A rapid, mild, efficient, and solvent-free Friedel-Crafts acylation of N-acetyltetrahydroharmine

Article abstract of DOI:10.1081/SCC-200046479

The first solid-phase, rapid, and mild synthesis of 10-acyl and 12-acyl analogues of N-acetyltetrahydroharmine by Friedel-Crafts acylation has been developed. The products were obtained in high overall yields. The method also results in the high-yield synthesis of natural product jafrine.

Full text of DOI:10.1081/SCC-200046479

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A Rapid, Mild, Efficient,
and Solvent‐Free
Friedel‐Crafts Acylation of
N‐Acetyltetrahydroharmine
Sabira Begum a , Syed Imran Hassan a & Bina S.
Siddiqui a
a H. E. J. Research Institute of Chemistry,
International Centre for Chemical Sciences ,
University of Karachi , Karachi, 75270, Pakistan
Published online: 05 Aug 2006.
To cite this article: Sabira Begum , Syed Imran Hassan & Bina S. Siddiqui
(2005) A Rapid, Mild, Efficient, and Solvent‐Free Friedel‐Crafts Acylation of
N‐Acetyltetrahydroharmine, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 35:1, 23-39, DOI: 10.1081/
SCC-200046479
To link to this article: http://dx.doi.org/10.1081/SCC-200046479
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Synthetic Communicationsw, 35: 23–39, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200046479
A Rapid, Mild, Efficient, and Solvent-Free
Friedel-Crafts Acylation of
N-Acetyltetrahydroharmine
Sabira Begum, Syed Imran Hassan, and Bina S. Siddiqui
H. E. J. Research Institute of Chemistry, International Centre for
Chemical Sciences, University of Karachi, Karachi, Pakistan
Abstract: The first solid-phase, rapid, and mild synthesis of 10-acyl and 12-acyl
analogues of N-acetyltetrahydroharmine by Friedel-Crafts acylation has been
developed. The products were obtained in high overall yields. The method also
results in the high-yield synthesis of natural product jafrine.
Keywords: Solid-phase reaction, Friedel-Crafts acylation, b-carboline, N-acetyltetra-
hydroharmine, acyl N-acetyltetrahydroharmines
INTRODUCTION
Development of basic carbon-carbon bond forming reactions in solid phase is
one of the most important tasks. In recent years solid-phase organic synthesis
has been recognized as a powerful tool for the preparation of a large number of
organic compounds.[1–3] The acylation and alkylation of aromatic compounds
are carried out through Friedel-Crafts method. Generally, Friedel-Crafts
reactions involve addition of a Lewis acid catalyst such as AlCl3 to a well-
stirred mixture of an alkyl or acyl halide and an aromatic compound under
inert conditions.[4,5] Usually, these reactions require high temperature, long
reaction time, and tedious workup. Use of metal triflates in ionic liquids for
Received in India October 14, 2004
Address correspondence to Sabira Begum, H. E. J. Research Institute of Chemistry,
International Centre for Chemical Sciences, University of Karachi, Karachi 75270,
Pakistan. E-mail: sabira@khi.comsats.net.pk

