Antimycobacterial activity of 1-substituted indolizines

Article abstract of DOI:10.1002/ardp.200390019

Indolizine derivatives were tested as antimycobacterials against Mycobacterium tuberculosis H₃₇Rv (ATCC 27294) in BACTEC 12B medium using the Microplate Alamar Blue Assay. The most active compounds examined carry an α-hydroxybenzyl substituent in the indolizine 1-position. MICs against Mycobacterium tuberculosis for these compounds were 6.25 μg/mL.

Full text of DOI:10.1002/ardp.200390019

Arch. Pharm. Pharm. Med. Chem. 2003, 336, 191–195
Antimycobacterial Indolizines 191
Lise-Lotte Gundersen,
Ayele H. Negussie,
Frode Rise,
Antimycobacterial Activity of 1-Substituted
Indolizines
Ole Benny Østby
Indolizine derivatives were tested as antimycobacterials against Mycobacterium tu-
berculosis H37Rv (ATCC 27294) in BACTEC 12B medium using the Microplate
Alamar Blue Assay.The most active compounds examined carry an α-hydroxyben-
zyl substituent in the indolizine 1-position. MICs against Mycobacterium tuberculo-
sis for these compounds were 6.25 µg/mL
Department of Chemistry,
University of Oslo, Blindern,
Oslo, Norway
Key Words: Indolizines; Tuberculosis; Antimycobacterial
Received: November 15, 2002 [FP744]
Introduction
Tuberculosis (TB) is the major cause of death from a sin-
gle infectious agent among adults in developing coun-
tries, and in the industrial world there has been an unfor-
tunate revival of the disease. Human immunodeficiency
virus (HIV) infections have further increasedTB morbidi-
ty and mortality. Multi-drug resistant tuberculosis (MDR-
TB) defined as resistance to the two most important
drugs, isoniazid (INH) and rifampin (RMP), is a growing
problem among HIV-infected patients. Ca. 1/3 of the
world’s population is infected with Mycobacterium tuber-
culosis, including those carrying dormant infections. It
has been estimated that ca. 30 million people will die
from tuberculosis in the next 10-year period [1].
In recent years, our screening of a number of heterocy-
clic compounds for antimycobacterial activity has result-
ed in identification of certain purine derivatives as potent
inhibitors of M. tuberculosis [2–4].We are now reporting
antimycobacterial activity for 1-substituted indolizines,
some of them previously studied as potential antioxi-
dants [5–7].
Results and discussion
The syntheses of the novel compounds are outlined in
Scheme 1. The 1-benzylindolizine 3b was formed by
Negishi coupling, essentially as previously reported for
the synthesis of 3a, but when the reaction was per-
formed with the bromide 2a, a substantial amount of the
indolizine 1 was formed and the isolated yield of com-
pound 3b was low. The more reactive iodide 2b, on the
other hand, gave the desired benzylindolizine 3b in 70%
yield. Reaction of the bromide 2a with butyllithium fol-
lowed by trapping with DMF, acid chlorides, aldehydes,
Scheme 1. Reagents and conditions: i, 1. BuLi, THF,
–78°C, 2. I2; ii, PhCH2ZnBr, (Ph3P)4Pd, dioxane, 100°C;
iii, 1. BuLi, THF, –78°C, 2. DMF or PhCOCl; iv, NaBH4,
EtOH; iv, CH3Li, THF, –78°C; vi, 1. BuLi, THF, –78°C, 2.
RCOR’; vii, NaH, CH3I, THF.
or ketones gave the indolizinyl aldehyde and ketones 4
or alcohols 5 d–5 h, generally in high yields.
Reaction of the aldehyde 4a with sodium borohydride or
methyllithium gave the alcohols 5a and 5b.The hydroxy
group in compound 5c was alkylated to give the ether 6.
The syntheses of compounds 1, 2a, 3a, 3c, 4b, and 5c
(Figure 1) have been reported before [6].
Correspondence:L.-L.Gundersen, Department of Chemistry,
University of Oslo, P. O. Box 1033, Blindern, N-0315 Oslo,
Norway. Phone: +4722857019, fax: + 4722855507, e-mail:
l.l.gundersen@kjemi.uio.no.
© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
0365-6233/03/0191 $ 17.50+.50/0

192 Gundersen et al.
Arch. Pharm. Pharm. Med. Chem. 2003, 336, 191–195
The parent indolizine 1 exhibited essentially no inhibitory
activity against Mycobacterium tuberculosis. Moderate
activity was found when an alkyl substituent 3a and 3b,
or acyl substituent, compounds 4, was introduced. The
1-arylindolizine 3c was inactive.Active compounds was,
however, found among the indolizines 5 carrying a 1-hy-
droxyalkyl substituent in the 1-position. The most effec-
tive compound was the benzaldehyde adduct 5c and the
para substituted analogs 5f and 5g.Introducing a methyl
groupintheα-position 5d, or on the hydroxy group 6, result-
ed in a small decrease in activity against M. tuberculosis.
Compound 5c and related structures are, to the best of
our knowledge, the first antimycobacterial indolizines re-
ported. The need for new antituberculosis drugs, espe-
cially due to the growing problem with multi-drug resist-
ant tuberculosis, makes the indolizine 5c an interesting
lead compound. Synthesis of both enantiomers of 5c as
well as further structure optimization of antimycobacteri-
al indolizines are in progress.
Figure 1. Structure of previously reported compounds.
Acknowledgements
The indolizines 1–6 were tested as antimycobacterials
against Mycobacterium tuberculosis H37Rv (ATCC
27294) in BACTEC 12B medium using the Microplate
Alamar Blue Assay (MABA) [8], and the results are sum-
marized in Table 1.
Quota Program Scholarship to AHN is greatly acknowl-
edged. Antimycobacterial data were provided by the Tu-
berculosis Antimicrobial Acquisition and Coordinating
Facility (TAACF) through a research and development
Table 1. Antimycobacterial activity for indolizines 1–6.
Compds
Substituent in the indolizine
1-position
% Inhibition of
M.tuberculosis at
6.25 µg/mL
MIC, M. tuberculosis
(µg/mL)
1
H
Br
CH3
CH2Ph
Ph
CHO
COCH3
COPh
CH2OH
9
69
41
43
8
35
21
33
67
78
100
71
90
95
90
87
74
n.d.a
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
6.25
n.d.
>6.25
6.25
6.25
n.d.
n.d.
2a
3a
3b
3c
4a
4b
4c
5a
5b
5c
5d
5e
5f
CH(OH)CH3
CH(OH)Ph
C(CH3)(OH)Ph
CH(OH)-cyclohexyl
CH(OH)-p-C6H4-Cl
CH(OH)-p-C6H4-CH3
CH(OH)-p-C6H4-OCH3
CH(OCH3)Ph3
5g
5h
6
a
Not determined.

Arch. Pharm. Pharm. Med. Chem. 2003, 336, 191–195
Antimycobacterial Indolizines 193
hexane, 1:4). – 1H-NMR (200 MHz, CDCl3): δ (ppm) = 4.17 (s,
2H, CH2), 6.50 (dd, J = 7.4 and 1.7 Hz, 1H, H-6), 7.02–7.44 (m,
15H, Ph), 7.70 (dd, 1H, J = 1.7 and 0.9 Hz, H-8), 8.04 (dd, J =
7.4 and 0.9 Hz, 1H, H-5). – 13C-NMR (50 MHz, CDCl3): δ (ppm)
= 30.6, 98.6, 110.6, 116.7, 119.9, 122.8, 125.6, 126.3, 126.6,
127.4, 128.5, 128.6, 128.7, 129.0, 129.3, 129.4, 130.4, 130.7,
131.1, 131.3, 134.3, 141.4. – MS (EI): 384 (M+, 100), 307 (48),
153 (6). – HRMS: Calcd. for C20H28N2: 384.1626; found
384.1637.
contract with the US National Institute of Allergy and In-
fectious Diseases. We are thankful for all help provided
by Dr. Cecil Kwong and his co-workers. The Norwegian
Research Council is gratefully acknowledged for partial
financing of Bruker Avance NMR instruments used in
this study.
