Synthesis and cytotoxicity of 5-amino-1-(chloromethyl)-3-[(5,6,7- trimethoxyindol-2-yl)carbonyl], 1,2 dihydro-3H-benz[e]indole (Amino-seco- CBI-TMI) and related 5-alkylamino analogues: New DNA minor groove alkylating agents

Article abstract of DOI:10.1021/jo981395w

The first synthesis of seco-CBI-TMI alkylating agents with 5-nitrogen substituents is reported. The parent 5-amino compound was prepared in a 15- step synthesis from 1-hydroxynaphthalene-2-carboxylic acid. Reductive alkylation of the 5-amino compound gave the corresponding 5-methylamino and 5-dimethylamino analogues, while resolution of an intermediate by chiral HPLC allowed preparation of the R and S enantiomers of the 5-amino analogue. Absolute configuration was assigned by X-ray crystallography. The S enantiomer was about 65-fold more cytotoxic than the R enantiomer in cell line assays. The 5-amino and 5-methylamino compounds had in vitro cytotoxicities comparable to that of the known 5-hydroxy analogue (0.2-0.5 nM), while the 5-dimethylamino derivative was about 10-fold less potent. The high potencies of the 5-amino and 5-methylamino analogues make them of interest for the formation of relatively stable amine-based prodrugs.

Full text of DOI:10.1021/jo981395w

9414
J . Org. Chem. 1998, 63, 9414-9420
Syn th esis a n d Cytotoxicity of
5-Am in o-1-(ch lor om eth yl)-3-[(5,6,7-tr im eth oxyin d ol-2-yl)ca r bon yl]-1,2-
d ih yd r o-3H-ben z[e]in d ole (Am in o-seco-CBI-TMI) a n d
Rela ted 5-Alk yla m in o An a logu es: New DNA Min or Gr oove
Alk yla tin g Agen ts
Graham J . Atwell,† Moana Tercel,† Maruta Boyd,† William R. Wilson,‡ and
William A. Denny*,†
Auckland Cancer Society Research Centre and Section of Oncology, Department of Pathology, Faculty of
Medicine and Health Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand
Received J uly 17, 1998
The first synthesis of seco-CBI-TMI alkylating agents with 5-nitrogen substituents is reported.
The parent 5-amino compound was prepared in a 15-step synthesis from 1-hydroxynaphthalene-
2-carboxylic acid. Reductive alkylation of the 5-amino compound gave the corresponding 5-me-
thylamino and 5-dimethylamino analogues, while resolution of an intermediate by chiral HPLC
allowed preparation of the R and S enantiomers of the 5-amino analogue. Absolute configuration
was assigned by X-ray crystallography. The S enantiomer was about 65-fold more cytotoxic than
the R enantiomer in cell line assays. The 5-amino and 5-methylamino compounds had in vitro
cytotoxicities comparable to that of the known 5-hydroxy analogue (0.2-0.5 nM), while the
5-dimethylamino derivative was about 10-fold less potent. The high potencies of the 5-amino and
5-methylamino analogues make them of interest for the formation of relatively stable amine-based
prodrugs.
In tr od u ction
We have therefore been investigating the analogous
amino-seco compounds because of their greater potential
for forming relatively stable, nontoxic prodrugs through
modification of the amino function. We have recently
reported the synthesis and initial evaluation of the
analogues 5-8 in the seco-CI-TMI series,7-9 and we
report here an efficient synthesis of the CBI congeners
10-12 via the corresponding nitro analogue 9 (Chart 1
and Schemes 2-4). A preliminary account of this work
has been published.10
The cyclopropylindole antitumor antibiotics, exempli-
fied by CC-10651 and duocarmycin SA (1),2 are extremely
cytotoxic DNA alkylating agents, with IC50s against
mammalian cell lines in the low picomolar range for some
analogues.1-3 The full complexity of the natural products
is not required for high potency, with simplified ana-
logues such as CBI-TMI (2) being essentially as cytotoxic
as 1 in cell culture (IC50s of 20 and 10 pM, respectively,
in L1210 leukemia for a 72 h exposure).4 The phenolic
seco forms of these compounds (e.g., 3) also retain
essentially the full cytotoxicity of the corresponding
cyclopropyldienones, indicating that ring closure to form
the cyclopropane ring is rapid under cell culture condi-
tions.3,5 Carbamate prodrug forms of these phenolic seco
compounds have been reported (e.g., carzelesin 4) which
are labile in plasma, rapidly and nonspecifically releasing
the corresponding phenol.6 While this is a desirable
property for systemic release of a drug, we have been
interested in the preparation of more stable prodrugs that
may persist in plasma but allow specific release in tumor
tissue by a localized enzyme-activation step.
Resu lts a n d Discu ssion
Syn th esis of 5-Am in o-seco-CBI-TMI (10). Our ini-
tial approach to 10, starting from 1-chloro-2,4-dini-
tronaphthalene (13), followed one of our recent synthe-
ses7,9 of the amino-seco-CI compound 6 (Scheme 1).
Conversion of 13 to the malonate 14, followed by nitro
reduction with Na2S, gave a good yield of the single
nitroaniline isomer 15, resulting from selective reduction
of the less hindered nitro group. This is in contrast to
the related amino-seco-CI case, where a mixture of
isomers was obtained.9 The structure of 15 was con-
firmed by X-ray crystallography (Supporting Informa-
tion). A number of amine-protected analogues of 15 were
prepared and subjected to DIBALH reduction, but only
the benzyl analogue 16 gave any of the required diol (17),
and then in only poor yield. Reduction of 16 with
† Auckland Cancer Society Research Centre.
‡ Department of Pathology.
(1) Reynolds, V. L.; McGovren, J . P.; Hurley, L. H. J . Antibiot. 1986,
34, 319.
(2) Yasuzawa, T.; Muroi, K.; Ichimura, M.; Takahashi, I.; Ogawa,
T.; Takahashi, K.; Sano, H.; Saitoh, Y. Chem. Pharm. Bull. 1995, 43,
378.
(3) Boger, D. L.; J ohnson, D. S. Angew. Chem., Int. Ed. Engl. 1996,
35, 1438.
(4) Boger, D. L.; Yun, W. J . Am. Chem. Soc. 1994, 116, 7996.
(5) Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Kitos, P. A.; Sun-
tornwat, O. J . Org. Chem. 1990, 55, 4499.
(7) Tercel, M.; Denny, W. A.; Wilson, W. R. Bioorg. Med. Chem. Lett.
1996, 6, 2735.
(8) Tercel, M.; Denny, W. A.; Wilson, W. R. Bioorg. Med. Chem. Lett.
1996, 6, 2741.
(9) Tercel, M.; Denny, W. A. J . Chem. Soc., Perkin Trans. 1 1998,
(6) Li, L. H.; DeKoning, T. F.; Kelly, R. C.; Krueger, W. C.;
McGovren, J . P.; Padbury, G. E.; Petzold, G. L.; Wallace, T. L.; Ouding,
R. J .; Prairie, M. D.; Gebhard, I. Cancer Res. 1992, 52, 4904.
509.
(10) Atwell, G. J .; Wilson, W. R.; Denny, W. A. Bioorg. Med. Chem.
Lett. 1997, 7, 1493.
10.1021/jo981395w CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/20/1998

seco-CBI-TMI Alkylating Agents
J . Org. Chem., Vol. 63, No. 25, 1998 9415
Ch a r t 1
Sch em e 2a
a
(i) NaHCO3 (1.05 mol equiv), then 4-methoxybenzyl chloride,
66%; (ii) 70% HNO3/AcOH, 61%; (iii) (Tf)2O/Et3N, 81%; (iv)
CH2(COOMe)2/K2CO3, 88%; (v) TFA/PhOCH3, 93%.
