Regiocontrolled Synthesis of the Antitumor Antibiotic AT2433-A1

Article abstract of DOI:10.1021/jo000911r

The indolo[2,3-α]carbazole glycosides are potent antitumor antibiotics currently undergoing clinical trials for the treatment of numerous types of cancer. AT2433-A1 is the most complex member of this family of compounds possessing a unique disaccharide with a sensitive aminodeoxysugar and an unsymmetric aglycon. The synthesis of this natural product requires a method for glycosylation that sets the stereochemistry of the anomeric center and the regiochemistry of the aglycon. These goals were accomplished by carrying out the Mannich cyclization of a bis-3,4-(3-indolyl)succinimide to give a key class of indoline intermediates that could be glycosylated stereoselectively with complex carbohydrates without hydroxyl protection or activation. The regiochemistry of the Mannich cyclization was precisely controlled by choosing between kinetic or thermodynamic conditions. This strategy culminated in the first synthesis of the antitumor antibiotic AT2433-A1.

Full text of DOI:10.1021/jo000911r

J . Org. Chem. 2000, 65, 7541-7553
7541
Regiocon tr olled Syn th esis of th e An titu m or An tibiotic AT2433-A1
J ohn D. Chisholm and David L. Van Vranken*
Department of Chemistry, University of California, Irvine, California 92697
dlvanvra@uci.edu
Received J une 15, 2000
The indolo[2,3-a]carbazole glycosides are potent antitumor antibiotics currently undergoing clinical
trials for the treatment of numerous types of cancer. AT2433-A1 is the most complex member of
this family of compounds possessing a unique disaccharide with a sensitive aminodeoxysugar and
an unsymmetric aglycon. The synthesis of this natural product requires a method for glycosylation
that sets the stereochemistry of the anomeric center and the regiochemistry of the aglycon. These
goals were accomplished by carrying out the Mannich cyclization of a bis-3,4-(3-indolyl)succinimide
to give a key class of indoline intermediates that could be glycosylated stereoselectively with complex
carbohydrates without hydroxyl protection or activation. The regiochemistry of the Mannich
cyclization was precisely controlled by choosing between kinetic or thermodynamic conditions. This
strategy culminated in the first synthesis of the antitumor antibiotic AT2433-A1.
I. In tr od u ction
Interest in the indolo[2,3-a]carbazole glycosides comes
from their potent antineoplastic properties. There are two
classes of indolocarbazole glycosides, differing both in
structure and in mechanism of action. The straurosporine
class is characterized by two bonds between the glycoside
and indolocarbazole heterocycle. These fused structures
exhibit potent inhibition of protein kinases.1 In contrast,
the rebeccamycin2 class of indolocarbazole glycosides
have a single glycosidic linkage and have shown remark-
able activity in the poisoning of DNA topoisomerase I.3,4
The only clinically used antitumor drugs that selectively
target topoisomerase I are irinotecan and topotecan,
derivatives of camptothecin. Both camptothecin and the
indolocarbazole glycosides have been shown to stabilize
the intermediate DNA-topoisomerase I complex, leading
to cell death.5 Currently, rebeccamycin derivatives are
in phase II clinical trials for the treatment of a wide
range of malignancies including refractory pediatric
neuroblastoma, advanced renal cell carcinoma, meta-
static or locally recurrent colorectal cancer, and stage IIIB
or IV breast cancer.
lectively. Finally, in cases where the aglycon is unsym-
metrical, as in AT2433-A1 and AT2433-A2, the glycosy-
lation reaction must differentiate between the two indole
nitrogens.
Unlike other indolocarbazole natural products, AT2433-
A1, AT2433-A2, AT2433-B1, and AT2433-B2 possess a
unique disaccharide with a sensitive 2-deoxy amino-
sugar.8,9 The complexity of these targets requires an
efficient method for regioselective glycosylation in the
presence of diverse functionality. While rebeccamycin has
chlorine atoms at the 1 and 11 positions of the aromatic
sector, AT2433 A1 and A2 have chlorine atoms only at
the 1 position. Thus, the disaccharide must be joined to
the more hindered, less nucleophilic nitrogen atom.
A number of chemical approaches are available for the
glycosylation of indoles and indolocarbazoles,4,10-20 but
The excellent antitumor activity of indolocarbazole
glycosides has led to a significant synthetic effort in this
area, especially in the past 5 years.6,7 The greatest
challenge in the synthesis of the indolocarbazole glyco-
sides is the formation of the N-glycosidic bond. There are
three challenges associated with glycosylation. First, the
nucleophilicity of the indole nitrogen is attenuated by
aromaticity. Second, glycosylation must occur stereose-
(1) Tamaoki, T.; Nomoto, H.; Takahashi, Y.; Kato, M.; Morimoto,
M.; Tomita, F. Biochem. Biophys. Res. Commun. 1986, 135, 397.
(2) Nettleton, D. E.; Doyle, T. W.; Krishnan, B.; Matsumoto, G. K.;
Clardy, J . Tetrahedron Lett. 1985, 26, 4011.
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T.; Doyle, T. W.; Horan, A. C.; Patel, M. J . Antibiot. 1989, 42, 1547.
(9) Golik, J .; Doyle, T. W.; Krishnan, B.; Dubay, G.; Matson, J . A.
J . Antibiot. 1989, 42, 1784.
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58, 343.
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10.1021/jo000911r CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/05/2000

7542 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
Sch em e 1
all of these approaches require full protection of the
carbohydrate hydroxyl groups and the imide nitrogen.
In cases where the indolocarbazole aglycon is unsym-
metrical, one of the indole nitrogens must also be
protected.
Mannich dimerization of indoles21 is an important
strategy for the synthesis of indolo[2,3-a]carbazole gly-
cosides because the dimers can be glycosylated stereo-
selectively using unprotected, unactivated carbohy-
drates.22-27 This method is even more efficient when the
Mannich dimerization occurs intramolecularly as part of
a cyclization reaction. When one indole is deactivated by
a chlorine substituent, the regiochemistry can be con-
trolled by carrying out the cyclization under kinetic or
thermodynamic conditions as recently demonstrated in
the synthesis of the antifungal compound tjipanazole
F1.28,29 The application of this strategy to AT2433-A1 and
AT2433-A2 is complicated by the overall complexity of
the target. Despite initial uncertainties about the gen-
erality of this strategy it has led to the first synthesis of
AT2433-A1.
Sch em e 2
II. Ma n n ich Stu d ies
Indolines, such as 4 and 5, are readily prepared by
Mannich cyclization of bis-3,4-(3-indolyl)succinimides.21
The indoline nitrogen undergoes facile glycosylation
without requiring hydroxyl protection or anomeric acti-
vation to give good yields of glycosylated products. The
N-glycosides obtained by this method possess the â
anomeric stereochemistry found in the indolocarbazole
glycoside natural products. Aromatization of the in-
dolylindoline-N-glycosides can be easily effected with
mild oxidizing agents such as DDQ30 or, in some cases,
light.31
cyclization of 1a is accompanied by an undesired opening
of the indoline ring to give carbazole 2, unless the
indoline intermediate is oxidized in situ.34 This same
rearrangement was observed by Steglich during at-
tempted cyclization of 1a with CSA in refluxing toluene
(Scheme 1).32
Aromatization of the bisindolylmaleimide being too
facile, cyclization of the dl-succinimide 3 was investi-
gated. This compound was readily prepared as a 24:1
mixture (1H NMR) of dl/meso isomers by conjugate
reduction with magnesium in refluxing methanol. Man-
nich cyclization of the dl-succinimide was sluggish rela-
tive to intermolecular Mannich dimerization of 3-substi-
tuted indoles, provided two hexacyclic products, (()-4 and
(()-5, after 24 h in neat TFA (Scheme 2).
The relative stereochemistry of the two products was
assigned on the basis of double pulsed field gradient
spin-echo-NOEs (DPFGSE-NOEs). Irradiation of H4b in
diastereomer 4 produced moderate enhancements to the
signals from protons H7a and H12b, but not H4c,
suggesting an anti-anti-cis stereochemistry. In contrast,
irradiation of H4b in diastereomer 5 led to moderate
enhancements of the signals from protons H4c and H12b,
but not H7a, suggesting an anti-cis-cis stereochemistry.
These compounds were unstable in solution, rapidly
undergoing oxidation in EtOAc/hexane mixtures, making
their purification difficult. The instability and difficulty
in working with mixtures of products led us to further
investigate this cyclization of the meso succinimide, 6a
(Figure 1).
N-Methylarcyriarubin A (1a ) is readily available
through literature procedures.32,33 Attempted Mannich
(14) Bailly, C.; Qu, X.; Anizon, F.; Prudhomme, M.; Riou, J .-F.;
Chaires, J . B. Mol. Pharmacol. 1999, 55, 377.
(15) Kaneko, T.; Wong, H.; Okamoto, K. T.; Clardy, J . Tetrahedron
Lett. 1985, 26, 4015.
(16) Bonjouklian, R.; Smitka, T. A.; Doolin, L. E.; Molloy, R. M.;
Debono, M.; Shaffer, S. A.; Moore, R. E.; Stewart, J . B.; Patterson, G.
M. L. Tetrahedron 1991, 47, 7739.
(17) Tanaka, S.; Ohkubo, M.; Kojiri, K.; Suda, H. J . Antibiot. 1992,
45, 1797.
(18) Bakhmedova, A. D.; Garaeva, L. D.; Goryunova, O. V.; Miniker,
T. D.; Plikhtyak, I. L.; Ektova, L. V.; Adanin, V. M.; Ivanova, T. P.;
Yartseva, I. V.; Melnik, S. Y. Biorg. Khim. 1997, 23, 667.
(19) Ohkubo, M.; Kawamoto, H.; Ohno, T.; Nakano, M.; Morishima,
H. Tetrahedron 1997, 53, 585.
(20) Ohkubo, M.; Nishimura, T.; Kawamoto, H.; Nakano, M.;
Honma, T.; Yoshinari, T.; Arakawa, H.; Suda, H.; Morishima, H.;
Nishimura, S. Bioorg. Med. Chem. Lett. 2000, 10, 419.
(21) Bergman, J .; Koch, E.; Pelcman, B. Tetrahedron Lett. 1995, 36,
3945.
(22) Suvorov, N. N.; Preobrazhenskaya, M. N. Zh. Obsch. Khim.
1961, 31, 2839.
(23) Preobrazhenskaya, M. N.; Suvorov, N. N. Zh. Obsch. Khim.
1965, 35, 893.
(24) Preobrazhenskaya, M. N.; Vigdorchik, M. M.; Suvurov, N. N.
Tetrahedron 1967, 23, 4653.
(25) Preobrazhenskaya, M. N. Russ. Chem. Rev. 1967, 36, 753.
(26) Miniker, T. D.; Mukhanov, V. I.; Chkanikov, N. D.; Yartzeva,
I. V.; Preobrazhenskaya, M. N. Carbohydr. Res. 1978, 64, 17.
(27) Chisholm, J . D.; Van Vranken, D. L. J . Org. Chem. 1995, 60,
6672.
(28) Gilbert, E. J .; Van Vranken, D. L. J . Am. Chem. Soc. 1996, 118,
5500.
The corresponding cis-bisindolylsuccinimide 6b cyclizes
efficiently in neat trifluoroacetic acid (TFA) in less than
1 h. In contrast to the cyclization of the anti-bisindolyl-
(29) Gilbert, E. J .; Ziller, J . W.; Van Vranken, D. L. Tetrahedron
1997, 53, 16553.
(30) Bergman, J .; Carlsson, R.; Misztal, S. Acta Chem. Scand. 1976,
30, 853.
(32) Steglich, W. Pure Appl. Chem. 1989, 61, 281.
(33) Faul, M. M.; Sullivan, K. A.; Winneroski, L. L. Synthesis 1995,
1511.
(31) Carter, D. S.; Van Vranken, D. L. Tetrahedron Lett. 1996, 37,
5629.
(34) J oyce, R. P.; Gainor, J . A.; Weinreb, S. M. J . Org. Chem. 1987,
52, 2, 1177.

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7543
Sch em e 4
F igu r e 1. DPFGSE-NOEs (tmix) 1 s) establish the stereo-
chemistry of the indolylindolines (()-4 and (()-5.
Sch em e 5
Sch em e 3
succinimide, the product of this reaction is a single
racemic diastereomer. This cyclization works the same
for free imide 1b35 as well, the methyl group not being
required. Cyclization product (()-7a also undergoes
oxidation in solution, but more slowly than the trans
isomers. During attempts to recrystallize from acetone/
EtOAc, the fully aromatic indolocarbazole 8 crystallizes
from solution as it is formed. The same product is formed
by oxidation with 2 equiv of DDQ in dioxane. Indolocar-
bazole 8 is identical to material prepared by Gribble
using a twin Fisher indole cyclization. Indoline (()-7a
may be conveniently precipitated from methanol at room
temperature without oxidation (Scheme 3).
The relative stereochemistry of cyclization product (()-
7a was assigned on the basis of steady-state NOEs.
Initial attempts were hampered by overlapping signals
in the 1H NMR spectrum, but conversion to the triflamide
9 spread the NMR signals over a larger range, making
protons easier to irradiate selectively. Irradiation of H4b
produced sizable enhancements to the signals from
protons H7a, H12b, and H4c, suggesting a cis-syn-cis
stereochemistry (Scheme 4).
side. Importantly, these reactions also proceed in good
yield without protection of the imide nitrogen. This
particular synthetic route stands out because all other
methods of glycosylation require imide protection (Scheme
5).
Melnik has shown that glycosylation of indolines
proceeds smoothly with the disaccharide lactose.36,37 To
explore the potential of this coupling strategy for the
synthesis of AT2433, aglycon 7a was condensed with a
series of mono-, di-, and trisaccharides. Good glycosyla-
tion yields were realized for all sugars tested. While most
of these indolocarbazole glycosides have disappointing
solubility, the N-melibioside 13 was somewhat soluble
in water (Table 1).
IV. Syn th esis of AT2433-B1
With a viable route toward indolocarbazole glycosides
bearing complex carbohydrates, a synthesis of AT2433-
B1 was undertaken. The disaccharide of AT2433-B1
consists of a glucose and an aminosugar subunit, 2,4-
dideoxy-4-amino-L-xylose. Derivatives of this aminosugar
are present in the enediyne antitumor antibiotics cali-
cheamicin and esperamicin.26,38,39 Several known routes
exist to 2,4-dideoxy-4-amino-xylosides,40-44 but the method
of Roush45 was adopted for this synthesis based upon our
III. Ca r boh yd r a te Ca p tu r e by In d olin es
The glycosylation of indolines was first studied by
Praeobrazhenskaya.25 Later, this method of synthesizing
glycosylated indoles was extended and optimized for the
2,2′-biindole system.27 Gratifyingly, treatment of (()-7a
under these optimized conditions (three equiv of D-glucose
in refluxing methanol) led to the formation of N-glyco-
sylated products in good yield. Because the indoline is
racemic and the sugar is a single enantiomer, two
diastereomeric products are formed. Convergent oxida-
tion of the two diastereomers with DDQ gives a single
product, a fully functionalized indolocarbazole â-glyco-
(36) Melnik, S. Y.; Bakhmedova, A. D.; Garaeva, L. D.; Goryunova,
O. V.; Miniker, T. D.; Plikhtyak, I. L.; Ektova, L. V.; Ivanova, T. P.;
Yartseva, I. V. Bioorg. Khim. 1996, 22, 458.
(37) Melnik, S. Y.; Bakhmedova, A. D.; Garaeva, L. D.; Miniker, T.
D.; Plikhtyak, I. L.; Ektova, L. V.; Ivanova, T. P.; Adanin, V. M.;
Yartseva, I. V. Bioorg. Khim. 1996, 22, 726.
(38) Lee, M. D.; Dunne, T. S.; Chang, C. C.; Ellestad, G. A.; Siegel,
M. M.; Morton, G. O.; McGahren, W. J .; Borders, D. B. J . Am. Chem.
Soc. 1987, 109, 3466.
(39) Golik, J .; Clardy, J .; Dubay, G.; Groenewold, G.; Kawaguchi,
H.; Konishi, M.; Krishnan, B.; Ohkuma, H.; Saitoh, K.; Doyle, T. W.
J . Am. Chem. Soc. 1987, 109, 3461.
(35) Davis, P. D.; Hill, C. H.; Lawton, G. L.; Nixon, J . S.; Wilkinson,
S. E.; Hurst, S. A.; Keetch, E.; Turner, S. E. J . Med. Chem. 1992, 35,
177.
(40) Groneberg, R. D.; Miyazaki, T.; Stylianides, N. A.; Schulze, T.
J .; Stahl, W.; Schreiner, E. P.; Suzuki, T.; Iwabuchi, Y.; Smith, A. L.;
Nicolaou, K. C. J . Am. Chem. Soc. 1993, 115, 7593.

