Substituted pyrrolo[3,4-a]carbazoles from reactions between 3-(1-methoxy-vinyl)indoles and maleimides

Article abstract of DOI:10.1007/s00706-005-0363-2

5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed into the hydroxy derivatives by treatment with H₂SO₄

Full text of DOI:10.1007/s00706-005-0363-2

Monatshefte f€ur Chemie 136, 1799–1809 (2005)
DOI 10.1007/s00706-005-0363-2
Substituted Pyrrolo[3,4-a]carbazoles
from Reactions between 3-(1-Methoxy-
vinyl)indoles and Maleimides
ꢀ
Michaela Bleile and Hans-Hartwig Otto
Department of Pharmaceutical=Medicinal Chemistry, Institute of Pharmacy,
University of Greifswald, D-17487 Greifswald
Received February 3, 2005; accepted March 1, 2005
Published online September 5, 2005 # Springer-Verlag 2005
Summary. 5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloaddi-
tions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed
into the hydroxy derivatives by treatment with H2SO4, selectively reduced to the ether by H2=Pd–C,
and in the imide moiety by L-Selectride+. From the analogous BOC protected indole derivative the
parent ꢀ,ꢁ-unsaturated ketones were obtained, which were transformed into hydroxyimino com-
pounds, and which could be deprotected by heating to the melting point. Deprotection of the tosyl
derivatives was not successful. The imide part of the molecule was hydrolyzed using methanolic
NaOH. The stereochemistry of all products was elucidated mainly by spectroscopic methods, and
compared with results of calculations.
Keywords. 3-Vinylindole; Pyrrolo[3,4-a]carbazole; Maleimide; Cycloaddition.
Introduction
Carbazole and other annelated indole derivatives form the basic structure of many
valuable, and highly potent drugs like camptothecine and its derivatives topotecane
and irinotecane used as inhibitors of the enzyme topoisomerase I against different
types of cancer, or like vincamine used in the therapy of Alzheimer disease [1].
Many synthesis procedures in this area start with the cycloaddition of appropriate
dienes to substituted 2- or 3-vinylindoles [2]. We have described reactions of
maleimides and related systems with cyclopentadiene and with 1-(1-siloxyvinyl)
naphthalene [3], and in a preceding paper we have reported about unusual reactions
between maleimides and silylated indole derivatives [4]. Here we report about the
synthesis of pyrrolo[3,4-a]carbazole derivatives by cycloadditions between male-
imides and 3-(1-methoxyvinyl)indole derivatives.
ꢀ
Corresponding author. E-mail: ottohh@pharmazie.uni-greifswald.de

1800
M. Bleile and H.-H. Otto
Results and Discussion
The indole derivative 1 was prepared from 3-acetyl-1-tosylindole by reaction with
trimethyl orthoformiate via the ketal 3-(ꢀ,ꢀ-dimethoxyethyl)-1-tosylindole by
elimination of MeOH with KHSO4 at 100ꢁC with yields up to 95%. It was obtained
as an unstable compound which easily polymerized. Therefore, we had to use it
immediately for reactions with 2a, 2b, and 2c, which were done by stirring a
Scheme 1

Substituted Pyrrolo[3,4-a]carbazoles
1801
solution of 1 and the maleimide in toluene at room temperature. After standard
work-up we obtained the crystalline pyrrolo[3,4-a]carbazole derivatives 3a, 3b,
and 3c (Scheme 1). IR spectra of these compounds were characterized by the
strong carbonyl bands at 1779 and 1709 cmꢂ1 (3b) caused by the carbonyl groups
in positions 1 and 3. The structure was established using 1H,1H- and 1H,13C–COSY
spectra and NOE experiments. The following coupling constants were found in
1
the H NMR spectra (3c): J3a-H=4-HA ¼ 6.6 Hz, J3a-H=4-HB ¼ 1.7 Hz, J3a-H=10b-H
¼
8.7 Hz, and J10a-H=10b-H ¼ 7.1 Hz. A calculation of the torsion angles (MM2,
SYBYL [5]) resulted in ’(3a-H=4-HA) ¼ ꢂ59.3ꢁ, ’(3a-H=4-HB) ¼ 57.0ꢁ, ’(3a-
H=10b-H) ¼ 8.5ꢁ, and ’(10a-H=10b-H) ¼ 48.6ꢁ. These values demonstrate the cis
addition (3a-H=10b-H), and the endo (cis) orientation of 10b-H and 10a-H. NOE
experiments showed that 3a-H, 10b-H, and 10a-H were orientated to the same side
of the molecule, which agreed with the calculated distances 10a-H ꢂ 10b-H ¼
˚
˚
˚
˚
2.47 A, 10aH ꢂ 4-HA ¼ 2.57 A, 3a-H ꢂ 4-HA ¼ 2.54 A, and 3a-H ꢂ 4-HB ¼ 2.47 A.
The calculated data agreed with the data obtained by NMR experiments, and
thereby we propose a structure as given in Fig. 1. Spectral data of 3a and 3b
showed no significant differences, thus, they should have analogue structures.
The double bond between C-5 and C-5a of 3a, 3b, and 3c was hydrogenated
with H2=Pd–C at room temperature yielding 4a, 4b, and 4c with yields of 60–75%.
This hydrogenation occurred stereoselectively as a cis addition whereby 5-H and
5a-H were cis orientated. The structure agreed with the following data. Positive
NOEs were observed (4a) between 5a-H and 5-H, 5a-H and 10a-H, 3a-H and
1
10b-H, 10b-H and 10a-H, and 5-H and 4-HB. In the H NMR spectrum of 4b
the following characteristic coupling constants were found: J5-H=5a-H ¼ 5.1 Hz,
J5a-H=10a-H ¼ 11 Hz, J10a-H=10b-H ¼ 7.8 Hz, and J10b-H=3a-H ¼ 9.7 Hz. Finally, the cal-
culated structure fitted to that one deduced from the NMR data. In contrast to the
reduction with H2=Pd–C the reduction using L-Selectride+ in THF at ꢂ78ꢁC
Fig. 1. Calculated structure of 3c with observed NOEs

1802
M. Bleile and H.-H. Otto
attacked the carbonyl group at position 3, and we isolated 6a and 6b with yields up
to 85%.
The IR spectra of 6a and 6b showed significant differences when compared
with the spectra of 3a and 3b. Instead of the two carbonyl bands of the imide
moiety we found one amide band at 1684 cmꢂ1 and an H–O-band at 3440 cmꢂ1.