Sch em e 3a
Sch em e 1a
a
(i) DPPA/Et3N; (ii) Pd/C/H2; (iii) KHCO3, then NaN3/TBAB/
PhOP(O)Cl2, then PhMe/reflux; (iv) NaN3/pyridine/[SOCl2/DMF (1:
1)]; (v) PhMe/heat, 81% (from 26).
The successful synthesis of 10 (Schemes 2-4) involved
generation of the required amino substituent from a nitro
group in the last step, a strategy successfully employed8,9
in an alternative synthesis of 6. Commercially available
1-hydroxynaphthalene-2-carboxylic acid (21) was mono-
protected as the 4-methoxybenzyl ester 22, and this was
nitrated under mild conditions (70% HNO3/AcOH) to give
the 4-nitro isomer 23 in 61% isolated yield (Scheme 2).
This was converted to the trifluoromethanesulfonate
derivative 24, which on reaction with dimethyl malonate
anion gave the 1-malonyl derivative 25. Selective cleav-
age of the 4-methoxybenzyl ester group with TFA/anisole
then gave the key acid 26.
Conversion of 26 to the desired nitrolactam 29 in an
acceptable yield proved difficult (Scheme 3). Attempted
Curtius rearrangement of 26 employing diphenylphos-
phoryl azide (DPPA) under a number of reaction condi-
tions gave none of the desired product. In particular,
conditions similar to those used9 in the synthesis of the
amino-seco-CI derivative 6 (DPPA/Et3N) gave an excel-
lent yield of a lactam, but this proved to be the isomeric
compound 27. The fact that 27 was not the desired
a
(i) Na/CH2(CO2Et)2, 83%; (ii) Na2S, 69%; (iii) PhCHO/TsOH,
then NaBH3CN/H+, 77%; (iv) DIBALH, 20%; (v) Na2S2O4, 37%;
(vi) NaH/CH(CO2Me)3, 37%; (vii) Fe/H+, 3%.
dithionite gave only the lactam 18 (in moderate yield),
resulting presumably from cyclization followed by decar-
boxylation, and approaches via 16 were therefore aban-
doned. An alternative synthesis from 13, involving an
initial condensation with trimethyl methanetricarboxy-
late to give the triester 19, was also explored. However,
while reduction of 19 was exhaustively studied, the
desired aminolactam 20 was isolated only in trace
amounts.

9416 J . Org. Chem., Vol. 63, No. 25, 1998
Atwell et al.
Sch em e 4a
a
(i) BH3‚Me2S, 57%; (ii) (BOC)2O/N-methylimidazole, 82%; (iii)
F igu r e 1. ORTEP drawing of (-)-(R)-38.
NaOMe, then TFA, 98%; (iv) DIBALH, 70%; (v) MsCl, 89%; (vi)
LiCl, 87%; (vii) HCl, then EDCl‚HCl/TMI acid, 77%; (viii) H2/PtO2,
94%; (ix) MeCO2CHO, then BH3‚Me2S, 42%; (x) NaBH3CN/
aqueous HCl/HCHO, 68%.
(HCl/dioxane) and coupled with 5,6,7-trimethoxyindole-
2-carboxylic acid (TMI acid) to give 9. Catalytic reduction
of this over platinum oxide gave the target racemic
amino-seco-CBI analogue 10 in excellent yield. Racemic
10 was mono- and dimethylated by formylation/borane
reduction9,12 and reductive amination9 to give respectively
racemic 11 and 12.
Resolu tion of En a n tiom er s. The alcohol, mesylate,
and chloro intermediates 37-39 were all resolvable on
a Diacel Chiralcel OD semipreparative column, as de-
scribed4 for related phenolic CBI derivatives [R values
1.14 in i-PrOH/hexane (1:1), 1.40 in i-PrOH/hexane (1:
1), and 1.10 in i-PrOH/hexane (7:3), respectively]. The
mesylate 38 not only was the most soluble of the three
but also showed an unusually large R value, allowing
baseline resolution of the enantiomers. An X-ray crystal
structure determination (Figure 1) of the faster-running
mesylate showed it to be the R enantiomer (Flack
parameter13 of -0.0054). Both enantiomers were con-
verted to the corresponding 5-nitro-seco-CBI-TMI deriva-
tives (-)-(R)-9 and (+)-(S)-9, and these in turn were
converted to the amino compounds (-)-(R)-10 and (+)-
(S)-10.
In Vitr o Cytotoxicity. The cytotoxicities of the
amino compounds 10-12 were evaluated14 in a panel of
three cell lines. AA8 is a Chinese hamster ovary cell line,
UV4 is a subline of AA8 that is deficient in excision repair
and hypersensitive to drugs that produce bulky DNA
adducts or cross-links,15 and EMT6 is a murine mam-
mary carcinoma cell line. Results are recorded in Table
1 for 4 h drug exposures. Under these conditions, the
natural enantiomer of the known seco-phenol 3 had an
IC50 of 0.1-0.2 nM across the cell line panel. The
reported4 IC50 of 2 (the ring-closed form of 3) is somewhat
lower than that of 3 (0.03 nM) but in a different cell line
(L1210) for a longer exposure time (72 h). The corre-
sponding 5-amino analogue (+)-(S)-10 showed toxicity
product was shown initially when catalytic hydrogenation
of this compound gave an aminolactam (28) that was
different from the aminolactam (20) obtained in Scheme
1. The structure of the nitrolactam 27 was confirmed
by X-ray crystallography (Supporting Information). This
compound is presumably formed by intramolecular trap-
ping of the intermediate carbonyl azide 31 by the
malonate anion (which would be expected to be more
acidic than the corresponding compound in the CI series
because of increased resonance) under the basic condi-
tions of the reaction.
Reaction of 26 with phenyl dichlorophosphate/NaN3/
pyridine followed by thermolysis of the crude product in
refluxing toluene gave a low yield (16%) of the desired
nitrolactam 29, with the major product being the iso-
chromene 30. This is analogous to the isochromene
formed in the CI series.9 The acid 26 was finally
converted successfully to 29 in excellent yield (81%) by
formation of the intermediate carbonyl azide 31 with
N,N-dimethyl(chlorosulfonyl)methaniminium chloride
(SOCl2/DMF adduct)11 and NaN3. Thermal rearrange-
ment of this product under neutral conditions (refluxing
toluene) then resulted in the formation of the expected
product 29 (Scheme 3) via formation and trapping of the
isocyanate. In contrast, treatment of azide 31 with an
anhydrous base (Et3N/CH2Cl2, 40 °C) gave predominantly
the isomeric nitrolactam 27, as shown by TLC analysis.
Selective reduction of the nitrolactam 29 with BH3‚
Me2S gave the desired benzindoline 32 together with ca.
5% of the benzindole 33 (Scheme 4). The mixture was
not separable by chromatography, but reaction with
(BOC)2O allowed separation of the unwanted product 35
from the required N-BOC benzindoline 34. The latter
was then treated with NaOMe to give the monoester 36.
Reduction of 36 with DIBALH gave the alcohol 37 which
was converted, via the mesylate 38, to the chloromethyl
compound 39. This key intermediate was deprotected
(12) Krishnamurthy, S. Tetrahedron Lett. 1982, 23, 3315.