7544 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
Sch em e 6
Ta ble 1. Glycosyla tion /Oxid a tion of (()-7a (Sch em e 5)
Sch em e 7
Sch em e 8
secondary alcohol using methyl iodide and sodium hy-
dride provided the 4′-O-methyl derivative, 16. Selective
removal of the 6′ PMB protecting group under oxidative
conditions led to glucoside 17, ready for glycosylation at
the free 6′-OH (Scheme 6).
Following the procedure of Roush and Hunt, homoallyl
alcohol 18 was prepared from R-Garner’s aldehyde using
an allyl dioxaborolane derived from R,R-diisopropyl
tartrate.45 Homoallyl alcohol 18 was formed as an 88:12
mixture of diastereomers differing in stereochemistry at
the alcohol stereocenter. The mixture of diastereomers
was then benzylated, and the latent aldehyde was
revealed by dihydroxylation of the double bond with
catalytic osmium tetroxide followed by cleavage of the
diol with sodium metaperiodate. At the aldehyde stage
the undesired diastereomer was separated chromato-
graphically. Selective removal of the acetonide49 led to
the lactol 21, which was then converted to the glycosyl
fluoride by the action of DAST (Scheme 7).
Coupling of the primary alcohol 17 with glycosyl
fluoride 22 was performed under Mukaiyama-Nico-
laou40,50 conditions (Scheme 8). Within 15 min, the
equatorial and axial glycosides are formed in a 2:1 ratio,
consistent with recent results of Deslongshamps51 and
Woerpel.52 However, within 1 h, equilibration equalizes
previous experience.46 While 4-O-methylglucose has been
previously prepared,47 a strategy was needed for dif-
ferential protection of the hydroxyl groups at the 6
position, 4 position, and positions 1-3. A suitable inter-
mediate was prepared using the method of Samuelsson
involving reductive opening of a 4,6-p-methoxyben-
zylidene acetal to give glucoside 15.48 Methylation of the
(41) Golik, J .; Wong, H.; Vyas, D. M.; Doyle, T. W. Tetrahedron Lett
1989, 30, 2497.
(42) Mash, E. A.; Nimkar, S. K. Tetrahedron Lett. 1993, 34, 385.
(43) Kim, S. H.; Augeri, D.; Yang, D.; Kahne, D. J . Am. Chem. Soc.
1994, 116, 1766.
(44) Halcomb, R. L.; Boyer, S. H.; Danishefsky, S. J . Angew. Chem.,
Int. Ed. Engl. 1992, 31, 338.
(45) Roush, W. R.; Hunt, J . A. J . Org. Chem. 1995, 60, 798.
(46) Chisholm, J . D.; Golik, J .; Krishnan, B.; Matson, J . A.; Van
Vranken, D. L. J . Am. Chem. Soc. 1999, 121, 3801.
(47) Bouveng, H. O.; Lindberg, B.; Theander, O. Acta Chem. Scand.
1957, 11, 1788.
(48) J ohansson, R.; Samuelsson, B. J . Chem. Soc., Perkin 1 1984,
2371.
(49) Garner, P. Tetrahedron Lett. 1984, 25, 5855.
(50) Mukaiyama, T.; Murai, Y.; Shoda, S. I. Chem. Lett. 1981, 431.
(51) Miljkovic, M.; Yeagley, D.; Deslongchamps, P.; Dory, Y. L. J .
Org. Chem. 1997, 62, 7597.
(52) Romero, J . A. C.; Tabacco, S. A.; Woerpel, K. A. J . Am. Chem.
Soc. 2000, 122, 168.

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7545
Sch em e 9
Sch em e 10
the ratio of R and â anomers and a yield of 80% is
obtained. Unfortunately, attempts improve the ratio of
axial glycoside to equatorial glycoside by equilibrating
under long reaction times led to decomposition.
The equatorial and axial anomers were inseparable
until the N-Boc group was reduced to the corresponding
methylamino group. Reprotection of the methylamino
group as the Boc derivative led to problems during the
consummate deprotection due to the sensitivity of the
2-deoxypyranoside linkage.46 Instead, the methylamino
group of disaccharide 24 was then protected as the
N-trimethylsilylethyl carbamate (Teoc) derivative.
With the disaccharide in hand, elaboration to AT2433-
B1 was undertaken. Debenzylation with palladium and
hydrogen provided the deprotected disaccharide 26 (not
shown). Refluxing of lactol 26 with 3 equiv of (()-7a in
methanol for 72 h gave 84% yield of glycosylated product.
Oxidative aromatization of the mixture of diastereomers
with DDQ led to the protected natural product 27 in 80%
yield. Finally, deprotection of the Teoc carbamate with
TBAF provided AT2433-B1 in good yield (Scheme 9).
Sch em e 11
V. Ma n n ich Cycliza tion Stu d ies on Ch lor in a ted
Su bstr a tes
slowed the reaction, without changing slowing the hy-
drogenolysis side reaction.
The synthesis of the chlorinated indolocarbazoles
presents a more dramatic problem of selectivity. AT2433-
A1 and A2 both possess a chlorine atom at the 1-position
of the indolocarbazole. Building on previous work with
the tjipanazole natural products, we envisioned that the
electron withdrawing chlorine atom would allow selective
Mannich cyclization of an unsymmetrical bis-indole.
Toward this end, an unsymmetrical bisindolylmaleimide
was synthesized.
The Grignard anion of 7-chloroindole was added to 1
equiv of N-methyl dibromomaleimide to provide the
monoaddition product 29. The second addition of indolyl-
magnesium bromide required more vigorous conditions,
but also proceeded smoothly (Scheme 10).33
As expected, hydrogenation of the tetrasubstituted
maleimide double bond proved to be problematic. The
rate of hydrogenation of tetrasubstituted double bonds
known to be slow while hydrogenolysis of aryl halides is
facile.53 Heterogeneous ruthenium and iridium catalysts
proved to be unreactive, whereas rhodium on carbon or
alumina gave mixtures of the meso and dl succinimides.
In contrast, hydrogenation with palladium on carbon in
DMF afforded a 60% yield of the meso succinimide, the
balance of the material having been de-chlorinated.
Attempts to slow hydrogenolysis of the aryl chloride bond
with less polar solvents (THF/MeOH mixtures) only
Two products are possible in the Mannich cyclization
of unsymmetrical bis-indoles such as (()-31: the chloro-
indole regioisomer (()-32 and the chloroindoline regio-
isomer (()-33. In previous studies of simple tethered
indoles,29 it was demonstrated that Mannich cyclization
was reversible in neat trifluoroacetic acid, but essentially
irreversible with camphorsulfonic acid in chloroform.
Mannich cyclization of the chlorinated bisindolylsuccin-
imide (()-31 with methanesulfonic acid in chloroform
provided isomer (()-33 with high regio- and stereoselec-
tivity. The regioselectivity is readily rationalized based
on classical Curtin-Hammett conditions (Scheme 11). The
7-chloro group in bis-indole 31 is expected to exert a
powerful inductive effect during the key cyclization event
and probably makes the less stable indolenium ion cyclize
faster (Scheme 11). However, the resulting product (()-
33, is probably destabilized by the same inductive effect,
making it less stable than the alternative product (()-
32. A dramatic reversal in regiochemistry is achieved by
carrying out the cyclization in refluxing trifluoroacetic
acid. Under these conditions, the more stable product (()-
32 is obtained with excellent selectivity, although the
yield is somewhat diminished due to decomposition
(Table 2).
The stereochemistry of indolylindolines (()-32 and (()-
33 were verified using NOE experiments. Significant
(53) Rylander, P. N. Hydrogenation Methods; Academic Press: San
Diego, 1985.

7546 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
Sch em e 13
Ta ble 2. Ma n n ich Cycliza tion of Un sym m etr ica l
Bis-In d olylsu ccin im id e (()-31
conditions
time (h)
ratio (32:33)
yield (%)
MSA (5 equiv), CHCl3
MSA (5 equiv), CHCl3
TFA (neat)
TFA (neat)
TFA (neat)
2
24
.25
24
72
2
<1:20
<1:20
1:9
1:5
1:3
4:1
>20:1
94
93
90
90
93
90
82
TFA (neat), reflux
TFA (neat), reflux
12
Sch em e 14
F igu r e 2. DPFGSE-NOEs (tmix ) 1 s) establish the stereo-
chemistry of the indolylindolines (()-32 and (()-33.
Sch em e 12
â-glucoside is obtained as a 1:1 mixture of diastereomers.
By using 20 equiv of D-glucose the yield could be
increased to 61%. When the product is resubmitted to
the reaction conditions (0.33 equiv CSA in wet DMF) it
is observed to hydrolyze, suggesting that the yield is
ultimately limited by the thermodynamic stability of the
product. Glycosylation of the non-chlorinated aglycon (()-
7a with 3 equiv of D-glucose gave 85% yield under the
same conditions, speaking to the detrimental effect of the
chlorine atom.
The presence of the chlorine substituent peri to the
glucosyl moiety makes the oxidative aromatization lag-
gardly, but the combination of excess DDQ (5 equiv) and
long reaction times (5 days) provided reasonable yields
of the fully aromatic chlorinated indolocarbazole 35. With
the ability to glycosylate and aromatize aglycon 33,
attention was focused on elaboration into AT2433-A1
(Scheme 13).
NOE enhancements were seen upon irradiation of the
same protons as in the nonchlorinated systems.
As with Mannich products (()-4 and (()-5, the relative
stereochemistry of the hexacyclic products (()-32 and (()-
33 was assigned on the basis of double pulsed field
gradient spin-echo-NOEs (DPFGSE-NOEs). Irradiation
of H4b in diastereomer produced moderate enhancements
to the signals from protons H4c and H12b, confirming a
syn relationship between protons H4b, H4c, and H12b.
Proton H7c is also on the same face since irradiation
leads to enhancement of H4c (Figure 2).
VI. Ca r boh yd r a te Ca p tu r e by Ch lor in a ted
Su bstr a tes
VII. Syn th esis of AT2433-A1
The aminodisaccharide 26, used in the synthesis of
AT2433-B1, was condensed with 3 equiv of aglycon (()-
33 in 35% yield. Both starting materials could be
recovered unchanged and recycled. After two more cycles,
an overall yield of 75% was obtained for the diastereo-
meric mixture of glycosylated products. Surprisingly,
oxidative aromatization again proved very difficult. After
5 days with 5 equiv of DDQ only an 8% yield of the
oxidized product was realized. This demanded a search
for other conditions that could effect this transformation.
Ultimately, dehydrohalogenation could be accomplished
with DBU and iodine in methylene chloride. While this
procedure gave lower yields than DDQ in other cases,
here a 52% yield was obtained in a much shorter reaction
time (4 h). Finally, deprotection of the teoc group with
TBAF provided material that matched AT2433-A1
(Scheme 14).
With both regioisomers available using Mannich chem-
istry, we began to elaborate the chlorinated indolines (()-
32 and (()-33 into indolocarbazole glycosides. Mannich
cyclization product (()-32 showed similar reactivity to
the non-chlorinated aglycon, (()-7a . Glycosylation and
oxidation under standard conditions provided the fully
functionalized, regioselectively chlorinated indolocarba-
zole glycoside 34 in 66% overall yield (Scheme 12).
Elaboration of the racemic indolylindoline (()-33 proved
much more challenging. The addition of the sterically
encumbering, electron withdrawing chloride atom ortho
to the reactive amine nitrogen decimated the reactivity
of the center. No product was observed using the stan-
dard glycosylation conditions: refluxing methanol, 3
equiv of D-glucose, and catalytic (NH4)2SO4. After some
experimentation, alternative conditions for the glycosy-
lation were found. Glycosylation could be effected with
0.33 equiv of d-10-camphorsulfonic acid (CSA) in DMF
at room temperature using 3 equiv D-glucose, albeit in
31% yield. Both enantiomers of the aglycon react and the
This work has capitalized upon a Mannich cyclization/
glycosylation route for the synthesis of indolocarbazole
glycosides. The pentacyclic indoline intermediates pre-
pared by Mannich cyclization are readily glycosylated

