe

N

H

OMe

H

– NH₂H

H

NH

N

series "b"

26

N

H

Intermediate 2

Scheme 6 Plausible explanation for the prevalent formation of indoles of series ‘b’

The results given in Table 1 show the predominance of

the indoles of type ‘b’ in the regioisomeric mixture. This

can be explained by polar interactions of the amide group

oxygen with the ammonium proton in intermediate 2

(Scheme 6) during the [3,3′]-sigmatropic rearrangement,

stabilizing this intermediate and finally leading to the pref-

erential formation of the ‘b’ isomers of the indole products.

In the absence of such an interaction, the less sterically hin-

dered isomers ‘a’ might be expected to form more easily.

However, a more bulky group at the future α-position of

the final indole moves the regioselectivity toward isomer

‘a’. Since the thermodynamically controlled product is

formed exclusively, this explains the shift of regioselectivity

between entries 2 and 3/4 in Table 1.

can be explained by the substantially different, ‘helical’ con-

formation¹⁶of the type ‘b’ compounds, possibly due to the

steric hindrance caused by the amide group.

The synthetic methodology, proposed in this work, pro-

vides the first relatively selective way leading to indole-de-

rived allocolchicines with [2,3-e] ring fusion (indoles of the

‘b’ series) instead of the more easily available [3,2-f]-fused

analogues (‘a’ type indoles).^8a,d,e

Our previous research^8aindicated that the [2,3-e] deriv-

atives exhibit significantly higher cytotoxic activity in com-

parison with [3,2-f] isomers. Indeed, compound 15b

demonstrated much higher cytotoxic activity towards HEK-

293 (human embryonic kidney) and SKOV3 (human ovarian

cancer) cell lines than its 15a analogue (Table 2). Recently, it

was shown that methylation of the N–H fragment in pyrro-

lo-allocolchicinoids significantly improves antitumor prop-

erties.^8eThus, the cytotoxic activity of methylated indole

27a (Table 2) is 3 orders of magnitude higher than that of

the non-methylated analogue 15a. At the same time, meth-

ylation of compound 15b led to a drop in the cytotoxic ac-

tivity. Presumably, the trimethyl-substituted pyrrole 27a

participates more effectively in hydrophobic interactions

with the colchicine site of tubulin than its analogue 27b,

where the alkylated pyrrole moiety is differently directed.

Despite the rather harsh reaction conditions applied in

several transformations, total racemization does not occur.

Amine 11, aryl iodide 13, and hydrazines 14a and 14b were

20

obtained as optically active nonracemic compounds ([α]_D

–84 (c 1.07, CHCl₃), –98 (c 1.54, CHCl₃), –59 (c 0.60, CHCl₃),

and –82 (c 0.50, CHCl₃), respectively).

Interestingly, in the case of type ‘b’ indoles, the opposite

sign of optical rotation in comparison with type ‘a’ indoles

20

is observed (e.g., [α]_D–28 (c 1.31, CHCl₃) for compound

15a, [α]_D²⁰+38 (c 0.40, CHCl₃) for compound 15b). This fact

F

E. S. Shchegravina et al.

Paper

Synthesis

Table 2 Cytotoxicity^aof N-Methylated 27a,b and N-Non-methylated 15a,b Indoles

Cell line

N

NH

N

H

15b

27b

15a

27a

HEK-293

SKOV3

2000

1

5

160

800

4000

2000

^aIC₅₀Values are given in nM. Each compound concentration was tested in triplicate, and the SE of each point is <10%.

In conclusion, we have developed a semisynthetic ap-

proach towards nonracemic pyrrolo-allocolchicinoids, with

both possible orientations of the heterocyclic D-fragment,

starting from naturally occurring colchicine. As the key

steps, we used Ullmann copper-mediated amination, lead-

ing to the formation of hydrazine-substituted allocolchi-

cine, followed by the Fischer reaction to create the indole

ring system. Our synthetic scheme gives an easy access to

libraries of substituted pyrrolo-allocolchicines, a new gen-

eration of tubulin-binding agents. Biological studies of the

newly prepared compounds and further development of

the demonstrated synthetic strategy are currently under-

way.

IR: 3254, 3045, 2992, 2829, 1704, 1656, 1601, 1592, 1541, 1485,

1349, 1320, 1273, 1134, 1091, 1005, 983, 955, 854, 771, 726 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 2.04 (s, 3 H, NHAc), 2.26–2.54 (m, 4 H,

H-5, H-6), 3.53 (s, 3 H, OMe), 3.88 (s, 3 H, OMe), 3.92 (s, 3 H, OMe),

4.72–4.81 (m, 1 H, H-7), 5.75 (d, J = 8.1 Hz, 1 H, H-12), 5.91 (d, J = 8.1

Hz, 1 H, H-11), 6.54 (s, 1 H, H-4), 6.87 (s, 1 H, H-8), 7.49 (d, J = 7.9 Hz,

1 H, NHAc).

Colchiceine (1.07 g, 2.68 mmol, 1 equiv), obtained in the previous

step, was dissolved in H₂O (26 mL), NaOH (1.11 g, 27.75 mmol, 10

equiv) was added, and the mixture was cooled to 0 °C. NaI (9.30 g,

62.00 mmol, 23 equiv) and I₂(2.06 g, 8.11 mmol, 3 equiv) were dis-

solved in H₂O (120 mL), and this solution was added dropwise to the

colchiceine solution within 1 h, keeping temperature below 5 °C. The

mixture was stirred for 1 h at 0 °C and monitored by TLC. After reac-

tion completion, the mixture was allowed to warm to r.t. The excess I₂

was quenched with solid Na₂S₂O₃, and the mixture was acidified with

concd HCl to pH 2, and extracted with AcOEt (3 × 50 mL). The com-

bined extract was dried over Na₂SO₄and volatiles were removed un-

der reduced pressure, giving iodocolchinol 7 as a yellow powder (1.24

g, 2.56 mmol, 95%). The product was used without further purifica-

tion.

¹H NMR and ¹³C NMR spectra were recorded on Agilent DDR2 400,

Bruker Avance DRX 500 and Bruker AV 300 spectrometers at 25 °C.

Chemical shifts (δ) are reported in ppm for a solution of the com-

pound in CDCl₃or DMSO-d₆with TMS as internal reference; J values

are in hertz. Elemental analysis was performed using an Elementar

(vario MICRO cube) apparatus, and the final compounds have a purity

of >99%. IR spectra (thin film) were detected on an IR Prestige-21

Shimadzu spectrometer. Optical rotations [α]_Dwere measured on a

PerkinElmer 341 polarimeter at 20 °C and λ = 589 nm (cuvette length:

1.0 cm, volume: 1.0 mL). Mass spectrometric analysis was performed

on a Bruker microflex LT spectrometer in positive-charged ion mode.

Separation by column chromatography was performed using Merck

Kieselgel 60 (70–230 mesh). All reactions were performed with com-

mercially available reagents (Aldrich, Alfa Aesar, Acros, Serva). Sol-

vents were purified according to standard procedures. Petroleum

ether refers to the fraction with distillation range 40–70 °C.

Mp 235–238 °C (Lit.^9a238 °C).

IR: 3256, 2989, 2930, 2849, 2250, 1647, 1595, 1538, 1433, 1371,

1321, 1276, 1191, 1156, 1049, 954, 927, 862, 791, 758, 726 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.87 (s, 3 H, NHAc), 1.88–1.93 (m, 1

H, H-6), 2.07–2.16 (m, 2 H, H-5), 2.44–2.50 (m, 1 H, H-6), 3.48 (s, 3 H,

OMe), 3.77 (s, 3 H, OMe), 3.82 (s, 3 H, OMe), 4.33–4.40 (m, 1 H, H-7),

6.76 (s, 1 H, H-4), 6.86 (s, 1 H, H-8), 7.56 (s, 1 H, H-11), 8.38 (d, J = 8.0

Hz, 1 H, NHAc), 10.28 (s, 1 H, OH).