(13) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(14) Palmer, B. D.; Wilson, W. R.; Anderson, R. F.; Boyd, M.; Denny,
W. A. J . Med. Chem. 1996, 39, 2518.
(11) Arrieta, A.; Aizpurua, J . M.; Palomo, C. Tetrahedron Lett. 1984,
25, 3365.
(15) Hoy, C. A.; Salazar, E. P.; Thompson, L. H. Mutat. Res. 1984,
130, 321.

seco-CBI-TMI Alkylating Agents
J . Org. Chem., Vol. 63, No. 25, 1998 9417
Ta ble 1. Cytotoxicity (IC50s in n M, 4 h Exp osu r e, (SE)
for Nitr ogen -Su bstitu ted seco-CBI-TMI An a logu esa
were determined on a digital melting point apparatus and are
as read. NMR spectra were measured at 400 MHz (1H) or 100
MHz (13C) and are referenced to Me4Si. Mass spectra were
recorded at nominal 5000 resolution. All compounds tested
for cytotoxicity were >96% pure by HPLC. Compound 3 was
made by a reported4 method.
4-Meth oxyben zyl 1-Hyd r oxyn a p h th a len e-2-ca r boxy-
la te (22). 4-Methoxybenzyl chloride (98%, 46.7 g, 0.29 mol)
was added to a suspension of the powdered sodium salt of
1-hydroxynaphthalene-2-carboxylic acid (21) (61.3 g, 0.29 mol;
prepared from the acid and 1.05 mol equiv of aqueous
NaHCO3) in DMSO (205 mL) at 20 °C, and the mixture was
stirred at 70 °C for 1 h. After cooling, the mixture was poured
into dilute aqueous KHCO3 (3.5 L), and the resulting precipi-
tate was collected, washed with water, and dried. The solid
was extracted with boiling petroleum ether (bp 90-95 °C, 1.1
L), and the hot extracts were treated with decolorizing
charcoal, filtered, and cooled for a prolonged period at 0 °C to
compound
AA8
UV4
EMT6
3
0.21 ( 0.06
0.21 ( 0.03
13.6 ( 3.2
0.46 ( 0.05
0.17 ( 0.02
5.6 ( 0.56
0.09 ( 0.004
0.14 ( 0.01
2.7 ( 0.21
0.29 ( 0.02
0.12 ( 0.01
3.7 ( 0.01
0.13 ( 0.01
0.13 ( 0.01
7.0 ( 0.66
0.27 ( 0.03
0.11 ( 0.01
3.9 ( 1.25
(+)-(S)-10
(-)-(R)-10
(()-10
(()-11
(()-12
a
Average of two or more determinations.
almost identical to that of 3. This is in marked contrast
to the CI series, where the (racemic) amino compound 6
is 50-120-fold less cytotoxic than the corresponding
(racemic) phenol in the same panel.7 In the 5-amino-CBI
series, the R enantiomer was much less cytotoxic than
the S enantiomer (65-fold in AA8, 19-fold in UV4, and
54-fold in EMT6). This follows the pattern seen with 2
and its enantiomer where the ratio was 90-fold.3 We
have also investigated the sequence specificity of DNA
alkylation by (+)-(S)-10 and (-)-(R)-1016 and have found
exclusive adenine alkylation with the strongest cleavage
at polyA sequences. The S enantiomer was at least 10-
fold more effective than the R enantiomer, showing
strong alkylation at a drug concentration as low as 10-8
M.
The (racemic) 5-methylamino analogue 11 was slightly
more potent than (()-10, but the (racemic) dimethyl-
amino compound 12 was at least 10-fold less cytotoxic.
One possible explanation for this loss of potency is that
12 (unlike 10 or 11) is unable to ring-close to a cyclic
intermediate (i.e., similar to the loss in potency on
alkylating a seco-CI phenol17). However, in the amino-
CI series, 8 was no less toxic than 6 or 7.8 Thus the most
likely reason is that steric interaction of the peri hydro-
gen with the bulky dimethylamino group of 12 rotates
the latter significantly out of plane, resulting in consider-
able deconjugation.
provide crude 22 (59.4 g, 66%), suitable for further use.
A
sample was recrystallized from i-Pr2O/petroleum ether: mp
1
92-93 °C; H NMR [(CD3)2SO] δ 11.91 (s, 1 H), 8.31 (d, J )
8.2 Hz, 1 H), 7.92 (d, J ) 8.1 Hz, 1 H), 7.73 (d, J ) 8.8 Hz, 1
H), 7.71 (t, J ) 7.5 Hz, 1 H), 7.61 (t, J ) 7.6 Hz, 1 H), 7.48 (d,
J ) 8.6 Hz, 2 H), 7.42 (d, J ) 8.9 Hz, 1 H), 6.99 (d, J ) 8.6 Hz,
2 H), 5.40 (s, 2 H), 3.78 (s, 3 H). Anal. Calcd for C19H16O4:
C, 74.01; H, 5.23. Found: C, 73.72; H, 5.22.
4-Met h oxyb en zyl 1-H yd r oxy-4-n it r on a p h t h a len e-2-
ca r boxyla te (23). A warm, vigorously stirred solution of 22
(25.4 g, 0.082 mol) in AcOH (290 mL) was cooled to 25 °C and
treated in one portion with a solution of HNO3 (70% w/w, 18.6
g, 0.20 mol) in AcOH (25 mL). The temperature rose to 35 °C
(controlled with external cooling), and a solid was separated.
After being stirred for a further 10 min at 30 °C, the mixture
was cooled to 0 °C. The precipitate was collected, washed with
cold AcOH and i-Pr2O, and recrystallized from CH2Cl2/i-Pr2O
to give 23 (17.9 g, 61%): mp 163-164 °C; 1H NMR [(CD3)2SO]
δ 12.50 (br s, 1 H), 8.60 (s, 1 H), 8.60 (d, J ) 8.6 Hz, 1 H), 8.47
(d, J ) 8.3 Hz, 1 H), 7.97 (ddd, J ) 8.5, 7.2, 1.2 Hz, 1 H), 7.79
(t, J ) 7.7 Hz, 1 H), 7.50 (d, J ) 8.6 Hz, 2 H), 7.00 (d, J ) 8.7
Hz, 2 H), 5.43 (s, 2 H), 3.78 (s, 3 H). Anal. Calcd for C19H15
-
NO6: C, 64.58; H, 4.28; N, 3.97. Found: C, 64.66; H, 3.97; N,
4.24.
4-Meth oxyben zyl 4-Nitr o-1-(tr iflu or om eth a n esu lfon yl-
oxy)n a p h th a len e-2-ca r boxyla te (24). A suspension of 23
(12.90 g, 36.5 mmol) in CH2Cl2 (180 mL) was treated with Et3N
(6.58 mL, 47.5 mmol), and the resulting solution was cooled
to 0 °C and treated dropwise with trifluoromethanesulfonic
anhydride (7.82 mL, 43.8 mmol). The mixture was stirred at
0 °C for 30 min and then treated with additional Et3N (1.00
mL, 7.2 mmol) followed by trifluoromethanesulfonic anhydride
(1.19 mL, 6.7 mmol). After being stirred for a further 2 h at
20 °C, the mixture was washed twice with water, then dried
(Na2SO4), and concentrated under reduced pressure. The
residue was extracted with boiling petroleum ether (bp 90-
95 °C, 450 mL) in the presence of decolorizing charcoal, and
the filtered solution was then cooled to 65 °C and refiltered
through a Celite pad. Following prolonged cooling, the sepa-
rated solid was collected and washed with petroleum ether to
give crude 24 (14.29 g, 81%), suitable for further use. A sample
was recrystallized from i-Pr2O/petroleum ether: mp 74-75 °C;
1H NMR (CDCl3) δ 8.71 (s, 1 H), 8.57 (d, J ) 8.7 Hz, 1 H),
8.30 (d, J ) 8.4 Hz, 1 H), 7.92 (ddd, J ) 8.6, 7.1, 1.4 Hz, 1 H),
7.84 (ddd, J ) 8.5, 7.2, 1.2 Hz, 1 H), 7.44 (d, J ) 8.7 Hz, 2 H),
6.93 (d, J ) 8.8 Hz, 2 H), 5.43 (s, 2 H), 3.82 (s, 3 H). Anal.