In the 13C NMR spectrum (6b) only one carbonyl C was observed at 170 ppm.
1
Comparing the H NMR spectra we found significant shifts of the signal of 3a-H
and 4-HA from 3.20=3.29 ppm (3b) to 2.45 ppm (6b), whereas the resonance sig-
nals of 10a-H and 10b-H showed only small differences. In NOE experiments,
irradiation at 5.56 ppm (H–O) caused positive effects at the signals of 3-H,
3a-H, and 4-HB. Thus, they support that the reduction had occurred at C-3, and
that the hydroxyl group in 6a and 6b is orientated to the down side.
Cleavage of the enol ether was successful when 3a and 3b were treated with
H2SO4 yielding the enols 5a and 5b, and by refluxing of 5b in EtOH, the ꢀ,ꢁ-
Scheme 2

Substituted Pyrrolo[3,4-a]carbazoles
1803
unsaturated ketone 7 was obtained with ꢃ70% yield. Finally, when we tried to
deprotect the indole nitrogen by cleavage of the sulfonamide bond by heating of 3b
with a mixture of MeOH and aq. NaOH (20%) [6] we isolated a mixture of the two
isomeric compounds 8I and 8II which we did not separate.
A different behavior was observed when we reacted the BOC-protected indole
derivative 9 with the maleimides 2a, 2b, and 2c in toluene at room temperature
(Scheme 2). After usual work-up, the crystalline ꢀ,ꢁ-unsaturated ketone deriva-
tives 10a, 10b, and 10c were isolated with poor yields (ꢄ35%). The structure was
comparable with that of 7, as could be deduced from the spectroscopic data, and
the carbonyl group at C-5 was reacted with H2NOH yielding the oxime derivatives
12a and 12b with high yields. Finally, the BOC group was deleted thermally by
heating of 10a and 10b to the melting point yielding the deprotected pyrrolocar-
bazole derivatives 13a and 13b. The crystalline oxime 15a was obtained from 13b
by reaction with H2NOH (72%), whereas the analogous derivative 15b was pre-
pared by thermal elimination of the BOC group from 12b with 90% yield. As could
be seen from IR and NMR data, during these reactions the stereochemistry of the
ring system was not modified.
Finally, we compared the reactivity of the O-phosphorylated N-tosyl protected
indole diene 11, prepared from 3-acetyl-1-tosylindole by reaction with n-BuLi and
Cl(EtO)2PO at ꢂ78ꢁC, with that of 1 and 9 in the reaction with 2a (Scheme 2). We
isolated the adduct 14 after a reaction time of 4 d at room temperature with a yield
of 25%, and stopped further experiments. The general structure and stereochem-
istry of 14 did not differ from that of 3a.
Experimental
Melting points: Mel-Temp II apparatus (uncorrected); IR spectra (KBr): Perkin-Elmer IR 841; NMR
spectra: 1H: Varian T 60 (60 MHz), Bruker WP 80 (80 MHz), room temperature (27ꢁC), internal TMS,
Varian Unity 300 (300 MHz), room temperature (27ꢁC), 13C: Varian Unity 300 (75.43 MHz), room
temperature (27ꢁC), related to ꢂ (CDCl3) ¼ 77.00 ppm; all NMR values from spectra in CDCl3, if not
otherwise noted; MS spectra: Finnigan MAT 312, MAT 44 S, EI, 70eV; elemental analyses: Pharm.
Inst. or Chemisches Laboratorium, University of Freiburg or Pharmazeutisches Institut, University of
Greifswald, Perkin Elmer Analyzer 2400; the results agreed with the calculated values within experi-
mental error. Column chromatography (CC): silica gel 60 Merck 7734. TLC ¼ thin layer chromatog-
raphy (pre-coated silica gel plates 60 F254, Merck 5549). Lithium diisopropylamide (LDA) was
freshly prepared by mixing of equimolar amounts of diisopropylamine in THF and n-butyl lithium
(BuLi, 1.6 M solution in n-hexane) at ꢂ78ꢁC. Solvents were purified=dried according to literature
procedures. Abbreviations: AcOEt¼ ethyl acetate; ar ¼ aromatic; Tos ¼ p-tosyl. The following com-
pounds were prepared according to lit. procedures: 3-Acetyl-1-tosylindole [7], 3-acetyl-1-(2,2-
dimethylpropanoyl)indole [8], 3-acetyl-1-(tert-butoxycarbonyl)indole [9].
3-(ꢀ,ꢀ-Dimethoxyethyl)-1-tosylindole (1a, C19H21NO4S)
3-Acetyl-1-tosylindole (6.24 g, 20mmol), 10–12cm3 HC(OMe)3, and 1 cm3 MeSO3H were suspended
at 0ꢁC in 40 cm3 MeOH, and stirred for 14h (TLC control). Then, the mixture was neutralized by a
methanolic solution of NaOH (50%), and poured into 20cm3 ice-H2O. After extraction with
3ꢅ100 cm3 Et2O, the combined organic layers were washed with 150 cm3 H2O, dried (MgSO4),
and evaporated. Yield 6.7 g (93%); colorless crystals; mp 85ꢁC (MeOH); IR: ꢃꢀ¼ 2829 (OMe), 1123
(COC), 1369, 1180 (SO2) cmꢂ1; 1H NMR (60 MHz): ꢂ ¼ 1.60 (s, Me), 2.30 (s, Me), 3.15 (s, 2 OMe),
7.00–8.00 (m, 9 ar H) ppm.

1804
M. Bleile and H.-H. Otto
3-(ꢀ-Methoxyvinyl)-1-tosylindole (1, C18H17NO3S)
A mixture of 6.7 g 1a (18.6 mmol) and 100 mg KHSO4 was heated to 100ꢁC at 14ꢅ133 Pa. After
cooling to room temperature 100 cm3 of xylene were added, and after stirring for 5 min and filtration,
the solvent was evaporated in vacuo. Yield 5.7 g (93%, not purified); IR (Film): ꢃꢀ¼ 3052 (¼CH2),
2833 (OMe), 1656, 1643 (¼CH2), 1372, 1175 (SO2) cmꢂ1; 1H NMR (60 MHz): ꢂ ¼ 2.30 (s, Me), 3.15
(s, OMe), 4.35, 4.45 (¼CH2), 7.00–8.00 (m, 9 ar H) ppm; MS: m=z (%) ¼ 327 (25) [Mþ], 359 (10).