To a mixture of iodocolchinol 7 (1.00 g, 2.06 mmol) and Zn dust (2.95

g, 45.4 mmol, 22 equiv), glacial AcOH (25 mL) was added, and the re-

sulting solution was stirred at 120 °C for 3 h. After cooling to r.t., the

mixture was poured onto ice, diluted with cold H₂O, and the solid res-

idue was filtered off and washed with AcOH. The filtrate was extract-

ed with CHCl₃(3 × 40 mL). The combined organic phase was dried

over Na₂SO₄and the solvent was removed. N-Acetylcolchinol was ob-

tained as a white powder (0.74 g, 2.06 mmol, 99%).

(aR,5S)-N-(3-Hydroxy-9,10,11-trimethoxy-6,7-dihydro-5H-diben-

zo[a,c]cyclohepten-5-yl)acetamide

The synthesis was carried out according to a literature protocol.^14b

Colchicine (1; 1.20 g, 3.00 mmol) was dissolved in glacial AcOH (11.5

mL), 0.1 N HCl (70 mL) was added, and the mixture was stirred for 3 h

at 100 °C, cooled to r.t., neutralized with NaHCO₃to pH 6 and extract-

ed with CHCl₃(3 × 60 mL). The combined organic layer was dried over

Na₂SO₄and the solvent removed under reduced pressure. Colchiceine

was obtained as yellowish-green foam (1.13 g, 2.83 mmol, 98%) and

used in the next step without further purification.

Mp 211–214 °C (Lit.¹⁷213–215 °C).

IR: 3288, 3065, 2986, 2849, 2679, 2150, 1703, 1644, 1605, 1540,

1478, 1449, 1322, 1221, 1191, 1099, 1048, 1002, 960, 926, 818, 755,

729 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.79–1.86 (m, 1 H, Н-6), 1.87 (s, 3

H, NHAc), 2.02–2.15 (m, 2 H, Н-5), 2.41–2.49 (m, 1 H, Н-6), 3.46 (s, 3

H, OMe), 3.76 (s, 3 H, OMe), 3.81 (s, 3 H, OMe), 4.42–4.51 (m, 1 H, Н-

Mp 150–151 °C (Lit.^9a150 °C).

G

E. S. Shchegravina et al.

Paper

Synthesis

7), 6.68 (dd, J = 8.3, 2.3 Hz, 1 H, Н-10), 6.74 (s, 1 H, Н-4), 6.76 (d, J = 2.3

Hz, 1 H, Н-8), 7.11 (d, J = 8.3 Hz, 1 H, Н-11), 8.33 (d, J = 8.5 Hz, 1 H,

NHAc), 9.40 (s, 1 H, OH).

Allocolchicinic Acid (10)

A Schlenk flask was charged with colchicine (1; 3.00 g, 7.50 mmol),

and a freshly prepared solution of MeONa in MeOH [Na metal (2.90 g)

dissolved in anhyd MeOH (45 mL); 17 equiv] was added via septum

under vigorous stirring. The reaction mixture was heated at 65 °C for

4 h. When the reaction was completed (TLC), MeOH was removed un-

der reduced pressure. To the residue, H₂O (15 mL) was added, and the

mixture was stirred for 20 min. The solution was acidified with concd

HCl to pH 1, and the precipitate was collected and dried in vacuo at

60 °C. Allocolchicinic acid was obtained as a pale-yellow solid in a

nearly quantitative yield (2.88 g, 7.50 mmol) and was used without

further purification.

(aR,5S)-N-(3-Trifluoromethylsulfonyloxy-9,10,11-trimethoxy-6,7-

dihydro-5H-dibenzo[a,c]cyclohepten-5-yl)acetamide (8)

N-Acetylcolchinol (200 mg, 0.56 mmol) was dissolved in anhyd CH₂-

Cl₂(15 mL). Pyridine (0.12 mL, 1.45 mmol, 2.6 equiv) was added, and

the solution was cooled to 0 °C. Triflic anhydride (0.168 mL, 1 mmol,

1.8 equiv) was added, and the mixture was stirred for 3 h, while the

temperature was allowed to rise from 0 °C to ambient. The reaction

mixture was quenched with 10% HCl (1 mL), the organic phase was

washed with sat. NaHCO₃, and the aqueous phases were reextracted

with CH₂Cl₂. The organic phases were combined and, after removal of

the volatiles, the residue was purified using column chromatography

(petroleum ether–AcOEt–EtOH, 8:1:1), giving triflate 8 as a pale-yel-

low solid (207 mg, 0.43 mmol, 76%).

Mp 260–261 °C (Lit.¹⁹260–262 °C).

IR: 3496, 2934, 2855, 1723, 1687, 1596, 1456, 1405, 1322, 1101,

1096, 997, 834, 739 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.89 (s, 3 H, NHAc), 1.92–1.98 (m, 1

H, H-6), 2.01–2.11 (m, 1 H, H-5), 2.14–2.21 (m, 1 H, H-5), 2.52–2.58

(m, 1 H, H-6), 3.50 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.84 (s, 3 H, OMe),

4.52–4.60 (m, 1 H, H-7), 6.82 (s, 1 H, H-4), 7.43 (d, J = 8.0 Hz, 1 H, H-

11), 7.87 (d, J = 8.0 Hz, 1 H, H-10), 7.97 (s, 1 H, H-8), 8.62 (d, J = 8.4 Hz,

1 H, NHAc).

Mp 165–167 °C; [α]_D²⁰–47 (c 1.12, CHCl₃).

IR: 3270, 3237, 3193, 3063, 2938, 2866, 1662, 1583, 1547, 1415,

1327, 1220, 1135, 1100, 881, 734 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.88 (s, 3 H, NHAc), 1.89–2.07 (m, 2

H, H-5, H-6), 2.15–2.27 (m, 1 H, H-5), 2.52–2.60 (m, 1 H, H-6), 3.55 (s,

3 H, OMe), 3.79 (s, 3 H, OMe), 3.85 (s, 3 H, OMe), 4.47–4.57 (m, 1 H, H-

7), 6.83 (s, 1 H, H-4), 7.34 (d, J = 2.6 Hz, 1 H, H-8), 7.43 (dd, J = 8.5, 2.6

Hz, 1 H, H-10), 7.50 (d, J = 8.5 Hz, 1 H, H-11), 8.49 (d, J = 8.3 Hz, 1 H,

NHAc).

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.50, 29.80, 38.15, 48.22, 55.87,

60.53, 60.77, 108.25, 116.68, 117.94, 118.95, 122.48, 131.82, 134.69,

134.81, 140.50, 143.66, 148.17, 150.24, 153.10, 168.60.

(aR,5S)-N-(3-Amino-9,10,11-trimethoxy-6,7-dihydro-5H-diben-

zo[a,c]cyclohepten-5-yl)acetamide (11)

Allocolchicinic acid (10; 3.00 g, 7.83 mmol) was treated with NaN₃

(1.50 g, 23.07 mmol, 3 equiv) and di-tert-butyl dicarbonate (10.20 g,

46.8 mmol, 6 equiv) in 1,4-dioxane (40 mL) at 90 °C for 2 d. The excess

NaN₃was filtered off, and the filtrate was concentrated under reduced

pressure. The residue was purified by column chromatography (pe-

troleum ether–AcOEt–EtOH, 10:1:1). Boc-Protected allocolchamine

was isolated as a white powder (2.75 g, 6.03 mmol, 77% yield).

Anal. Calcd for C₂₁H₂₂F₃NO₇S: C, 51.53; H, 4.53. Found: C, 51.30; H,

4.25.

Mp 103–105 °C; [α]_D²⁰–91 (c 2.06, CHCl₃).

(aR,5S)-N-(3-(2-(Diphenylmethylene)hydrazinyl)-9,10,11-trime-

thoxy-6,7-dihydro-5H-dibenzo[a,c]cyclohepten-5-yl)acetamide

IR: 3397, 2939, 2927, 1776, 1748, 1705, 1652, 1596, 1532, 1482,

1235, 1156, 1115, 1036, 1021, 851, 762, 732 cm^–1

.