24
S. Begum, S. I. Hassan, and B. S. Siddiqui
Friedel-Crafts acylation is also reported, but this method is limited to
highly activated substrates and also requires high temperature.[6] Acylation
of aromatic compounds using moisture insensitive InCl3 impregnated
Si-MCM-41 catalyst in CH2Cl2 has been reported, but it also required 808C
temperature for completion.[7] Recently it was reported that Friedel-Crafts
reactions in solvent-free condition without any protection by mixing the
corresponding aromatic compounds, the respective acyl halide and AlCl3 in
an agate mortar for 45 min at room temperature followed by simple workup
are effective for reaction of simple aromatic compounds.[8] In the present
studies we extended these findings to more-complex indole alkaloid N-acetyl-
tetrahydroharmine (1)[9] prepared from tetrahydroharmine. Tetrahydrohar-
mine is a reduction product of a b-carboline alkaloid harmaline which we
isolated from Peganum harmala following the method reported earlier.[10]
As a result several 10-acyl (2–11) and 12-acyl (12–21) analogues were
obtained in high overall yields. Compounds 3–6, 8–11, 13–21 are reported
for the first time. These compounds were characterized with the help of
spectral data including 1D and 2D NMR techniques.
RESULTS AND DISCUSSION
Reactions of 1 with different acylating agents (acetic anhydride, propionyl
chloride, butyric anhydride, isobutyric anhydride, valeryl chloride, hexanoyl
chloride, heptanoyl chloride, capryloyl chloride, benzoyl chloride, and
cinnamoyl chloride) and AlCl3 were carried out in solid phase, which
resulted in the formation of the respective two ortho substituted 10-acyl
(2–11) and 12-acyl (12–21) analogues in high overall yields (Table 1). These
isomers were separated by preparative thick-layer chromatography (vide
experimental). It was noted that the former is the main product. However,
with small agents (Entry A and B) considerable amount of 12-substituted
1
products were formed. Further, the mass and H NMR analysis of the crude
reaction products indicated the presence of traces of demethylated compounds
also, which could not be separated in the present studies. Compounds 3–6,
8–11, 13–21 are new whereas compound 7 has been reported during the
compilation of our work as a natural product jafrine isolated from the
flowers of Tagetes patula.[11] In the same communication, preparation of
jafrine was described through reaction of acetyltetrahydroharmine with
hexanoyl chloride in nitrobenzene in the presence of AlCl3 at room tempera-
ture for 48 h. However, it was obtained in a low yield (8%) along with two
degradation products and other minor unidentified products. Under the
present reaction conditions (room temp.; 45 min) benzene ring acylation
occurred smoothly without any degradation, and + jafrine (7) was obtained
in 60% yield along with other ortho substituted product 12-hexanoylacetyl-
tetrahydroharmine (17) in 18% yield after chromatographic separation.

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
25

26
S. Begum, S. I. Hassan, and B. S. Siddiqui
Further, the authors[11] reported compounds 2 and 12 in 0.9% and 0.4%
yields, respectively, by carrying out the reaction of 1 with acetic anhydride
and AlCl3 for 48 h. The main products were degraded compounds. In the
present studies 2 and 12 have been obtained in 52% and 35% yields,
respectively (Table 1). These results indicate that Friedel-Crafts reactions
in solid phase can be applied to more complex aromatic compounds
successfully.
These derivatives have been characterized by spectral studies, including
IR, UV, EIMS, HREIMS (see Experimental), 1D (1H NMR and 13C NMR;
Broad Band decoupled, DEPT), and 2D-NMR (COSY-45, TOCSY, HMQC
and HMBC) (see Tables 2–7; Fig. 1 and Fig. 2) and comparison of spectral
data with reported values of similar compounds.[12,13,16,17] For 10-acyl
analogues, the characteristic peaks of H-9 and H-12 appeared as one proton
1
singlets at ꢀd 7.8 and 6.8, respectively, in the H NMR spectra (Tables 2
1
and 3), showing the substitution at C-10. The H NMR spectra of 12-acyl
analogues showed characteristic two sets of one proton doublet at ꢀd 7.5
and 6.7 (Tables 4 and 5) assigned to H-9 and H-10, respectively, showing
the substitution on C-12. The 13C NMR signals of quaternary carbons were
particularly assigned on the basis of HMBC connectivities observed for
these carbons with various protons, which are shown in Fig. 1 for 10-acyl
1
analogues and in Fig. 2 for 12-acyl analogues. In the H and 13C NMR
spectra two sets of signals were observed for all these derivatives due to
restricted rotation around NH-CO bond. At an elevated temperature (908C)
some signals were broadened and others collapsed to single peaks as noted
earlier for other N-acylated compounds.[14,15] In Tables 2–7 the values for
1H and 13C NMR are given for the major rotational isomers.
To the best of our knowledge, b-carboline alkaloids having acyl substitu-
ents on C-10 or C-12 are rare in nature, hence the spectral data presented in
this paper will be a useful addition for structural elucidation of related
natural products.
EXPERIMENTAL
General
Melting points were determined using a Buchi-535 melting point apparatus
and are uncorrected. Ultraviolet spectra were measured on a Hitachi U-3200
spectrophotometer. Infrared spectra were recorded on a JASCO A-302 spec-
1
trophotometer. The H, and 13C NMR spectra were recorded on a Bruker
Aspect AM spectrometer. Mass spectra were run on a Jeol JMS-HX110
(high-resolution, e.i. probe, 70 eV) and a Varian MAT 311 A (low-resolution,
i.e. probe, 70 eV) instrument.