Experimental
1-Formyl-2,3-diphenyl-7-indolizinecarbonitrile (4a)
The 1H NMR spectra were recorded at 500 MHz with a Bruker
Avance DRX 500 instrument, at 300 MHz with a Bruker Avance
DPX 300 instrument, or at 200 MHz with a Bruker Avance DPX
200 or a Varian Gemini 200 instrument and the 13C NMR spec-
tra were recorded at 125, 75, or MHz using the above men-
tioned spectrometers. Mass spectra were recorded at 70 eV
ionising voltage with a VG Prospec instrument, and are pre-
sented as m/z (% rel.int.).Elemental analyses were performed
by Ilse Beetz Mikroanalytisches Laboratorium, Kronach, Ger-
many. Melting points are uncorrected. THF and dioxane were
distilled from Na/benzophenone, and DMF was distilled from
BaO. All other reagents were commercially available and used
as received.Synthesis of compounds 1, 2a, 3a, 3c, 4b, and 5c
have been reported before [6].
n-Butyllithium (1.25 mL of a 1.32 M solution in hexane, 1.65
mmol) was added dropwise to a stirred solution of compound
2a (560 mg, 1.5 mmol) in dry THF (30 mL) at –78°C under N2.
After 1 h, dry DMF (0.58 mL, 7.5 mmol) was added and the re-
sulting mixture was stirred for additional 2 h before the reaction
mixture was heated to room temperature. EtOAc (100 mL), di-
ethyl ether (100 mL), and saturated aqueous ammonium chlo-
ride (100 mL) were added to the cold reaction mixture. The
phases were separated and the organic layer washed with wa-
ter (100 mL), dried (MgSO4), and evaporated in vacuo. The
product was purified by flash chromatography eluting with
EtOAc-hexane (1:29) followed by (1:19), (1:9) and finally (1:4).
Yield 445 mg (92%), yellow crystals. – Mp 205–207°C. – Rf =
0.29 (SiO2, EtOAc-hexane, 1:4).-1H-NMR (300 MHz, CDCl3):δ
(ppm) = 6.82 (dd, J = 7.3 and 1.8 Hz, 1H, H-6), 7.15–7.30 (m,
7H, Ph), 7.35–7.40 (m, 3H, Ph), 8.06 (dd, J = 7.3 and 0.9, 1H,
H-5), 8.83 (dd, J = 1.8 and 0.9 Hz, 1H, H-8), 9.90 (s, 1H, CHO).
1-Iodo-2,3-diphenyl-7-indolizinecarbonitrile (2b)
n-Butyllithium (0.784 mL of a 1.32 M solution in hexane,
1.05 mmol) was added dropwise to a stirred solution of com-
pound 2a (373 mg, 1.0 mmol) in dry THF (20 mL) at –78°C un-
der N2. After 30 min, iodine (508 mg, 2.0 mmol) in THF (5 mL)
was added and the resulting mixture was stirred for 1.5 h.
EtOAc (75 mL), diethyl ether (75 mL) and saturated aqueous
ammonium chloride (50 mL) were added to the cold reaction
mixture.The phases were separated and the organic layer was
washed with water (3 × 75 mL), dried (MgSO4), and evaporated
in vacuo. The product was purified by flash chromatography,
eluting with hexane followed by EtOAc-hexane (1:39).Yield 383
mg (91%), yellow powdery crystals. – Mp 226–228°C. – Rf =
0.47 (SiO2, EtOAc-hexane, 1:4). – 1H-NMR (200 MHz, CDCl3):
δ (ppm) = 6.57 (dd, 1H, J = 7.4 and 1.7 Hz, H-6), 7.21–7.39 (m,
10H, Ph), 7.89 (dd, 1H, J = 1.7 and 0.9 Hz, H-8), 7.97 (dd, 1H,
J = 7.4 and 0.9 Hz, H-5). – 13C-NMR (50 MHz, CDCl3): δ (ppm)
= 63.3, 101.0, 111.1, 118.7, 123.3, 127.1, 127.2, 127.5, 128.1,
128.8, 129.1, 129.2, 130.4, 130.6, 131.7, 133.3, 133.7. – MS
(EI): 420 (M+, 100), 293 (31), 292 (38), 264 (7), 146 (12). –
HRMS: Calcd. for C21H13N2I: 420.0124; found 420.0123.