(9)

¹H NMR (400 MHz, DMSO-d₆): δ = 1.48 (s, 9 H, NHBoc), 1.87 (s, 3 H,

NHAc), 1.90–1.98 (m, 1 H, H-6), 2.04–2.17 (m, 2 H, H-5), 2.40–2.49

(m, 1 H, H-6), 3.45 (s, 3 H, OMe), 3.77 (s, 3 H, OMe), 3.82 (s, 3 H, OMe),

4.41–4.47 (m, 1 H, H-7), 6.76 (s, 1 H, H-4), 7.18 (d, J = 8.3 Hz, 1 H, H-

11), 7.33 (dd, J = 8.3, 1.9 Hz, 1 H, H-10), 7.49 (d, J = 1.8 Hz, 1 H, H-8),

8.36 (d, J = 8.1 Hz, 1 H, NHAc), 9.36 (s, 1 H, NHBoc).

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.62, 27.40, 27.81, 28.17, 38.61,

47.85, 55.83, 60.44, 60.58, 108.13, 122.24, 123.74, 125.21, 129.67,

132.79, 134.78, 137.85, 140.53, 140.90, 150.40, 151.38, 152.60,

168.15.

Benzophenone hydrazone was synthesized according to a literature

protocol.¹⁸

Triflate 8 (40 mg, 0.08 mmol), benzophenone hydrazone (24 mg, 0.12

mmol, 1.5 equiv), Pd(OAc)₂(2 mg, 0.01 mmol, 0.1 equiv), rac-BINAP

(15 mg, 0.024 mmol, 0.3 equiv) and K₃PO₄(35 mg, 0.16 mmol, 2

equiv) were placed into an argon-filled Schlenk flask. Anhyd toluene

(5 mL) was added and the mixture was stirred at 80 °C overnight. The

solvent was removed; product 9 was obtained, after column chroma-

tography (petroleum ether–AcOEt–EtOH, 16:1:1 → 7:1:1), as a yellow

solid (6 mg, 0.01 mmol, 14%).

MALDI-MS (DCTB, pos): m/z (%) = 456.0 (100), 457.1 (61), 400.9 (53).

Mp 126–128 °C.

Anal. Calcd for C₂₅H₃₂N₂O₆: C, 65.77; H, 7.07. Found: C, 65.58; H, 6.93.

IR: 3329, 3296, 3090, 2924, 1651, 1645, 1602, 1563, 1487, 1444,

Cleavage of the Boc group of N-protected allocolchamine (2.75 g, 6.03

mmol) was carried out in a stirred mixture of concd HCl (9 mL) and

CH₂Cl₂(27 mL) at r.t. (monitored by TLC). When the reaction reached

completion (ca. 2 h), the mixture was neutralized with sat. aq NaHCO₃

to pH 8, the aqueous phase was extracted with CH₂Cl₂(3 × 100 mL),

the combined organic phase was dried over Na₂SO₄, and the solvent

was removed under reduced pressure. Allocolchamine (11) was ob-

tained as a yellow powder (2.01 g, 5.67 mmol, 94% yield).

1320, 1236, 1101, 955, 773, 764 cm^–1

.

¹H NMR (300 MHz, DMSO-d₆): δ = 1.72 (s, 3 H, NHAc), 1.84–1.95 (m, 2

H, H-5, H-6), 2.01–2.09 (m, 1 H, H-5), 2.11–2.22 (m, 1 H, H-6), 3.55 (s,

3 H, OMe), 3.78 (s, 3 H, OMe), 3.84 (s, 3 H, OMe), 4.44–4.58 (m, 1 H, H-

7), 6.82 (s, 1 H, H-4), 7.47 (d, J = 6.0 Hz, 2 H, phenyl rings), 7.51–7.74

(m, 12 H, phenyl rings, NH-hydrazone, H-11, H-10), 8.44 (d, J = 8.2 Hz,

1 H, NHAc).

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.43, 27.97, 48.28, 55.88, 60.52,

60.88, 69.80, 108.17, 123.16, 126.96, 127.64, 127.99, 128.71, 128.80,

128.82, 131.43, 131.48, 131.52, 131.57, 132.00, 135.01, 140.48,

150.36, 153.10, 168.38.

Mp 154–156 °C; [α]_D²⁰–84 (c 1.07, CHCl₃).

IR: 3370, 3285, 2930, 2860, 1661, 1634, 1560, 1482, 1477, 1321,

1143, 1107, 998, 748 cm^–1

.

Anal. Calcd for C₃₃H₃₃N₃O₄: C, 74.00; H, 6.21. Found: C, 73.77; H, 6.50.

H

E. S. Shchegravina et al.

Paper

Synthesis

¹H NMR (500 MHz, DMSO-d₆): δ = 1.86 (s, 3 H, NHAc), 1.88–1.94 (m, 1

H, H-6), 2.06–2.14 (m, 2 H, H-5), 2.38–2.46 (m, 1 H, H-6), 3.45 (s, 3 H,

OMe), 3.75 (s, 3 H, OMe), 3.80 (s, 3 H, OMe), 4.41–4.47 (m, 1 H, H-7),

5.03 (br s, 2 H, NH₂), 6.48 (dd, J = 8.1, 2.3 Hz, 1 H, H-10), 6.54 (d, J = 2.2

Hz, 1 H, H-8), 6.70 (s, 1 H, H-4), 6.97 (d, J = 8.1 Hz, 1 H, H-11), 8.25 (d,

J = 8.5 Hz, 1 H, NHAc).

¹³C NMR (126 MHz, DMSO-d₆): δ = 22.66, 30.21, 38.48, 48.12, 55.78,

60.15, 60.41, 107.89, 108.65, 111.70, 121.28, 125.37, 129.80, 134.61,

140.52, 140.76, 147.49, 150.26, 151.34, 168.05.

Compound 14a

Mp 112–114 °C; [α]_D²⁰–59 (c 0.60, CHCl₃).

IR: 3467, 2932, 1701, 1685, 1654, 1482, 1368, 1349, 1327, 1105,

1020, 820, 725 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.46 (s, 9 H, NBoc), 1.87 (s, 3 H,

NHAc), 1.88–1.96 (m, 1 H, H-6), 2.02–2.19 (m, 2 H, H-5), 2.50–2.57

(m, 1 H, H-6), 3.52 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.83 (s, 3 H, OMe),

4.46–4.61 (m, 1 H, H-7), 5.08 (s, 2 H, NH₂), 6.77 (s, 1 H, H-4), 7.21 (d,

J = 8.4 Hz, 1 H, H-10), 7.37 (d, J = 8.4 Hz, 1 H, H-11), 7.95 (s, 1 H, H-8),

8.43 (d, J = 8.3 Hz, 1 H, NHAc).

MALDI-MS (pos): m/z (%) = 355.8 (100), 297.8 (31), 326.7 (8).

¹³C NMR (101 MHz, DMSO-d₆): δ = 27.95, 30.76, 35.77, 38.53, 48.21,

55.82, 60.51, 60.57, 80.29, 108.03, 118.05, 120.71, 124.24, 128.89,

134.84, 139.90, 140.55, 142.66, 150.37, 152.29, 154.56, 162.30,

168.25.

Anal. Calcd for C₂₀H₂₄N₂O₄: C, 67.40; H, 6.79. Found: C, 67.28; H, 6.95.

(aR,5S)-N-(3-Iodo-9,10,11-trimethoxy-6,7-dihydro-5H-diben-

zo[a,c]cyclohepten-5-yl)acetamide (13)

MALDI-MS (pos): m/z (%) = 494.0 (100) [M + Na⁺], 510.0 (79) [M + K⁺],

394.0 (71), 377.0 (46), 410.0 (32).

Amine 11 (1.00 g, 2.81 mmol) was dissolved in concd HCl (5 mL), and

the solution was cooled to 0 °C. A solution of NaNO₂(210 mg, 3.04

mmol, 1.1 equiv) in H₂O (2 mL) was added to the cold mixture. The

mixture was stirred at 0 °C for 30 min, and a cold solution of KI (4.64

g, 27.95 mmol, 10 equiv) in H₂O (15 mL) was added dropwise. The

mixture was stirred for 30 h at r.t. The excess I₂was quenched with

solid Na₂S₂O₃, and the mixture was extracted with CH₂Cl₂(3 × 50 mL).

The combined organic phase was washed with brine, dried over Na₂-

SO₄and concentrated under reduced pressure. The product was iso-

lated by column chromatography (petroleum ether–AcOEt–EtOH,

8:1:1) as a pale-yellow solid (0.83 g, 1.78 mmol, 64%).