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
27
d
d
d
d
d

28
S. Begum, S. I. Hassan, and B. S. Siddiqui
d
d
d
d
d

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
29
d
d
d
d
d

30
S. Begum, S. I. Hassan, and B. S. Siddiqui
d
d
d
d
d

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
31
d
d
d
d
d
d
d
d
d
d

32
S. Begum, S. I. Hassan, and B. S. Siddiqui
d
d
d
d
d
d
d
d
d
d

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
33
Figure 1. Significant HMBC (1H ! 13C) interactions of 10-acyl analogues of 1.
Acetyltetrahydroharmine (1)
1 was prepared by acetylation [(CH3CO)2O/Py] of tetrahydroharmine (1 gm),
which was obtained on reduction (Zn/HCl) of harmaline isolated from
Peganum harmala according to reported method[9,10] in theoretical yield.
Mp: 2428C (Lit.[9] mp 2428C); IR (KBr): 3300, 1640, 1620-1420,
1160 cm21; UV (MeOH): 296, 267, 227, 202 nm; 1H NMR (400 MHz;
CDCl3): d 1.42 (3H, d, J 6.3, H-14), 2.22 (3H, s, NCOCH3), 2.78 (2H, m,
H-6), 3.46 (1H, ddd, J 15.8, 11.3 and 4.8, H-5ax), 3.82 (3H, s, OCH3), 3.98
(1H, m, H-5eq), 5.72 (1H, q, J 6.3, H-3), 6.74 (1H, dd, J 8.6 and 2.0,
H-10), 6.83 (1H, d, J 2.0, H-12), 7.30 (1H, d, J 8.6, H-9), 7.94 (1H, br s,
NH); EIMS m/z (%): 258.1359 (Mþ C15H18N2O2 requires 258.1368) (25),
.
243 (20), 215 (14), 201 (34), 186 (10), 43 (100).
Figure 2. Significant HMBC interactions of 12-acyl analogues of 1.

34
S. Begum, S. I. Hassan, and B. S. Siddiqui
Solid-phase Friedel-Crafts Acylation: General Procedure
A mixture of N-acetyltetrahydroharmine (1) (50 mg), acylating agents (2.5 ml;
for Entry J 100 mg, [Table 1]) and anhydrous AlCl3 (200 mg) was thoroughly
ground in an agate mortar and pestle for 45 min in a fume cupboard. The
reaction mixture was then poured into crushed ice, basified with 10%
aqueous NaOH, and extracted with EtOAc. The EtOAc layer after usual
workup gave a solid mass which on thick layer chromatography (silica gel
PF254, Merck, CHCl3-MeOH [9.5 : 0.5]) afforded the respective 10-(2–11)
and 12-acylated (12–21) products in order of decreasing polarity in high
overall yields (Table 1).
4-Acetyl-10-acetyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (2)
Colorless crystalline solid (MeOH) (30.1 mg); Mp: 174–1758C; IR (KBr):
3253, 2926, 2851, 1695, 1660, 1615–1430, 1165 cm21; UV (MeOH):
1
203.2, 253.1, 301.2 nm; H NMR (400 MHz, CDCl3): Table 2; 13C NMR
(100 MHz, CDCl3): Table 6; EIMS m/z (%): 300.1481 (Mþ C17H20N2O3
.
requires 300.1474) (46), 285 (71), 257 (10), 243 (100), 229 (11), 214 (12),
200 (9), 186 (4).
4-Acetyl-10-propionyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (3)
Colorless crystalline solid (MeOH) (27.1 mg); Mp: 171–1728C; IR (KBr):
3260, 2930, 2856, 1690, 1660, 1620–1425, 1163 cm21; UV (MeOH):
1
202.4, 255.2, 300.1 nm; H NMR (400 MHz, CD3OD): Table 2; 13C NMR
(100 MHz, CD3OD): Table 6; EIMS m/z (%): 314.1620 (Mþ C18H22N2O3
.
requires 314.1630) (28), 299 (67), 257 (100), 243 (22), 227 (20), 214 (36),
200 (20), 186 (20).
4-Acetyl-10-butyryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (4)
Colorless crystalline solid (MeOH) (40.1 mg); Mp: 168–1698C; IR (KBr):
3276, 2928, 2860, 1690, 1655, 1616–1435, 1160 cm21; UV (MeOH):
1
202.8, 253.2, 301.5 nm; H NMR (300 MHz, CDCl3:CD3OD 1 : 1): Table 2;
13C NMR (75 MHz, CDCl3:CD3OD 1 : 1): Table 6; EIMS m/z (%)
328.1779 (Mþ C19H24N2O3 requires 328.1787) (54), 313 (100), 285 (34),
.
271 (91), 257 (6), 243 (4), 227 (11), 214 (18), 199 (8), 186 (5).