–
13C-NMR (75 MHz, CDCl3): δ (ppm) = 106.4, 114.0, 114.6,
117.9, 118.1, 123.5, 126.6, 127.0, 127.9, 128.4, 129.3, 129.3,
130.6, 131.0, 131.2, 132.2, 133.9, 186.5. – MS (EI): 322 (M+,
100), 321 (80), 293 (29), 292 (22), 161 (6), 146 (11). – HRMS:
Calcd. for C22H14N2O: 322.1106; found 322.1097.
1-Benzoyl-2,3-diphenyl-7-indolizinecarbonitrile (4c)
n-Butyllithium (0.416 mL of a 1.32 M solution in hexane,
0.55 mmol) was added dropwise to a stirred solution of com-
pound 2a (199 mg, 0.50 mmol) in dry THF (20 mL) at –78°C
under N2. After 1 h, benzoyl chloride (0.290 mL, 351 mg, 2.5
mmol) was added and the resulting mixture was stirred for addi-
tional 2 h before the reaction mixture was heated to ambient
temperature.EtOAc (100 mL), diethyl ether (100 mL), and satu-
rated aqueous ammonium chloride (100 mL) were added to the
cold reaction mixture. The phases were separated and the or-
ganic layer washed with water (100 mL), dried (MgSO4), and
evaporated in vacuo.The product was purified by flash chroma-
tography eluting with EtOAc-hexane (1:29) followed by (1:19),
(1:9), and finally (1:4). Yield 151 mg (76%), yellow crystals. –
1-Benzyl-2,3-diphenyl-7-indolizinecarbonitrile (3b)
1
A solution of benzylmagnesium chloride (0.50 mL of a 2.0 M so-
lution in THF, 1.0 mmol) was added dropwise to a stirred solu-
tion of zinc bromide (0.90 mL of a 1.49 M solution in THF,
1.3 mmol) in dryTHF (3 mL) at –78°C under N2.When the addi-
tion was complete, the resulting mixture was stirred for 1 h at
–78°C and at ambient temperature for 30 min. Tetrakis-
(triphenylphosphine)palladium(0) [generated in situ from tris-
(dibenzylideneacetone)dipalladium chloroform adduct (13 mg,
13 µmol) and triphenylphosphine (26 mg, 0.1 mmol)] in dry di-
oxane (1 mL) and compound 2b (210 mg, 0.50 mmol) in dry di-
oxane (3 mL) were added and the reaction mixture was stirred
for 48 h at 100°C. After cooling to ambient temperature, EtOAc
(50 mL) and diethyl ether (50 mL) were added and the mixture
was washed with saturated ammonium chloride solution
(50 mL) and water (3 × 50 mL), dried (MgSO4), and evaporated
in vacuo. The product was purified by flash chromatography,
eluting with EtOAc-hexane (1:99).Yield 136 mg (70%), yellow
powdery crystals. – Mp 186–187°C. – Rf = 0.44 (SiO2, EtOAc-
Mp 215–216°C. – Rf = 0.34 (SiO2, EtOAc-hexane, 1:4). – H-
NMR (200 MHz, CDCl3):δ (ppm) = 6.70 (dd, J = 7.3 and 1.8 Hz,
1H, H-6), 6.80–6.95 (m, 5H, Ph), 6.95-7.10 (m, 2H, Ph), 7.10–
7.25 (m, 3H, Ph), 7.40–7.30 (m, 3H, Ph), 7.45–7.55 (m, 2H,
Ph), 8.01 (dd, J = 7.3 and 1.0 Hz, 1H, H-5), 8.38 (dd, J = 1.8 and
1.0 Hz, 1H, H-8).– 13C-NMR (50 MHz, CDCl3):δ (ppm) = 104.3,
112.6, 115.8, 118.3, 123.2, 126.5, 126.8, 127.6, 128.9, 129.0,
129.3, 129.1, 129.5, 130.8, 130.9, 131.7, 131.8, 132.8, 133.2,
192.1. – MS (EI): 398 (M+, 100), 321 (61), 293 (25), 292 (18),
199 (9), 105 (7). – HRMS: Calcd. for C28H18N2O: 398.1419;
found 398.1410. – Anal: Found: C, 84.18; H, 4.65; N, 6.72.
C28H18N2O requires C, 84.40; H, 4.55; N, 7.03%.