Anal. Calcd for C₂₅H₃₃N₃O₆: C, 63.68; H, 7.05. Found: C, 63.44; H, 7.29.

Compound 14b

Mp 110–113 °C; [α]_D²⁰–82 (c 0.50, CHCl₃).

IR: 3405, 2930, 1742, 1647, 1600, 1482, 1476, 1454, 1403, 1324,

1234, 1150, 1101, 1009, 736 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.49 (s, 9 H, NHBoc), 1.87 (s, 3 H,

NHAc), 1.89–1.96 (m, 1 H, H-6), 2.03–2.20 (m, 3 H, H-6, H-5), 3.45 (s, 3

H, OMe), 3.76 (s, 3 H, OMe), 3.82 (s, 3 H, OMe), 4.38–4.48 (m, 1 H, H-

7), 6.76 (s, 1 H, H-4), 7.18 (d, J = 8.3 Hz, 1 H, H-10), 7.31 (d, J = 8.1 Hz,

1 H, H-11), 7.34 (s, 1 H, NHNHBoc), 7.48 (s, 1 H, H-8), 8.36 (d, J = 8.0

Hz, 1 H, NHAc), 9.36 (s, 1 H, NHBoc).

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.67, 27.40, 28.17, 38.13, 48.45,

55.82, 60.45, 60.53, 78.85, 107.99, 113.13, 115.97, 124.40, 127.62,

129.56, 134.78, 138.41, 140.53, 140.85, 150.34, 152.08, 152.83,

168.36.

Mp 137–139 °C; [α]_D²⁰–98 (c 1.54, CHCl₃).

IR: 3307, 2930, 1654, 1531, 1453, 1406, 1323, 1106, 1096, 998, 832,

739 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.80–1.88 (m, 1 H, H-6), 1.88 (s, 3

H, NHAc), 1.98–2.08 (m, 1 H, H-5), 2.11–2.21 (m, 1 H, H-5), 2.52–2.54

(m, 1 H, H-6), 3.49 (s, 3 H, OMe), 3.77 (s, 3 H, OMe), 3.83 (s, 3 H, OMe),

4.45–4.54 (m, 1 H, H-7), 6.80 (s, 1 H, H-4), 7.11 (d, J = 8.6 Hz, 1 H, H-

10), 7.65 (s, 1 H, H-8), 7.67 (d, J = 8.5 Hz, 1 H, H-11), 8.42 (d, J = 8.5 Hz,

1 H, NHAc).

MALDI-MS (pos): m/z (%) = 423.0 (100), 494.0 (44) [M + Na⁺], 439.0

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.67, 29.88, 38.50, 47.82, 55.85,

60.55, 60.72, 93.31, 108.20, 123.30, 131.69, 131.75, 133.68, 134.73,

134.82, 140.55, 142.80, 150.16, 152.78, 168.48.

(33).

Anal. Calcd for C₂₅H₃₃N₃O₆: C, 63.68; H, 7.05. Found: C, 63.41; H, 7.38.

MALDI-MS (pos): m/z (%) = 489.8 (100) [M + Na⁺], 505.8 (84) [M + K⁺],

Pyrrolo-allocolchicinoids 15–22; General Procedure

152.8 (32), 365.0 (28), 408.9 (23), 466.9 (20).

Hydrazine 14a (50 mg, 0.11 mmol, 1 equiv) and p-TsOH·H₂O (51 mg,

0.26 mmol, 2.5 equiv) were dissolved in a small amount of EtOH, a

ketone (0.33 mmol, 3 equiv) was added to the mixture, and the solu-

tion was stirred for 8 h at 100 °C (the reaction was carried out in a

vial). When the reaction was completed (TLC), the volatiles were re-

moved, and the residue was purified by chromatography (petroleum

ether–AcOEt–EtOH, 9:1:1). The corresponding pyrrolo-allocolchici-

noids were generally obtained as solids. For atomic numeration for

NMR assignments, see the Supporting Information.

Anal. Calcd for C₂₀H₂₂INO₄: C, 51.41; H, 4.75. Found: C, 51.19; H, 4.91.

(aR,5S)-N-(3-(1-(tert-Butoxycarbonyl)hydrazinyl)-9,10,11-trime-

thoxy-6,7-dihydro-5H-dibenzo[a,c]cyclohepten-5-yl)acetamide

(14a) and (aR,5S)-N-(3-(2-(tert-Butoxycarbonyl)hydrazinyl)-

9,10,11-trimethoxy-6,7-dihydro-5H-dibenzo[a,c]cyclohepten-5-

yl)acetamide (14b)

Into a Schlenk flask under argon was placed aryl iodide 13 (0.50 g,

1.07 mmol), CuI (10 mg, 0.05 mmol, 0.05 equiv), 1,10-phenanthroline

(36 mg, 0.20 mmol, 0.2 equiv), Cs₂CO₃(700 mg, 2.14 mmol, 2 equiv)

and anhyd DMF (15 mL). tert-Butoxycarbonyl hydrazide (183 mg, 1.39

mmol, 1.3 equiv) was dissolved in DMF (2 mL) and added into the

flask. The mixture was stirred overnight at 80 °C, then the solvent was

removed under reduced pressure. H₂O (30 mL) was added, and the

mixture was extracted with CH₂Cl₂(3 × 50 mL). The combined organ-

ic phase was washed with brine, dried over Na₂SO₄and concentrated

under reduced pressure. Compounds 14a and 14b were isolated by

column chromatography (petroleum ether–AcOEt–EtOH, 9:1:1) as

pale-yellow solids (14a: 247 mg, 0.52 mmol, 49%; 14b: 105 mg, 0.22

mmol, 21%).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-2′′,3′′-dimethylindole (15a)

Isolated as a white solid (10 mg, 0.02 mmol, 22%).

Mp 132–134 °C; [α]_D²⁰–28 (c 1.31, CHCl₃).

IR: 3397, 2921, 1650, 1453, 1438, 1405, 1397, 1348, 1238, 740 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.78–1.87 (m, 1 H, H-6), 1.89 (s, 3

H, NHAc), 1.97–2.12 (m, 2 H, H-5), 2.13 (s, 3 H, C10-CH₃), 2.30 (s, 3 H,

C9-CH₃), 2.42–2.48 (m, 1 H, H-6), 3.41 (s, 3 H, OMe), 3.79 (s, 3 H,

I

E. S. Shchegravina et al.

Paper

Synthesis

OMe), 3.83 (s, 3 H, OMe), 4.62 (dd, J = 16.6, 9.6 Hz, 1 H, H-7), 6.74 (s, 1

H, H-4), 7.19 (s, 1 H, H-11), 7.26 (s, 1 H, H-8), 8.42 (d, J = 8.7 Hz, 1 H,

NHAc), 10.61 (s, 1 H, NH-pyrrole).

¹³C NMR (101 MHz, DMSO-d₆): δ = 8.44, 11.23, 22.75, 30.34, 38.81,

48.29, 55.80, 60.35, 60.56, 104.66, 104.89, 107.78, 118.26, 124.07,

126.35, 127.36, 131.05, 132.92, 134.55, 134.77, 140.59, 150.46,

151.58, 168.03.

IR: 3404, 3056, 2978, 2934, 1684, 1635, 1508, 1456, 1244, 1093, 739

cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.04 (t, J = 7.5 Hz, 3 H, CH₃-side

chain), 1.45 (s, 3 H, NHAc), 1.68–1.82 (m, 2 H, H-5), 1.87–1.99 (m, 2 H,

H-6), 2.42 (s, 3 H, C8-CH₃), 2.70 (q, J = 7.5 Hz, 2 H, CH₂-side chain),

3.38 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.85 (s, 3 H, OMe), 5.86 (d, J = 7.8

Hz, 1 H, NHAc), 5.94 (t, J = 7.6 Hz, 1 H, H-7), 6.83 (s, 1 H, H-4), 7.00 (d,

J = 8.3 Hz, 1 H, H-10), 7.17 (d, J = 8.3 Hz, 1 H, H-11), 10.72 (s, 1 H, NH-

pyrrole).

¹³C NMR (101 MHz, DMSO-d₆): δ = 7.29, 13.23, 17.80, 21.66, 29.26,

33.87, 45.81, 55.83, 59.60, 60.64, 105.26, 108.60, 108.65, 123.43,

124.65, 125.78, 127.67, 131.89, 133.50, 134.70, 135.29, 140.95,

150.16, 151.64, 166.95.