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7547
1-Meth yl-cis-3,4-bis(3-in d olyl)-2,5-p yr r olid in ed ion e 6a .
Bisindolylmaleimide 1a (1.056 g, 3.09 mmol) was dissolved in
20 mL of DMF. 10% Palladium on carbon (0.411 g, 0.38 mmol)
was then added, and the reaction mixture was shaken in a
parr shaker under 50 psi of hydrogen. After 13 h, the reaction
was filtered through Celite with ethanol and concentrated in
vacuo (the DMF being removed by distillation under hi-vac).
The residue was purified using silica gel chromatography (50%
EtOAc/50% hexanes) to give 0.980 g (93%) of cis-succinimide
6a as an orange foam.
6a : mp 250-252 °C (crystals from EtOAc); Rf ) 0.22 in 50%
EtOAc/hexanes; IR (film) 3402, 1692 cm-1; 1H NMR (acetone-
d6, 500 MHz) δ 9.81 (s, 2H), 7.40 (d, 2H, J ) 7.6 Hz), 7.14 (d,
2H, J ) 8.0 Hz), 6.93 (t, 2H, J ) 8.1 Hz), 6.87 (m, 4H), 5.00 (s,
2H), 3.17 (s, 3H); 13C NMR (DMSO-d6, 125 MHz) δ 178.3,
135.4, 126.9, 124.5, 120.7, 118.4, 118.3, 111.3, 108.1, 45.5, 24.8;
MS (CI+) 343; HRMS (CI+) calcd for C21H17N3O2 343.1320,
found 343.1318. Anal. Calcd for C21H17N3O2: C, 73.45; H, 4.99;
N, 12.24. Found: C, 73.33; H, 5.12; N, 12.02.
(4b R,4cR,7a R,12b S)-r el-6-Met h yl-4b ,4c,6,7,7a ,12,12b ,-
13-octa h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r ba zole-5,7-d i-
on e (()-7a. cis-N-Methyl-2,3-bis(3-indolyl)succinimide 6a (0.836
g, 2.43 mmol) was dissolved in 20 mL of trifluoroacetic acid.
After 30 min, the TFA was removed in vacuo and the reaction
mixture taken up in 50 mL of EtOAc. The reaction mixture
was then poured into 150 mL of saturated aqueous NaHCO3.
The layers were separated, and the aqueous layerwas ex-
tracted with EtOAc (3 × 50 mL). The combined organic layers
were then dried (Na2SO4) and concentrated. Purification by
silica gel chromatography (40% EtOAc/hexanes) afforded (()-
7a (0.760 g, 91% yield) as an orange foam.
with unactivated sugars without protection of the sugar
hydroxyl groups or the imide moiety of the aglycon. The
regiochemistry of the Mannich cyclization can be pre-
cisely controlled using kinetic or thermodynamic condi-
tions. This strategy has culminated in the first synthesis
of the antitumor antibiotic AT2433-A1.
Exp er im en ta l Section
General experimental procedures may be found in the
Supporting Information of another publication.54
1-Me t h yl-t r a n s-3,4-b is(3-in d olyl)-2,5-p yr r olid in e d i-
on e, 3. Bisindolylmaleimide 1a (350 mg, 1.02 mmol) was
suspended in 10 mL of dry MeOH. Mg turnings (450 mg, 18.5
mmol) were then added, and the reaction was heated to reflux.
After 20 min, the reaction was cooled to room temperature
and poured into 50 mL of 1 N HCl. The reaction was then
extracted with EtOAc (3×), and the extracts were dried (Na2-
SO4) and concentrated. Purification by silica gel chromatog-
raphy (50% EtOAc/hexanes) provided 325 mg (93%) of the
trans-bisindolylsuccinimide 3 as a buff foam.
3: mp 196-198 °C (EtOAc); Rf ) 0.14 (40% EtOAc/hexanes);
IR (KBr) 3388, 3069, 2900, 1779, 1694 cm-1; 1H NMR (DMSO-
d6, 500 MHz) δ 11.08 (s, 2H), 7.40-7.44 (m, 4H), 7.11 (td, 2H,
J ) 7.9, 0.8 Hz), 6.98 (td, 2H, J ) 8.0, 0.8 Hz), 4.62 (s, 2H),
3.10 (s, 3H); 13C NMR (DMSO-d6, 125 MHz) δ 177.1, 136.5,
126.3, 124.1, 121.3, 118.8, 118.6, 111.7, 109.8, 45.9, 25.0; MS
(CI+) 343; HRMS (CI+) calcd for C21H17N3O2 343.1320, found
343.1307. Anal. Calcd for C21H17N3O2: C, 73.45; H, 4.99; N,
12.24. Found: C, 73.39; H, 5.03; N, 12.12.
(4bR,4cS,7a R,12bS)-r el-6-Meth yl-4b,4c,6,7,7a ,12,12b,13-
oct a h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r b a zole-5,7-d i-
on e (()-4 a n d (4bR,4cR,7a S,12bS)-r el-6-Meth yl-4b,4c,6,7,-
7a,12,12b,13-octahydroindolo[2,3-a ]pyrrolo [3,4-c]carbazole-
5,7-d ion e (()-5. trans-Bisindolylsuccinimide 3 (536 mg, 0.326
mmol) was dissolved in 6 mL (78 mmol) of TFA and protected
from light with aluminum foil. After 26 h, the reaction mixture
was poured into 200 mL of 1 N NaOH and extracted with
EtOAc (3×). The extracts were then dried (Na2SO4) and
concentrated. Purification by silica gel chromatography pro-
vided 145 mg (27%) of the anti-anti-syn indoline (()-4 and 318
mg (59%) of the anti-syn-syn indoline (()-5. Both compounds
are off-white foams which quickly undergo oxidation in EtOAc
or acetone solution.
(()-7a : mp 178-182 °C; Rf ) 0.36 (40% EtOAc/hexanes);
IR (film) 3368, 1607 cm-1; 1H NMR (CD3CN, 500 MHz) δ 9.19
(s, 1H), 7.82 (d, 1H, J ) 7.6 Hz), 7.30 (d, 1H, J ) 8.0 Hz), 7.16
(d, 1H, J ) 7.6 Hz), 7.10 (t, 1H, J ) 7.6 Hz), 7.02 (t, 1H, J )
7.6 Hz), 6.94 (t, 1H, J ) 7.6 Hz), 6.67 (t, 1H, J ) 7.6, Hz), 6.56
(d, 1H, J ) 7.6 Hz), 4.97 (s, 1H), 4.80 (d, 1H, J ) 7.6 Hz), 4.30
(d, 1H, J ) 7.2 Hz), 4.20 (d, 1H, J ) 7.6 Hz), 4.01 (dd, 1H,
J ) 7.6, 2.0 Hz), 2.82 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ
179.3, 177.9, 150.6, 137.4, 135.2, 130.1, 129.0, 126.8, 123.6,
123.3, 121.4, 120.4, 119.6, 111.9, 110.8, 106.4, 54.5, 41.1, 40.7,
38.8, 25.1; MS (CI+) 343; HRMS (CI+) calcd for C21H17N3O2
343.1321, found 343.1320. Anal. Calcd for C21H17N3O2: C,
73.45; H, 4.99; N, 12.24. Found: C, 73.51; H, 5.04; N, 12.27.
(4b R,4cR,7a R,12b S)-r el-4b,4c,6,7,7a ,12,12b,13-oct a h y-
d r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r ba zole-5,7-d ion e (()-7b.
Bisindolylsuccinimide 6b (962 mg, 2.92 mmol) was suspended
in 30 mL of CHCl3. Trifluoroacetic acid (2.25 mL, 29.2 mmol)
was then added. After 1 h, the reaction was quenched by
pouring it into 100 mL of 1 N NaOH. The mixture was then
extracted with EtOAc (3×). The combined extracts were then
dried (Na2SO4) and concentrated. Purification by silica gel
chromatography (45% EtOAc/hexanes) provided pure (()-7b
(916 mg, 95% yield) as an off-white solid.
(()-7b: mp 300-302 °C (EtOAc); Rf ) 0.28 (50% EtOAc/
hexanes); IR (KBr) 3418, 3351, 3284, 3056, 2908, 1706, 1606
cm-1; 1H NMR (acetone-d6, 500 MHz) δ 10.14 (s, 1H), 9.96 (bs,
1H), 7.88 (d, 1H, J ) 8.0 Hz), 7.29 (d, 1H, J ) 8.4 Hz), 7.25 (d,
1H, J ) 7.6 Hz), 7.64 (dt, 1H, J ) 7.6, 1.0 Hz), 6.99 (dt, 1H,
J ) 8.0, 0.8 Hz), 6.90 (t, 1H, J ) 7.6 Hz), 6.64 (t, 1H, J ) 7.6
Hz), 6.53 (d, 1H, J ) 7.6 Hz), 5.50 (bs, 1H), 4.93 (d, 1H, J )
8.0 Hz), 4.34 (m, 1H), 4.31 (dd, 1H, J ) 7.5, 2.9 Hz), 4.22 (dd,
1H, J ) 7.5, 1.2 Hz); 13C NMR (acetone-d6, 125 MHz) δ 179.7,
177.8, 150.8, 137.7, 135.3, 129.9, 128.7, 127.1, 123.3, 122.9,
121.6, 120.1, 119.3, 111.7, 110.6, 106.3, 54.4, 42.6, 40.5, 40.3;
MS (CI+) 329; HRMS (CI+) calcd for C20H15N3O2 329.1164,
found 329.1160. Anal. Calcd for C20H15N3O2: C, 72.94; H, 4.59;
N, 12.76. Found: C, 72.79; H, 4.70; N, 12.58.
(()-4: mp 228-230 °C (acetone); Rf ) 0.59 (50% EtOAc/
hexanes); IR (KBr) 3385, 3268, 3181, 2902, 1776, 1654 cm-1
;
1H NMR (acetone-d6, 500 MHz) δ 10.23 (s, 1H), 8.43 (d, 1H,
J ) 8.0 Hz), 7.78 (d, 1H, J ) 7.5 Hz), 7.38 (d, 1H, J ) 8.0 Hz),
6.98-7.12 (m, 3H), 6.72 (t, 1H, J ) 7.4 Hz), 6.62 (d, 1H, J )
7.8 Hz), 5.41 (s, 1H), 5.12 (bd, 1H, J ) 8.4 Hz), 4.27 (d, 1H,
J ) 10.7 Hz), 4.01 (dd, 1H, J ) 11.6, 8.5 Hz), 3.19 (t, 1H, J )
11.1 Hz); 13C NMR (DMSO-d6, 125 MHz) δ 175.7, 174.4, 150.7,
135.8, 135.4, 128.5, 128.0, 127.8, 126.0, 124.3, 121.5, 121.2,
119.0, 117.5, 111.3, 109.1, 106.0, 56.0, 46.4, 43.3, 41.6, 23.9;
MS (CI+) 343; HRMS (CI+) calcd for C21H17N3O2 343.1320,
found 343.1309. Anal. Calcd for C21H17N3O2: C, 73.45; H, 4.99;
N, 12.24. Found: C, 73.33; H, 5.08; N, 12.21.
(()-5: mp 196-198 °C (MeOH); Rf ) 0.34 (50% EtOAc/
hexanes); IR (KBr) 3382, 3043, 2902, 1773, 1603 cm-1; 1H NMR
(acetone-d6, 500 MHz) δ 11.10 (s, 1H), 8.13 (d, 1H, J ) 8.0
Hz), 7.33 (d, 1H, J ) 8.0 Hz), 7.06 (t, 1H, J ) 7.7 Hz), 6.98
(t, 1H, J ) 7.7 Hz), 6.86-6.93 (m, 2H), 6.54 (t, 1H, J ) 7.4
Hz), 6.51 (d, 1H, J ) 7.8 Hz), 5.80 (s, 1H), 5.15 (d, 1H, J ) 8.9
Hz), 4.40 (dd, 1H, J ) 8.8, 2.8 Hz), 3.86 (d, 1H, J ) 10.8 Hz),
3.67 (dd, 1H, J ) 10.8, 3.1 Hz), 2.94 (s, 3H); 13C NMR (DMSO-
d6, 125 MHz) δ 175.3, 174.8, 152.3, 137.6, 135.8, 128.1, 125.3,
124.4, 124.3, 121.3, 121.2, 119.0, 117.6, 111.3, 109.7, 106.6,
56.5, 47.7, 39.7, 30.4, 24.2; MS (CI+) 343; HRMS (CI+) calcd
for C21H17N3O2 343.1320, found 343.1326. Anal. Calcd for
1-Tr iflu or om eth a n esu lfon yl-6-m eth yl-4b,4c,6,7,7a ,12,-
12b ,13-oct a h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r b a zole-
5,7-d ion e (()-9. Aglycon indolylindoline (()-7a (117 mg, 0.341
mmol) was dissolved in 10 mL of dry CH2Cl2. Triethylamine
(150 µL, 1.08 mmol) was added, and the reaction was cooled
to -78 °C in a dry ice/acetone bath. Triflic anhydride (125 µL,
0.750 mmol) was then added. After 1 h, the reaction was
C
21H17N3O2: C, 73.45; H, 4.99; N, 12.24. Found: C, 73.20; H,
4.99; N, 12.13.
(54) Gilbert, E. J .; Chisholm, J . D.; Van Vranken, D. L. J . Org.
Chem. 1999, 64, 5670.