1-(Hydroxymethyl)-2,3-diphenyl-7-indolizinecarbonitrile (5a)
Compound 4a (148 mg, 0.46 mmol) and sodium borohydride
(26 mg, 0.69 mmol) was dissolved in absolute ethanol (50 mL)
and stirred at ambient temperature for 48 h.Saturated aqueous

194 Gundersen et al.
Arch. Pharm. Pharm. Med. Chem. 2003, 336, 191–195
HRMS: Calcd. for C29H22N2O: 414.1732; found 414.1718. –
Anal: Found: C, 81.16; H, 5.43; N, 6.29. C29H22N2O requires C,
84.03; H, 5.35; N, 6.76%.
ammonium chloride (1 mL) was carefully added to the resulting
mixture before it was evaporated in vacuo. EtOAc (100 mL), di-
ethyl ether (100 mL), and saturated aqueous ammonium chlo-
ride (100 mL) were added to the residue.The phases were sep-
arated and the organic layer washed with water (100 mL), dried
(MgSO4), and evaporated in vacuo.The product was purified by
flash chromatography eluting with EtOAc-hexane (1:29) fol-
lowed by (1:19), (1:9), (1:4), and finally (1:1). Yield 107 mg
(72%), yellow crystals. – Mp. 204–206°C. – Rf = 0.31 (SiO2,
1-[1-Hydroxycyclohexylmethyl]-2,3-diphenyl-7-indolizinecar-
bonitrile (5e)
The compound was prepared as described for compound 5d
and purified by flash chromatography eluting with EtOAc-
hexane (1:39) followed by (1:9). Yield 257 mg (63%), yellow
powdery crystals. – Mp 204–206 °C. – Rf = 0.28 (SiO2, EtOAc-
1
EtOAc-hexane, 1:4). – H-NMR (300 MHz, CDCl3): δ (ppm) =
1
1.7 (br s, 1H, –OH), 4.88 (s, 2H, CH2), 6.55 (dd, J = 7.4 and
1.8 Hz, 1H, H-6), 7.20–7.30 (m, 5H, Ph), 6.95–7.10 (m, 2H,
Ph), 7.30–7.43 (m, 3H, Ph), 8.00 (dd, J = 7.4 and 1.0 Hz, 1H,
H-5), 8.07 (dd, J = 1.8 and 1.0 Hz, 1H, H-8). – 13C-NMR
(75 MHz, CDCl3): δ (ppm) = 55.3, 99.4, 110.6, 116.1, 119.1,
122.5, 124.9, 125.9, 127.2, 128.3, 128.5, 129.1, 129.5, 129.8,
130.3, 130.4, 130.5, 133.2.– MS (EI):324 (M+, 100), 307 (100),
305 (15), 292 (12), 229 (5), 203 (7), 153 (16). – HRMS: Calcd.
for C22H16N2O: 324.1263; found 324.1271.
hexane, 1:4). – H-NMR (500 MHz, CDCl3): δ (ppm) = 0.67–
0.71 (m, 1H, c-hex), 0.96–1.28 (m, 4H, c-hex), 1.56–1.59 (m,
3H, c-hex), 1.72–1.78 (m, 2H, c-hex), 1.96 (d, J = 2.5 Hz, 1H,
OH), 2.04 (m, 1H, c-hex), 4.66 (dd, J = 8.5 and 2.5 Hz, 1H,
CH), 6.52 (dd, J = 7.4 and 1.8 Hz, 1H, H-6), 7.13–7.33 (m,
10H, Ph), 7.99 (dd, J = 7.4 and 0.9 Hz, 1H, H-5), 8.23 (dd, J =
1.8 and 0.9 Hz, 1H, H-8). – 13C-NMR (125 MHz, CDCl3): δ
(ppm) = 25.8, 26.0, 26.2, 29.6, 29.7, 45.6, 73.0, 98.5, 110.2,
119.3, 119.4, 122.4, 125.8, 127.0, 127.1, 127.9, 128.1, 128.2,
128.9, 129.8, 130.2, 130.4, 130.7, 133.9. – MS (EI): 406 (M+,
13), 388 (19), 324 (36), 323 (100), 307 (10), 294 (7), 217 (5). –
HRMS: Calcd. for C28H26N2O: 406.2045; found 406.2055.