MALDI-MS (pos): m/z (%) = 408.0 (100), 350.0 (36), 154.8 (18).

Anal. Calcd for C₂₄H₂₈N₂O₄: C, 70.57; H, 6.91. Found: C, 70.34; H, 7.15.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-2′′,3′′-dimethylindole (15b)

Isolated as a white solid (22 mg, 0.05 mmol, 51%).

Mp 125–127 °C; [α]_D²⁰+38 (c 0.40, CHCl₃).

MALDI-MS (pos): m/z (%) = 422.2 (100), 406.2 (73), 379.2 (51), 364.2

(45), 334.2 (34).

IR: 3428, 2921, 1651, 1485, 1399, 1321, 1232, 1143, 1105, 1102, 734

Anal. Calcd for C₂₅H₃₀N₂O₄: C, 71.07; H, 7.16. Found: C, 70.87; H, 7.34.

cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.46 (s, 3 H, NHAc), 2.14–2.21 (m, 2

H, H-5), 2.31 (s, 3 H, C8-CH₃), 2.41 (s, 3 H, C9-CH₃), 2.42–2.49 (m, 2 H,

H-6), 3.38 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.85 (s, 3 H, OMe), 5.86 (d,

J = 7.8 Hz, 1 H, NHAc), 5.90–5.96 (m, 1 H, H-7), 6.83 (s, 1 H, H-4), 6.99

(d, J = 8.3 Hz, 1 H, H-10), 7.15 (d, J = 8.3 Hz, 1 H, H-11), 10.73 (s, 1 H,

NH-pyrrole).

¹³C NMR (101 MHz, DMSO-d₆): δ = 11.19, 11.84, 22.71, 30.24, 34.19,

45.81, 55.83, 59.60, 60.64, 105.26, 108.60, 108.65, 123.43, 124.65,

125.78, 127.67, 131.79, 131.83, 134.78, 135.29, 140.95, 150.16,

151.64, 166.95.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-3′′-isopropyl-2′′-methylindole (17a)

Isolated as a beige solid (12 mg, 0.03 mmol, 25%).

Mp 109–110 °C; [α]_D²⁰–27 (c 1.15, CHCl₃).

IR: 3263, 3209, 2934, 1652, 1596, 1456, 1404, 1283, 1270, 1101,

1088, 733 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.30 (t, J = 7.0 Hz, 3 H, CH₃-side

chain), 1.35 (t, J = 7.0 Hz, 3 H, CH₃-side chain), 1.81–1.86 (m, 1 H, H-6),

1.88 (s, 3 H, NHAc), 2.10–2.15 (m, 2 H, H-5), 2.32 (s, 3 H, C9-CH₃),

2.44–2.48 (m, 1 H, H-6), 3.09–3.15 (m, 1 H, CH-side chain), 3.48 (s, 3

H, OMe), 3.78 (s, 3 H, OMe), 3.83 (s, 3 H, OMe), 4.57–4.62 (m, 1 H, H-

7), 6.74 (s, 1 H, H-4), 7.19 (s, 1 H, H-8), 7.48 (s, 1 H, H-11), 8.41 (d, J =

8.6 Hz, 1 H, NHAc), 10.58 (s, 1 H, NH-pyrrole).

MALDI-MS (pos): m/z (%) = 408.4 (100), 367.4 (33), 350.4 (16), 377.4

(11).

Anal. Calcd for C₂₄H₂₈N₂O₄: C, 70.57; H, 6.91. Found: C, 70.39; H, 7.20.

¹³C NMR (101 MHz, DMSO-d₆): δ = 22.72, 28.52, 30.11, 30.35, 34.02,

38.60, 49.60, 55.90, 60.61, 60.69, 108.10, 123.04, 124.39, 125.18,

126.03, 127.03, 129.46, 132.73, 133.97, 134.87, 140.19, 140.58,

150.35, 152.50, 168.48.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-2′′-ethyl-3′′-methylindole (16a)

Isolated as a pale-beige solid (7 mg, 0.02 mmol, 15%).

Mp 127–128 °C; [α]_D²⁰–36 (c 0.97, CHCl₃).

MALDI-MS (pos): m/z (%) = 436.2 (100), 422.2 (87), 393.2 (42), 378.2

IR: 3214, 3174, 2901, 1627, 1581, 1524, 1426, 1246, 1175, 1138,

(33).

1093, 748 cm^–1

.

Anal. Calcd for C₂₆H₃₂N₂O₄: C, 71.53; H, 7.39. Found: C, 71.29; H, 7.73.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.22 (t, J = 7.5 Hz, 3 H, CH₃-side

chain), 1.79–1.86 (m, 1 H, H-6), 1.89 (s, 3 H, NHAc), 2.01–2.13 (m, 2 H,

H-5), 2.14 (s, 3 H, C10-CH₃), 2.42–2.48 (m, 1 H, H-6), 2.69 (q, J = 7.5

Hz, 2 H, CH₂-side chain), 3.41 (s, 3 H, OMe), 3.79 (s, 3 H, OMe), 3.83 (s,

3 H, OMe), 4.57–4.66 (m, 1 H, H-7), 6.74 (s, 1 H, H-4), 7.21 (s, 1 H, H-

11), 7.27 (s, 1 H, H-8), 8.43 (d, J = 8.6 Hz, 1 H, NHAc), 10.62 (s, 1 H, NH-

pyrrole).

¹³C NMR (101 MHz, DMSO-d₆): δ = 8.36, 14.31, 18.87, 22.74, 30.34,

38.74, 48.35, 55.81, 60.38, 60.57, 103.98, 104.79, 107.81, 118.42,

124.08, 126.37, 127.28, 133.04, 134.57, 134.78, 136.98, 140.60,

150.47, 151.59, 168.03.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-3′′-isopropyl-2′′-methylindole (17b)

Isolated as a pale-beige solid (18 mg, 0.04 mmol, 39%).

Mp 107–109 °C; [α]_D²⁰+56 (c 0.97, CHCl₃).

IR: 3303, 3271, 2978, 2936, 1657, 1616, 1525, 1397, 1231, 1142, 744

cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 0.94 (t, J = 6.6 Hz, 6 H, 2 CH₃-side

chain), 1.77–1.87 (m, 1 H, H-6), 1.88 (s, 3 H, NHAc), 1.96–2.05 (m, 1 H,

H-5), 2.05–2.25 (m, 2 H, H-6, H-5), 2.30 (s, 3 H, C9-CH₃), 3.07–3.17 (m,

1 H, CH-side chain), 3.48 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.84 (s, 3 H,

OMe), 5.64–5.71 (m, 1 H, H-7), 5.97 (d, J = 4.1 Hz, 1 H, NHAc), 6.79 (s,

1 H, H-4), 7.17 (d, J = 7.6 Hz, 1 H, H-10), 7.24 (d, J = 7.4 Hz, 1 H, H-11),

10.57 (s, 1 H, NH-pyrrole).

MALDI-MS (pos): m/z (%) = 422.2 (100), 379.2 (47), 364.2 (37), 334.2

(27).

Anal. Calcd for C₂₅H₃₀N₂O₄: C, 71.07; H, 7.16. Found: C, 70.81; H, 7.45.

¹³C NMR (101 MHz, DMSO-d₆): δ = 21.19, 23.02, 34.01, 34.02, 38.60,

42.26, 46.85, 50.52, 52.35, 54.95, 108.36, 112.45, 118.22, 122.67,

128.88, 129.22, 129.86, 131.31, 133.94, 136.73, 149.49, 155.10,

157.57, 168.16, 172.17.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-2′′-ethyl-3′′-methylindole (16b)

Isolated as a white solid (21 mg, 0.05 mmol, 48%).

Mp 110–112 °C; [α]_D²⁰+45 (c 1.02, CHCl₃).

MALDI-MS (pos): m/z (%) = 436.2 (100), 393.2 (37), 378.2 (32), 348.2

(25), 420.2 (16).

J

E. S. Shchegravina et al.

Paper

Synthesis

Anal. Calcd for C₂₆H₃₂N₂O₄: C, 71.53; H, 7.39. Found: C, 71.34; H, 7.76.