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
35
4-Acetyl-10-isobutyryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (5)
Colorless crystalline solid (MeOH) (32.8 mg); Mp: 172–1738C; IR (KBr):
3270, 2940, 2865, 1685, 1650, 1615–1440, 1163 cm21; UV (MeOH):
1
203.1, 250.2, 300.0 nm; H NMR (400 MHz, CDCl3): Table 2; 13C NMR
(100 MHz, CDCl3): Table 6; EIMS m/z (%): 328.1776 (Mþ C19H24N2O3
.
requires 328.1787) (40), 313 (100), 285 (37), 271 (36), 257 (5), 243 (8),
214 (10), 200 (10), 186 (7).
4-Acetyl-10-valeryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (6)
Colorless crystalline solid (MeOH) (41.7 mg); Mp: 167–1688C; IR (KBr):
3270, 2920, 2855, 1695, 1640, 1610–1430, 1175 cm21; UV (MeOH):
1
202.8, 252.2, 301.2 nm; H NMR (400 MHz, CDCl3): Table 2; 13C NMR
(100 MHz, CDCl3): Table 6; EIMS m/z (%): 342.1933 (Mþ C20H26N2O3
.
requires 342.1943) (48), 327 (85), 285 (100), 271 (32), 227 (5), 214 (9),
200 (5), 186 (5).
4-Acetyl-10-hexanoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (7)
Colorless crystalline solid (MeOH) (41.6 mg); Mp: 165–1668C; IR (KBr):
3255, 2920, 2850, 1695, 1665, 1610–1420, 1150 cm21; UV (MeOH):
1
203.1, 254.0, 303.1 nm; H NMR (400 MHz, C5D5N): Table 3; 13C NMR
(100 MHz, C5D5N): Table 6; EIMS m/z (%): 356.2089 (Mþ C21H28N2O3
.
requires 356.2100) (35), 341 (45), 313 (15), 299 (32), 285 (100), 214 (8),
200 (14), 186 (10).
4-Acetyl-10-heptanoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (8)
Colorless crystalline solid (MeOH) (42.8 mg); Mp: 167–1688C; IR (KBr):
3250, 2925, 2860, 1690, 1660, 1615–1430, 1160 cm21; UV (MeOH):
1
202.9, 253.1, 301.2 nm; H NMR (400 MHz, C5D5N): Table 3; 13C NMR
(100 MHz, C5D5N): Table 6; EIMS m/z (%): 370.2245 (Mþ C22H30N2O3
.
requires 370.2256) (56), 355 (100), 313 (51), 299 (3), 214 (12), 199 (7),
186 (7).