The product was immediately used for further reactions.
5-Methoxy-2-phenyl-10-tosyl-4,10,10a,10b-tetrahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (3a, C28H24N2O5S)
From 1 (4.3g, 13mmol) and 2.25 g 2a (13 mmol) in 100 cm3 of toluene with stirring for 16 h and
evaporation of the solvent in vacuo. Yield 2.25 g (24%); colorless crystals; mp 194ꢁC (AcOEt); IR:
ꢃꢀ¼ 2825 (MeO), 1711 (CO), 1680 (¼C–OSi), 1361, 1170 (SO2) cmꢂ1; 1H NMR (300MHz): ꢂ ¼ 2.28
(ddd, J4A=10a ¼ 2 Hz, J4A=3a ¼ 6.6 Hz, J4A=4B ¼ 16.1Hz, 4-HA), 2.34 (s, Me), 3.37 (dd, J4B=3a ¼ 2 Hz,
J4B=4A ¼ 15.9 Hz, 4-HB), 3.37 (m, 3a-H), 3.63 (s, MeO), 4.1 (dd, J10b=10a ¼ 6.8 Hz, J10b=3a ¼ 8.8 Hz,
10b-H), 4.66 (dd, J10a=4A ¼ 2 Hz, J10a=10b ¼ 6.8 Hz, 10a-H), 6.92–7.75 (m, 13 ar H) ppm.
5-Methoxy-2-methyl-10-tosyl-4,10,10a,10b-tetrahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (3b, C23H22N2O5S)
From 1 (4.3g, 13mmol) and 1.44g 2b (13 mmol) as described for 3a, stirring for 72h at room
temperature. Yield 1.6 g (28%); colorless crystals; mp 205ꢁC (AcOEt); IR: ꢃꢀ¼ 2943 (CH), 2848
(MeO), 1779, 1709 (CO), 1596, 1492 (ar C–C), 1459, 1435, 1382 (CH), 1360, 1166 (SO2) cmꢂ1
;
1H NMR (300 MHz): ꢂ ¼ 2.22 (ddd, J4A=10a ¼ 2.2 Hz, J4A=3a ¼ 6.6 Hz, J4A=4B ¼ 15.6 Hz, 4-HA), 2.34
(s, Me), 2.84 (s, NMe), 3.2 (ddd, J3a=4B ¼ 1.7 Hz, J3a=4A ¼ 6.6 Hz, J3a=10b ¼ 8.7 Hz, 3a-H), 3.29 (dd,
J4B=3a ¼ 1.7 Hz, J4B=4A ¼ 15.9Hz, 4-HB), 3.63 (s, MeO), 3.85 (dd, J10b=10a ¼ 7.1 Hz, J10b=3a ¼ 8.8 Hz,
10b-H), 4.59 (dd, J10a=4A ¼ 2.2 Hz, J10a=10b ¼ 7.1 Hz, 10a-H), 6.94 (ddd, J7=9 ¼ 1.2 Hz, J7=6 ¼ 7.6 Hz,
J7=8 ¼ 7.6Hz, 7-H), 7.12 (ddd, J8=6 ¼ 1.2 Hz, J8=7 ¼ 7.6 Hz, J8=9 ¼ 7.8 Hz, 8-H), 7.21 (d, J ¼ 7.8 Hz, 2
ar H), 7.48 (dd, J9=7 ¼ 1.2 Hz, J9=8 ¼ 7.6 Hz, 9-H), 7.61 (dd, J6=8 ¼ 0.7 Hz, J6=7 ¼ 7.3 Hz, 6-H), 7.75
(dd, J ¼ 1.7 Hz, J ¼ 6.6 Hz, 2 ar H) ppm.
2-Ethyl-5-methoxy-10-tosyl-4,10,10a,10b-tetrahydro-3aH-pyrrolo[3,4-a]carbazole-1,3-dione
(3c, C24H24N2O5S)
From 1 (4.3g, 13 mmol) and 1.7 g 2c (13 mmol) as described for 3a, but reflux for 2 d, and stirring for
3 d at room temperature. Yield 1.4 g (24%); colorless crystals; mp 200ꢁC (AcOEt); IR: ꢃꢀ¼ 2940, 2845
(CH), 1770, 1696 (CO), 1595 (ar C–C), 1455, 1404 (CH), 1360, 1165 (SO2) cmꢂ1 1H NMR
;
(300 MHz): ꢂ ¼ 0.86 (t, J ¼ 7.1 Hz, Me), 2.18 (ddd, J4A=10a ¼ 2.2 Hz, J4A=3a ¼ 6.6 Hz, J4A=4B
¼
15.9Hz, 4-HA), 2.32 (s, Me), 3.16 (ddd, J3a=4B ¼ 2 Hz, J3a=4A ¼ 6.6 Hz, J3a=10b ¼ 8.6 Hz, 3a-H), 3.27
(dd, J4B=3a ¼ 2 Hz, J4B=4A ¼ 15.9 Hz, 4-HB), 3.37 (dq, J ¼ 1.7 Hz, J ¼ 7.1 Hz, CH2), 3.65 (s, MeO), 3.9
(dd, J10b=10a ¼ 6.8 Hz, J10b=3a ¼ 8.6 Hz, 10b-H), 4.56 (dd, J10a=4A ¼ 2 Hz, J10a=10b ¼ 6.8 Hz, 10a-H),
6.91 (ddd, J7=9 ¼ 1 Hz, J7=6 ¼ 7.6 Hz, J7=8 ¼ 7.6 Hz, 7-H), 7.09 (ddd, J8=6 ¼ 1.5 Hz, J8=7 ¼ 7.6 Hz,
J8=9 ¼ 7.8Hz, 8-H), 7.18 (d, J ¼ 8.1 Hz, 2 ar H), 7.44 (dd, J9=7 ¼ 1 Hz, J9=8 ¼ 7.6 Hz, 9-H), 7.59 (d,
J6=7 ¼ 8.1Hz, 6-H), 7.73 (dd, J ¼ 1.7 Hz, J ¼ 8.3 Hz, 2 ar H) ppm.