¹³C NMR (101 MHz, DMSO-d₆): δ = 13.84, 16.14, 22.76, 22.91, 28.51,

34.01, 42.26, 46.84, 49.59, 55.84, 60.44, 60.58, 104.91, 107.85, 111.94,

118.58, 123.99, 126.19, 126.31, 133.03, 134.80, 134.88, 140.62,

150.44, 151.62, 168.10, 172.20.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-2′′-methyl-3′′-propylindole (18a)

MALDI-MS (pos): m/z (%) = 450.2 (100), 434.2 (88), 422.2 (63), 393.2

Isolated as a white solid (9 mg, 0.02 mmol, 19%).

(41), 407.2 (35), 362.2 (19).

Mp 115–118 °C; [α]_D²⁰–42 (c 0.86, CHCl₃).

Anal. Calcd for C₂₇H₃₄N₂O₄: C, 71.97; H, 7.61. Found: C, 71.73; H, 7.94.

IR: 3274, 3263, 2928, 2864, 1653, 1629, 1406, 1211, 1107, 759 cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 0.84 (t, J = 3.6 Hz, 3 H, CH₃-side

chain), 1.26–1.32 (m, 4 H, CH₂CH₂-side chain), 1.81–1.86 (m, 1 H, H-

6), 1.88 (s, 3 H, NHAc), 2.03–2.13 (m, 2 H, H-5), 2.30 (s, 3 H, C9-CH₃),

2.43–2.48 (m, 1 H, H-6), 3.43 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.83 (s,

3 H, OMe), 4.57–4.64 (m, 1 H, H-7), 6.74 (s, 1 H, H-4), 7.19 (s, 1 H, H-

8), 7.31 (s, 1 H, H-11), 8.42 (d, J = 8.6 Hz, 1 H, NHAc), 10.61 (s, 1 H, NH-

pyrrole).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-3′′-ethyl-2′′-propylindole (19b)

Isolated as a pale-beige solid (18 mg, 0.04 mmol, 38%).

Mp 97–99 °C; [α]_D²⁰+50 (c 1.16, CHCl₃).

IR: 3390, 3366, 3342, 2957, 1653, 1597, 1456, 1238, 1098, 1004, 744

cm^–1

.

¹³C NMR (101 MHz, DMSO-d₆): δ = 13.84, 16.14, 17.04, 22.76, 22.91,

31.26, 34.01, 55.84, 57.84, 60.44, 60.58, 104.91, 107.85, 111.94,

118.58, 123.99, 126.19, 126.31, 133.03, 134.77, 134.80, 134.88,

140.62, 150.44, 151.62, 172.20.

¹H NMR (400 MHz, DMSO-d₆): δ = 0.88–0.93 (m, 6 H, 2 CH₃-side

chains), 1.11–1.13 (m, 2 H, C9-CH₂CH₂), 1.18 (s, 3 H, NHAc), 1.61–1.69

(m, 4 H, C10-CH₂, C9-CH₂CH₂), 2.61–2.66 (m, 4 H, H-5, H-6), 3.27 (s, 3

H, OMe), 3.69 (s, 3 H, OMe), 3.79 (s, 3 H, OMe), 6.09 (dt, J = 10.6, 5.3

Hz, 1 H, H-7), 6.58 (d, J = 10.5 Hz, 1 H, NHAc), 6.71 (s, 1 H, H-4), 7.16

(d, J = 4.1 Hz, 1 H, H-10), 7.65 (d, J = 4.3 Hz, 1 H, H-11), 10.60 (s, 1 H,

NH-pyrrole).

MALDI-MS (pos): m/z (%) = 436.2 (100), 420.2 (79), 393.2 (42), 406.2

(18), 379.2 (10).

Anal. Calcd for C₂₆H₃₂N₂O₄: C, 71.53; H, 7.39. Found: C, 71.27; H, 7.80.

¹³C NMR (101 MHz, DMSO-d₆): δ = 14.01, 16.63, 22.76, 22.94, 28.52,

30.35, 34.02, 46.85, 52.35, 55.87, 59.71, 60.66, 108.53, 109.01, 112.15,

123.57, 124.73, 127.74, 131.26, 135.03, 135.23, 136.30, 140.96,

150.12, 151.68, 166.99, 172.17.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-2′′-methyl-3′′-propylindole (18b)

Isolated as a white solid (18 mg, 0.04 mmol, 38%).

Mp 102–104 °C; [α]_D²⁰+34 (c 0.67, CHCl₃).

MALDI-MS (pos): m/z (%) = 450.2 (100), 434.2 (97), 418.2 (57), 407.2

(42), 392.2 (26).

IR: 3295, 3270, 2935, 1652, 1641, 1549, 1428, 1273, 1141, 1042, 740

Anal. Calcd for C₂₇H₃₄N₂O₄: C, 71.97; H, 7.61. Found: C, 71.86; H, 7.77.

cm^–1

.

¹H NMR (400 MHz, DMSO-d₆): δ = 0.87 (t, J = 6.5 Hz, 3 H, CH₃-side

chain), 1.32–1.37 (m, 4 H, CH₂CH₂-side chain), 1.46 (s, 3 H, NHAc),

2.16–2.27 (m, 2 H, H-5), 2.30 (s, 3 H, C9-CH₃), 2.41–2.46 (m, 1 H, H-6),

2.55–2.64 (m, 1 H, H-6), 3.40 (s, 3 H, OMe), 3.77 (s, 3 H, OMe), 3.85 (s,

3 H, OMe), 5.75 (t, J = 7.1 Hz, 1 H, H-7), 5.82 (d, J = 6.8 Hz, 1 H, NHAc),

6.82 (s, 1 H, H-4), 6.98 (d, J = 8.3 Hz, 1 H, H-10), 7.17 (d, J = 8.3 Hz, 1 H,

H-11), 10.78 (s, 1 H, NH-pyrrole).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-2′′-methyl-3′′-nonylindole (20a)

Isolated as a pale-yellow oil (9 mg, 0.02 mmol, 17%).

[α]_D²⁰–49 (c 1.25, CHCl₃).

IR: 3389, 3333, 3258, 2934, 1651, 1598, 1490, 1405, 1314, 1193,

1141, 1001, 751 cm^–1

.

¹³C NMR (101 MHz, DMSO-d₆): δ = 14.01, 16.63, 22.76, 22.94, 28.52,

34.02, 45.93, 55.87, 57.85, 59.71, 60.66, 108.53, 109.01, 112.15,

123.57, 124.73, 127.74, 131.26, 135.03, 135.23, 136.30, 140.96,

150.12, 151.68, 166.99, 172.17.

¹H NMR (400 MHz, DMSO-d₆): δ = 0.83 (t, J = 5.9 Hz, 3 H, C10-CH₃),

1.19–1.34 (m, 12 H, C10-side chain), 1.49–1.57 (m, 4 H, C10-CH₂CH₂),

1.78–1.86 (m, 1 H, H-6), 1.88 (s, 3 H, NHAc), 1.98–2.21 (m, 3 H, H-6,

H-5), 2.30 (s, 3 H, C9-CH₃), 3.42 (s, 3 H, OMe), 3.78 (s, 3 H, OMe), 3.83

(s, 3 H, OMe), 4.56–4.63 (m, 1 H, H-7), 6.74 (s, 1 H, H-4), 7.18 (s, 1 H,

H-8), 7.30 (s, 1 H, H-11), 8.41 (d, J = 8.7 Hz, 1 H, NHAc), 10.60 (s, 1 H,

NH-pyrrole).

MALDI-MS (pos): m/z (%) = 436.2 (100), 378.2 (51), 393.2 (47), 348.2

(34), 406.2 (8).

Anal. Calcd for C₂₆H₃₂N₂O₄: C, 71.53; H, 7.39. Found: C, 71.38; H, 7.44.

¹³C NMR (101 MHz, DMSO-d₆): δ = 11.44, 14.13, 22.27, 22.86, 28.51,

28.60, 30.34, 30.51, 30.64, 31.26, 31.42, 34.01, 49.59, 52.34, 55.97,

60.49, 60.71, 104.88, 107.95, 110.52, 118.58, 124.14, 126.37, 126.88,

131.15, 132.93, 134.71, 134.94, 140.69, 150.55, 151.73, 168.45.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-3′′-ethyl-2′′-propylindole (19a)

Isolated as a white solid (9 mg, 0.02 mmol, 19%).