7548 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
queched with 5 mL of saturated aqueous NaHCO3 and poured
into 5 mL of CH2Cl2. The organic layer was separated, and
the aqueous layer was extracted with CH2Cl2 (2 × 10 mL).
The combined organic layers were dried (Na2SO4) and con-
centrated in vacuo. Purification via silica gel chromatography
(30% EtOAc/hexanes) gave 105 mg (69%) of (()-9 as a white
foam.
129.7, 128.4, 127.0, 126.8, 124.5, 121.4, 121.1, 121.0, 120.7,
120.4, 119.4, 118.4, 116.9, 112.1, 111.8, 84.5, 78.5, 76.6, 73.0,
67.5, 58.3; MS (FAB+) 487; HRMS (FAB+) calcd for C26H21N3O7
487.1379, found 487.1371. Anal. Calcd for C26H21N3O7 + H2O:
C, 61.78; H, 4.59; N, 8.31. Found: C, 62.20; H, 4.75; N, 7.97.
6-Met h yl-12-[â-D-xylosyl]-6,7,12,13-t et r a h yd r oin d olo-
[2,3-a ]p yr r olo[3,4-c]ca r ba zole-5,7-d ion e (+)-11. Indolylin-
doline (()-7a (201 mg, 0.585 mmol) and D-xylose (263 mg, 1.76
mmol) were refluxed in 4 mL of MeOH for 8 h. The reaction
mixture was then preadsorbed on silica gel and purified by
silica gel chromatography (7% MeOH/CHCl3) to give 236 mg
(85%) of a 1:1 mixture of glycosylated diastereomers. The
mixture of diastereomers was then dissolved in 4 mL of 1,4-
dioxane. DDQ (242 mg, 1.06 mmol) was then added. After 48
h, the reaction mixture was poured into 100 mL of EtOAc and
washed with saturated aqueous NaHCO3 (3×), dried (Na2SO4),
and concentrated. Purification by silica gel chromatography
(50% EtOAc/hexanes) provided 174 mg (74%, 63% from (()-
7a ) of (+)-11 as an orange solid.
(+)-11: mp 345 °C dec (EtOAc); [R]D +103.2 (c 0.45, DMSO);
Rf ) 0.10 (50% acetone/hexanes); IR (KBr) 3372, 3052, 2923,
1749, 1693 cm-1; 1H NMR (DMSO-d6, 500 MHz, 398K) δ 10.86
(s, 1H), 9.21 (d, 1H, J ) 8.0 Hz), 9.13 (d, 1H, J ) 8.0 Hz), 7.92
(d, 1H, J ) 8.5 Hz), 7.82 (d, 1H, J ) 8.5 Hz), 7.53-7.59 (m,
2H), 7.35-7.39 (m, 2H), 6.16 (d, 1H, J ) 9.0 Hz), 4.40-4.80
(bs, 3H), 4.33 (dd, 1H, J ) 10.8, 5.0 Hz), 3.93-3.97 (m, 2H),
3.86 (t, 1H, J ) 10.8 Hz), 3.70 (t, 1H, J ) 8.7 Hz), 3.23 (s, 3H);
13C NMR (DMSO-d6, 125 MHz, 300K, 2 sets of signals) δ 169.6,
142.4, 140.8, 140.4, 139.3, 130.1, 129.2, 128.1, 127.2, 127.0,
126.0, 124.6, 124.2, 122.8, 121.4, 120.9, 120.8, 120.6, 120.4,
120.0, 119.3, 118.6, 117.8, 117.1, 116.6, 114.5, 112.9, 111.8,
111.7, 87.5, 85.8, 77.6, 76.9, 72.9, 70.8, 69.4, 69.2, 68.3, 23.7;
MS (FAB+) 472, 391, 339; HRMS (FAB+) calcd for C26H21N3O6
471.1430, found 471.1430. Anal. Calcd for C26H21N3O6 + H2O:
C, 63.79; H, 4.74; N, 8.58. Found: C, 63.39; H, 4.48; N, 8.30.
6-Met h yl-12-[O-(r-D-glu cop yr a n osyl)-(1f4)-â-D-glu -
cop yr a n osyl]-6,7,12,13-t et r a h yd r oin d olo[2,3-a ]p yr r olo-
[3,4-c]ca r ba zole-5,7-d ion e, (+)-12. Aglycon indolylindoline
(()-7a (0.589 mmol, 202 mg), maltose (1.78 mmol, 636 mg),
and (NH4)2SO4 (0.04 mmol, 1 mg) were suspended in 7 mL of
methanol and warmed to reflux. After 25 h, the reaction was
preabsorbed on silica gel and purified by silica gel chroma-
tography (20% methanol/chloroform) to give a mixture of
diastereomers (389 mg, 96%). This mixture was dissolved in
10 mL of THF and DDQ (1.34 mmol, 304 mg) was added. After
44 h the reaction was concentrated in vacuo and purified by
silica gel chromatography (20% methanol/chloroform). The
product of this purification was contaminated with silica gel,
but this was removed by filtratation through an HPLC filter
with 7% MeOH/THF to give 286 mg (69% from (()-7a ) of the
indolocarbazole (+)-12.
(()-9: mp 262-264 °C (CH3CN); Rf ) 0.28 (30% EtOAc/
hexanes); IR (KBr) 3359, 3059, 2945, 1700 cm-1 1H NMR
;
(acetone-d6, 500 MHz) δ 9.33 (s, 1H), 7.85 (d, 1H, J ) 8.0 Hz),
7.44 (m, 1H), 7.42 (d, 1H, J ) 6.3 Hz), 7.39 (m, 1H), 7.37 (m,
2H), 7.24 (t, 1H, J ) 1.0 Hz), 7.23 (t, 1H, J ) 2.2 Hz), 7.15 (dt,
1H, J ) 1.2, 7.2 Hz), 7.05 (dt, 1H, J ) 7.8, 0.8 Hz), 5.76 (d,
1H, J ) 7.5 Hz), 4.75 (d, 1H, J ) 7.4 Hz), 4.27 (dd, 1H, J )
7.6, 1.2 Hz), 4.14 (dd, 1H, J ) 2.0, 7.6 Hz), 2.83 (s, 3H); 13C
NMR (acetone-d6, 125 MHz) δ 178.1, 177.2, 138.4, 138.2, 134.7,
130.1, 129.3, 128.0, 126.4, 125.0, 124.3, 121.8, 120.9, 117.6,
112.6, 112.5, 108.5, 61.1, 40.3, 40.1, 38.0, 25.3; MS (CI+) 475;
HRMS (CI+) calcd for C22H16N3O4SF3 475.0813, found 475.0806.
Anal. Calcd for C22H16N3O4SF3: C, 55.57; H, 3.39; N, 8.84.
Found: C, 55.65; H, 3.37; N, 8.77.
6-Meth yl-12-[â-D-glu copyr an osyl]-6,7,12,13-tetr ah ydr oin -
d olo[2,3-a ]p yr r olo[3,4-c]ca r ba zole-5,7-d ion e (+)-10a . (()-
7a (101 mg, 0.292 mmol) was dissolved in 3 mL of methanol.
R-D-Glucose (158 mg, 0.876 mmol) was then added, and the
reaction mixture was heated to reflux. After 60 h, the reaction
mixture was allowed to cool to room temperature and purified
by silica gel chromatography (9% MeOH/CHCl3) to give a 1:1
mixture of diastereomers by 1H NMR (0.128 g, 87%). This was
dissolved in 2 mL of 1,4-dioxane, and DDQ (127 mg, 0.56
mmol) was added. After 24 h, the reaction mixture was taken
up in 40 mL of EtOAc and washed with saturated NaHCO3
solution (3 × 40 mL). The organic layer was then dried (Na2-
SO4) and concentrated. Purification using silica gel chroma-
tography (3% MeOH/EtOAc) gave (()-10a (107 mg, 84%) as
an orange solid.
(+)-10a : mp 331 °C dec; [R]D +198.5 (c 0.90, THF); Rf )
1
0.38 (5% MeOH/EtOAc); IR (film) 3341, 2990, 1688 cm-1; H
NMR (acetone-d6, 500 MHz) δ 11.30 (s, 1H), 9.08 (d, 1H, J )
7.6), 8.84 (d, 1H, J ) 8.0), 7.79 (d, 1H, J ) 8.3), 7.51 (d, 1H,
J ) 8.3), 7.48 (t, 1H, J ) 7.7), 7.36 (t, 1H, J ) 8.2), 7.27 (t,
1H, J ) 7.6), 7.22 (t, 1H, J ) 7.6), 6.30 (d, 1H, J ) 9.2), 5.11
(t, 1H, J ) 3.7), 4.77 (s, 1H), 4.66 (s, 1H), 4.48 (d, 1H, J )
5.2), 4.38 (dd, 1H, J ) 9.6, 3.6), 4.08-4.11 (m, 3H), 3.90-3.94
(m, 2H), 2.79 (s, 3H); 13C NMR (acetone-d6, 125 MHz) δ 170.4,
170.3, 143.2, 142.1, 130.8, 129.2, 127.6, 125.8, 125.4, 122.7,
122.6, 121.4, 121.1,121.0, 119.7, 119.1, 118.7, 112.6, 112.5,
111.8, 86.1, 80.1, 78.2, 74.6, 69.0, 60.1, 23.5; MS (FAB+) 517,
501, 339; HRMS (FAB+) calcd for C27H23N3O7 501.1536, found
501.1522. Anal. Calcd for C27H23N3O7 + H2O: C, 62.42; H, 4.85;
N, 8.09. Found: C, 62.46; H, 4.84; N, 8.03.
12-[â-D-glu cop yr a n osyl]-6,7,12,13-t et r a h yd r oin d olo-
[2,3-a ]pyr r olo[3,4-c]ca r ba zole-5,7-dion e (+)-10b. Indolylin-
doline (()-7b (218 mg, 0.658 mmol) and R-D-glucose (355 mg,
1.975 mmol) were refluxed in 2 mL of MeOH for 79 h. The
reaction mixture was then preadsorbed on silica gel and
purified by silica gel chromatography (12% MeOH/CHCl3) to
give 250 mg (77%) of a 1:1 mixture of glycosylated diastereo-
mers. The mixture of diastereomers was then dissolved in 4
mL of 1,4-dioxane. DDQ (242 mg, 1.06 mmol) was then added.
After 24 h, the reaction mixture was poured into 100 mL of
EtOAc and washed with saturated aqueous NaHCO3 (3×),
dried (Na2SO4), and concentrated. Purification by silica gel
chromatography (3% MeOH/EtOAc) provided 168 mg (68%,
52% from (()-7b) of (+)-10b as an orange solid.
(+)-10b: mp 340-342 °C dec (methanol); [R]D +187.1 (c
0.30, DMSO); Rf ) 0.55 (5% methanol/EtOAc); IR (KBr) 3334,
3218, 2920, 1694 cm-1; 1H NMR (DMSO-d6, 500 MHz) δ 11.67
(s, 1H), 11.12 (s, 1H), 9.16 (d, 1H, J ) 8.0 Hz), 9.08 (d, 1H, J
) 8.0 Hz), 7.97 (d, 1H, J ) 8.7 Hz), 7.69 (d, 1H, J ) 8.0 Hz),
7.54-7.60 (m, 2H), 7.36 (aq, 2H, J ) 6.8 Hz), 6.28 (d, 1H, J )
8.8 Hz), 6.01 (t, 1H, J ) 4.0 Hz), 5.40 (d, 1H, J ) 5.2 Hz), 5.15
(d, 1H, J ) 5.2 Hz), 4.92 (d, 1H, J ) 5.3 Hz), 4.06-4.12 (m,
2H), 3.95-4.01 (m, 2H), 3.81-3.84 (m, 1H), 3.54-3.59 (m, 1H);
13C NMR (DMSO-d6, 125 MHz) δ 171.1, 171.0, 142.1, 140.8,
(+)-12: mp 345 °C dec; [R]D ) +151.0 (c 0.05, 1:1 MeOH/
DMF); Rf ) 0.22 (25% MeOH/CHCl3); IR (KBr) 3329, 2922,
1745, 1690 cm-1 1H NMR (500 MHz, DMSO-d6) δ 11.62 (s,
;
1H), 9.17 (d,1H, J ) 8.0 Hz), 9.10 (d, 1H, J ) 8.0 Hz), 7.96
(d,1H, J ) 8.5 Hz), 7.75 (d, 1H, J ) 8.1 Hz), 7.55-7.61 (m,
2H), 7.36-7.40 (m, 2H), 6.36 (d, 1H, J ) 9.0 Hz), 6.04 (bs,
1H), 5.72 (bs, 1H), 5.54 (bs, 1H), 5.30 (d, 1H, J ) 3.5 Hz), 5.10-
5.21 (m, 3H), 4.69 (bs, 1H), 4.26 (bd, 1H, J ) 9.6 Hz), 4.16-
4.21 (m, 2H), 3.92 (t, 1H, J ) 8.4 Hz), 3.84 (bd, 1H, J ) 10.7
Hz), 3.78 (d, 1H, J ) 11.0 Hz), 3.66-3.69 (m, 1H), 3.55-3.63
(m, 3H), 3.50 (t, 1H, J ) 9.1 Hz), 3.34-3.36 (m, 1H), 3.15 (t,
1H, J ) 9.4 Hz); 13C NMR (DMSO-d6, 125 MHZ) δ 169.7, 169.6,
142.2, 140.9, 129.5, 128.0, 127.1, 126.9, 124.3, 124.2, 121.4,
121.0, 120.7, 120.5, 120.1, 118.5, 118.4, 117.2, 112.4, 111.8,
100.9, 84.0, 77.8, 77.0, 76.0, 73.8, 73.4, 72.5, 70.0, 61.1, 58.4,
23.7; MS(FAB+) 686 (M + Na); HRMS (FAB+) calcd for
C
33H37N3O14 663.2064, found 663.2081.
6-Meth yl-12-[O-(r-D-ga la cotop yr a n osyl)-(1f6)-â-D-glu -
cop yr a n osyl]-6,7,12,13-t et r a h yd r oin d olo[2,3-a ]p yr r olo-
[3,4-c]ca r ba zole-5,7-d ion e, (+)-13. Indolylindoline (()-7a
(230 mg, 0.67 mmol), melibiose hydrate (0.72 g, 2.01 mmol),
and (NH4)2SO4 (7 mg, 0.05 mmol) were suspended in 4 mL of
MeOH and warmed to reflux. After 72 h, the reaction mixture
was adsorbed on silica gel and purified (30% MeOH/CHCl3,