36
S. Begum, S. I. Hassan, and B. S. Siddiqui
4-Acetyl-10-capryloyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (9)
Colorless crystalline solid (MeOH) (41.3 mg); Mp: 166–1678C; IR (KBr):
3270, 2925, 2860, 1695, 1650, 1616–1435, 1160 cm21; UV (MeOH):
1
202.9, 252.9, 300.1 nm; H NMR (400 MHz, C5D5N): Table 3; 13C NMR
(100 MHz, C5D5N): Table 6; EIMS m/z (%): 384.2402 (Mþ C23H32N2O3
.
requires 384.2413) (58), 369 (100), 327 (44), 313 (23), 214 (11), 200 (9),
186 (7).
4-Acetyl-10-benzoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (10)
Colorless crystalline solid (MeOH) (19.8 mg); Mp: 171–1728C; IR (KBr):
3269, 2926, 2845, 1695, 1660, 1618–1433, 1159 cm21; UV (MeOH):
1
227.4, 255.8, 282.5 nm; H NMR (300 MHz, CDCl3): Table 3; 13C NMR
(75 MHz, CDCl3): Table 6; EIMS m/z (%): 362.1641 (Mþ C22H22N2O3
.
requires 362.1630) (15), 347 (100), 305 (31), 291 (7), 214 (13), 200 (5),
186 (7).
4-Acetyl-10-cinnamoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (11)
Colorless crystalline solid (MeOH) (12.1 mg); Mp: 167–1688C; IR (KBr):
3280, 2924, 2852, 1690, 1660, 1620–1454, 1165 cm21; UV (MeOH):
1
203.4, 236.1, 293.0 nm; H NMR (300 MHz, CDCl3): Table 3; 13C NMR
(75 MHz, CDCl3): Table 6; EIMS m/z (%): 388.1776 (Mþ C24H24N2O3
.
requires 388.1787) (55), 331 (100), 317 (20), 214 (17), 200 (9), 186 (5).
4-Acetyl-12-acetyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (12)
Colorless crystalline solid (MeOH) (20.1 mg); Mp: 191–1928C; IR (KBr):
3390, 2923, 2850, 1690, 1645, 1630–1425, 1170 cm21; UV (MeOH):
1
219.6, 231.8, 331.6 nm; H NMR (500 MHz, CDCl3): Table 4; 13C NMR
(125 MHz, CDCl3): Table 7; EIMS m/z (%): 300.1466 (Mþ C17H20N2O3
.
requires 300.1474) (31), 285 (54), 257 (23), 243 (100), 229 (9), 214 (6),
200 (6), 186 (15).
4-Acetyl-12-propionyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (13)
Colorless crystalline solid (MeOH) (24.1 mg); Mp: 187–1888C; IR (KBr):
3400, 2920, 2854, 1680, 1650, 1620–1420, 1175 cm21; IR (MeOH): 220.1,

Friedel-Crafts Acylation of N-Acetyltetrahydroharmine
37
232.4, 330.9 nm; 1H NMR (400 MHz, CD3OD): Table 4; 13C NMR (100 MHz,
CD3OD): Table 7; EIMS m/z (%): 314.1619 (Mþ C18H22N2O3 requires
.
314.1630) (63), 299 (100), 257 (94), 243 (45), 214 (10), 201 (37), 186 (14).
4-Acetyl-12-butyryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (14)
Colorless crystalline solid (MeOH) (15.7 mg); Mp: 185–1868C; IR (KBr):
3408, 2924, 2854, 1697, 1640, 1610–1420, 1175 cm21; UV (MeOH):
1
218.7, 231.5, 330.6 nm; H NMR (400 MHz, CDCl3): Table 4; 13C NMR
(100 MHz, CDCl3): Table 7; EIMS m/z (%): 328.1795 (Mþ C19H24N2O3
.
requires 328.1787) (55), 313 (100), 285 (16), 271 (98), 257 (11), 243 (9),
214 (8), 200 (6), 186 (7).
4-Acetyl-12-isobutyryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (15)
Colorless crystalline solid (MeOH) (7.5 mg); Mp: 188–1898C; IR (KBr):
3400, 2920, 2850, 1690, 1645, 1610–1420, 1173 cm21; UV (MeOH):
1
219.5, 230.8, 331.5 nm; H NMR (400 MHz, CDCl3): Table 4; 13C NMR
(100 MHz, CDCl3): Table 7; EIMS m/z (%): 328.1775 (Mþ C19H24N2O3
.
requires 328.1787) (45), 313 (100), 285 (18), 271 (31), 257 (9), 243 (5),
214 (18), 200 (9), 186 (5).
4-Acetyl-12-valeryl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (16)
Colorless crystalline (MeOH) solid (11.2 mg); Mp: 183–1848C; IR (KBr):
3396, 2930, 2845, 1690, 1655, 1620–1430, 1175 cm21; UV (MeOH):
1
218.9, 231.0, 330.1 nm; H NMR (400 MHz, CDCl3): Table 4; 13C NMR
(100 MHz, CDCl3): Table 7; EIMS m/z (%): 342.1931 (Mþ C20H26N2O3
.
requires 342.1943) (27), 327 (100), 285 (31), 200 (13), 186 (3).
4-Acetyl-12-hexanoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (17)
Colorless crystalline solid (MeOH) (12.3 mg); Mp: 179–1808C; IR (KBr):
3409, 2927, 2839, 1690, 1650, 1620–1420, 1170 cm21; UV (MeOH):
1
220.0, 231.0, 329.0 nm; H NMR (400 MHz, C5D5N): Table 5; 13C NMR
(100 MHz, C5D5N): Table 7; EIMS m/z (%): 356.2090 (Mþ C21H28N2O3
.
requires 356.2100) (20), 341 (60), 313 (10), 299 (29), 285 (100), 214 (9),
200 (10), 186 (7).