MALDI-MS (pos): m/z (%) = 520.1 (100), 462.3 (93), 504.3 (55), 406.1

(51), 477.3 (35), 421.1 (27).

Mp 102–104 °C; [α]_D²⁰–35 (c 1.02, CHCl₃).

IR: 3273, 3264, 2934, 1652, 1549, 1426, 1404, 1236, 1087, 732 cm^–1

¹H NMR (400 MHz, DMSO-d₆): δ = 0.89–0.94 (m, 3 H, C10-CH₃), 1.11–

1.16 (m, 3 H, C9-CH₃), 1.60–1.68 (m, 2 H, C9-CH₂CH₂), 1.87 (s, 3 H,

NHAc), 1.94–2.21 (m, 4 H, H-5, H-6), 2.57–2.68 (m, 4 H, C9-CH₂CH₂,

C10-CH₂), 3.44 (s, 3 H, OMe), 3.77 (s, 3 H, OMe), 3.81 (s, 3 H, OMe),

4.53–4.61 (m, 1 H, H-7), 6.73 (s, 1 H, H-4), 7.18 (s, 1 H, H-8), 7.32 (s, 1

H, H-11), 8.44 (d, J = 7.7 Hz, 1 H, NHAc), 10.56 (s, 1 H, NH-pyrrole).

.

Anal. Calcd for C₃₂H₄₄N₂O₄: C, 73.81; H, 8.52. Found: C, 73.66; H, 8.82.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-2′′-methyl-3′′-nonylindole (20b)

Isolated as a pale-yellow oil (19 mg, 0.04 mmol, 35%).

[α]_D²⁰+29 (c 0.48, CHCl₃).

IR: 3322, 3288, 2937, 2690, 1684, 1602, 1456, 1275, 1138, 1093, 751

cm^–1

.

K

E. S. Shchegravina et al.

Paper

Synthesis

¹H NMR (400 MHz, DMSO-d₆): δ = 0.83 (t, J = 4.4 Hz, 3 H, C8-CH₃),

1.13–1.42 (m, 12 H, C8-side chain), 1.44 (s, 3 H, NHAc), 1.51–1.59 (m,

4 H, C8-CH₂CH₂), 2.28 (s, 3 H, C9-CH₃), 2.37–2.46 (m, 2 H, H-5), 2.51–

2.61 (m, 2 H, H-6), 3.38 (s, 3 H, OMe), 3.75 (s, 3 H, OMe), 3.83 (s, 3 H,

OMe), 5.71 (d, J = 7.4 Hz, 1 H, H-7), 5.81 (d, J = 7.4 Hz, 1 H, NHAc), 6.80

(s, 1 H, H-4), 6.95 (d, J = 8.3 Hz, 1 H, H-10), 7.15 (d, J = 8.3 Hz, 1 H, H-

11), 10.76 (s, 1 H, NH-pyrrole).

¹³C NMR (101 MHz, DMSO-d₆): δ = 10.70, 13.39, 21.53, 22.12, 27.77,

27.86, 29.61, 29.90, 30.52, 30.68, 48.85, 51.60, 55.23, 59.76, 60.27,

103.14, 107.22, 109.78, 117.74, 123.40, 125.63, 126.14, 130.41,

132.19, 133.98, 134.20, 139.96, 150.99, 157.90, 161.71.

Mp 122–124 °C; [α]_D²⁰–41 (c 0.51, CHCl₃).

IR: 3295, 2925, 1480, 1462, 1456, 1452, 1318, 1137, 1103, 1098, 1085

cm^–1

¹H NMR (400 MHz, DMSO-d₆): δ = 1.75–1.87 (m, 2 H, H-5, H-6), 1.92

(s, 3 H, NHAc), 2.00–2.08 (m, 1 H, H-5), 2.17 (s, 3 H, C9-CH₃), 2.33 (s, 3

H, C10-CH₃), 2.41–2.48 (m, 1 H, H-6), 3.50 (s, 3 H, OMe), 3.65 (s, 3 H,

NMe), 3.79 (s, 3 H, OMe), 3.83 (s, 3 H, OMe), 4.59–4.73 (m, 1 H, H-7),

6.75 (s, 1 H, H-4), 7.27 (s, 1 H, H-11), 7.30 (s, 1 H, H-8), 8.40 (d, J = 8.5

Hz, 1 H, NHAc).

¹³C NMR (101 MHz, DMSO-d₆): δ = 8.80, 9.92, 22.88, 29.43, 30.34,

48.38, 55.84, 60.38, 60.63, 69.82, 103.04, 104.95, 107.88, 118.53,

124.37, 126.20, 126.40, 132.76, 133.13, 134.79, 135.56, 140.62,

150.49, 151.69, 168.33.

.

MALDI-MS (pos): m/z (%) = 520.3 (100), 462.3 (98), 505.3 (57), 406.1

(43), 477.3 (36).

Anal. Calcd for C₃₂H₄₄N₂O₄: C, 73.81; H, 8.52. Found: C, 73.49; H, 8.79.

MALDI-MS (pos): m/z (%) = 422.2 (100), 408.2 (79), 379.2 (55), 364.2

(39), 406.2 (24), 360.2 (18).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-2′′-phenylindole (21a)

Anal. Calcd for C₂₅H₃₀N₂O₄: C, 71.07; H, 7.16. Found: C, 71.19; H, 7.32.

Isolated as a colorless oil (traces).

[α]_D²⁰–19 (c 0.73, CHCl₃).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[2,3-e]1H-N, 2′′,3′′-trimethylindole (27b)

IR: 3304, 2953, 2912, 1651, 1592, 1495, 1417, 1324, 1085, 749 cm^–1

.

Isolated as a white solid (28 mg, 0.07 mmol, 94%).

Mp 147–149 °C; [α]_D²⁰+74 (c 0.43, CHCl₃).

¹H NMR (400 MHz, DMSO-d₆): δ = 1.88 (s, 3 H, NHAc), 2.01–2.05 (m, 2

H, H-5), 2.15–2.17 (m, 2 H, H-6), 3.48 (s, 3 H, OMe), 3.78 (s, 3 H, OMe),

3.84 (s, 3 H, OMe), 4.53–4.56 (m, 1 H, H-7), 6.75 (s, 1 H, H-4), 7.18 (t,

J = 8.3 Hz, 1 H, 3′-H phenyl subst.), 7.30–7.32 (m, 6 H, H-8, H-11; H-1′,

H-2′, H-4′, H-5′ phenyl subst.), 8.40 (d, J = 4.0 Hz, 1 H, H-10), 8.42 (d,

J = 3.5 Hz, 1 H, NHAc), 9.38 (s, 1 H, NH-pyrrole).

IR: 3307, 2918, 1669, 1455, 1445, 1398, 1321, 1116, 1090, 788, 736

cm^–1

.

¹H NMR (400 MHz, CD₃OD): δ = 1.57 (s, 3 H, NHAc), 2.21–2.31 (m, 1 H,

H-5), 2.36 (s, 3 H, C8-CH₃), 2.38–2.48 (m, 2 H, H-5, H-6), 2.51 (s, 3 H,

C9-CH₃), 2.52–2.58 (m, 1 H, H-6), 3.50 (s, 3 H, OMe), 3.65 (s, 3 H,

NMe), 3.88 (s, 3 H, OMe), 3.91 (s, 3 H, OMe), 6.07 (d, J = 7.7 Hz, 1 H,

NHAc), 6.13 (t, J = 7.2 Hz, 1 H, H-7), 6.82 (s, 1 H, H-4), 7.18 (d, J = 8.4

Hz, 1 H, H-11), 7.24 (d, J = 8.5 Hz, 1 H, H-10).

MALDI-MS (pos): m/z (%) = 456.2 (100), 440.2 (86), 413.2 (48), 397.2

(31), 368.2 (9).

Anal. Calcd for C₂₈H₂₈N₂O₄: C, 73.66; H, 6.18. Found: C, 73.42; H, 6.44.