5-Methoxy-2-phenyl-10-tosyl-4,5,5a,10,10a,10b-hexahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (4a, C28H26N2O5S)
Pd–C (10%, 0.4 g) was added to a soln. of 1.0 g 3a (2mmol) in a mixture of 40cm3 CH2Cl2 and 40cm3
MeOH. The mixture was hydrogenated for 12h at room temperature, the catalyst was separated, the
solvent was removed in vacuo, a 1:1 mixture of cyclohexane and AcOEt was added to the residue, and
the insoluble part was separated and washed with the mixture of solvents until no impurities could be
detected in the solvent (TLC control). Yield 660 mg (66%); colorless crystals; mp 274ꢁC; IR: ꢃꢀ¼ 1710

Substituted Pyrrolo[3,4-a]carbazoles
1805
(CO), 1597, 1499, 1479 (ar C–C), 1351, 1163 (SO2), 1114, 1090 (C–O–C) cmꢂ1
;
1H NMR
(300 MHz): ꢂ ¼ 1.73 (ddd, J4A=5 ¼ 0.7 Hz, J4A=3a ¼ 8.5 Hz, J4A=4B ¼ 14.7 Hz, 4-HA), 2.71 (ddd,
J4B=3a ¼ 1 Hz, J4B=5 ¼ 4.4 Hz, J4B=4A ¼ 14.9Hz, 4-HB), 2.35 (s, Me), 3.14 (s, MeO), 3.22 (ddd,
J3a=4B ¼ 1 Hz, J3a=4A ¼ 8.5 Hz, J3a=10b ¼ 10.0Hz, 3a-H), 3.45 (dd, J5a=5 ¼ 6.1 Hz, J5a=10a ¼ 11Hz, 5a-
H), 3.74 (dd, J10b=3a ¼ 10.0 Hz, J10b=10a ¼ 7.8 Hz, 10b-H), 3.90 (dd, J5=5a ¼ 5.1 Hz, J5=4B ¼ 5.1 Hz, 5-
H), 4.68 (dd, J10a=10b ¼ 7.8 Hz, J10a=5a ¼ 11 Hz, 10a-H), 6.91–7.67 (m, 13 ar H) ppm.
5-Methoxy-2-methyl-10-tosyl-4,5,5a,10,10a,10b-hexahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (4b, C23H24N2O5S)
From 3b (1.0g, 2.3 mmol) as described for 4a. Yield 720 mg (72%); colorless crystals; mp 240ꢁC;
IR: ꢃꢀ¼ 2851 (Me), 1701 (CO), 1597 (ar C–C), 1346, 1163 (SO2), 1111, 1090 (C–O–C), 835,
1
815 (ar) cmꢂ1; H NMR (300MHz): ꢂ ¼ 1.67 (dd, J4A=3a ¼ 7.8 Hz, J4A=4B ¼ 14.2Hz, 4-HA), 2.38
(s, Me), 2.66 (dd, J4B=5 ¼ 4.6 Hz, J4B=4A ¼ 14.2Hz, 4-HB), 2.82 (s, NMe), 3.08 (s, MeO), 3.06–3.12 (m,
3a-H), 3.42 (dd, J5a=5 ¼ 6.1 Hz, J5a=10a ¼ 11Hz, 5a-H), 3.60 (dd, J10b=3a ¼ 9.7 Hz, J10b=10a ¼ 7.8 Hz,
10b-H), 3.85 (dd, J5=5a ¼ 5.1 Hz, J5=4B ¼ 5.1 Hz, 5-H), 4.62 (dd, J10a=10b ¼ 7.8 Hz, J10a=5a ¼ 11Hz,
10a-H), 6.89 (d, J6=7 ¼ 7.3 Hz, 6-H), 7.01 (ddd, J7=9 ¼ 1 Hz, J7=6 ¼ 7.5 Hz, J7=8 ¼ 7.5Hz, 7-H), 7.21
(d, J ¼ 8.1 Hz, 2 ar H), 7.26 (dd, J8=9 ¼ 7.6 Hz, J8=7 ¼ 7.2 Hz, 8-H), 7.66 (d, J ¼ 8.3 Hz, 2 ar H),
7.71 (d, J9=8 ¼ 8.1 Hz, 9-H) ppm.
5-Methoxy-2-ethyl-10-tosyl-4,5,5a,10,10a,10b-hexahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (4c, C24H26N2O5S)
From 3c (1.0g, 2.2 mmol) as described for 4a. Yield 650 mg (65%); colorless crystals; mp 221–223ꢁC;
IR: ꢃꢀ¼ 1697 (CO), 1599 (ar C–C), 1352, 1167 (SO2), 1090 (C–O–C), 837, 815 (ar) cmꢂ1; 1H NMR
(300 MHz): ꢂ ¼ 1.0 (t, J ¼ 7.1 Hz, Me), 1.61 (ddd, J4A=10a ¼ 0.9 Hz, J4A=3a ¼ 8.3 Hz, J4A=4B ¼ 14.7Hz,
4-HA), 2.33 (s, Me), 2.59 (ddd, J4B=3a ¼ 1.3 Hz, J4B=5 ¼ 4.7 Hz, J4B=4A ¼ 14.7Hz, 4-HB), 3.00 (ddd,
J3a=4B ¼ 1.3 Hz, J3a=4A ¼ 9 Hz, J3a=10b ¼ 9 Hz, 3a-H), 3.05 (s, MeO), 3.34 (dq, J ¼ 1.8 Hz, J ¼ 7.1 Hz,
CH2), 3.37 (m, 5a-H), 3.52 (dd, J10b=3a ¼ 9.8 Hz, J10b=10a ¼ 8.1 Hz, 10b-H), 3.80 (dd, J5=5a
¼
4.9 Hz, J5=4B ¼ 4.8 Hz, 5-H), 4.57 (dd, J10a=5a ¼ 10.9Hz, J10a=10b ¼ 7.9 Hz, 10a-H), 6.85 (d,
J6=7 ¼ 7.5Hz, 6-H), 6.96 (ddd, J7=9 ¼ 1.1 Hz, J7=6 ¼ 7.5 Hz, J7=8 ¼ 7.5Hz, 7-H), 7.16 (dd, J ¼ 0.6 Hz,
J ¼ 8.6 Hz, 2 ar H), 7.20 (dd, J8=7 ¼ 7.5 Hz, J8=9 ¼ 7.5 Hz, 8-H), 7.60 (d, J ¼ 8.4 Hz, 2 ar H), 7.66
(d, J9=8 ¼ 8.1 Hz, 9-H) ppm.