1-(1-Hydroxyetyl)-2,3-diphenyl-7-indolizinecarbonitrile (5b)
Methyllithium (0.309 mL of a 1.6 M solution in hexane,
0.495 mmol) was added dropwise to a stirred solution of com-
pound 4a (145 mg, 0.45 mmol) in dry THF (20 mL) at –78°C
under N2.The reaction mixture was stirred at –78°C for 4 h be-
fore saturated aqueous ammonium chloride (1 mL) was added
dropwise.The reaction mixture was heated to ambient temper-
ature and EtOAc (100 mL), diethyl ether (100 mL), and saturat-
ed aqueous ammonium chloride (100 mL) were added. The
phases were seperated and the organic layer washed with wa-
ter (100 mL), dried (MgSO4), and evaporated in vacuo. The
product was purified by flash chromatography eluting with
EtOAc-hexane (1:29) followed by (1:19), (1:9), and finally (1:4).
Yield 148 mg (97%), yellow crystals. – Mp 197–198°C. – Rf =
0.35 (SiO2, EtOAc-hexane, 1:4). – 1H-NMR (200 MHz, CDCl3):
δ (ppm) = 1.68 (d, J = 13.0 Hz, 3H, CH3), 2.12 (br d, J = 2.2 Hz,
1H, OH), 5.27 (dq, J = 13.0 and 2.2 Hz, 1H, CH), 6.58 (dd, J =
7.4 and 1.8 Hz, 1H, H-6), 7.15–7.45 (m, 10H, Ph), 8.05 (dd, J =
7.4 and 1.0 Hz, 1H, H-5), 8.39 (dd, J = 1.8 and 1.0 Hz, 1H, H-8).
– MS (EI): 338 (M+, 42), 323 (100), 320 (78), 319 (82), 293 (7),
242 (9), 215 (10), 152 (8). – HRMS: Calcd. for C23H18N2O:
338.1419; found 338.1429.
1-[1-Hydroxy(4-chlorophenyl)methyl]-2,3-diphenyl-7-indol-
izinecarbonitrile (5f)
The compound was prepared as described for compound 5d
above and purified by flash chromatography, eluting with
EtOAc-hexane (1:29) followed by (1:9). Yield 183 mg (84%),
yellow crystals. – Mp 186–188 °C. – Rf = 0.25 (SiO2, EtOAc-
hexane, 1:4). – 1H-NMR (500 MHz, CDCl3): δ (ppm) = 2.26 (d,
J = 3.4 Hz, 1H, OH), 6.12 (d, J = 3.4 Hz, 1H, CH), 6.54 (dd, J =
7.4 and 1.7 Hz, 1H, H-6), 7.10–7.39 (m, 14H, Ph), 7.92 (br s,
1H, H-8), 8.01 (br d, J = 7.4 Hz, 1H, H-5). – 13C-NMR
(125 MHz, CDCl3): δ (ppm) = 69.3, 99.9, 111.1, 119.3, 119.5,
123.1, 126.3, 126.9, 127.8, 128.2, 128.8, 128.9, 129.0, 129.5,
129.9, 130.6, 130.7, 131.0, 133.6, 133.7, 142.4.– MS (EI):436/
434 (M+, 35/100), 418 (25), 417 (43), 323 (50), 293 (19), 292
(20), 139 (12), 195 (17), 77 (11). – HRMS: Calcd. for
C28H19ClN2O: 434.1186; found 434.1311. – Anal: Found: C,
77.00;H, 4.73;N, 6.05.C28H19ClN2O requires C, 77.33;H, 4.40;
N, 6.44%.
1-[1-Hydroxy(4-methylphenyl)methyl]-2,3-diphenyl-7-indol-
izinecarbonitrile (5g)
1-[1-Hydroxy-1-phenylethyl]-2,3-diphenyl-7-indolizinecarboni-
The compound was prepared as described for compound 5d
above and purified by flash chromatography, eluting with
EtOAc-hexane (1:29) followed by (1:9). Yield 115 mg (55%),
yellow crystals. – Mp 158–160°C. – Rf = 0.23 (SiO2, EtOAc-
hexane, 1:4). – 1H-NMR (500 MHz, CDCl3): δ (ppm) = 2.34 (s,
4H, OH and CH3), 6.11 (s, 1H, CH), 6.51 (dd, J = 7.3 and
1.3 Hz, 1H, H-6), 7.12–7.37 (m, 14H, Ph), 7.97 (br s, 1H, H-8),
8.06 (br d, J = 7.3 Hz, 1H, H-5). – 13C-NMR (125 MHz, CDCl3):
δ (ppm) = 21.1, 69.3, 98.9, 110.4, 119.5, 112.4, 125.3, 125.6,
125.8, 126.9, 127.1, 127.8, 128.1, 128.3, 128.9, 129.1, 129.7,
130.1, 130.2, 130.6, 133.4, 137.1, 140.6. – MS (EI): 414 (M+,
100), 413 (10), 398 (24), 397 (48), 323 (39), 321 (10), 295 (15),
91 (7), 91 (6). – HRMS: Calcd. for C29H22N2O: 414.1732; found
414.1725.