Calcd for C20H14F3NO8S: C, 49.49; H, 2.91; N, 2.89; S, 6.61.
Found: C, 49.69; H, 2.79; N, 2.86; S, 6.56.
All of the compounds were slightly more cytotoxic in
the repair-deficient UV4 cell line, although the dif-
ferentials (ca. 2-fold) were less than those usually ob-
served,15 including those with analogous amino-CI alkyl-
ators.7
Con clu sion s
Although care must be taken with the key Curtius
rearrangement of the malonate 26 to form the indolone
29, the described method offers a robust synthesis of the
5-amino-seco-CBI alkylating agent 10 (15 steps in 6%
overall yield from 22), suitable for multigram synthesis.
Both the 5-amino and 5-methylamino derivatives (10 and
11) have subnanomolar in vitro cytotoxicities, comparable
to that of the corresponding phenol 3. Like 3 and its
enantiomer, the enantiomers of 10 show large dif-
ferentials in cytotoxicity, with the “natural” S enantiomer
being the more potent. The high potencies of the 5-amino
analogues make this class of compounds attractive for
use in prodrug strategies.18
Exp er im en ta l Section
4-Meth oxyben zyl 1-[Di(m eth oxyca r bon yl)m eth yl]-4-
n itr on a p h th a len e-2-ca r boxyla te (25). A stirred solution
of 24 (13.20 g, 27.2 mmol) and dimethyl malonate (5.39 g, 40.8
mmol) in DMF (85 mL) was cooled to -10 °C and treated with
powdered K2CO3 (22.53 g, 163 mmol). The mixture warmed
to 20 °C over 4 h, and after being stirred for a further 12 h at
20 °C, it was poured slowly into cold, stirred 0.5 N HCl (1750
mL). The resulting solid was dissolved in CH2Cl2, and the
solution was washed twice with water, dried (Na2SO4), and
Analyses were performed by the Microchemical Laboratory,
University of Otago, Dunedin, New Zealand. Melting points
(16) Gieseg, M. A.; Denny, W. A. Manuscript submitted to Anti-
Cancer Drug Des.
(17) Boger, D. L.; Munk, S. A.; Zarrinmayeh, H.; Ishzaki, T.; Haught,
J .; Bina, M. Tetrahedron 1991, 47, 2661.
(18) Denny, W. A. Curr. Pharm. Des. 1996, 2, 281.

9418 J . Org. Chem., Vol. 63, No. 25, 1998
Atwell et al.
evaporated to dryness. The residue was crystallized from CH2-
Cl2/i-Pr2O to give 25 (11.21 g, 88%), suitable for further use.
A sample was recrystallized from MeOH: mp 124-125 °C; 1H
NMR (CDCl3) δ 8.62 (s, 1 H), 8.45 (d, J ) 8.6 Hz, 1 H), 8.21
(d, J ) 8.7 Hz, 1 H), 7.79 (ddd J ) 8.4, 7.0, 1.2 Hz, 1 H), 7.69
(ddd, J ) 8.6, 7.1, 1.4 Hz, 1 H), 7.41 (d, J ) 8.7 Hz, 2 H), 6.94
(d, J ) 8.7 Hz, 2 H), 6.62 (s, 1 H), 5.37 (s, 2 H), 3.83 (s, 3 H),
3.69 (s, 6 H). Anal. Calcd for C24H21NO9: C, 61.67; H, 4.53;
N, 3.00. Found: C, 61.64; H, 4.67; N, 3.14.
with CH2Cl2 gave a solid that was recrystallized from EtOAc/
i-Pr2O to give 30 (198 mg, 42%): mp 178.5-179 °C; H NMR
1
[(CD3)2SO] δ 8.63 (s, 1 H), 8.47 (d, J ) 8.6 Hz, 1 H), 7.97 (ddd,
J ) 8.5, 7.0, 1.3 Hz, 1 H), 7.90 (d, J ) 8.1 Hz, 1 H), 7.82 (ddd,
J ) 8.5, 7.0, 1.3 Hz, 1 H), 4.14 (s, 3 H), 3.87 (s, 3 H); 13C NMR
δ 165.8, 160.9, 157.6, 143.3, 142.2, 132.2, 128.1, 127.12, 127.08,
126.4, 123.5, 122.7, 110.6, 89.9, 57.4, 52.8; HRMS (EI) calcd
for C16H11NO7 (M+) 329.0536, found 329.0533. Anal. Calcd
for C16H11NO7: C, 58.36; H, 3.37; N, 4.25. Found: C, 58.30;
H, 3.38; N, 3.93.
1-[Di(m eth oxyca r bon yl)m eth yl]-4-n itr on a p h th a len e-
2-ca r boxylic Acid (26). TFA (36 mL) was added in one
portion to a mixture of 25 (9.20 g, 19.7 mmol) and anisole (2.16
g, 20 mmol), and the resulting solution was stirred at 20 °C
for 10 min and then diluted with cold water (800 mL). The
precipitated semisolid was collected and dissolved in EtOAc,
and the solution was washed with water, dried (Na2SO4), and
concentrated under reduced pressure and below 30 °C until
the appearance of a crystalline solid. Addition of i-Pr2O
completed the precipitation of the product, which was recrys-
tallized from EtOAc/i-Pr2O/petroleum ether/AcOH (1 drop) to
give 26 (6.37 g, 93%): mp 153-154 °C (dec); 1H NMR [(CD3)2-
SO] δ 14.1 (br s, 1 H), 8.62 (s, 1 H), 8.36 (d, J ) 8.2 Hz, 1 H),
8.30 (d, J ) 8.7 Hz, 1 H), 7.92 (t, J ) 7.6 Hz, 1 H), 7.84 (ddd,
J ) 8.4, 7.0, 1.1 Hz, 1 H), 6.65 (s, 1 H), 3.63 (s, 6 H); 13C NMR
δ 167.25, 167.23, 146.3, 137.8, 133.0, 130.7, 129.0, 128.6, 126.3,
125.2, 123.1, 122.8, 52.7, 51.2. Anal. Calcd for C16H13NO8:
C, 55.34; H, 3.77; N, 4.03. Found: C, 55.36; H, 3.80; N, 3.74.
Further elution with CH2Cl2/EtOAc (6:1) gave the lactam
29 (79 mg, 16% crude yield) (characterized below).