¹³C NMR (101 MHz, CD₃OD): δ = 9.98, 12.72, 22.84, 29.82, 31.61,

41.69, 48.51, 56.57, 60.77, 61.66, 106.92, 108.19, 109.59, 124.99,

126.44, 126.74, 129.36, 132.53, 134.85, 137.45, 137.99, 142.71,

151.84, 153.69, 170.70.

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]cyclohexa[1,2:b]1H-indole (22a)

Isolated as a colorless oil (traces).

[α]_D²⁰–23 (c 1.05, CHCl₃).

MALDI-MS (pos): m/z (%) = 422.2 (100), 379.2 (52), 363.2 (36), 408.2

(29), 406.2 (13).

IR: 3397, 2939, 1649, 1596, 1451, 1387, 1233, 1088, 849, 737 cm^–1

.

Anal. Calcd for C₂₅H₃₀N₂O₄: C, 71.07; H, 7.16. Found: C, 71.23; H, 7.02.

¹H NMR (400 MHz, DMSO-d₆): δ = 1.43–1.47 (m, 8 H, CH₂-cyclohexyl

ring), 1.89 (s, 3 H, NHAc), 2.02–2.07 (m, 2 H, H-5), 2.13–2.18 (m, 2 H,

H-6), 3.40 (s, 3 H, OMe), 3.79 (s, 3 H, OMe), 3.85 (s, 3 H, OMe), 4.61–

4.68 (m, 1 H, H-7), 6.74 (s, 1 H, H-4), 7.22 (s, 1 H, H-8), 7.24 (s, 1 H, H-

11), 8.59 (d, J = 8.4 Hz, 1 H, NHAc), 10.71 (s, 1 H, NH-pyrrole).

MTT-assay

Cytotoxic effect of compounds was estimated by a standard 3-(4, 5-

dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT,

Sigma). All the compounds were dissolved in dimethyl sulfoxide to 20

mM concentration and stored at –20 °C until the assay. Different dilu-

tions of the new compounds from 20 μM to 0.1 nM were prepared

separately and transferred in 100 μL to the plates with the cells. Non-

treated cells served as controls. Plates were incubated for 72 hrs. For

the last 6 hours, 5 mg/mL of MTT was added in the amount of 10 μL to

each well. After the incubation, culture medium was removed and

100 μL dimethyl sulfoxide was added to each well. Plates were incu-

bated in a shaker for 15 min to dissolve the formed formazan product.

Optical density was read on spectrophotometer Titertek (UK) at 540

nm. Results were analyzed by Excel package (Microsoft). Cytotoxic

concentration giving 50% of the maximal toxic effect (IC₅₀) was calcu-

lated from the titration curves. The inhibition of proliferation (inhibi-

tion index, II) was calculated as [1 – (ODexperiment/ODcontrol)],

where OD was MTT optical density.

MALDI-MS (pos): m/z (%) = 434.2 (100), 419.2 (77), 376.2 (51), 391.2

(44), 346.2 (37), 390.2 (22).

Anal. Calcd for C₂₆H₃₀N₂O₄: C, 71.87; H, 6.96. Found: C, 71.62; H, 7.09.

Methylated Indoles 27a and 27b

Indole 15a or 15b (30 mg, 0.07 mmol, 1 equiv) and NaH (60% in min-

eral oil; 12 mg, 0.29 mmol, 4.1 equiv) were stirred in anhyd THF (10

mL) at 0 °C, and MeI (31 mg, 0.22 mmol, 3 equiv) was added. The mix-

ture was stirred at 0 °C for 2 h, then the temperature was raised to

65 °C and stirring continued overnight. The solvent was removed un-

der reduced pressure and the residue was purified using column

chromatography (petroleum ether–AcOEt–EtOH, 6:1:1).

1′,2′,3′-Trimethoxybenzo[4′,5′:4,5]1H-(aR,1S)-1-acetamido-6,7-di-

hydrocyclohepta[3,2-f]1H-N,2′′,3′′-trimethylindole (27a)

Isolated as a white solid (20 mg, 0.05 mmol, 67%).

L

E. S. Shchegravina et al.

Paper

Synthesis

Funding Information

(7) (a) Dickinson, M.; Juneja, S. Br. J. Haematol. 2009, 146, 465.

(b) Finkelstein, Y.; Aks, S. E.; Hutson, J. R.; Juurlink, D. N.;

Nguyen, P.; Dubnov-Raz, G.; Pollak, U.; Koren, G.; Bentur, Y. Clin.

Toxicol. 2010, 48, 407. (c) Malysheva, Y. B.; Combes, S.; Allegro,

D.; Peyrot, V.; Knochel, P.; Gavryushin, A. E.; Fedorov, A. Yu.

Bioorg. Med. Chem. 2012, 20, 4271. (d) Kuznetsova, N. R.;

Svirshchevskaya, E. V.; Sitnikov, N. S.; Abodo, L.; Sutorius, H.;

Zapke, J.; Velder, J.; Thomopoulou, P.; Oschkinat, H.; Prokop, A.;

Schmalz, H.-G.; Fedorov, A. Yu.; Vodovozova, E. L. Russ. J. Bioorg.

Chem. 2013, 39, 543.

T This work was supported by the Russian Science Foundation (Proj-

ect 16-13-10248).

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Acknowledgment

We thank I. M. Ryzhov and E. L. Vodovozova (IBCh RAS, Moscow, Rus-

sian Federation) for collaboration in work with optical rotation mea-

surements.

(8) (a) Sitnikov, N.; Velder, J.; Abodo, L.; Cuvelier, N.; Neudörfl, J.;

Prokop, A.; Krause, G.; Fedorov, A. Y.; Schmalz, H.-G. Chem. Eur.

J. 2012, 18, 12096. (b) Sitnikov, N. S.; Kokisheva, A. S.; Fukin, G.

K.; Neudörfl, J.-M.; Sutorius, H.; Prokop, A.; Fokin, V. V.;

Schmalz, H.-G.; Fedorov, A. Yu. Eur. J. Org. Chem. 2014, 6481.

(c) Sitnikov, N. S.; Sintsov, A. V.; Allegro, D.; Barbier, P.; Combes,

S.; Abodo, O. L.; Prokop, A.; Schmalz, H.-G.; Fedorov, A. Yu. Med-

ChemComm 2015, 6, 2158. (d) Shchegravina, E. S.; Knyazev, D. I.;

Beletskaya, I. P.; Svirshchevskaya, E. V.; Schmalz, H.-G.; Fedorov,

A. Yu. Eur. J. Org. Chem. 2016, 5620. (e) Shchegravina, E. S.;

Maleev, A. A.; Ignatov, S. K.; Gracheva, Iu. A.; Stein, A.; Schmalz,

H.-G.; Gavryushin, A. E.; Zubareva, A. A.; Svirshchevskaya, E. V.;

Fedorov, A. Yu. Eur. J. Med. Chem. 2017, 141, 51.

(9) (a) Voitovich, Y. V.; Shegravina, E. S.; Sitnikov, N. S.; Faerman, V.;

Fokin, V. V.; Schmalz, H.-G.; Combes, S.; Allegro, D.; Barbier, P.;

Beletskaya, I. P.; Svirshchevskaya, E. V.; Fedorov, A. Yu. J. Med.

Chem. 2015, 58, 692. (b) Gracheva, Iu. A.; Voitovich, I. V.;

Faerman, V. I.; Sitnikov, N. S.; Myrsikova, E. V.; Schmalz, H.-G.;

Svirshevskaya, E. V.; Fedorov, A. Yu. Eur. J. Med. Chem. 2017, 126,

432. (c) Gracheva, I. A.; Svirshchevskaya, E. V.; Zaburdaeva, E. A.;

Fedorov, A. Yu. Synthesis 2017, 49, 4335. (d) Gracheva, Iu. A.;

Svirshchevskaya, E. V.; Faerman, V. I.; Beletskaya, I. P.; Fedorov,

A. Yu. Synthesis 2018, 50, 2753.

Supporting Information

Supporting information for this article is available online at

https://doi.org/10.1055/s-0037-1610673.

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A Facile Synthetic Approach to Nonracemic Substituted Pyrrolo-allocolchicinoids Starting from Natural Colchicine

DOI: 10.1055/s-0037-1610673

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