trile (5d)
n-Butyllithium (0.42 mL of a 1.32 M solution in hexane,
0.56 mmol) was added dropwise to a stirred solution of com-
pound 2a (187 mg, 0.50 mmol) in dry THF (10 mL) at –78°C
under N2. After 30 min, acetophenone (0.177 mL, 1.50 mmol)
was added and the resulting mixture was stirred for additional
1.5 h. EtOAc (50 mL), diethyl ether (50 mL), and saturated
aqueous ammonium chloride (30 mL) were added to the cold
reaction mixture. The phases were separated and the organic
layer was washed with water (3 × 30 mL), dried (MgSO4), and
evaporated in vacuo.The product was purified by flash chroma-
tography eluting with EtOAc-hexane (1:29) followed by (1:9).
Yield 47 mg (22%), yellow powdery crystals. – Mp 170–171°C,
1
– Rf = 0.33 (SiO2, EtOAc-hexane, 1:4). – H-NMR (500 MHz,
1-[1-Hydroxy(4-methoxyphenyl)methyl]-2,3-diphenyl-7-indol-
izinecarbonitrile (5h)
CDCl3):δ (ppm) = 1.77 (s, 3H, CH3), 2.31 (s, 1H, OH), 6.49 (dd,
J = 7.3 and 1.4 Hz, 1H, H-6), 6.86 (m, 2H, Ph), 7.04–7.18 (m,
5H, Ph), 7.2–7.4 (m, 8H, Ph), 7.91 (br d, 1H, J = 7.3 Hz, H-5),
8.31 (br s, 1H, H-8). – 13C-NMR (125 MHz, CDCl3): δ (ppm) =
32.6, 76.4, 99.3, 110.4, 120.0, 122.9, 124.1, 126.1, 127.4,
127.5, 127.6, 127.9, 128.0, 128.6, 128.6, 129.1, 129.8, 130.1,
130.7, 131.5, 135.3, 148.8, one signal was hidden. – MS (EI):
414 (M+, 4), 397 (27), 396 (100), 319 (18), 291 (8), 159 (6). –
The compound was prepared as described for compound 5d
above and purified by flash chromatography, eluting with
EtOAc-hexane (1:29) followed by (1:9). Yield 162 mg (75%),
yellow crystals. – Mp 111–112°C. – Rf = 0.25 (SiO2, EtOAc-
hexane, 1:4). – 1H-NMR (300 MHz, CDCl3): δ (ppm) = 2.42 (s,
1H, OH), 3.79 (s, 3H, OCH3), 6.11 (s, 1H, CH), 6.51 (dd, J = 7.2

Arch. Pharm. Pharm. Med. Chem. 2003, 336, 191–195
Antimycobacterial Indolizines 195
12B medium using the Microplate Alamar Blue Assay (MABA).
Compounds exhibiting fluorescence were tested in the
BACTEC 460-radiometric system, and compounds demon-
strating at least 90% inhibition in the primary screen were re-
tested at lower concentrations against M.tuberculosis H37Rv to
determine the actual minimum inhibitory concentration (MIC) in
the MABA. MIC for rifampin was 0.25 µg/mL.
and 1.5 Hz, 1H, H-6), 6.84 (m, 2H, Ph), 7.12–7.36 (m, 12H,
Ph), 7.99–8.02 (m, 2H, H-5 and H-8). – 13C-NMR (125 MHz,
CDCl3): δ (ppm) 55.2, 69.3, 98.9, 110.4, 113.8, 119.3, 119.5,
122.4, 125.6, 127.0, 127.2 (2 C), 127.6, 128.1, 128.3, 128.9,
129.6, 130.0, 130.2, 130.6, 133.4, 135.8, 158.8. – MS (EI): 430
(M+, 100), 414 (63), 413 (73), 323 (19), 321 (13), 305 (11), 294
(11), 292 (17), 135 (8). – HRMS: Calcd. for C29H22N2O2:
430.1681; found 430.1677.