5-Hydroxy-2-phenyl-10-tosyl-4,10,10a,10b-tetrahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (5a, C27H22N2O5S)
Compound 3a (500mg, 1 mmol) was suspended in a mixture of 20 cm3 dil. H2SO4 (98 g ꢆ dmꢂ3) and
10cm3 conc. H2SO4, the mixture was refluxed until the reaction was completed (TCL control), and
after cooling to room temperature the precipitate was separated and washed with H2O until H2O
1
reacted neutral. Yield 3–5 mg; H NMR (300MHz): ꢂ ¼ 2.31 (s, Me), 2.62 (dd, J4A=4B ¼ 15.8Hz,
J4A=3a ¼ 7.7 Hz, 4-HA), 2.88 (d, J4B=4A ¼ 15.8 Hz, 4-HB), 3.42 (dd, J3a=10b ¼ 7.1 Hz, J3a=4A ¼ 7.1 Hz,
3a-H), 3.92 (dd, J10b=10a ¼ 6.8 Hz, J10b=3a ¼ 8.7 Hz, 10b-H), 4.85 (dd, J10a=4A ¼ 1.5 Hz, J10a=10b
6.8 Hz, 10a-H), 6.9–8.0 (m, 13 ar H), 9.8 (bs, H–O) ppm.
¼
5-Hydroxy-2-methyl-10-tosyl-4,10,10a,10b-tetrahydro-3aH-pyrrolo[3,4-a]carbazole-
1,3-dione (5b, C22H20N2O5S)
From 3b (400 mg, 0.9 mmol) as described for 5a. Yield 140 mg (40%); colorless crystals; mp 245ꢁC;
IR: ꢃꢀ¼ 3432 (OH), 1777, 1702 (CO), 1595 (ar C–C), 1361, 1166 (SO2) cmꢂ1; 1H NMR (300MHz):
ꢂ ¼ 2.32 (s, Me), 2.53 (ddd, J4A=10a ¼ 2 Hz, J4A=3a ¼ 7.3 Hz, J4A=4B ¼ 15.6Hz, 4-HA), 2.72 (s, NMe),
2.95 (dd, J4B=3a ¼ 1.5 Hz, J4B=4A ¼ 15.8Hz, 4-HB), 3.27 (ddd, J3a=4B ¼ 1.5 Hz, J3a=4A ¼ 7.6 Hz,
J3a=10b ¼ 7.8 Hz, 3a-H), 3.88 (dd, J10b=3a ¼ 8.8 Hz, J10b=10a ¼ 6.6 Hz, 10b-H), 4.78 (dd, J10a=4A ¼ 2 Hz,
J10a=10b ¼ 6.6 Hz, 10a-H), 6.89 (ddd, J7=9 ¼ 1 Hz, J7=6 ¼ 7.6 Hz, J7=8 ¼ 7.6Hz, 7-H), 7.03 (ddd,

1806
M. Bleile and H.-H. Otto
J8=6 ¼ 1.2 Hz, J8=7 ¼ 8.1 Hz, J8=9 ¼ 8.1 Hz, 8-H), 7.31 (d, J ¼ 8.1 Hz, 2 ar H), 7.38 (d, J6=7 ¼ 6.6 Hz,
6-H), 7.54 (d, J9=8 ¼ 8.1 Hz, 9-H), 7.77 (dd, J ¼ 1.7, 8.3 Hz, 2 ar H), 9.60 (bs, H–O) ppm; MS
(CI(Isobutane), 170 eV: m=z (%) ¼ 425 (100) [Mþ].
3-Hydroxy-5-methoxy-2-phenyl-10-tosyl-3,3a,4,10,10a,10b-
hexahydropyrrolo[3,4-a]carbazole-1-one (6a, C28H26N2O5S)
Under a N2 atmosphere, 1.8 cm3 of a L-Selectride+ soln. (1.8mmol) were added at ꢂ78ꢁC to a soln. of
500 mg 3a (1mmol) in THF, and the mixture was stirred for 1 h. Then 1.5 cm3 MeOH were added, and
stirring was continued for 10min. The mixture was allowed to warm to room temperature, 1.5 cm3
H2O and 3 g Na2SO4 were added, after 30min the mixture was filtered, the residue was washed with
Et2O, and the combined org. layers were evaporated in vacuo. Yield 210 mg (42%); colorless crystals;
mp 170–172ꢁC (EtOH); IR: ꢃꢀ¼ 3435 (OH), 1685 (CO), 1597 (ar C), 1359, 1167 (SO2), 1110, 1091
1
(C–O) cmꢂ1; H NMR (300MHz, CDCl3=DMSO-d6 1=1): ꢂ ¼ 1.98 (s, Me), 2.06 (ddd, J4A=10a
¼
2.2 Hz, J4A=3a ¼ 8.5 Hz, J4A=4B ¼ 16.4Hz, 4-HA), 2.29 (d, J4B=4A ¼ 16.4Hz, 4-HB), 2.39 (dd,
J3a=4A ¼ 8.3 Hz, J3a=10b ¼ 8.3 Hz, 3a-H), 3.22 (s, MeO), 3.72 (dd, J10b=3a ¼ 8.3 Hz, J10b=10a ¼ 5.1 Hz,
10b-H), 4,13 (dd, J10a=4A ¼ 1.7 Hz, J10a=10b ¼ 4.6 Hz, 10a-H), 4.77 (d, J3=OH ¼ 8.1 Hz, 3-H), 5.99
(d, JOH=3 ¼ 8.3 Hz, H–O), 6.52–7.36 (m, 13 ar H) ppm.