1,1-Di(m eth oxyca r bon yl)-5-n itr o-1,3-d ih yd r o-2H-ben z-
[e]in d ol-2-on e (29). A stirred suspension of 26 (7.00 g, 20.16
mmol) and powdered NaN3 (3.28 g, 50.44 mmol) in CH2Cl2 (100
mL) was treated with pyridine (3.99 g, 50.44 mmol), then
cooled to -5 °C, and treated in one portion with N,N-dimethyl-
(chlorosulfonyl)methaniminium chloride [SOCl2/DMF adduct]11
(4.26 g, 22.18 mmol). After being stirred at 20 °C for 2 h, the
mixture was washed twice with water, dried (Na2SO4), and
filtered through a short column of silica gel, eluting with
further CH2Cl2 (400 mL). Removal of the solvent under
reduced pressure and below 30 °C gave the crude carbonyl
azide 31, which was immediately heated with stirring in dry
toluene (65 mL) under reflux for 8 min. The mixture was
cooled to 0 °C to complete precipitation of the product, which
was collected and washed with toluene. This solid was stirred
as a suspension in CH2Cl2 (25 mL) for 10 min at 20 °C and
diluted with i-Pr2O, and the resulting solid was collected and
washed with i-Pr2O to give 29 (5.60 g, 81%). A sample was
crystallized from EtOAc/i-Pr2O: mp 219-221 °C (dec); 1H
NMR [(CD3)2SO] δ 11.59 (s, 1 H, NH), 8.21 (d, J ) 8.7 Hz, 1
H, H-6), 7.95 (s, 1 H, H-4), 7.87 (d, J ) 8.5 Hz, 1 H, H-9), 7.74
(t, J ) 7.6 Hz, 1 H, H-8), 7.65 (t, J ) 7.7 Hz, 1 H, H-7), 3.72
(s, 6 H, 2 × CO2CH3); 13C NMR δ 168.4 (C-2), 164.1 (CO2CH3),
148.4 (C-5), 140.5 (C-3a), 129.6 (C-9a), 129.2 (C-8), 127.1 (C-
7), 123.3 (C-6), 123.1 (C-9), 121.7 (C-5a), 120.7 (C-9b), 108.8
(C-4), 66.8 (C-1), 53.9 (OCH3). Signal assignments were
confirmed by HMQC, HMBD, and COSY spectra. HRMS (EI)
calcd for C16H12N2O7 (M+) 344.0645, found 344.0642. Anal.
Calcd for C16H12N2O7: C, 55.82; H, 3.51; N, 8.14. Found: C,
56.01; H, 3.55; N, 8.12.
1,1-Di(m eth oxyca r bon yl)-5-n itr o-1,2-d ih yd r o-3H-ben z-
[e]isoin d ol-3-on e (27). A solution of 26 (3.00 g, 8.64 mmol)
in THF (25 mL) was treated at 0 °C with DPPA19 (4.76 g, 17.28
mmol) followed by Et3N (2.41 mL, 17.28 mmol), and the
mixture was stirred at 20 °C under N2 for 12 h. The reaction
was quenched by pouring it into excess 0.1 N HCl, and the
precipitated semisolid was collected and dissolved in CH2Cl2.
The solution was washed with water, dried (Na2SO4), diluted
with an equal volume of EtOAc, and filtered through a column
of silica gel. Removal of solvent followed by trituration of the
residue with i-Pr2O gave a crystalline solid that was recrystal-
lized from CH2Cl2/i-Pr2O to give 27 (2.52 g, 85%): mp 192-
194 °C; 1H NMR [(CD3)2SO] δ 10.42 (s, 1 H), 8.41 (s, 1 H),
8.38-8.30 (m, 2 H), 8.01-7.91 (m, 2 H), 3.78 (s, 6 H); 13C NMR
δ 167.5, 166.4, 149.3, 142.0, 131.0, 129.2, 129.1, 128.5, 126.1,
126.0, 123.3, 116.2, 71.6, 54.1; HRMS (EI) [M+] calcd for
1,1-Di(m eth oxyca r bon yl)-5-n itr o-1,2-d ih yd r o-3H-ben z-
[e]in d ole (32). BH3‚Me2S (9.2 mL, 92 mmol) was added to a
solution of 29 (17.60 g, 51 mmol) in THF (150 mL), and the
mixture was stirred under reflux for 2 h. After the mixture
had cooled, MeOH (15 mL) was slowly added followed by water
(30 mL), and the mixture was then concentrated under reduced
pressure and below 30 °C to a small volume. Addition of water
provided a semisolid, which was collected and dissolved in CH2-
Cl2. The solution was washed twice with water, dried (Na2-
SO4), and concentrated under reduced pressure to provide a
solid which was chromatographed on silica gel. Elution with
CH2Cl2/EtOAc (10:1) provided the crude product which was
recrystallized from i-Pr2O and, following cooling, was collected
to give 32 (9.62 g, 57%), which was contaminated with ca. 3%
1-(methoxycarbonyl)-5-nitro-3H-benz[e]indole (33). Multiple
recrystallizations of a sample from i-Pr2O gave pure 32: mp
C
C
16H12N2O7 (M+) 344.0645, found 344.0647. Anal. Calcd for
16H12N2O7: C, 55.82; H, 3.51; N, 8.14. Found: C, 55.76; H,
3.38; N, 8.15.
5-Am in o-1,1-di(m eth oxycar bon yl)-1,2-dih ydr o-3H-ben z-
[e]isoin d ol-3-on e (28). Hydrogenation of 27 in THF/MeOH
(1:1) over Pd/C at 50 psi for 1.5 h gave 28 (91%): mp (EtOAc)
1
228-231 °C; H NMR [(CD3)2SO] δ 9.69 (s, 1 H), 8.22 (d, J )
8.2 Hz, 1 H), 8.02 (dd, J ) 8.3, 1.0 Hz, 1 H), 7.59 (ddd, J )
8.2, 7.0, 1.2 Hz, 1 H), 7.54 (ddd, J ) 8.3, 6.9, 1.4 Hz, 1 H),
6.86 (s, 1 H), 6.35 (s, 2 H), 3.71 (s, 6 H); 13C NMR δ 170.4,
168.0, 148.1, 131.1, 128.6, 127.0, 125.5, 125.2, 124.7, 124.2,
123.3, 98.9, 70.7, 53.3; HRMS (EI) calculated for C16H14N2O5
(M+) 314.0903, found 314.0902.
Met h yl 2-Met h oxy-6-n it r o-4-oxo-4H -b en z[f]isoch r o-
m en e-1-ca r boxyla te (30). A mixture of 26 (500 mg, 1.44
mmol) and KHCO3 (158 mg, 1.58 mmol) in MeOH (20 mL) and
water (20 mL) was stirred at 20 °C until homogeneous and
then evaporated under reduced pressure and below 30 °C. The
residue was shaken with CH2Cl2 (20 mL), and the resulting
suspension was treated sequentially with NaN3 (187 mg, 2.88
mmol), tetrabutylammonium bromide (TBAB) (46 mg, 0.15
mmol), and phenyl dichlorophosphate (330 mg, 1.56 mmol).