1-[Methoxyphenylmethyl]-2,3-diphenyl-7-indolizinecarboni-
trile (6)
Sodium hydride (26 mg, 1.1 mmol) was added to a stirred solu-
tion of compound 5c in dry THF (15 mL) at ambient tempera-
ture, under N2 and the resulting mixture was stirred for 30 min,
before iodomethane (156 mg, 1.1 mmol) was added dropwise.
After stirring of 36 h, the reaction was quenched with saturated
aqueous NH4Cl solution (2 mL). The mixture was extracted
with EtOAc (50 mL) and diethyl ether (50 mL) and the organic
layer was washed with water (3 × 30 mL), dried (MgSO4), and
evaporated in vacuo.The product was purified by flash chroma-
tography eluting with EtOAc-hexane (1:29). Yield 172 mg
(83%), yellow crystals. – Mp 68–70°C. – Rf = 0.46 (SiO2,
References
[1] K. Duncan, Chem. Ind. 1997, 861–865.
[2] A. K. Bakkestuen, L.-L. Gundersen, G. Langli, F. Liu, J. M.
J. Nolsøe, Bioorg.Med.Chem.Lett.2000, 10, 1207–1210.
[3] G. Andresen, L.-L. Gundersen, J. Nissen-Meyer, G. Rise,
B. Spilsberg, Bioorg. Med. Chem. Lett 2002, 12, 567–569.
[4] L.-L. Gundersen, J. Nissen-Meyer, B. Spilsberg, J. Med.
Chem. 2002, 45, 1383–1386.
1
EtOAc-hexane, 1:4). – H-NMR (300 MHz, CDCl3): δ (ppm) =
3.34 (s, 3H, OCH3), 5.53 (s, 1H, CH), 6.50 (dd, J = 7.4 and
1.8 Hz, 1H, H-6), 7.97 (dd, J = 7.4 and 0.7 Hz, 1H, H-5), 7.07–
7.11 (m, 2H, Ph), 7.20–7.31 (m, 13H, Ph), 8.02 (br s, 1H, H-8).
[5] A. I. Nasir, L.-L. Gundersen, F. Rise, Ø. Antonsen, T. Kris-
tensen, B. Langhelle, A. Bast, I. Custers, G. R. M. M.
Haenen, H. Wikström, Bioorg. Med. Chem. Lett. 1998, 8,
1829–1832.
–
13C-NMR (75 MHz, CDCl3):δ (ppm) = 57.4, 79.3, 99.5, 110.9,
118.0, 119.8, 122.9, 126.2, 126.9, 127.4, 127.6, 127.8, 128.1,
128.6, 128.7, 128.8, 129.4, 130.2, 130.6, 131.1, 131.3, 134.1,
142.3. – MS (EI): 414 (M+, 35), 384 (45), 383 (17), 383 (100),
337 (15), 307 (10), 305 (25), 292 (15), 298 (8), 191 (9), 105 (8),
77 (5), 28 (32).– HRMS:Calcd.for C29H22N2O:414.1732;found
414.1757.
[6] O. B. Østby, B. Dalhus, L. –L. Gundersen, F. Rise, A. Bast,
G. R. M. M. Haenen, Eur. J. Org. Chem. 2000, 9, 3763–
3770.
[7] O. B. Østby, L.-L. Gundersen, F. Rise, Ø. Antonsen, K.
Fosnes, V.Larsen, A.Bast, I.Custers, G.R.M.M.Haenen,
Arch. Pharm. Pharm. Med. Chem. 2001, 334, 21–24.
Activity against mycobacteria [8]
The primary screening was conducted at 6.25 µg/mL against
Mycobacterium tuberculosis H37Rv (ATCC 27294) in BACTEC
[8] L.Collins, S.G.Franzblau.Antimicrob.Agents Chemother.
1997, 41, 1004–1009.

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