3-Hydroxy-5-methoxy-2-methyl-10-tosyl-3,3a,4,10,10a,10b-
hexahydropyrrolo[3,4-a]carbazole-1-one (6b, C23H24N2O5S)
From 3b (1.0g, 2.3 mmol) and 4.1 cm3 of a L-Selectride+ soln. as described for 6a. Yield 850 mg
(83%); colorless crystals; mp 164–166ꢁC (EtOH); IR: ꢃꢀ¼ 3440 (OH), 1684 (CO), 1596 (ar C), 1356,
1
1167 (SO2), 1109, 1090 (C–O) cmꢂ1; H NMR (300MHz, CDCl3=DMSO-d6 5=1): ꢂ ¼ 2.06 (ddd,
J4A=10a ¼ 2.4 Hz, J4A=3a ¼ 8.3 Hz, J4A=4B ¼ 16.6Hz, 4-HA), 2.16 (s, Me), 2.5 (m, 3a-H, 4-HB, NMe),
3.45 (s, MeO), 3.64 (dd, J10b=3a ¼ 8.9 Hz, J10b=10a ¼ 5.6 Hz, 10b-H), 4,23 (dd, J10a=4A ¼ 2.4 Hz,
J10a=10b ¼ 5.6 Hz, 10a-H), 4.34 (dd, J3=OH ¼ 8.2 Hz, J ¼ 1 Hz, 3-H), 5.56 (d, JOH=3 ¼ 8.3 Hz, H–O),
6.72 (ddd, J7=6 ¼ 7.6 Hz, J7=8 ¼ 7.6 Hz, J7=9 ¼ 1 Hz, 7-H), 6.89 (ddd, J8=7 ¼ 7.6 Hz, J8=9 ¼ 7.6 Hz,
J8=6 ¼ 1.2 Hz, 8-H), 7.02 (dd, J ¼ 7.8 Hz, J ¼ 0.7 Hz, 2 ar H), 7.27 (d, J9=8 ¼ 7.3 Hz, 9-H), 7.35 (d,
J6=7 ¼ 8.1Hz, 6-H), 7.53 (dd, J ¼ 6.6 Hz, J ¼ 1.7 Hz, 2 ar H).
2-Methyl-10-tosyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-1,3,5-trione
(7, C22H18N2O5S)
Compound 5b (120 mg, 0.28mmol) was refluxed in EtOH for 30min. Yield 85mg (71%); colorless
crystals; mp 236–239ꢁC; IR: ꢃꢀ¼ 1779, 1709, 1678 (CO), 1595 (ar C–C), 1379, 1171 (SO2),
1
813 (ar) cmꢂ1; H NMR (300 MHz): ꢂ ¼ 2.4 (s, Me), 2.81 (dd, J4A=4B ¼ 17.2Hz, J4A=3a ¼ 9.0 Hz,
4-HA), 3.07 (dd, J4B=4A ¼ 17.2 Hz, J4B=3a ¼ 8.1 Hz, 4-HB), 3.08 (s, NMe), 3.79 (ddd, J3a=4A ¼ 8.8 Hz,
J3a=4B ¼ 8.4 Hz, J3a=10b ¼ 8.4 Hz, 3a-H), 5.39 (d, J10b=3a ¼ 7.8 Hz, 10b-H), 7.3 (m, 7-H, 8-H, 2 ar H),
7.73 (m, 1 ar H), 8.05 (d, J ¼ 8.5 Hz, 2 ar H), 8.22 (m, 1 ar H) ppm.
3-(ꢀ,ꢀ-Dimethoxyethyl)-1-(tert-butoxycarbonyl)indole (9a, C17H23NO4)
From 3-acetyl-1-(tert-butoxycarbonyl)indole (5.18 g, 20 mmol) as described for 1a. Yield 5.75g
(94%); mp 108–110ꢁC (MeOH); IR: ꢃꢀ¼ 3049 (ar CH), 2990 (CH), 2827 (OMe), 1730 (CO), 1610
(ar C–C), 1430 (Me), 1248, 1211 (CMe3) cmꢂ1; 1H NMR (60 MHz): ꢂ ¼ 1.70 (s, Me, CMe3), 3.20 (s, 2
OMe), 7.10–8.40 (m, 5 ar H) ppm.
3-(ꢀ-Methoxyvinyl)-1-(tert-butoxycarbonyl)indole (9, C16H19NO3)
From 9a (6.1g, 20 mmol) as described for 1. Yield 4.9 g (90%, not purified); IR (Film): ꢃꢀ¼ 2980 (CH),
1
1737 (CO), 1606 (ar C–C), 1245 (C(Me)3) cmꢂ1; H NMR (60 MHz): ꢂ ¼ 1.70 (s, CMe3), 3.20 (s,
OMe), 4.40, 4.70 (¼CH2), 7.00–8.30 (m, 5 ar H) ppm. The product was immediately used for further
reactions.

Substituted Pyrrolo[3,4-a]carbazoles
1807
10-(tert-Butoxycarbonyl)-2-phenyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-
1,3,5-trione (10a, C25H22N2O5)
From 9 (4.9g, 18mmol) and 1.73g 2a (10 mmol) in toluene with stirring for 5 d at room tem-
perature, and evaporation of the solvent in vacuo. Yield 1.51 g (35%); colorless crystals; mp
190ꢁC (AcOEt); IR: ꢃꢀ¼ 2986 (CH), 1756, 1722, 1661 (CO), 1596 (ar C–C), 1455, 1371, 1208
1
(Me) cmꢂ1; H NMR (300 MHz): ꢂ ¼ 1.75 (s, CMe3), 3.08 (d, J4=3a ¼ 7.6 Hz, 4-HA, 4-HB), 3.89
(dt, J3a=10b ¼ 8.4 Hz, J3a=4 ¼ 7.6 Hz, 3a-H), 5.52 (d, J10b=3a ¼ 8.5Hz, 10b-H), 7.20–8.30 (m, 9 ar H)
ppm.
10-(tert-Butoxycarbonyl)-2-methyl-3a,4,10,10b-terahydropyrrolo[3,4-a]carbazole-
1,3,5-trione (10b, C20H20N2O5)
From 9 (4.9g, 18 mmol) and 1.1g 2b (10 mmol) as described for 10a. Yield 1.2 g (33%); colorless
crystals; mp 176ꢁC (AcOEt); IR: ꢃꢀ¼ 2982 (CH), 1745, 1697, 1666 (CO), 1454, 1375 (Me) cmꢂ1
;
1H NMR (300MHz): ꢂ ¼ 1.80 (s, CMe3), 2.98 (s, NMe), 2.99 (d, J4A=3a ¼ 8.1 Hz, 4-HA), 3.01 (d,
J4B=3a ¼ 5.6 Hz, 4-HB), 3.70 (ddd, J3a=4B ¼ 6.1 Hz, J3a=4A ¼ 8.3 Hz, J3a=10b ¼ 8.3 Hz, 3a-H), 5.32 (d,
J10b=3a ¼ 8.3 Hz, 10b-H), 7.7–8.25 (m, 4 ar H) ppm.