The mixture was stirred at 20 °C for 3 h and then filtered
through a short column of silica gel, eluting with further CH2-
Cl2. After evaporation of the solvent, the resulting solid was
heated with stirring in dry toluene (10 mL) at reflux for 15
min. The mixture was concentrated under reduced pressure,
and the residue was chromatographed on silica gel. Elution
1
141 °C; H NMR (CDCl3) δ 8.25 (d, J ) 8.7 Hz, 1 H), 7.82 (d,
J ) 8.6 Hz, 1 H), 7.59 (s, 1 H), 7.51 (ddd, J ) 8.5, 7.0, 1.2 Hz,
1 H), 7.42 (ddd, J ) 8.6, 7.1, 1.3 Hz, 1 H), 4.36 (d, J ) 2.3 Hz,
2 H), 4.23 (br s, 1 H), 3.79 (s, 6 H); 13C NMR δ 169.9, 149.1,
148.4, 131.9, 128.1, 125.2, 123.6, 122.1, 120.6, 109.9, 64.64,
56.6, 53.4. Anal. Calcd for C16H14N2O6: C, 58.18; H, 4.27; N,
8.48. Found: C, 58.23; H, 4.02; N, 8.57.
3-(ter t-Bu tyloxyca r bon yl)-1,1-d i(m eth oxyca r bon yl)-5-
n itr o-1,2-d ih yd r o-3H-ben z[e]in d ole (34). A mixture of
crude 32 (9.35 g, 28.3 mmol), di-tert-butyl dicarbonate (97%,
8.28 g, 36.8 mmol), and 1-methylimidazole (3.02 g, 36.8 mmol)
in THF (100 mL) was stirred at 45 °C for 1 h and then
concentrated under reduced pressure. The residue was par-
titioned between CH2Cl2 and 0.1 N AcOH, and the organic
layer was washed twice with water, dried (Na2SO4), and
concentrated under reduced pressure. The residue was stirred
with CH2Cl2 (40 mL), then cooled, and filtered to remove some
(19) Ninomiya, K.; Shioiri, T.; Yamada, S. Tetrahedron 1974, 30,
2151.

seco-CBI-TMI Alkylating Agents
J . Org. Chem., Vol. 63, No. 25, 1998 9419
of the minor product 3-(tert-butyloxycarbonyl)-1-(methoxycar-
bonyl)-5-nitro-3H-benz[e]indole (35): mp (EtOAc) 247-249 °C;
1H NMR (CDCl3) δ 9.73-9.66 (m, 1 H), 9.18 (s, 1 H), 8.57-
8.51 (m, 1 H), 8.55 (s, 1 H), 7.77-7.68 (m, 2 H), 4.01 (s, 3 H),
1.75 (s, 9 H); HRMS (EI) calcd for C19H18N2O6 (M+) 370.1165,
found 370.1164. Anal. Calcd for C19H18N2O6: C, 61.61; H,
4.90; N, 7.57. Found: C, 61.64; H, 4.94; N, 7.27.
The CH2Cl2 solution was evaporated, and the residue was
chromatographed on silica gel. Elution with CH2Cl2/petroleum
ether (1:1) provided a further quantity of 35, and continued
elution with CH2Cl2 gave a solid which was triturated with
i-Pr2O/petroleum ether to give 34 (9.98 g, 82%). A sample was
recrystallized from i-Pr2O: mp 151 °C; 1H NMR (CDCl3) δ 8.85
(br s, 1 H), 8.28 (br s, 1 H), 7.93 (d, J ) 7.8 Hz, 1 H), 7.61-
7.51 (m, 2 H), 4.69 (s, 2 H), 3.80 (s, 6 H), 1.61 (s, 9 H). Anal.
Calcd for C21H22N2O8: C, 58.60; H, 5.15; N, 6.51. Found: C,
58.65; H, 5.38; N, 6.42.
1.56 (s, 9 H). Anal. Calcd for C19H22N2O7S: C, 54.02; H, 5.25;
N, 6.63; S, 7.59. Found: C, 54.25; H, 5.36; N, 6.87; S, 7.39.
3-(ter t-Bu t yloxyca r b on yl)-1-(ch lor om et h yl)-5-n it r o-
1,2-d ih yd r o-3H-ben z[e]in d ole (39). A mixture of 38 (0.51
g, 1.21 mmol) and LiCl (0.21 g, 5 mmol) in DMF (2.5 mL) was
stirred at 80 °C for 30 min, then cooled, and diluted with water.
The precipitated solid was dissolved in CH2Cl2 and filtered
through a column of silica gel. The eluate was concentrated
to a small volume under reduced pressure and diluted with
i-Pr2O/petroleum ether to give 39 (0.38 g, 87%). A sample was
recrystallized from i-Pr2O: mp 168-169 °C; 1H NMR (CDCl3)
δ 8.88 (br s, 1 H), 8.42 (br s, 1 H), 7.80 (d, J ) 8.1 Hz, 1 H),
7.67-7.51 (m, 2 H), 4.34 (br s, 1 H), 4.20 (t, J ) 10.2 Hz, 1 H),
4.17-4.08 (m, 1 H), 3.92 (dd, J ) 11.2, 2.5 Hz, 1 H), 3.54 (t, J
) 10.3 Hz, 1 H), 1.62 (s, 9 H). Anal. Calcd for C18H19ClN2O4:
C, 59.59; H, 5.28; N, 7.72; Cl, 9.77. Found: C, 59.84; H, 5.23;
N, 7.70; Cl, 9.73.
1-(Ch lor om eth yl)-5-n itr o-3-[(5,6,7-tr im eth oxyin d ol-2-
yl)ca r bon yl]-1,2-d ih yd r o-3H-ben z[e]in d ole (9). A solution
of 39 (170 mg, 0.47 mmol) in dioxane (5 mL) was saturated
with dry HCl, stirred at 20 °C for 2 h, and then evaporated
under reduced pressure and below 30 °C. [1-(3-Dimethylami-
no)propyl)-3-ethylcarbodiimide hydrochloride (EDCI‚HCl)20
(226 mg, 1.18 mmol), 5,6,7-trimethoxyindole-2-carboxylic acid
(124 mg, 0.49 mmol), and DMA (2.0 mL) were then added, and
the mixture was stirred at 20 °C for 2.5 h. Addition of dilute
KHCO3 precipitated a crude product that was recrystallized
from CH2Cl2/EtOAc (decolorizing charcoal) to give 9 (178 mg,
3-(ter t-Bu tyloxyca r bon yl)-1-(h yd r oxym eth yl)-5-n itr o-
1,2-d ih yd r o-3H-ben z[e]in d ole (37). NaOMe (30.46 mL of
a 0.913 M solution in MeOH, 27.81 mmol) was added dropwise
to a stirred solution of 34 (7.98 g, 18.54 mmol) in THF (120
mL) at 10 °C. After 30 min at 20 °C, TFA (2.34 mL, 30.58
mmol) was added in one portion, causing dissipation of the
deep purple color. The reaction mixture was diluted with
saturated NaCl and extracted twice with CH2Cl2. The extracts
were washed twice with water, dried (Na2SO4), and concen-
trated under reduced pressure and below 30 °C. The resulting
oil was refrigerated (-20 °C), providing a solid that was
triturated with i-Pr2O/petroleum ether to give crude (tert-
butyloxycarbonyl)-1-(methoxycarbonyl)-5-nitro-1,2-dihydro-3H-
benz[e]indole (36) (6.76 g, 98%), which was used without
further purification: 1H NMR (CDCl3) δ 8.89 (br s, 1 H), 8.38
(br s, 1 H), 7.87 (d, J ) 8.3 Hz, 1 H), 7.63-7.51 (m, 2 H), 4.61
(dd, J ) 10.5, 3.9 Hz, 1 H), 4.56-4.44 (m, 1 H), 4.32 (t, J )
11.1 Hz, 1 H), 3.72 (s, 3 H), 1.61 (s, 9 H).
1
77%): mp 243-245 °C; H NMR (CDCl3) δ 9.44 (s, 1 H), 9.24
(s, 1 H), 8.43 (dd, J ) 7.9, 1.2 Hz, 1 H), 7.87 (dd, J ) 7.7, 1.5
Hz, 1 H), 7.70-7.60 (m, 2 H), 7.03 (d, J ) 2.5 Hz, 1 H), 6.87
(s, 1 H), 4.88 (dd, J ) 10.8, 2.1 Hz, 1 H), 4.74 (dd, J ) 10.4,
8.9 Hz, 1 H), 4.36-4.26 (m, 1 H), 4.10 (s, 3 H), 3.99 (dd, J )
11.4, 3.1 Hz, 1 H), 3.95 (s, 3 H), 3.92 (s, 3 H), 3.58 (dd, J )
11.4, 9.9 Hz, 1 H); 13C NMR δ 160.5, 150.4, 147.8, 140.8, 140.5,
138.9, 130.0, 129.8, 128.9, 128.5, 127.8, 125.9, 124.4, 123.5,
122.9, 122.8, 115.5, 106.9, 97.6, 61.5, 61.2, 56.3, 54.7, 45.5, 43.6.
