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G.A. Elmegeed et al. / European Journal of Medicinal Chemistry 42 (2007) 1285e1292
1
was filtered off, washed several times with water, dried and
crystallized from the appropriate solvent.
2865 (CH2), 1692 (C]O). H NMR (d ppm): 1.87 (s, 3H,
COCH3), 3.05 (t, J ¼ 7.0 Hz, 2H, CH2), 3.47 (t, J ¼ 7.0 Hz,
2H, CH2), 3.80 (s, 3H, OCH3), 4.95 (brs, H, NH, D2O-
exchangeable), 5.25 (s, 2H, NH2, D2O-exchangeable), 6.17
(s, 1H, pyrrole H-b), 7.67e7.88 (m, 3H, aromatic-H), 8.58,
8.72 (2brs, 2H, 2NH, D2O-exchangeable). 13C NMR (d):
22.8 (COCH3), 171.5 (COCH3), 23.5, 38.2 (2CH2), 54.9
(OCH3), 134.8 (C-1), 108.7 (C-2), 133.6 (C-3), 109.6 (C-5),
110.7 (C-6), 152.9 (C-7), 100.3 (C-8), 112.8 (C-9), 126.9,
131.4 (fused-aromatic-C), 118.3 (fused pyrrole-C). MS (EI):
3.1.3.1. 10-[2-(Acetylamino)ethyl]-9-imino-2-methoxy-7-phenyl-
6,9-dihydropyrido[1,2-a]indole-8-carbonirile(9a). Brown pow-
der, from EtOH, yield 0.65 g (82%), mp 181e182 ꢃC. IR (y/
cmꢀ1): 3356e3375 (2NH), 3040 (CH-aromatic), 2974 (CH3),
2853 (CH2), 2225 (CN), 1695 (C]O). 1H NMR (d ppm):
1.87 (s, 3H, COCH3), 3.07 (t, J ¼ 7.2 Hz, 2H, CH2), 3.47 (t,
J ¼ 7.2 Hz, 2H, CH2), 3.79 (s, 3H, OCH3), 4.94 (brs, 1H,
NH, D2O-exchangeable), 7.55e8.04 (m, 8H, aromatic-H),
8.35 (s, 2H, pyridine H-a), 8.75 (brs, 1H, NH, D2O-exchange-
able). 13C NMR (d): 22.7 (COCH3), 173.2 (COCH3), 23.4, 37.8
(2 CH2), 54.8 (OCH3), 122.6 (CN), 101.3 (C-1), 152.5 (C-2),
110.2 (C-3), 109.8 (C-4), 115.0 (C-6), 151.6 (C-7), 114.8 (C-
8), 133.5 (C-9), 113.2 (C-10), 149.3 (fused pyridine-C),
128.3, 132.2 (fused-aromatic-C), 148.3, 113.2, 113.8, 129.3,
ꢄ
m/z (%): 314 (MHþ , 52), 282 (25), 176 (30), 145 (100).
Anal. Calcd. for C16H19N5O2 (313.362): C, 61.32; H, 6.11;
N, 22.34; found: C, 61.15; H, 6.31; N, 22.57.
3.1.5. N-[2-(1-(3,5-Dimethylpyrazol-1-yl)-3-imino-7-
methoxy-1H-pyrrolo[1,2-a]indol-9-yl)ethyl]acetamide (14)
A mixture of compound 12 (1.56 g, 0.005 mol) and acetyl
acetone 2 (0.5 g, 0.005 mol) in absolute ethanol (25 mL)
was boiled under reflux for 3 h until all starting materials
had disappeared as indicated by TLC. Then the reaction mix-
ture was concentrated under vacuum, whereby the resulted oily
product was triturated with petroleum ether (bp 60e80 ꢃC).
The formed solid product was filtered off, dried and crystal-
lized from MeOH to yield 1.35 g (72%) of compound 14,
brown crystals, mp 239e241 ꢃC. IR (y/cmꢀ1): 3380e3295
(2NH), 3035 (CH-aromatic), 2977 (CH3), 2875 (CH2), 1695
ꢄ
129.5, 131.4 (phenyl-C). MS (EI): m/z (%): 398 (Mþ , 40),
367 (38), 321 (48), 292 (100), 77 (67). Anal. Calcd. for
C24H22N4O2 (398.462): C, 72.34; H, 5.56; N, 14.06; found:
C, 72.52; H, 5.29; N, 13.90.
3.1.3.2. Ethyl 10-[2-(acetylamino)ethyl]-9-imino-2-methoxy-7-
phenyl-6,9-dihydropyrido[1,2-a]indole-8-carboxylate (9b).