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7549
isolated the UV active streak at Rf ) 0.5 in 30% MeOH/CHCl3).
The resulting mixture of diatereomers was suspended in 10
mL of 1,4-dioxane, and DDQ (276 mg, 1.22 mmol) was added.
After 70 h the dioxane was evaporated and the residue purified
by RPHPLC (60% MeOH/40% 50 mM pH 9.0 NH4OAc). The
product was then purified by silica gel chromatography (15%
MeOH/EtOAc) to remove the NH4OAc. The product of this
purification was contaminated with silica gel, and was there-
fore dissolved in 5% MeOH/THF and filtered through an HPLC
filter. This provided pure (+)-13 (214 mg, 47% yield from (()-
7a ) as an orange amorphous solid.
(+)-13: mp 296-298 °C (MeOH/CHCl3); [R]D +99.0 (c 0.40,
DMSO); Rf ) 0.16 (20% MeOH/CHCl3); IR (KBr) 3391, 2933,
1745, 1680 cm-1; 1H NMR (DMSO-d6, 500 MHz, 423K) δ 9.22
(d, 1H, J ) 8.0 Hz), 9.13 (d, 1H, J ) 8.0 Hz), 8.02 (d, 1H, J )
8.3 Hz), 7.84 (d, 1H, J ) 8.2 Hz), 7.53-7.57 (m, 2H), 7.35 (aq,
2H, J ) 8.1 Hz), 6.36 (d, 1H, J ) 8.5 Hz), 4.87 (bs, 1H), 4.15-
4.18 (m, 1H), 4.09 (dd, 1H, J ) 11.5, 4.7 Hz), 4.05 (bt, 1H, J )
8.8 Hz), 3.94 (dd, 1H, J ) 11.5, 2.2 Hz), 3.84-3.86 (m, 2H),
3.79-3.81 (m, 2H), 3.69 (bd, 2H, J ) 1.4 Hz), 3.57 (dd, 1H,
J ) 11.1, 5.6 Hz), 3.50 (dd, 1H, J ) 11.1, 5.8 Hz), 3.24 (s, 3H);
13C NMR (DMSO-d6, 125 MHz) δ 1169.8, 169.7, 141.0, 139.4,
130.0, 128.1, 127.2, 127.0, 124.4, 124.3, 122.7, 120.9, 120.8,
120.4, 119.3, 118.6, 117.7, 116.7, 115.4, 112.0, 99.0, 86.7, 77.5,
76.4, 71.1, 69.7, 69.3, 69.0, 68.5, 65.6, 60.7, 23.8; MS (CI+)
686 (M + Na), 663; HRMS (CI+) calcd for C33H33N3O12
663.2064, found 663.2078.
6-Meth yl-12-[O-(r-D-glu cop yr a n osyl)-(1f4)-O-(r-D-glu -
cop yr a n osyl)-(1f4)-â-D-glu cop yr a n osyl]-6,7,12,13-t et -
r ah ydr oin dolo[2,3-a ]pyr r olo[3,4-c]car bazole-5,7-dion e, (+)-
14. Indolylindoline (()-7a (378 mg, 1.10 mmol), maltotriose
hydrate (1.66 g, 3.30 mmol), and (NH4)2SO4 (7 mg, 0.05 mmol)
were suspended in 11 mL of MeOH and warmed to reflux.
After 32 h, the reaction mixture was adsorbed on silica gel
and purified (10-30% MeOH/CHCl3, isolated the UV active
streak at Rf ) 0.5 in 20% MeOH/CHCl3). The resulting mixture
of diatereomers was suspended in 25 mL of 1,4-dioxane, and
DDQ (500 mg, 2.2 mmol) was added. After 72 h, the dioxane
was evaporated and 100 mL of saturated aqueous NaHCO3
was added. The reaction was stirred vigorously for 1 h and
then filtered. The filtrate was then purified by silica gel
chromatography (30% MeOH/CHCl3). The product of this
purification was contaminated with silica gel, and was there-
fore dissolved in 10% MeOH/THF and filtered through an
HPLC filter. This provided pure (+)-14 (583 mg, 64% yield
from (()-7a ) as an orange amorphous solid.
(3 × 80 mL), the extracts combined, dried (Na2SO4), and
concentrated. Purification by silica gel chromatography (30%
EtOAc/hexanes) gave 2.26 g (99%) of benzyl ether 16 as a clear
syrup.
16: [R]D +1.4 (c 0.85, CHCl3); Rf ) 0.55 (30% EtOAc/
1
hexanes); IR 3017, 2908 cm-1; H NMR (CDCl3, 500 MHz) δ
7.37 (d, 1H, J ) 8.0 Hz), 7.15-7.32 (m, 16H), 6.86 (d, 2H, J )
8.8 Hz), 4.96 (d, 1H, J ) 11.9 Hz), 4.94 (d, 1H, J ) 9.6 Hz),
4.88 (d, 1H, J ) 10.7 Hz), 4.77 (d, 1H, J ) 10.7 Hz), 4.70 (d,
1H, J ) 9.9 Hz), 4.65 (d, 1H, J ) 11.9 Hz), 4.59 (d, 1H, J )
11.5 Hz), 4.51 (d, 1H, J ) 11.9 Hz), 4.48 (dd, 1H, J ) 7.6, 1.2
Hz), 3.76 (s, 3H), 3.75 (m, 1H), 3.66-3.69 (m, 1H), 3.49-3.55
(m, 2H), 3.47 (s, 3H), 3.35-3.37 (m, 1H), 3.30 (m, 1H); 13C NMR
(CDCl3, 125 MHz) δ 159.1, 138.6, 138.4, 137.4, 130.2, 129.2,
128.3, 128.2, 128.1, 128.0, 127.8, 127.6, 127.5, 113.6, 102.4,
84.5, 82.0, 79.7, 75.4, 74.9, 74.8, 73.0, 70.9, 68.6, 60.5, 55.1;
MS (FAB+) 607; HRMS (FAB+) calcd for C36H40O7Na (M +
Na)+ 607.2672, found 607.2683. Anal. Calcd for C36H40O7: C,
73.95; H, 6.90. Found: C, 73.74; H, 6.90.
4-O-Meth yl-1,2,3-O-ben zyl-â-D-glu copyr an oside, 17. Pro-
tected glucoside 16 (54 mg, 0.92 mmol) was dissolved in 2 mL
of CH2Cl2, and 0.2 mL of H2O was added. DDQ (22 mg, 0.10
mmol) was then added. After 5 h, the reaction was poured into
15 mL of saturated aqueous NaHCO3 and extracted with CH2-
Cl2 (3 × 15 mL). The extracts were dried (Na2SO4) and
concentrated. Purification by silica gel chromatography (30%
EtOAc/hexanes) gave 27 mg (63% yield) of alcohol 17.
17: mp 92-94 °C; [R]D +10.8 (c 1.05, CHCl3); Rf ) 0.47 (40%
EtOAc/hexanes); IR (film) 3391, 3308, 2960 cm-1 1H NMR
;
(CDCl3, 500 MHz) δ 7.25-7.37 (m, 15 H), 4.93 (d, 1H, J ) 8.7
Hz), 4.90 (d, 1H, J ) 9.5 Hz), 4.88 (d, 1H, J ) 10.7 Hz), 4.77
(d, 1H, J ) 11.1 Hz), 4.71 (d, 1H, J ) 11.1 Hz), 4.68 (d, 1H,
J ) 11.9 Hz), 4.54 (d, 1H, J ) 8.0 Hz), 3.88 (m, 1H), 3.73 (m,
1H), 3.55 (s, 3H), 3.52-3.54 (m, 2H), 3.43 (dd, 1H, J ) 9.2
Hz), 3.28 (m, 2H), 1.95 (m, 1H); 13C NMR (CDCl3, 125 MHz) δ
138.5, 138.3, 137.3, 128.5, 128.3, 128.1, 127.9, 127.6, 127.5,
102.7, 84.4, 82.1, 79.7, 75.6, 75.1, 75.0, 71.6, 62.0, 60.8; MS
(CI+) 357, 265; HRMS (CI+) calcd for C28H32O6 464.2198,
found 464.2186. Anal. Calcd for C28H32O6: C, 72.39; H, 6.94.
Found: C, 72.54; H,0.7.04.
ter t-Bu tyl (4R,1′R)-2,2-Dim eth yl-4-(1′-ben zyloxy-3-bu -
ten yl)oxa zolid in e-3-ca r boxyla te, 19. Homoallylic alcohol 18
(1.51 g, 5.57 mmol) was dissolved in 20 mL of dry DMF.
Sodium hydride (60% suspension, 0.450 g, 11.14 mmol) was
added followed by benzyl bromide (1.35 mL, 11.14 mmol). After
90 min, the reaction was quenched with the addition of 5 mL
of saturated aqueous NH4Cl and taken up in 100 mL of EtOAc.
The organic layer was washed with water (50 mL), and brine
(2 × 50 mL), dried (Na2SO4), and concentrated in vacuo.
Purification by silica gel chromatography (8% EtOAc/hexanes)
afforded 1.60 g (80% yield) of 19 as a clear syrup.
(+)-112: mp 300-304 °C (THF/MeOH); [R]D +151.5 (c 0.60,
DMSO); Rf ) 0.10 (30% MeOH/CHCl3); IR (KBr) 3331, 2923,
1745, 1680 cm-1 1H NMR (DMSO-d6, 500 MHz) δ 11.60 (s,
;
1H), 9.16 (d, 1H, J ) 8.1 Hz), 9.09 (d, 1H, J ) 8.0 Hz), 7.94 (d,
1H, J ) 8.5 Hz), 7.73 (d, 1H, J ) 8.2 Hz), 7.54-7.61 (m, 2H),
7.35-7.39 (m, 2H), 6.33 (d, 1H, J ) 9.1 Hz), 6.06 (t, 1H, J )
3.8 Hz), 5.70 (d, 1H, J ) 3.6 Hz), 5.62 (d, 1H, J ) 6.4 Hz),
5.53 (d, 1H, J ) 3.2 Hz), 5.50 (d, 1H, J ) 6.2 Hz), 5.29 (d, 1H,
J ) 3.6 Hz), 5.09 (d, 1H, J ) 5.7 Hz), 5.05 (d, 1H, J ) 3.7 Hz),
4.93 (d, 1H, J ) 6.1 Hz), 4.91 (d, 1H, J ) 6.1 Hz), 4.68 (t, 1H,
J ) 5.5 Hz), 4.55 (t, 1H, J ) 5.6 Hz), 3.90 (td, 1H, J ) 8.3, 3.3
Hz), 4.15-4.20 (m, 3H), 3.64-3.84 (m, 7H), 3.59 (ddd, 1H,
J ) 14.7, 9.0, 5.7 Hz), 3.36-3.54 (m, 3H), 3.24-3.29 (m, 2H),
3.20 (s, 3H), 3.09 (ddd, 1H, J ) 14.9, 9.2, 5.7 Hz); 13C NMR
(DMSO-d6, 125 MHz) δ 169.7, 169.6, 142.2, 140.9, 129.6, 128.1,
127.1, 127.0, 124.9, 124.4, 124.3, 121.4, 121.1, 120.8, 120.5,
120.2, 118.6, 118.5, 117.2, 112.4, 111.8, 100.8, 100.7, 84.1, 79.6,
77.9, 76.9, 76.0, 73.5, 73.4, 73.3, 72.5, 72.1, 69.9, 60.9, 60.6,
58.5, 23.7 (One resonance was not resolved); MS (FAB+) 848,
825; HRMS (FAB+) calcd for C39H43N3O17 825.2592, found
825.2599. Anal. Calcd for C39H43N3O17 + H2O C, 55.51; H, 5.38;
N, 4.98. Found: C, 55.51; H, 5.61; N, 4.56.
19: [R]D +21.5 (c 0.85, CHCl3); Rf ) 0.47 (20% EtOAc/
hexanes); IR (neat) 3069, 2977, 2935, 1701 cm-1 1H NMR
;
(DMSO-d6, 500 MHz, 80 °C) δ 7.30-7.35 (m, 4H), 7.26-7.28
(m, 1H), 5.85-5.91 (m, 1H), 5.08 (d, 1H, J ) 17.1 Hz), 5.02 (d,
1H, J ) 11.1 Hz), 4.58 (d, 1H, J ) 11.9 Hz), 4.53 (d, 1H, J )
11.9 Hz), 4.14 (bs, 1H), 3.99 (d, 1H, J ) 7.2 Hz), 3.95 (t, 1H,
J ) 15.4 Hz), 3.84 (m, 1H), 2.30-2.32 (m, 1H), 2.19-2.24 (m,
1H), 1.53 (s, 3H), 1.42 (s, 3H), 1.41 (s, 9H); 13C NMR (DMSO-
d6, 125 MHz, 80 °C) δ 151.4, 138.3, 135.5, 127.6, 126.9, 126.8,
115.8, 78.9, 77.7, 71.1, 62.8, 57.1, 35.8, 33.2, 27.7, 27.6; MS
(CI+) 362; HRMS (CI+) calcd for
C
21H32NO4 (M + H)+
362.2332, found 362.2325. Anal. Calcd for C21H32NO4: C,
69.76; H, 8.65; N, 3.88. Found: C, 69.52; H, 8.59; N, 3.82.
ter t-Bu tyl (4R,1′R)-2,2-Dim eth yl-4-(1′-ben zyloxy-3′-a l-
d eh yd o)oxa zolid in e-3-ca r boxyla te 20. Homoallyl ether 19
(2.46 g, 6.82 mmol) was dissolved in 40 mL of acetone.
N-Morpholine N-oxide (0.76 g, 7.50 mmol) was added followed
by OsO4 (2.5% solution in tBuOH, 1.22 mL, 0.095 mmol). The
reaction mixture turned yellow. After 2 h, the reaction was
concentrated in vacuo, taken up in EtOAc (50 mL), and washed
with 0.1 N HCl (3 × 50 mL). The organic layer was then dried
(Na2SO4) and concentrated. Purification by silica gel chroma-
tagraphy (70% EtOAc/hexanes) gave a mixture of diol diaster-
eomers that was dissolved in 50 mL of THF. To this solution
6-O-p -Met h oxyb en zyl-4-O-m et h yl-1,2,3-O-b en zyl-â-D-
glu cop yr a n osid e, 16. Protected glucoside 15 (2.23 g, 3.90
mmol) was dissolved in 20 mL of THF. Sodium hydride (60%
oil dispersion, 0.47 g, 11.7 mmol) was added followed by methyl
iodide (1.1 mL, 11.7 mmol). After 90 min, the reaction was
quenched with 10 mL of saturated aqueous NH4Cl and poured
into 100 mL of brine. The mixture was extracted with EtOAc