10-(tert-Butoxycarbonyl)-2-ethyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-
1,3,7-trione (10c, C21H22N2O5)
From 9 (4.9g, 18 mmol) and 1.3 g 2c (10 mmol) as described for 10a. Yield 0.76 g (20%); colorless
crystals; mp 169ꢁC (AcOEt); IR: ꢃꢀ¼ 2986 (CH), 1752, 1707, 1664 (CO), 1453, 1372 (Me) cmꢂ1; 1H
NMR (300 MHz): ꢂ ¼ 1.15 (t, J ¼ 7.3 Hz, Me), 1.8 (s, CMe3), 2.98 (d, J4=3a ¼ 7.7 Hz, 4-HA, 4-HB), 3.56
(q, J ¼ 7.3 Hz, CH2), 3.70 (dt, J3a=4 ¼ 7.6 Hz, J3a=10b ¼ 8.1 Hz, 3a-H), 5.31 (d, J10b=3a ¼ 8.5 Hz, 10b-H),
7.34–8.25 (m, 4 ar H) ppm.
3-(ꢀ-Diethylphosphoryloxyvinyl)-1-tosylindole (11, C21H24NO6S)
At ꢂ78ꢁC 3.12g 1a (10 mmol) in 20 cm3 THF were added to a soln. of 15mmol LDA in 20cm3 THF,
and after 10 min stirring 2.9cm3 of diethyl chlorophosphate (20 mmol) were added in one portion.
After warming to room temperature (ca. 2 h) 50cm3 of n-pentane were added, the organic layer was
separated, the aqueous layer was extracted with Et2O, the combined organic layers were washed with
100 cm3 satd. NaHCO3 solution, dried (MgSO4), and evaporated in vacuo: Yield 3 g (67%, not
purified). The product was immediately used for further reactions.
5-Hydroxyimino-2-methyl-10-(tert-butoxycarbonyl)-3a,4,10,10b-
tetrahydropyrrolo[3,4-a]carbazole-1,3-dione (12a, C20H21N3O5)
A mixture of 5.0 g AcONa (60 mmol) and 4.2g H2NOHꢅHCl (60 mmol) in 50cm3 EtOH was refluxed
for some min, filtered, 0.2g 10b (0.54 mmol) were added to the filtrate, which was then refluxed for
3 h. After evaporation of the solvent in vacuo, 20cm3 EtOH were added to the residue, and H2O was
added until milkiness. Yield 160 mg (78%); colorless crystals; mp 185ꢁC (EtOH); IR: ꢃꢀ¼ 3435 (OH),
1
2983 (CH), 1745, 1703 (CO), 1629 (C¼N), 1435, 1370, 1208 (Me) cmꢂ1; H NMR (300MHz):
ꢂ ¼ 1.80 (s, CMe3), 2.93 (dd, J4A=3 ¼ 7.3 Hz, J4A=4B ¼ 16.4Hz, 4-HA), 2.97 (s, NMe), 3.56 (m, 3a-
H), 3.63 (dd, J4B=3a ¼ 4.9 Hz, J4B=4A ¼ 16.1Hz, 4-HB), 5.22 (d, J10b=103a ¼ 8.3 Hz, 10b-H), 7.27 (dd, 1
ar H), 7.35 (dd, 1 ar H), 7.42 (s, 1 H–O), 8.08 (d, 2 ar H) ppm.
2-Ethyl-5-hydroxyimino-10-(tert-butoxycarbonyl)-3a,4,10,10b-
tetrahydropyrrolo[3,4-a]carbazole-1,3-dione (12b, C21H23N3O5)
From 250 mg 10c (0.65 mmol) as described for 12a. Yield 197 mg (77%); colorless crystals; mp 176ꢁC
(EtOH); IR: ꢃꢀ¼ 3439 (OH), 2982 (CH), 1742, 1709 (CO), 1624 (C¼N), 1456, 1371, 1223 (Me) cmꢂ1
;
1H NMR (300MHz): ꢂ ¼ 1.13 (t, J ¼ 7.3 Hz, Me), 1.85 (s, CMe3), 3.06 (dd, J4A=3a ¼ 7.8 Hz,
J4A=4B ¼ 16.6 Hz, 4-HA), 3.41 (dd, J4B=3a ¼ 5.9 Hz, J4B=4A ¼ 16.6Hz, 4-HB), 3.51 (ddd, J3a=4B
¼

1808
M. Bleile and H.-H. Otto
5.6 Hz, J3a=4A ¼ 8.1 Hz, J3a=10b ¼ 8.1Hz, 3a-H), 3.53 (q, J ¼ 7.3 Hz, CH2), 5.19 (d, J10b=3a ¼ 8.3 Hz,
10b-H), 7.27 (ddd, 1 ar H), 7.35 (ddd, 1 ar H), 7.41 (s, H–O), 8.10 (m, 2 ar H) ppm.
2-Phenyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-1,3,5-trione (13a) [10]
Compound 10a (0.3g, 0.7 mmol) was heated until melting. Yield 0.21 g (90%); colorless crystals; mp
1
275ꢁC (Ref. [10] 275–280ꢁC); IR: ꢃꢀ¼ 3408 (NH), 1712, 1629 (CO) cmꢂ1; H NMR (300 MHz,
acetone-d6): ꢂ ¼ 2.96 (dd, J4A=3a ¼ 8.5 Hz, J4A=4B ¼ 17.3 Hz, 4-HA), 3.15 (dd, J4B=3a ¼ 3.7 Hz,
J4B=4A ¼ 17.3Hz, 4-HB), 4.15 (ddd, J3a=4B ¼ 3.7 Hz, J3a=4A ¼ 8.3 Hz, J3a=10b ¼ 8.3 Hz, 3a-H), 4.82
(d, J10b=3a ¼ 8.3 Hz, 10b-H), 7.19–8.16 (m, 9 ar H), 11.1 (bs, H–N) ppm.
2-Methyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-1,3,5-trione (13b, C15H12N2O3) [4]
From 260 mg 10b (0.7mmol) as described for 13a. Yield 0.24g (90%); colorless crystals; mp 282ꢁC
1
(MeOH); IR: ꢃꢀ¼ 3227 (NH), 1779, 1703, 1626 (CO) cmꢂ1; H NMR (300MHz): ꢂ ¼ 2.59 (dd,
J4A=3a ¼ 8.8 Hz, J4A=4B ¼ 17.6 Hz, 4-HA), 2.68 (s, NMe), 2.88 (dd, J4B=3a ¼ 2.7 Hz, J4B=4A ¼ 17.3Hz,
4-HB), 3.45 (ddd, J3a=4B ¼ 2.7 Hz, J3a=4A ¼ 8.6 Hz, J3a=10b ¼ 8.6Hz, 3a-H), 4.19 (d, J10b=3a ¼ 8.3 Hz,
10b-H), 6.93 (m, 2 ar H), 7.22 (m, 1 ar H), 7.84 (m, 1 ar H), 11.4 (bs, H–N) ppm.