Anal. Calcd for C25H22ClN3O6: C, 60.55; H, 4.47; N, 8.48.
Found: C, 60.14; H, 4.53; N, 8.42.
Crude 36 (6.76 g, 18.15 mmol) was dissolved in THF (120
mL) and added dropwise over 20 min to a stirred solution of
DIBALH (81.7 mL of a 1 M solution in hexanes, 81.7 mmol)
in THF (200 mL) under N2 at 0 °C. The mixture was stirred
for a further 30 min at 5 °C, then poured into ice-cold 2 N
HCl (400 mL), and extracted twice with EtOAc. The combined
extracts were washed once with water, dried (Na2SO4), and
concentrated under reduced pressure and below 25 °C. The
residue was dissolved in CH2Cl2/EtOAc (2:1) and filtered
through a column of silica gel. The solvent was removed under
reduced pressure and below 25 °C, and the resulting solid was
dissolved in the minimum volume of hot CH2Cl2. Prolonged
cooling at -20 °C provided a crystalline product that was
collected and washed with a small volume of cold CH2Cl2 and
then i-Pr2O to give 37 (3.96 g). A further 0.41 g was obtained
from the mother liquor following chromatography on silica gel,
elution with CH2Cl2/EtOAc (4:1), and crystallization from CH2-
Cl2; total yield 4.37 g, 70%. A sample was recrystallized from
5-Am in o-1-(ch lor om eth yl)-3-[(5,6,7-tr im eth oxyin d ol-2-
yl)ca r bon yl]-1,2-d ih yd r o-3H-ben z[e]in d ole (10). A solu-
tion of 9 (60 mg, 0.12 mmol) in THF (15 mL) was hydrogenated
over PtO2 (15 mg) at 50 psi for 2 h. The catalyst was removed
by filtration, the solution was concentrated to a small volume
under reduced pressure and below 30 °C, and i-Pr2O was
added. The resulting solid was purified by precipitation from
a THF solution with i-Pr2O at 20 °C to give 10 (53 mg, 94%):
mp 199-204 °C; 1H NMR [(CD3)2SO] δ 11.41 (d, J ) 1.2 Hz, 1
H, NH), 8.07 (d, J ) 8.5 Hz, 1 H, H-6), 7.75 (d, J ) 8.3 Hz, 1
H, H-9), 7.63 (br s, 1 H, H-4), 7.45 (t, J ) 7.6 Hz, 1 H, H-8),
7.28 (t, J ) 7.7 Hz, 1 H, H-7), 7.03 (d, J ) 2.0 Hz, 1 H, H-3′),
6.96 (s, 1 H, H-4′), 5.98 (s, 2 H, NH2), 4.67 (dd, J ) 10.8, 8.9
Hz, 1 H, H-2), 4.41 (dd, J ) 10.9, 1.4 Hz, 1 H, H-2), 4.12-4.02
(m, 1 H, H-1), 3.96 (dd, J ) 11.0, 3.1 Hz, 1 H, CHHCl), 3.94
(s, 3 H, 7′-OCH3), 3.82 (s, 3 H, 5′-OCH3), 3.80 (s, 3 H, 6′-OCH3),
3.71 (dd, J ) 10.9, 8.2 Hz, 1 H, CHHCl); 13C NMR δ 160.1
(CO), 149.1 (C-5′), 146.1 (C-5), 142.5 (C-3a), 139.7 (C-6′), 139.0
(C-7′), 131.3 (C-2′), 130.0 (C-9a), 126.7 (C-8), 125.2 (C-7a′),
123.3 (C-6), 123.1 (C-3a′), 122.9 (C-9), 122.0 (C-7), 120.3 (C-
5a), 111.9 (C-9b), 105.8 (C-3′), 98.5 (C-4), 97.9 (C-4′), 61.0 (7′-
OCH3), 60.9 (6′-OCH3), 55.9 (5′-OCH3), 55.0 (C-2), 47.3 (CH2Cl),
41.2 (C-1). Signal assignments were confirmed by HMQC,
HMBD, and COSY spectra and by comparison with literature
1
i-Pr2O/petroleum ether: mp 176 °C; H NMR (CDCl3) δ 8.90
(br s, 1 H), 8.43 (br s, 1 H), 7.88 (d, J ) 7.9 Hz, 1 H), 7.62-
7.51 (m, 2 H), 4.34-4.24 (m, 1 H), 4.17 (dd, J ) 11.4, 9.5 Hz,
1 H), 4.04-3.93 (m, 2 H), 3.83-3.74 (m, 1 H), 1.61 (s, 9 H).
Anal. Calcd for C18H20N2O5: C, 62.78; H, 5.85; N, 8.13.
Found: C, 62.94; H, 6.13; N, 8.00.
3-(ter t-Bu t yloxyca r b on yl)-1-[(m et h a n esu lfon yloxy)-
m et h yl]-5-n it r o-1,2-d ih yd r o-3H -b en z[e]in d ole (38).
A
stirred solution of 37 (0.42 g, 1.22 mmol) in pyridine (1.5 mL)
was treated dropwise at 0 °C with MsCl (113 µL, 1.46 mmol)
and then stirred at 20 °C for a further 2 h. The mixture was
diluted with water, and the resulting solid was collected,
washed with water, and dried. This product was dissolved in
CH2Cl2, and the solution was filtered through a short column
of silica gel, eluting with further CH2Cl2. The resulting
product was triturated with i-Pr2O/petroleum ether to give 38
(0.46 g, 89%): mp 145-146 °C (dec); 1H NMR [(CD3)2SO] δ
8.75 (br s, 1 H), 8.32 (d, J ) 8.5 Hz, 1 H), 8.12 (d, J ) 8.2 Hz,
1 H), 7.77-7.63 (m, 2 H), 4.54 (dd, J ) 10.0, 3.7 Hz, 1 H), 4.43
(dd, J ) 10.0, 6.4 Hz, 1 H), 4.42-4.33 (m, 1 H), 4.25 (t, J )
10.3 Hz, 1 H), 4.14 (dd, J ) 11.4, 2.5 Hz, 1 H), 3.11 (s, 3 H),
values for related compounds. Anal. Calcd for
C25H24-
ClN3O4: C, 64.44; H, 5.19; N, 9.02; Cl, 7.61. Found: C, 64.76;
H, 5.31; N, 8.76; Cl, 7.60.
1-(Ch lor om eth yl)-5-m eth yla m in o-3-[(5,6,7-tr im eth oxy-
in d ol-2-yl)ca r bon yl]-1,2-d ih yd r o-3H-ben z[e]in d ole (11).
Acetic-formic anhydride [60 µL of a solution prepared from
formic acid (1.25 mL, 33 mmol) and acetic anhydride (2.5 mL,
27 mmol)] was added to a solution of 10 (206 mg, 0.44 mmol)
(20) Fukuda, Y.; Itoh, H.; Nakatani, K.; Terashima, S. Tetrahedron
1994, 50, 2793.