7550 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
was added sodium (meta)periodonate (6.4 mmol, 1.37 g) in 10
mL of water. After 1 h, the reaction was concentrated in vacuo
and poured into 50 mL of H2O. The water was extracted with
CH2Cl2 (3 × 50 mL) and the combined organic extracts dried
(Na2SO4) and concentrated. Purification by silica gel chroma-
tography (15% ethyl actetate/hexanes) gave 1.22 g (58%) of
aldehyde 20 as a clear oil and 0.17 g (8%) of the other
diastereomer at C-1′.
was then stirred for 2 h, filtered and concentrated. Purification
of the residue by silica gel chromatography (5% MeOH/EtOAc)
provided amine 24 (525 mg, 35%) and amine 23 (897 mg, 60%)
as yellow oils.
24: [R]D -13.5 (c 0.65, CHCl3); Rf ) 0.55 (5% MeOH/EtOAc);
IR (KBr) 3340, 3063, 2880 cm-1; 1H NMR (CDCl3 500 MHz) δ
7.24-7.41 (m, 20H), 4.97 (bt, 1H, J ) 2.5 Hz), 4.94 (d, 1H,
J ) 10.9 Hz), 4.92 (d, 1H, J ) 11.9), 4.89 (d, 1H, J ) 10.9 Hz),
4.76 (d, 1H, J ) 10.9 Hz), 4.71 (d, 1H, J ) 10.9 Hz), 4.65 (d,
1H, J ) 12.0 Hz), 4.61 (d, 1H, J ) 11.4 Hz), 4.46-4.48 (m,
2H), 3.94 (dd, 1H, J ) 1.8, 11.0 Hz), 3.74-3.81 (m, 2H), 3.52-
3.59 (m, 4H), 3.51 (s, 3H), 3.45 (dd, 1H, J ) 9.0, 2.3 Hz), 3.37
(ddd, 1H, J ) 9.8, 6.1, 1.6 Hz), 3.18 (t, 1H, J ) 9.1 Hz), 2.63
(ddd, 1H, J ) 9.5, 4.6, 4.4 Hz), 2.40 (s, 3H), 2.23 (ddd, 1H,
J ) 12.8, 4.5, 1.8 Hz), 1.66 (ddd, 1H, J ) 13.3, 10.4, 3.5 Hz);
13C NMR (CDCl3, 125 MHz) δ 138.6, 138.4, 138.3, 137.3, 128.5,
128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.8, 127.7, 127.6,
102.2, 98.5, 84.5, 82.1, 80.1, 75.6, 75.5, 74.8, 74.5, 70.9, 70.8,
66.6, 61.7, 60.7, 60.5, 34.6, 34.3; MS (FAB+) 684; HRMS
(FAB+) calcd for C41H49NO8: 684.3537 (M + H)+, found
684.3541 (M + H)+. Anal. Calcd for C41H49NO8: C, 72.01; H,
7.22; N, 2.05. Found: C, 72.05; H, 7.30; N, 2.11.
20: [R]D -14.5 (c 1.40, CHCl3); Rf ) 0.43 (20% EtOAc/
hexanes); IR (neat) 2978, 2882, 2724, 1727, 1698 cm-1 1H
;
NMR (DMSO-d6, 500 MHz, 80 °C) δ 9.68 (s, 1H), 7.24-7.34
(m, 5H), 4.59 (d, 1H, J ) 11.8 Hz), 4.54 (d, 1H, J ) 11.8 Hz),
4.39 (m, 1H), 4.18 (m, 1H), 3.93-3.99 (m, 2H), 2.60 (dd, 2H,
J ) 1.9, 7.1 Hz), 1.50 (s, 3H), 1.42 (s, 9H), 1.40 (s, 3H); 13C
NMR (DMSO-d6, 125 MHz, 80 °C) δ 201.0, 151.5, 138.0, 127.7,
127.0, 93.4, 79.3, 70.9, 62.6, 56.7, 43.3, 40.0, 27.6, 25.9, 25.8;
MS (CI+) 364, 306, 262, 200, 144; HRMS (CI+) calcd for
C
20H30NO5 (M + H)+ 364.2124, found 364.2120. Anal. Calcd
for C20H30NO5: C, 66.08; H, 8.05; N, 3.86. Found: C, 65.81;
H, 8.10; N, 3.82.
3-O-Ben zyl-4-(ter t-bu toxyca r boxa m id o)-2,4-d id eoxy-D-
xylose, (+)-21. Aldehyde 20 (1.028 g, 2.82 mmol) was dis-
solved in 27 mL of dioxane. Three milliliters of water was
added followed by toluenesulfonic acid monohydrate (538 mg,
2.82 mmol). After 21 h at room temperature, the reaction was
poured into 100 mL of saturated aqueous NaHCO3 and
extracted with EtOAc (3 × 100 mL). The extracts were then
dried (Na2SO4) and concentrated in vacuo. Purification via
silica gel chromatography (40% EtOAc/hexanes) gave 738 mg
(81%) of (+)-21 as a 1:1 mixture of anomers and a mixture of
partially hydrolyzed products (163 mg, 15% recovered).
(+)-21: mp 119-120 °C (CHCl3); [R]D ) +25.4 (c 0.90,
CHCl3); Rf ) 0.36 (50% EtOAc/hexanes); 1H NMR (CDCl3, 500
MHz) δ 7.24-7.36 (m, 5H), 5.31 (d, 0.5 H, J ) 6.3 Hz), 5.21
(d, 0.5 H, J ) 6.0 Hz), 5.10 (dd, 0.5 H, J ) 6.6, 3.3 Hz), 5.03
(bs, 1H), 4.70 (d, 0.5 H, J ) 11.5 Hz), 4.61 (d, 1H, J ) 11.7
Hz), 4.59 (bs, 1H), 4.37 (d, 0.5 H, J ) 11.8 Hz), 4.00 (d, 1H,
J ) 9.2 Hz), 3.79 (bd, 1H, J ) 14.3 Hz), 3.64-3.71 (m, 1.5 H),
2.08 (d, 0.5 H, J ) 14.0 Hz), 1.83-1.93 (m, 1 1/2 H), 1.44 (s,
9H); 13C NMR (CDCl3, 125 MHz) δ 155.3, 138.3, 137.3, 128.7,
128.6, 128.4, 128.0, 127.8, 127.6, 127.5, 127.4, 92.7, 92.1, 79.8,
79.6, 74.4, 73.9, 71.9, 70.9, 63.8, 58.6, 47.9, 46.9, 34.1, 31.4,
28.2, 27.9; MS(CI+) 324; HRMS (CI+) calcd for C17H25NO5
324.1808, found 324.1811. Anal. Calcd for C17H25NO5: C,
63.14; H, 7.79; N, 4.33. Found: C, 63.12; H, 7.72; N, 4.34.
Ben zyl-O-[3-O-ben zyl-4-m eth yla m in o-2,4-d id eoxy-â-L-
xylop yr a n osyl]-(1f6)-2,3-d i-O-ben zyl-4-O-m eth yl-â-D-glu -
cop yr a n osid e, 24, a n d Ben zyl-O-[3-O-ben zyl-4-m eth yl-
a m in o-2,4-d id e oxy-r-L-xylop yr a n osyl]-(1f6)-2,3-d i-O-
ben zyl-4-O-m eth yl-â-D-glu copyr an oside, 23. Lactol 21 (3.25
mmol, 1.051 g) and 4 Å mol sieves (400 mg) were suspended
in 20 mL of THF and cooled to -78 °C. DAST (8.13 mmol,
1.08 mL) was then added. After 20 min, the reaction was
warmed to 0 °C. Thirty minutes later, the reaction was filtered
through Celite with Et2O and washed with ice-cold NaHCO3
(3 × 50 mL). The organic layer was then dried (MgSO4) and
concentrated to give the unstable glycosyl fluoride as a yellow
solid (942 mg, 89% yield). The glycosyl fluoride 22 and
glucoside 17 were dissolved in 25 mL of THF and added to a
slurry of AgClO4 (3.07 mmol, 1.43 g), SnCl2 (6.14 mmol, 1.16
g), and 4 Å mol sieves (500 mg) in THF at -78 °C (the AgClO4
and SnCl2 were dried by azeotropic removal of benzene
followed by the addtion of the mol sieves). The reaction was
allowed to slowly warm to -15 °C over 6 h. The mixture was
then filtered through Celite with ether, which was then
washed with NaHCO3 (3 × 100 mL), brine (100 mL), dried
(MgSO4), and concentrated. The residue was then purified by
silica gel chromatography (40% EtOAc/60% hexanes) to give
1.68 g of a mixture of anomers inseparable by chromatography
(75%) and 286 mg (20%) of recovered 17. The mixture of
isomers were then dissolved in 20 mL of THF. LiAlH4 (1M in
THF, 4 mL, 4 mmol) was then added and the reaction warmed
to reflux. After 1 h, the reaction was cooled to room temper-
ature and quenched with the sequential addition of 500 µL of
water, 500 µL of 15% NaOH, and 1.5 mL of water. The reaction
23: [R]D +52.3 (c 0.9, CHCl3); Rf ) 0.30 (5% MeOH/EtOAc);
IR (KBr) 3342, 3030, 2862 cm-1; 1H NMR (CDCl3, 500 MHz) δ
7.25-7.40 (m, 20H), 4.94 (d, 1H, J ) 5.4 Hz), 4.92 (d, 1H, J )
6.4 Hz), 4.87 (d, 1H, J ) 10.9), 4.78 (d, 1H, J ) 10.9 Hz), 4.71
(d, 1H, J ) 11.0 Hz), 4.66 (d, 1H, J ) 11.4 Hz), 4.65 (d, 1H,
J ) 12.0 Hz), 4.52 (dd, 1H, J ) 6.6, 2.7 Hz), 4.46 (d, 1H, J )
7.7 Hz), 4.40 (d, 1H, J ) 11.4 Hz), 4.12 (dd, 1H, J ) 11.6, 4.6
Hz), 4.07 (dd, 1H, J ) 11.5, 3.8 Hz), 3.76 (dd, 1H, J ) 11.5,
1.5 Hz), 3.56 (s, 3H), 3.53 (t, 1H, J ) 9.0 Hz), 3.45 (t, 1H, J )
8.0 Hz), 3.35-3.40 (m, 2H), 3.28-3.30 (m, 1H), 3.09 (dd, 1H,
J ) 11.6, 9.7 Hz), 2.59 (ddd, 1H, J ) 9.2, 9.2, 4.6 Hz), 2.41-
2.44 (m, 1H), 2.40 (s, 3H), 1.59 (ddd, 1H, J ) 12.4, 10.6, 9.1
Hz); 13C NMR (CDCl3 125 MHz) δ 138.6, 138.4, 138.0, 137.4,
128.5, 128.4, 128.3, 128.1, 127.9, 127.8, 127.7, 127.6, 127.5,
127.4, 102.5, 100.7, 84.5, 82.0, 79.3, 77.1, 75.6, 74.8, 74.6, 71.1,
70.3, 66.9, 64.7, 60.7, 60.4, 35.0, 34.5; MS (FAB+) 684; HRMS
(CI+) calcd for C41H49NO8 684.3537 (M + H)+, found 684.3535
(M + H)+. Anal. Calcd forC41H49NO8: C, 72.01; H, 7.22; N,
2.05. Found: C, 72.25; H, 7.28; N, 2.03.
Ben zyl-O-[3-O-ben zyl-4-(2-tr im eth ylsilyloxyca r bon yl)-
m et h yla m in o-2,4-d id eoxy-â-L-xylop yr a n osyl]-(1f6)-2,3-
d i-O-ben zyl-4-O-m eth yl-â-D-glu cop yr a n osid e 25. Protected
disaccharide24 (400 mg, 0.584 mmol), p-nitrophenyl trimeth-
ylsilylethyl carbonate (292 mg, 1.03 mmol), and DMAP (126
mg, 1.03 mmol) were dissolved in 5 mL of NMP and warmed
to 75 °C. After 3 h, the reaction was taken up in EtOAc and
washed with 1 N NaOH (3×), dried (Na2SO4), and concen-
trated. Purification by silica gel chromatography (40% EtOAc/
hexane) provided 452 mg (93%) of Teoc carbamate 25 as a
colorless syrup.
25: [R]D -8.5 (c 1.2, MeOH); Rf ) 0.31 (30% EtOAc/
hexanes); IR (KBr) 3507, 3088, 2951, 1697 cm-1 1H NMR
;
(DMSO-d6, 500 MHz) δ 7.25-7.33 (m, 20H), 4.97 (bs, 1H),
4.77-4.82 (m, 3H), 4.71 (d, 1H, J ) 11.2 Hz), 4.64 (d, 1H, J )
11.4 Hz), 4.60 (d, 1H, J ) 12.1 Hz), 4.53-4.57 (m, 2H), 4.39
(dd, 1H, J ) 11.6, 4.6 Hz), 4.05-4.12 (m, 2H), 3.93-3.98 (m,
2H), 3.74-3.79 (m, 2H), 3.57 (dd, 1H, J ) 10.3, 4.7 Hz), 3.54
(t, 1H, J ) 9.1 Hz), 3.45 (s, 3H), 3.37-3.41 (m, 2H), 3.23 (t,
1H, J ) 8.3 Hz), 3.17 (t, 1H, J ) 9.4 Hz), 2.61 (s, 1.5H), 2.57
(s, 1.5H), 2.34 (d, 1H, J ) 12.5 Hz), 1.46-1.51 (m, 1H), 0.89-
0.93 (m, 2H), -0.01 (s, 9H); 13C NMR (DMSO-d6, 125 MHz) δ
156.0, 138.7, 138.5, 138.4, 137.6, 128.2, 128.1, 127.6, 127.5,
101.6, 97.1, 83.6, 81.6, 79.4, 74.4, 73.7, 73.5, 70.1, 69.3, 69.1,
69.0, 65.2, 62.7, 59.8, 59.5, 58.2, 56.3, 35.2, 17.2, -1.5; MS
(FAB+) 850, 486; HRMS (FAB+) calcd for C47H61N4O10Si
850.3962
(M + Na)+, found 850.3977. Anal. Calcd for C47H61N4O10Si: C,
68.17; H, 7.43; N, 1.69. Found: C, 68.12; H, 7.52; N, 1.75.
O-[4-(2-Tr im eth ylsilyloxyca r bon yl)m eth yla m in o-2,4-d i-
d eoxy-â-L-xylop yr a n osyl]-(1f6)-4-O-m eth yl-D-glu cop yr -
a n ose 26. Protected disaccharide 25 (442 mg, 0.533 mmol) was
dissolved in 3 mL of EtOH and 3 mL of EtOAc. Pd/C (10%,
227 mg, 0.213 mmol) was added. The reaction was then stirred