38
S. Begum, S. I. Hassan, and B. S. Siddiqui
4-Acetyl-12-heptanoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (18)
Colorless crystalline solid (MeOH) (14.1 mg); Mp: 176–1778C; IR (KBr):
3390, 2925, 2860, 1690, 1650, 1615–1425, 1170cm21; UV (MeOH): 219.0,
232.0, 330.7 nm; 1H NMR (400MHz, C5D5N): Table 5; 13C NMR (100MHz,
C5D5N): Table 7; EIMS m/z (%): 370.2246 (Mþ C22H30N2O3 requires
.
370.2256) (30), 355 (100), 313 (39), 299 (3), 214 (10), 200 (5), 186 (5).
4-Acetyl-12-capryloyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (19)
Colorless crystalline solid (MeOH) (9.4mg); Mp: 174–1758C; IR (KBr): 3400,
2930, 2840, 1685, 1650, 1610–1420, 1171cm21; UV (MeOH): 219.1, 231.1,
331.1 nm; 1H NMR (400MHz, C5D5N): Table 5; 13C NMR (100MHz,
C5D5N): Table 7; EIMS; m/z (%): 384.2405 (Mþ C23H32N2O3 requires
.
384.2413) (30), 369 (100), 327 (31), 313 (17), 214 (8), 200 (7), 186 (6).
4-Acetyl-12-benzoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (20)
Colorless crystalline solid (MeOH) (11.3 mg); Mp: 189–1908C; IR (KBr):
3400, 2935, 2840, 1690, 1640, 1610–1420, 1175cm21; UV (MeOH): 225.8,
1
251.8, 327.0 nm; H NMR (300MHz, CDCl3): Table 5; 13C NMR (75 MHz,
CDCl3): Table 7; EIMS m/z (%): 362.1618 (Mþ C22H22N2O3 requires
.
362.1630) (21), 347 (100), 305 (31), 291 (9), 214 (13), 200 (8), 186 (7).
4-Acetyl-12-cinnamoyl-11-methoxy-3-methyl-3,4,5,6-tetrahydro-
b-carboline (21)
Colorless crystalline solid (MeOH) (9.1 mg); Mp: 176–1778C; IR (KBr):
3422, 2920, 2865, 1695, 1650, 1610–1440, 1163 cm21; UV (MeOH):
1
202.0, 234.1, 328.6 nm; H NMR (400 MHz, CDCl3): Table 5; 13C NMR
(100 MHz, CDCl3): Table 7; EIMS m/z (%): 388.1777 (Mþ C24H24N2O3
.
requires 388.1787) (50), 331 (100), 317 (16), 214 (15), 200 (7), 186 (8).
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