9420 J . Org. Chem., Vol. 63, No. 25, 1998
Atwell et al.
in THF (20 mL) at 0 °C under N2. After the mixture was
stirred for 30 min at 0 °C, additional acetic-formic anhydride
(60 µL) was added to the heterogeneous mixture, and stirring
was continued for 2.5 h at 0 °C. The mixture was then
evaporated to dryness under very low pressure. THF (35 mL)
was added, and the suspension was treated with BH3‚Me2S
(0.15 mL, 1.5 mmol), and then stirred at reflux for 45 min.
The reaction was cooled, MeOH (2 mL) followed by 2 N HCl
(10 mL) was added, and the mixture was stirred at 20 °C for
15 min. Volatiles were removed under reduced pressure, and
the residue was shaken with aqueous KHCO3 and extracted
twice with EtOAc. The combined extracts were washed with
water, dried, and concentrated under reduced pressure. Chro-
matography of the residue on silica gel and elution with CH2-
Cl2/EtOAc (5:1) followed by precipitation from an EtOAc
solution with i-Pr2O at 20 °C gave 11 (89 mg, 42%): mp 122-
125 °C; 1H NMR [(CD3)2SO] δ 11.45 (d, J ) 1.4 Hz, 1 H), 8.09
(d, J ) 8.5 Hz, 1 H), 7.78 (d, J ) 8.1 Hz, 1 H), 7.48 (t, J ) 7.6
Hz, 1 H), 7.32 (t, J ) 7.6 Hz, 1 H), ca. 7.3 (underlying s, 1 H),
7.04 (d, J ) 1.8 Hz, 1 H), 6.97 (s, 1 H), 6.53 (q, J ) 4.6 Hz, 1
H), 4.67 (t, J ) 9.9 Hz, 1 H), 4.46 (dd, J ) 11.0, 1.5 Hz, 1 H),
4.17-4.07 (m, 1 H), 3.98 (dd, J ) 11.0, 3.0 Hz, 1 H), 3.92 (s, 3
H), 3.82 (s, 3 H), 3.80 (s, 3 H), 3.77 (dd, J ) 11.0, 8.2 Hz, 1 H),
2.80 (br s, 3 H). Anal. Calcd for C26H26ClN3O4: C, 65.06; H,
5.46; N, 8.76; Cl, 7.39. Found: C, 65.28; H, 5.55; N, 8.53; Cl,
7.11.
(0.8 mL) were injected and eluted in i-PrOH/hexane (50:50)
at a flow rate of 6.75 mL/min. This gave baseline separation
of the enantiomers (R value of 1.40), with the (-)-38 enanti-
omer having an RT of 30 min and the (+)-38 enantiomer an
RT of 42 min. The absolute configuration of the enantiomers
was determined by an X-ray crystal structure determination
of the faster eluting (-)-38 enantiomer, which showed the R
configuration (Figure 1). (-)-38 and (+)-38 were converted
via (R)-39 and (S)-39 to the corresponding nitro-seco-CBI-TMI
enantiomers (-)-9 and (+)-9, which were in turn reduced to
the amino-seco-CBI-TMI enantiomers (-)-10 and (+)-10.
(-)-(R)-38: mp 147-148 °C (dec); [R]D -60° (c 0.31, THF)
(+)-(S)-38: mp 147-148 °C (dec); [R]D +61° (c 0.31, THF)
(-)-(R)-39: mp 133-134 °C; [R]D -53° (c 0.34, THF)
(+)-(S)-39: mp 133-134 °C; [R]D +54° (c 0.35, THF)
(-)-(R)-9: mp 223-225 °C; [R]D -55° (c 0.23, THF)
(+)-(S)-9: mp 223-225 °C; [R]D +54° (c 0.23, THF)
(-)-(R)-10: mp 229-231 °C; [R]D -10° (c 0.20, THF)
(+)-(S)-10: mp 229-231 °C; [R]D +10° (c 0.20, THF)
1-(Chloromethyl)-5-(dimethylamino)-3-[(5,6,7-trimethoxy-
in d ol-2-yl)ca r bon yl]-1,2-d ih yd r o-3H-ben z[e]in d ole (12). A
mixture of 10 (181 mg, 0.39 mmol) and formaldehyde (0.30
mL of ca. 40% w/v, 4 mmol) in THF (5 mL) was treated with
solid NaBH3CN (63 mg, 1.0 mmol) followed by 2 N HCl (0.7
mL). The mixture was stirred at 20 °C for 2 h, then diluted
with water, and extracted three times with CH2Cl2. The
combined extracts were washed with water, dried, and con-
centrated under reduced pressure, and the residue was chro-
matographed on silica gel. Elution with CH2Cl2/EtOAc (4:1)
gave a gum which was triturated with EtOAc/i-Pr2O, and the
resulting crude product was purified by precipitation from a
CH2Cl2 solution with i-Pr2O at 20 °C to give 12 (130 mg,
The 1H NMR spectra of these enantiomers were identical to
those of the corresponding racemates.
In Vitr o Cytotoxicity Assa y. Growth inhibitory potency
under aerobic conditions was determined using log-phase
cultures in 96-well plates, as described previously.13,21 IC50
values were calculated as the drug concentration providing
50% inhibition of growth relative to the controls.
Ack n ow led gm en t. The authors thank Drs. J ohn
Matejovic and Ho Lee for the preparation of 3 and Karin
Tan, Susan Pullen, and Donna Murray for technical
assistance. This work was supported by the Auckland
Division of the Cancer Society of New Zealand, the
Health Research Council of New Zealand, and NCI
Contract NO1-CM 47019.
1
68%): mp 174-175 °C; H NMR [(CD3)2SO] δ 11.48 (d, J )
1.6 Hz, 1 H), 8.14 (d, J ) 8.3 Hz, 1 H), ca. 8.0 (underlying s,
1 H), 7.92 (d, J ) 8.2 Hz, 1 H), 7.54 (t, J ) 7.5 Hz, 1 H), 7.44
(t, J ) 7.6 Hz, 1 H), 7.07 (d, J ) 1.8 Hz, 1 H), 6.98 (s, 1 H),
4.73 (t, J ) 9.9 Hz, 1 H), 4.51 (dd, J ) 11.1, 1.8 Hz, 1 H),
4.30-4.20 (m, 1 H), 4.05 (dd, J ) 11.1, 3.1 Hz, 1 H), 3.93 (s, 3
H), 3.88 (dd, J ) 11.1, 7.6 Hz, 1 H), 3.82 (s, 3 H), 3.80 (s, 3 H),
2.80 (s, 6 H). Anal. Calcd for C27H28ClN3O4: C, 65.65; H, 5.78;
N, 8.51; Cl, 7.18. Found: C, 65.73; H, 5.98; N, 8.61; Cl, 7.13.
Resolu tion of En a n tiom er s. 38 was resolved by HPLC
on a Diacel Chiralcel OD semipreparative column (10 µm, 2
× 25 cm). Samples (15 mg, maximum permitted by solubility)
were dissolved in CH3CN and diluted to give a solution
comprising CH3CN/i-PrOH/hexane (25:37.5:37.5). Aliquots
Su p p or tin g In for m a tion Ava ila ble: Details of the syn-
thesis of 14-20 and the X-ray structures of 15, 27, and (-)-
(R)-38 (22 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
J O981395W
(21) Finlay, G. J .; Baguley, B. C.; Wilson, W. R. Anal. Biochem. l984,
139, 272.