5-(Diethylphosphoryloxy)-2-phenyl-10-tosyl-4,10,10a,10b-tetrahydro-3aH-
pyrrolo[3,4-a]carbazole-1,3-dione (14, C31H31N2O8PS)
From 3.0 g 11 (6.7mmol) and 1.73 g 2a (10 mmol) as described for 10a, purification CC
(AcOEt=cyclohexane 4=1). Yield 1.6 g (25%); colorless crystals; mp 204ꢁC; IR: ꢃꢀ¼ 1716 (C¼C),
1
1359, 1170 (SO2), 1271 (P¼O) cmꢂ1; H NMR (300MHz): ꢂ ¼ 1.25 (m, 2 Me), 2.36 (s, Me), 2.65
(dddd, J4A=10a ¼ 2.4 Hz, J4A=3a ¼ 7.8 Hz, J4A=4B ¼ 16.9 Hz, J4A=P ¼ 2.4 Hz, 4-HA), 3.35 (ddd,
J3a=4A ¼ 7.8 Hz, J3a=10b ¼ 8.9 Hz, J3a=P ¼ 1.5 Hz, 3a-H), 3.37 (d, J4B=4A ¼ 15.1Hz, 4-HB), 4.13 (m, 2
CH2), 4.17 (dd, J10b=3a ¼ 8.9 Hz, J10b=10a ¼ 6.6 Hz, 10b-H), 4.61 (ddd, J10a=10b ¼ 6.6 Hz, J10a=4A
¼
2.3 Hz, J10a=P ¼ 4.3Hz, 10a-H), 6.96–7.77 (m, 13 ar H) ppm. HREIMS: m=z ¼ calcd 622.154444;
found 622.153876 (0.9ppm).
5-Hydroxyimino-2-methyl-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-1,3-dione
(15a, C15H13N3O3)
From 200 mg 13b (0.75 mmol) as described for 12a. Yield 153 mg (72%); mp 252–255ꢁC (dec,
EtOH); IR: ꢃꢀ¼ 3366 (OH, NH), 1778, 1696 (CO), 1620 (C¼N) cmꢂ1
;
1H NMR (300 MHz,
CDCl3=DMSO-d6): ꢂ ¼ 2.29 (dd, J4A=3 ¼ 8.3 Hz, J4A=4B ¼ 17.3Hz, 4-HA), 2.53 (s, NMe), 3.22 (ddd,
J3a=4B ¼ 2.9 Hz, J3a=4A ¼ 8.2 Hz, J3a=10b ¼ 8.2 Hz, 3a-H), 3.48 (dd, J4B=3a ¼ 2.9 Hz, J4B=4A ¼ 17.4Hz,
4-HB), 3.95 (d, J10b=3a ¼ 8.1 Hz, 10b-H), 6.68 (dd, J ¼ 7.5, 7.5 Hz, 7(8)-H), 6.77 (dd, J ¼ 7.3, 7.3Hz,
8(7)-H), 7.05 (d, J ¼ 7.8 Hz, 9-H), 7.62 (d, J ¼ 7.9 Hz, 6-H), 9.9 (s, H–O), 10.6 (s, NH) ppm.
2-Ethyl-5-hydroxyimino-3a,4,10,10b-tetrahydropyrrolo[3,4-a]carbazole-1,3-dione
(15b, C16H15N3O3)
From 200 mg 12b (0.5mmol) as described for 12a. Yield 134mg (90%); mp 225–227ꢁC; IR: ꢃꢀ¼ 3439
(OH), 2982 (CH), 1742, 1709 (CO), 1624 (C¼N), 1456, 1371, 1223 (Me) cmꢂ1; 1H NMR (300 MHz,
CDCl3=DMSO-d6): ꢂ ¼ 0.88 (t, J ¼ 7.1 Hz, Me), 2.55 (dd, J4A=3a ¼ 8.4 Hz, J4A=4B ¼ 17.4 Hz, 4-HA),
3.27 (q, J ¼ 7.1 Hz, CH2), 3.33 (ddd, J3a=4 ¼ 3.1 Hz, J3a=4A ¼ 8.2 Hz, J3a=10b ¼ 8.3 Hz, 3a-H), 3.61 (dd,
J4B=3a ¼ 3.1 Hz, J4B=4A ¼ 17.4Hz, 4-HB), 4.07 (d, J10b=3a ¼ 8.2 Hz, 10b-H), 6.87 (ddd, J ¼ 1.1, 7.1,
7.1 Hz, 7(8)-H), 6.96 (ddd, J ¼ 1.3, 7.1, 7.1 Hz, (8)7-H), 7.22 (dd, J ¼ 1.1, 8.1 Hz, 9-H), 7.83 (dd,
J ¼ 0.6, 7.8Hz, 6-H), 9.85 (s, H–O), 10.30 (s, NH) ppm.
Acknowledgements
We thank Degussa AG for generous support with chemicals, E. Merck KGaG, Darmstadt, for con-
tinuous support with chromatography materials and biological testing, the ‘‘Fonds der Chemischen

Substituted Pyrrolo[3,4-a]carbazoles
1809
Industrie’’ for financial support, and Dr. M. Kindermann, Chemistry Dept. University of Greifswald,
for some NMR experiments.
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[5] SYBYL Molecular Modeling Program, version 6.2, Tripos, Ass Inc, 1995
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BBelBruno JJ (1992) J Org Chem 57: 5878
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¨
Verleger: Springer-Verlag GmbH, Sachsenplatz 4–6, 1201 Wien, Austria. – Herausgeber: Osterreichische Akademie der Wissen-
¨
schaften, Dr.-Ignaz-Seipel-Platz 2, 1010 Wien, und Gesellschaft Osterreichischer Chemiker, Eschenbachgasse 9, 1010 Wien,
Austria. – Redaktion: Getreidemarkt 9=163-OC, 1060 Wien, Austria. – Satz und Umbruch: Thomson Press Ltd., Chennai, India. –
Offsetdruck: Manz Crossmedia, 1051 Wien, Austria. – Verlagsort: Wien. – Herstellungsort: Wien. – Printed in Austria.