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7551
under a balloon of H2 for 90 min. The reaction was then filtered
through Celite with EtOAc and concentrated in vacuo. The
residue was purified by silica gel chromatography (10%
methanol/EtOAc) to give 240 mg (96%) of Teoc-protected
aminodisaccharide 26.
3.2 Hz), 4.80 (bs, 1H), 4.16 (ddd, 1H, J ) 9.7, 6.5, 1.8 Hz),
4.00-4.05 (m, 2H), 3.96 (t, 1H, J ) 8.6 Hz), 3.83 (dd, 1H, J )
11.5, 4.9 Hz), 3.70-3.72 (M, 1H), 3.68 (S, 3H), 3.62-3.65 (M,
1H), 3.60 (dd, 1H, J ) 11.1, 4.4 Hz), 3.34 (dd, 1H, J ) 11.1,
9.0 Hz), 3.23 (s, 3H), 2.27 (dt, 1H, J ) 8.4, 4.2 Hz), 2.24 (s,
3H), 2.03 (td, 1H, J ) 13.1, 4.2 Hz), 1.58 (ddd, 1H, J ) 9.9,
9.6, 3.4 Hz); 13C NMR (DMSO-d6, 125 MHz) δ 169.6, 169.5,
169.4, 142.2, 140.8, 140.0, 139.3, 129.9, 129.0, 128.1, 127.9,
127.4, 127.2, 127.0, 126.8, 124.5, 124.4, 124.2, 122.8, 121.4,
120.9, 120.7, 120.3, 120.0, 119.3, 118.9, 118.6, 118.4, 117.8,
117.1, 116.6, 114.7, 112.2, 111.8, 111.6, 98.6, 97.8, 86.5, 84.8,
79.1, 78.6, 77.2, 77.0, 76.2, 76.0, 73.1, 71.2, 66.4, 66.1, 65.7,
62.7, 61.5, 61.4, 61.1, 60.1, 60.0, 38.1, 36.7, 34.1, 33.7, 23.7;
MS (FAB+) 667, 645, 339; HRMS (FAB+) calcd for C34H36N4O8
645.2561 (M + H)+, found 645.2554.
2-Br om o-3-(7-ch lor o-1H -in d ol-3-yl)-N-m et h ylm a leim -
id e, 29. 7-Chloroindole (5.54 g, 34.45 mmol) was dissolved in
60 mL of toluene. Ethylmagnesium bromide (3 M in Et2O, 11.5
mL, 34.45 mmol) was then slowly added. After 30 min,
N-methyl dibromomaleimide (10.2 g, 37.9 mmol, in 50 mL of
toluene) was then cannulated into the indole solution. After
19 h, the reaction was poured into 200 mL of saturated
aqueous NH4Cl and extracted with EtOAc (3×). The combined
organic extracts were then dried (Na2SO4) and concentrated.
Purification by silica gel chromatography (20-40% EtOAc/
hexane) provided 8.37 g (72%) of the mixed maleimide 29 as
a yellow solid. (Note: the column must be run quickly in order
to avoid decomposition, the product being sensitive to silica
gel).
29: mp 176-178 °C (acetone); Rf ) 0.23 (30% EtOAc/
hexanes); IR (KBr) 3400, 3137, 2930, 1707, 1602 cm-1; 1H NMR
(DMSO-d6, 500 MHz) δ 12.45 (s, 1H), 8.01 (d, 1H, J ) 3.0 Hz),
7.82 (d, 1H, J ) 8.1 Hz), 7.30 (d, 1H, J ) 7.6 Hz), 7.15 (t, 1H,
J ) 7.9 Hz), 3.00 (s, 3H); 13C NMR (DMSO-d6, 125 MHz) δ
168.8, 166.3, 137.0, 133.3, 131.3, 126.3, 122.0, 121.3, 121.1,
116.5, 115.8, 104.8, 24.6; MS (CI+) 337; HRMS (CI+) calcd
for C13H8N2O2BrCl 337.9458, found 337.9463.
2-(7-Ch lor o-1H-in d ol-3-yl)-3-(1H-in d ol-3-yl)-N-m eth yl-
m a leim id e, 30. Indole (3.80 g, 32.25 mmol) was dissolved in
60 mL of toluene, and ethylmagnesium bromide (3 M in Et2O,
10.75 mL, 32.25 mmol) was added. The reaction was then
warmed to 50 °C for 30 min. The solution of indole Grignard
was then cannulated into a solution of bromomaleimide 29
(3.66 g, 10.75 mmol) in 15 mL of THF, 15 mL of toluene, and
3 mL of Et2O. The reaction mixture was then heated to reflux
for 21 h. The reaction was then allowed to cool to room
temperature and quenched with 50 mL of saturated aqueous
NH4Cl. The reaction mixture was then poured into 200 mL of
brine and extracted with EtOAc (3×). The extracts were then
dried (Na2SO4) and concentrated. Purification by silica gel
chromatography (5% acetone/CH2Cl2) gave 3.13 g (77%) of the
unsymmetrical bisindole 30 as a red foam.
26: mp 41 °C (MeOH); Rf ) 0.26 (10% MeOH/EtOAc); IR
1
(KBr) 3426, 2955, 1676 cm-1; H NMR (DMSO-d6, 500 MHz)
δ 6.67 (d, 0.4H, J ) 3.5 Hz), 6.32 (d, 0.6H, J ) 4.0 Hz), 5.03
(d, 0.6H, J ) 4.9 Hz), 4.94-4.97 (m, 1H), 4.84-4.87 (m, 1.8H),
4.81 (bs, 1H), 4.57 (d, 0.6H, J ) 6.5 Hz), 4.26 (t, 0.4H, J ) 6.4
Hz), 4.00-4.12 (m, 1.6H), 3.91-3.95 (m, 1.4H), 3.51-3.77 (m,
3.6 Hz), 3.41 (s, 3H), 3.23-3.37 (m, 2H), 3.09-3.14 (m, 1H),
2.84 (t, 2H, J ) 9.6 Hz), 2.73 (s, 1.5H), 2.72 (s, 1.5H), 1.98 (bd,
1H, J ) 9.8 Hz), 1.44-1.53 (m, 1H), 0.93 (t, 2H, J ) 8.1 Hz),
0.01 (s, 9H); 13C NMR (DMSO-d6, 125 MHz) δ 156.1, 97.4, 97.3,
96.6, 92.2, 80.2, 79.9, 76.4, 75.0, 73.5, 72.9, 72.5, 69.0, 66.3,
66.2, 62.7, 62.6, 61.7, 61.5, 59.6, 58.4, 58.1, 29.1, 29.0, 17.3,
-1.4; MS (FAB+) 490; HRMS (FAB+) calcd for C19H37NO10Si
490.2084 (M + Na)+, found 490.2091 Anal. Calcd for C19H37
-
NO10Si: C, 48.81; H, 7.98; N, 3.00. Found: C, 48.60; H, 8.03;
N, 3.14.
6-Meth yl-12-[O-[4-(2-tr im eth ylsilyloxyca r bon yl)m eth -
yla m in o-2,4-d id eoxy-â-L-xylop yr a n osyl]-(1f6)-4-O-m eth -
yl-â-D-glu cop yr a n osyl]-6,7,12,13-tetr a h yd r oin d olo[2,3-a ]-
p yr r olo[3,4-c]ca r ba zole-5,7-d ion e 27. The debenzylated
Teoc-protected disaccharide 26 (93 mg, 0.200 mmol) and
indolylindoline (()-7a (206 mg, 0.600 mmol) were suspended
in 3 mL of MeOH. (NH4)2SO4 (4 mg, 0.04 mmol) was then
added, and the reaction was warmed to reflux. After 72 h, the
reaction mixture was adsorbed on silica gel and purified by
silica gel chromatography (5% MeOH/EtOAc, isolated com-
pounds at Rf ) 0.5). The mixture of diastereomers (135 mg,
0.170 mmol, 85% yield) was dissolved in 3 mL of 1,4-dioxane.
DDQ (135 mg, 0.511 mmol) was added, and the reaction
mixture was stirred at room temperature for 45 h. The reaction
mixture was evaporated and taken up in EtOAc. The EtOAc
was washed with 0.1 N NaOH (3×), dried (Na2SO4), and
concentrated. Purification by silica gel chomatography (50%
hexane/acetone) gave 110 mg (82%, 70% from 26) of 27 as a
yellow solid.
27: mp 320 °C dec; [R]D +76.2 (c 0.5, THF); Rf ) 0.40 (50%
acetone/hexane); IR (KBr) 3363, 2939, 1747, 1694 cm-1 1H
;
NMR (DMSO-d6, 500 MHz, 398K) δ 10.83 (s, 1H), 9.22 (d, 1H,
J ) 7.9 Hz), 9.15 (d, 1H, J ) 8.2 Hz), 7.98 (d, 1H, J ) 8.2 Hz),
7.78 (d, 1H, J ) 8.2 Hz), 7.59 (t, 1H, J ) 8.2 Hz), 7.54 (t, 1H,
J ) 8.3 Hz), 7.35-7.38 (m, 2H), 6.27 (d, 1H, J ) 8.5 Hz), 4.0.91
(bs, 1H), 4.79 (bs, 2H), 4.16-4.19 (m, 1H), 4.01-4.06 (m, 5H),
3.93 (at, 2H, J ) 8.4 Hz), 3.80-3.85 (m, 1H), 3.67 (s, 3H), 3.55-
3.65 (m, 2H), 3.53 (t, 1H, J ) 6.9 Hz), 3.50 (dd, 1H, J ) 10.7,
5.0 Hz), 3.24 (s, 3H), 2.34 (s, 3H), 2.15 (dd, 1H, J ) 17.7, 4.4
Hz), 1.53-1.58 (m, 1H), 0.89 (t, 2H, J ) 8.0 Hz), -0.01 (s, 9H);
13C NMR (DMSO-d6, 125 MHz, 2 sets of signals) δ 169.9, 169.5,
169.4, 169.3, 155.9, 155.8, 140.8, 140.0, 139.4, 139.2, 129.9,
128.9, 128.0, 127.8, 127.7, 127.3, 127.1, 126.6, 124.8, 124.5,
124.4, 122.9, 121.5, 121.0, 120.8, 120.4, 119.9, 119.4, 119.0,
118.6, 118.3, 117.9, 117.2, 116.7, 114.4, 112.2, 111.7, 111.5,
98.1, 97.9, 86.6, 84.8, 79.5, 79.3, 79.0, 77.1, 76.5, 76.0, 73.2,
71.0, 66.6, 66.4, 62.7, 62.6, 61.9, 61.7, 61.6, 60.3, 60.2, 58.6,
58.3, 58.0, 55.8, 29.6, 28.7, 23.7, 17.2, -1.4, -1.5; MS (FAB+)
788, 339; HRMS (FAB+) calcd for C40H48N4O11Si 788.3088,
found 788.3088. Anal. Calcd for C40H48N4O11Si: C, 60.90; H,
6.13; N, 7.10. Found: C, 61.22; H, 6.39; N, 6.76.
AT2433-B1 (28). Teoc-protected indolocarbazole glycoside
27 (30 mg, 0.038 mmol) was dissolved in 2 mL of THF. 4 Å
mol sieves (200 mg) and TBAF (1 M in THF, 100 µL, 0.10
mmol) were then added. After 4 h, the reaction was filtered,
adsorbed on silica gel, and purified by silica gel chromatog-
raphy (10% MeOH/1% NH4OH/89% CHCl3). This provided 21
mg (86%) of AT2433-B1 (28) as a yellow solid.
28: mp 245 °C (CHCl3); [R]D +115.7 (c 0.50, 1:1 methanol/
CHCl3); Rf ) 0.34 (20% MeOH/CHCl3); IR (KBr) 3357, 2922,
1750, 1691 cm-1; 1H NMR (DMSO-d6, 423 K, 500 MHz) δ 9.22
(d, 1H, J ) 8.0 Hz), 9.15 (d, 1H, J ) 8.1 Hz), 7.99 (d, 1H, J )
8.4 Hz), 7.80 (d, 1H, J ) 8.2 Hz), 7.55-7.60 (m, 2H), 7.35-
7.39 (m, 2H), 6.27 (d, 1H, J ) 8.6 Hz), 4.91 (dd, 1H, J ) 3.4,
30: mp 246-250 °C (acetone); Rf ) 0.32 (30% EtOAc/
hexanes); IR (KBr) 3409, 3317, 2973, 1682 cm-1 1H NMR
;
(acetone-d6, 500 MHz) δ 11.09 (bs, 1H), 10.87 (bs, 1H), 7.92
(s, 1H), 7.88 (s, 1H), 7.41 (d, 1H, J ) 8.0 Hz), 7.04 (d, 1H, J )
7.6 Hz), 6.98 (t, 1H, J ) 7.2 Hz), 6.90 (d, 1H, J ) 8.0 Hz), 6.85
(d, 1H, J ) 8.0 Hz), 6.61-6.65 (m, 2H), 3.10 (s, 3H); 13C NMR
(acetone-d6, 125 MHz) δ 172.5, 137.2, 134.0, 130.3, 130.2, 130.1,
129.5, 128.6, 127.0, 126.4, 122.8, 122.2, 122.0, 121.2, 121.1,
120.5, 117.0, 112.4, 108.6, 107.1, 24.1; MS (CI+) 375, 329;
HRMS (CI+) calcd for C21H14N3O2Cl 375.0774, found 375.0776.
Anal. Calcd for C21H14N3O2Cl: C, 67.19; H, 3.76; N, 11.20.
Found: C, 67.4; H, 3.93; N, 10.93.
1-Met h yl-cis-3-(7-ch lor o-1H -in d ol-3-yl)-4-(1H -in d ol-3-
yl)-2,5-p yr r olid in ed ion e (()-31. Unsymmetrical maleimide
30 (2.35 g, 6.25 mmol) and palladium on carbon (10%, 665 mg,
0.626 mmol) were suspended in 40 mL of DMF. The reaction
mixture was then shaken on a Parr shaker under 50 psi of H2
for 26 h. The reaction was then filtered through Celite with
EtOAc, washed with water (1×) and brine (2×), dried (Na2-
SO4), and concentrated. Purification by silica gel chromatog-
raphy (50% EtOAc) provided (()-31 (1.44 g, 61%) as an off-
white solid.