Yellow powder, from MeOH, yield 0.66 g (75%), mp 217e
218 ꢃC. IR (y/cmꢀ1): 3350e3373 (2NH), 3050 (CH-aromatic),
2975 (CH3), 2869 (CH2), 1735, 1698 (2C]O). 1H NMR
(d ppm): 1.13 (t, J ¼ 6.8 Hz, 3H, ester CH3), 1.79 (s, 3H,
COCH3), 2.95 (t, J ¼ 7.2 Hz, 2H, CH2), 3.40 (t, J ¼ 7.2 Hz,
2H, CH2), 3.85 (s, 3H, OCH3), 4.25 (q, J ¼ 6.8 Hz, 2H, ester
CH2), 4.95 (brs, 1H, NH, D2O-exchangeable), 7.54e8.10
(m, 8H, aromatic-H), 8.45 (s, 2H, pyridine H-a), 8.82 (s,
1H, NH, D2O-exchangeable). 13C NMR (d): 22.1 (COCH3),
174.8 (COCH3), 23.8, 36.3 (2 CH2), 55.3 (OCH3), 15.8
(CO2CH2CH3), 24.2 (CO2CH2CH3), 172.6 (CO2CH2CH3),
102.0 (C-1), 153.7 (C-2), 110.2 (C-3), 109.2 (C-4), 115.7
(C-6), 152.4 (C-7), 114.5 (C-8), 134.5 (C-9), 113.5 (C-10),
148.4 (fused pyridine-C), 128.7, 131.9 (fused-aromatic-C),
148.5, 113.7, 114.3, 129.3, 129.7, 131.4 (phenyl-C). MS
1
(C]O). H NMR (d ppm): 1.75 (s, 3H, COCH3), 2.26 (s,
6H, 2CH3), 3.03 (t, J ¼ 7.0 Hz, 2H, CH2), 3.38 (t,
J ¼ 7.0 Hz, 2H, CH2), 3.85 (s, 3H, OCH3), 4.78 (brs, 1H,
NH, D2O-exchangeable), 6.12 (s, 1H, pyrrole H-b), 6.65 (s,
1H, pyrazole H-4), 7.68e7.92 (m, 3H, aromatic-H), 8.62
(brs, 1H, 1NH, D2O-exchangeable). 13C NMR (d): 22.3
(COCH3), 173.5 (COCH3), 23.5, 37.3 (2 CH2), 54.7 (OCH3),
25.3, 26.2 (2CH3), 134.8 (C-1), 108.6 (C-2), 133.6 (C-3),
109.2 (C-5), 110.3 (C-6), 152.8 (C-7), 101.3 (C-8), 112.8
(C-9), 125.3, 132.2 (fused-aromatic-C), 118.7 (fused pyrrole-
C), 135.2, 106.3, 136.7 (pyrazole-C). MS (EI): m/z (%): 377
ꢄ
(Mþ , 35), 356 (42), 282 (54), 271 (30), 145 (100), 95 (63).
Anal. Calcd. for C21H23N5O2 (377.452): C, 66.82; H, 6.14;
N, 18.55; found: C, 67.05; H, 6.32; N, 18.76.
ꢄ
(EI): m/z (%): 445 (Mþ , 24), 339 (35), 308 (100), 77 (56).
Anal. Calcd. for C26H27N3O4 (445.523): C, 70.09; H, 6.10;
N, 9.43; found: C, 70.25; H, 5.91; N, 9.65.
3.2. Pharmacological assay
3.1.4. N-[2-(3-Imino-1-hydrazino-7-methoxy-1H-pyrrolo
[1,2-a]indol-9-yl)ethyl]acetamide (12)
3.2.1. Animals
SpragueeDawley strain rats weighing 120e130 g or Swiss
albino mice 20e25 g body weight was used throughout the
experiments. Food and water were provided ad libitum. Exper-
iments were performed between 0900 and 1500 h.
Cyanoacetylhydrazide 10 (0.5 g, 0.005 mol) was added to
a solution of melatonin (1) (1.16 g, 0.005 mol) in absolute eth-
anol (30 mL) containing a catalytic amount of triethylamine.
The reaction mixture was refluxed for 3 h and then evaporated
to dryness under reduced pressure. The residue was dissolved
in diethyl ether and the solution was washed with saturated
sodium carbonate. The organic layer was separated, dried
over anhydrous magnesium sulfate and the solvent was re-
moved under reduced pressure. The resulting solid was recrys-
talized from 1,4-dioxane to give 1.25 g (80%) of compound
12, pale brown crystals, mp 219e220 ꢃC. IR (y/cmꢀ1):
3458e3295 (2NH, NH2), 3043 (CH-aromatic), 2970 (CH3),
3.2.2. Tests of inflammation: carrageenan-induced
paw oedema assay
All tested compounds were screened for anti-inflammatory
activity using the carrageenan-induced paw oedema assay in
rats. This model is widely used as a screening tool for evaluation
of putative anti-inflammatory agents. The activity of the com-
pounds was compared with melatonin at a dose of 4 mg/kg.
The dose of melatonin was chosen based on previous studies