7552 J . Org. Chem., Vol. 65, No. 22, 2000
Chisholm and Van Vranken
(()-31: mp 118-122 °C (EtOAc); Rf ) 0.23 (40% EtOAc/
hexanes); IR (KBr) 3386, 3055, 2863, 1773, 1697 cm-1; 1H NMR
(DMSO-d6, 500 MHz) δ 11.01 (s, 1H), 10.67 (s, 1H), 7.31 (d,
1H, J ) 8.0 Hz), 7.28 (d, 1H, J ) 7.9 Hz), 7.13 (d, 1H, J ) 8.1
Hz), 7.01 (d, 1H, J ) 7.0 Hz), 6.84-6.95 (m, 5H), 4.97 (d, 1H,
J ) 9.0 Hz), 4.93 (d, 1H, J ) 9.0 Hz), 3.12 (s, 3H); 13C NMR
(DMSO-d6, 125 MHz) δ 178.1, 178.0, 135.4, 132.2, 129.0, 126.7,
125.7, 124.5, 120.7, 120.3, 119.4, 118.4, 118.2, 117.5, 115.5,
111.3, 109.5, 108.1, 43.5, 43.4, 24.8; MS (CI+) 379, 377, 292;
HRMS (CI+) calcd for C21H16N3O2Cl 377.0931, found 377.0930.
Anal. Calcd for C21H16N3O2Cl: C, 66.76; H, 4.27; N, 11.12.
Found: C, 66.47; H, 4.34; N, 11.02.
(4bR,4cR,7a R,12bS)-r el-6-Meth yl-11-ch lor o-4b,4c,6,7,-
7a ,12,12b,13-octa h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r ba -
zole-5,7-d ion e, (()-32. Unsymmetrical bisindolylsuccinimide
(()-31 (298 mg, 0.784 mmol) was dissolved in TFA (5 mL, 64.9
mmol) and heated to reflux. After 12 h, the reaction was cooled
to room temperature and taken up in EtOAc. The reaction was
then washed with 1 N NaOH (3×), dried (Na2SO4), and
concentrated. Purification by silica gel chromatography (3%
acetone/CH2Cl2) provided chlorinated indolylindoline (()-32
(248 mg, 82% yield) as a buff foam.
(()-32: mp 288-290 °C (acetone); Rf ) 0.33 (4% acetone/
CH2Cl2); IR (KBr) 3379, 3031, 2922, 1774, 1690 cm-1; 1H NMR
(DMSO-d6, 500 MHz) δ 11.22 (s, 1H), 7.74 (d, 1H, J ) 8.0 Hz),
7.17 (d, 1H, J ) 7.3 Hz), 7.14 (d, 1H, J ) 7.6 Hz), 6.99 (t, 1H,
J ) 7.9 Hz), 6.89 (t, 1H, J ) 7.6 Hz), 6.59 (t, 1H, J ) 7.4 Hz),
6.53 (d, 1H, J ) 7.7 Hz), 6.06 (s, 1H), 4.75 (d, 1H, J ) 7.8 Hz),
4.29 (dd, 1H, J ) 7.7, 1.8 Hz), 4.17 (bd, 2H, J ) 7.6 Hz), 2.80
(s, 3H); 13C NMR (DMSO-d6, 125 MHz) δ 178.3, 176.6, 149.6,
135.9, 133.1, 128.4, 127.9, 127.4, 122.5, 121.1, 120.1, 119.3,
117.9, 115.5, 109.1, 105.9, 53.2, 39.4, 39.1, 37.7, 24.6; MS (CI+)
379, 377; HRMS (CI+) calcd for C21H16N3O2Cl 377.0931, found
377.0939. Anal. Calcd for C21H16N3O2Cl: C, 66.76; H, 4.27; N,
11.12. Found: C, 66.79; H, 4.39; N, 10.92.
(4b R,4cR,7a R,12b S)-r el-1-Ch lor o-6-m et h yl-4b ,4c,6,7,-
7a ,12,12b,13-octa h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r ba -
zole-5,7-d ion e, (()-33. Unsymmetrical bisindolylsuccinimide
(()-31 (1.37 g, 3.59 mmol) was dissolved in 50 mL of CHCl3,
and methanesulfonic acid (1.16 mL, 18 mmol) was added. After
3 h, the reaction was taken up in EtOAc and washed with 1
N NaOH (3×), dried (Na2SO4), and concentrated. Purification
by silica gel chromatography (4% acetone/CH2Cl2) provided
chlorinated indolylindoline (()-33 (1.29 g, 94% yield) as a buff
foam.
(()-33: mp 172-175 °C (acetone); Rf ) 0.44 (4% acetone/
CH2Cl2); IR (KBr) 3370, 3062, 2932, 1774, 1695 cm-1; 1H NMR
(acetone-d6, 500 MHz) δ 10.26 (s, 1H), 7.89 (d, 1H, J ) 8.0
Hz), 7.29 (d, 1H, J ) 8.0 Hz), 7.23 (d, 1H, J ) 7.3 Hz), 7.08 (t,
1H, J ) 7.2 Hz), 7.00 (t, 1H, J ) 7.9 Hz), 6.95 (d, 1H, J ) 8.6
Hz), 6.65 (t, 1H, J ) 7.8 Hz), 5.67 (s, 1H), 4.99 (d, 1H, J ) 7.9
Hz), 4.46 (bd, 1H, J ) 7.9 Hz), 4.28 (d, 1H, J ) 7.7 Hz), 4.25
(dd, 1H, J ) 9.9, 2.3 Hz), 2.85 (s, 3H); 13C NMR (acetone-d6,
125 MHz) δ 178.6, 177.1, 147.6, 137.7, 134.3, 132.0, 128.6,
127.0, 123.2, 122.1, 121.7, 120.4, 120.2, 115.4, 111.8, 106.5,
54.5, 41.3, 41.2, 39.0, 24.9; MS (CI+) 379, 378, 377, 319, 266;
HRMS (CI+) calcd for C21H16N3O2Cl 377.0931, found 377.0932.
Anal. Calcd for C21H16N3O2Cl: C, 66.76; H, 4.27; N, 11.12.
Found: C, 66.97; H, 4.39; N, 10.93.
6-Meth yl-11-ch lor o-12-[â-D-glu cop yr a n osyl]-6,7,12,13-
t et r a h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r b a zole-5,7-d i-
on e, (+)-34. Chlorinated indolylindoline (()-32 (248 mg, 0.650
mmol), R-D-glucose (351 mg, 1.95 mmol), and (NH4)2SO4 (1 mg,
0.007 mmol) were refluxed in 6 mL of MeOH for 26 h. The
reaction mixture was then preadsorbed on silica gel and
purified by silica gel chromatography (8% MeOH/CHCl3) to
give 301 mg (85%) of a 1:1 mixture of glycosylated diastereo-
mers. The mixture of diastereomers was then dissolved in 6
mL of THF. DDQ (315 mg, 1.38 mmol) was then added. After
26 h the reaction mixture was poured into 100 mL of saturated
aqueous NaHCO3 and stirred vigorously. The reaction was
then filtered and the filtrate purified by silica gel chromatog-
raphy (10% MeOH/CHCl3) provided 229 mg (77%, 66% from
(()-32) of chlorinated indolocarbazole (+)-34 as a yellow solid.
(+)-34: mp 342 °C dec (THF/MeOH); [R]D +166.4 (c 0.60,
THF); Rf ) 0.10 (10% MeOH/CHCl3); IR (KBr) 3370, 2922,
1748, 1691 cm-1 1H NMR (DMSO-d6, 500 MHz) δ 10.59 (s,
;
1H), 9.11 (d, 1H, J ) 7.5 Hz), 9.03 (d, 1H, J ) 8.0 Hz), 8.05 (d,
1H, J ) 8.5 Hz), 7.68 (d, 1H, J ) 7.7 Hz), 7.59 (t, 1H, J ) 7.9
Hz), 7.41 (t, 1H, J ) 7.9 Hz), 7.35 (t, 1H, J ) 7.5 Hz), 6.29 (d,
1H, J ) 9.5 Hz), 5.51 (d, 1H, J ) 5.0 Hz), 5.33 (d, 1H, J ) 5.0
Hz), 5.04-5.08 (m, 2H), 4.02-4.05 (m, 1H), 3.92-3.95 (m, 2H),
3.88 (td, 1H, J ) 9.1, 5.2 Hz), 3.79 (td, 1H, J ) 9.0, 5.8 Hz),
3.64 (td, 1H, J ) 8.8, 5.4 Hz), 3.17 (s, 3H); 13C NMR (DMSO-
d6, 125 MHz) δ 169.3, 169.2, 142.1, 137.1, 128.8, 128.0, 127.0,
126.5, 124.2, 123.5, 123.2, 121.8, 120.7, 120.6, 119.8, 119.6,
118.6, 117.1, 116.0, 111.7, 84.7, 81.0, 77.1, 73.3, 70.0, 60.6, 23.7;
MS (CI+) 535, 373; HRMS (FAB+) calcd for C27H22N3O7Cl
535.1146, found 535.1142. Anal. Calcd for C27H22N3O7Cl+H2-
O: C, 58.54; H, 4.37; N, 7.59. Found: C, 58.43; H, 4.33; N,
7.48.
1-Ch lor o-6-m et h yl-12-[â-D-glu cop yr a n osyl]-6,7,12,13-
t et r a h yd r oin d olo[2,3-a ]p yr r olo[3,4-c]ca r b a zole-5,7-d i-
on e, (+)-35. Chlorinated indolylindoline (()-33 (30 mg, 0.078
mmol), R-D-glucose (281 mg, 1.56 mmol) and CSA (18 mg, 0.078
mmol) were suspended in 1 mL of DMF for 65 h. The reaction
mixture was then taken up in EtOAc and washed with
saturated aqueous NaHCO3 (3×), dried (Na2SO4), and concen-
trated. Purification by silica gel chromatography (8% MeOH/
CHCl3) gave 28 mg (66%) of a 1:1 mixture of glycosylated
diastereomers. The mixture of diastereomers was then dis-
solved in 1 mL of THF. DDQ (54 mg, 0.239 mmol) was then
added. After 5 days the reaction mixture was poured into
saturated aqueous NaHCO3 and extracted with EtOAc (3×),
dried (Na2SO4) and concentrated. Purification by silica gel
chromatography (10% MeOH/CHCl3) provided 24 mg (86%,
57% from (()-33) of indolocarbazole glycoside (+)-35 as a
yellow solid.
(+)-35: mp 348 °C dec (THF/MeOH); [R]D +173.1 (c 0.35,
DMSO); Rf ) 0.20 (10% MeOH/CHCl3); IR (KBr) 3453, 3313,
3070, 2939, 1744, 1694 cm-1; 1H NMR (DMSO-d6, 500 MHz) δ
11.85 (s, 1H), 9.24 (d, 1H, J ) 8.0 Hz), 9.10 (d, 1H, J ) 8.0
Hz), 7.72 (d, 1H, J ) 8.1 Hz), 7.64 (d, 1H, J ) 7.7 Hz), 7.59 (t,
1H, J ) 7.7 Hz), 7.39 (aq, 2H, J ) 8.0 Hz), 6.91 (d, 1H, J ) 8.3
Hz), 6.15 (bt, 1H, J ) 3.5 Hz), 5.30 (d, 1H, J ) 5.5 Hz), 5.08
(d, 1H, J ) 5.0 Hz), 4.83 (d, 1H, J ) 4.5 Hz), 4.11 (dd, 1H,
J ) 10.8, 3.3 Hz), 3.96 (bd, 1H, J ) 10.6 Hz), 3.85-3.90 (m,
1H), 3.84 (t, 1H, J ) 9.0 Hz), 3.32-3.41 (m, 2H), 3.20 (s, 3H);
13C NMR (DMSO-d6, 125 MHz) δ 169.4, 169.3, 140.8, 138.2,
130.3, 129.8, 129.6, 127.4, 125.5, 124.5, 123.8, 122.3, 121.7,
121.0, 120.6, 119.3, 118.1, 117.4, 116.5, 112.1, 84.0, 79.0, 76.9,
72.0, 67.4, 58.4, 23.8; MS (FAB+) 535, 373; HRMS (FAB+)
calcd for C27H22N3O7Cl 535.1146, found 535.1148. Anal. Calcd
for C27H22N3O7Cl+H2O: C, 58.54; H, 4.37; N, 7.59. Found: C,
58.54; H, 4.32; N, 7.45.
1-Ch lor o-6-m eth yl-12-[O-[4-(2-tr im eth ylsilyloxycar bon -
yl)m eth yla m in o-2,4-d id eoxy-â-L-xylop yr a n osyl]-(1f6)-4-
O-m eth yl-â-D-glu copyr an osyl]-6,7,12,13-tetr ah ydr oin dolo-
[2,3-a ]p yr r olo[3,4-c]ca r ba zole-5,7-d ion e 36. Chlorinated
indolylindoline (()-33 (860 mg, 2.24 mmol), Teoc-protected
aminodisaccharide 26 (349 mg, 0.747 mmol), and CSA (58 mg,
0.247 mmol) were suspended in 4 mL of DMF for 67 h. The
reaction mixture was then quenched with NH4OH and con-
centrated in vacuo. The residue was then purified by silica
gel chromatography (5% MeOH/EtOAc) to give 219 mg (35%)
of a 1:1 mixture of glycosylated diastereomers. The mixture
of diastereomers was then dissolved in 2 mL of CH2Cl2. DBU
(120 µL, 0.789 mmol) was then added followed by I2 (201 mg,
0.789 mmol). After 23 h the reaction mixture was poured into
saturated aqueous NaHCO3 and extracted with EtOAc (3x),
dried (Na2SO4) and concentrated. Purification by silica gel
chromatography (5% MeOH/EtOAc) provided 113 mg (52%)
of indolocarbazole glycoside 36 as a yellow solid.
36: mp 330 °C dec; [R]D +110.3 (c 0.85, THF); Rf ) 0.55
(50% hexane/acetone); IR (KBr) 3445, 3359, 2952, 1748, 1698
1
cm-1; H NMR (DMSO-d6, 500 MHz, 323 K) δ 10.53 (s, 1H),
9.08 (d, 1H, J ) 7.9 Hz), 7.79 (d, 1H, J ) 8.0 Hz), 7.64-7.68
(m, 2H), 7.41 (aq, 2H, J ) 7.1 Hz), 6.89 (d, 1H, J ) 9.2 Hz),
5.40 (d, 1H, J ) 5.9 Hz), 5.07 (bs, 1H), 5.01 (d, 1H, J ) 5.8

Synthesis of the Antitumor Antibiotic AT2433-A1
J . Org. Chem., Vol. 65, No. 22, 2000 7553
Hz), 4.60 (bs, 1H), 4.10 (d, 1H, J ) 11.5 Hz), 4.04 (bd, 1H, J )
9.4 Hz), 3.90-3.98 (m, 3H), 3.81 (bs, 1H), 3.62 (s, 3H), 3.54-
3.59 (m, 3H), 3.30-3.32 (m, 1H), 3.18 (s, 3H), 2.31 (dd, 1H, J
) 13.0, 4.0 Hz), 2.08 (s, 3H), 1.62-1.65 (m, 1H), 0.80-0.86
(m, 2H), -0.05-0.03 (m, 2H), -0.09 (s, 9H); 13C NMR (acetone-
d6, 125 MHz) δ 169.0, 168.9, 155.8, 139.9, 137.8, 125.2, 124.5,
123.8, 122.4, 121.4, 121.1, 121.0, 119.0, 118.6, 117.6, 116.2,
112.0, 98.3, 84.6, 78.8, 77.8, 77.4, 72.0, 65.7, 65.5, 62.6, 62.5,
61.7, 60.2, 58.4, 57.9, 55.8, 38.5, 32.1, 29.6, 28.2, 23.6, 17.1,
2H), 6.83 (d, 1H, J ) 8.8 Hz), 5.38 (d, 1H, J ) 5.8 Hz), 5.05 (t,
1H, J ) 1.8 Hz), 4.98 (d, 1H, J ) 5.4 Hz), 4.91 (bs, 1H), 4.12
(d, 1H, J ) 10.4 Hz), 4.01 (bd, 1H, J ) 9.6 Hz), 3.92 (dd, 1H,
J ) 11.6, 3.1 Hz), 3.74 (dd, 1H, J ) 11.1, 3.7 Hz), 3.61-3.68
(m, 2H), 3.60 (s, 3H), 3.52-3.57 (m, 3H), 3.37-3.41 (m, 1H),
3.20 (s, 3H), 2.38 (bs, 1H), 2.21 (s, 3H), 2.19-2.20 (m, 1H),
1.69-01.74 (m, 1H); 13C NMR (DMSO-d6, 125 MHz) δ 169.1,
169.0, 140.0, 138.1, 129.8, 129.6, 129.4, 127.8, 125.3, 124.5,
123.8, 122.5, 121.5, 121.1, 121.0, 119.1, 118.6, 117.5, 116.4,
112.1, 98.7, 84.5, 78.4, 77.8, 77.3, 72.0, 66.3, 65.6, 61.7, 61.5,
60.1, 57.5, 338., 23.7; MS (FAB+) 679; HRMS (FAB+) calcd
for C34H35N4O9Cl (M + H) 679.2170, found 679.2170.
-1.5; MS (FAB+) 824, 822; HRMS (FAB+) calcd for C40H47
N4O11ClSi 822.2698, found 822.2685. Anal. Calcd for C40H47
-
-
N4O11ClSi: C, 58.35; H, 5.75; N, 6.80. Found: C, 58.11; H, 5.77;
N, 6.56.
Ack n ow led gm en t. This work was supported by the
American Cancer Society, PRF, and the UC Cancer
Research Coordinating Committee. J .D.C. was gener-
ously supported by a Bristol-Myers Squibb graduate
fellowship. D.V.V. gratefully acknowledges the support
of Eli Lilly and Glaxo Wellcome.
AT2433-A1, 37. Teoc-protected indolocarbazole glycoside 36
(58 mg, 0.070 mmol) was dissolved in 2 mL of THF. Molecular
sieves (4 Å) (200 mg) and TBAF (1 M in THF, 200 µL, 0.20
mmol) were then added. After 3 h, the reaction was filtered,
adsorbed on silica gel, and purified by silica gel chromatog-
raphy (10% MeOH/1% NH4OH/89% CHCl3). This provided 39
mg (82%) of AT2433-A1 (37) as a yellow solid.
37: mp 330 °C dec; [R]D +104.0 (c 0.3, DMSO); Rf ) 0.43
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
compounds 12, 13, 28, 29, and 37. This material is available
free of charge via the Internet at http://pubs.acs.org.
(10% MeOH/CHCl3); IR (KBr) 3422, 2927, 1745, 1694 cm-1
;
1H NMR (DMSO-d6, 500 MHz) δ 10.55 (s, 1H), 9.22 (d, 1H,
J ) 8.0 Hz), 9.10 (d, 1H, J ) 7.8 Hz), 9.10 (d, 1H, J ) 7.8 Hz),
7.79 (d, 1H, J ) 8.3 Hz), 7.62-7.70 (m, 2H), 7.41-7.46 (m,
J O000911R