Arch. Pharm. Chem. Life Sci. 2007, 340, 352–358
Synthesis and Pharmacology of Thienopyrimidines
357
Apparatus, Philadelphia, PA, USA) and are uncorrected. The IR
spectra were recorded in potassium bromide disks on a Perkin-
Elmer Model-398 spectrometer (Perkin-Elmer, Norwalk, CT,
USA). The 1H spectra were recorded on a DPX-300 MHz Bruker FT-
NMR spectrometer (Bruker Bioscience, Billerica, MA, USA). The
chemical shifts were reported as parts per million (d ppm) tetra-
methylsilane (TMS) as an internal standard. Mass spectra were
obtained on a JEOL-SX-102 instrument (JEOL, Tokyo, Japan) using
fast atom bombardment (FAB positive). Elemental analysis was
performed on a Perkin-Elmer 2400 C, H, N analyzer (Perkin-
Elmer) and values were within the acceptable limits of the calcu-
lated values. The progress of the reaction was monitored on
readymade silica gel plates (Merck, Darmstadt, Germany) using
chloroform-methanol (9:1) as a solvent system. Iodine was used
as a developing agent. Elemental (C, H, N) analysis indicated that
the calculated and observed values were within the acceptable
limits (l 0.4%). All chemicals and reagents were obtained from
Aldrich (USA), Lancaster (UK), or Spectrochem Pvt. Ltd (India)
and were used without further purification.
After the addition was completed, the reaction mixture was fur-
ther stirred for 3 h at room temperature. It was then poured into
ice water and the solid obtained was filtered, washed with water,
dried, and recrystallized from ethanol-acetone mixture. Yield =
79%, mp. 216–2198C; IR: 3350, 3330 (NH2), 1690 cm-1 (C=O); 1H-
NMR (CDCl3) d: 1.3–1.7 (m, 8H, (CH2)4), 3.9 (s, 3H, SCH3), 6.5 (s, 2H,
NH2, D2O exchangeable); MS (m/z) 267 [M+]; Anal. calcd. for
C11H13N3OS2: C, 49.42; H, 4.90; N, 15.71. Found: C, 49.49; H, 4.87;
N, 15.73.
General synthetic procedure for 3-subsituted-amino-2-
methylsulfanyl-5,6,7,8-tetrahydro-3H-benzo[4,5]thieno-
[2,3-d]pyrimidin-4-ones A1–A10
A mixture of 3-amino-2-methylsulfanyl-5,6,7,8-tetrahydro-3H-
benzo[4,5]thieno[2,3-d] pyrimidin-4-one 4 (1.0 g, 0.004 mol) and
appropriate ketones (0.3 mL, 0.004 mol) in glacial acetic acid
was refluxed for 30 h. The reaction mixture was poured into ice
water. The solid obtained was recrystallized from ethanol. The
physical and spectral data of the synthesized compounds are
presented in Table 1 and Table 2.
The
2-amino-3-carbethoxy-4,5,6,7-tetrahydrobenzo[b]thio-
phene 1, was prepared by the procedure described by Gewald et
al. [15].
Pharmacological screening
The synthesized compounds were evaluated for analgesic anti-
inflammatory activities and the ulcerogenic index. The test com-
pounds and the standard drugs were administered in the form
of a suspension (1% carboxy methyl cellulose as a vehicle) by oral
route of administration for the analgesic and anti-inflammatory
testing, but for ulcerogenicity studies intraperitoneally as sus-
pension in 10% v/v Tween-20. Each test group consisted of six ani-
mals. The animals were procured from the Tetrex Biological Cen-
ter, Madurai, India, and were maintained in colony cages at
25 l 28C, relative humidity of 45–55%, under a 12 h light-and-
dark cycle; they were fed standard animal feed. All the animals
were acclimatized for a week before use. The Institutional Ani-
mal Ethics Committee approved the protocol adopted for the
experimentation with animals.
2-Methylsulfanylthiocarbonylamino-4,5,6,7-tetrahydro-
benzo[b]thiophene-3-carboxylic acid ethyl ester 2
To a vigorously stirred solution of 2-amino-3-carbethoxy-4,5,6,7-
tetrahydrobenzo[b]thiophene 1 (4.5 g, 0.02 mol) in dimethyl
sulphoxide (10 mL) at room temperature, carbon disulphide
(1.98 g, 0.026 mol) and aqueous sodium hydroxide (1.2 mL,
20 mol solution) were added simultaneously over 30 min. Then
the mixture was allowed to stir for 30 min more. Dimethyl sul-
phate (2.5 g, 0.02 mol) was added dropwise to the reaction mix-
ture with stirring at 5–108C, it was further stirred for 2 h and
then poured into ice water; the solid obtained was filtered,
dried, and recrystallized from ethanol. Yield = 85%, mp. 135–
1378C. IR: 3210 (NH), 1690 (C=O), 1060 cm– 1 (C=S); 1H-NMR
(CDCl3): d 1.4–1.8 (m, 8H, (CH2)4), 2.0 (t, 3H, 2-COOCH2CH3), 4.1 (q,
2H, 2-COOCH2CH3), 4.4 (s, 3H, SCH3), 7.3 (s, 1H, NHCSSCH3, D2O
exchangeable); MS (m/z): 315 [M+]; Anal. calcd. for C13H17NO2S3: C,
49.51; H, 5.44; N, 4.47. Found: C, 49.49; H, 5.42; N, 4.51
Analgesic activity
Test for analgesic activity was performed by tail-flick technique
[16, 17] using Wistar albino mice (25–35 g) of either sex selected
by random sampling technique. Diclofenac sodium at a dose
level of 10 mg/kg and 20 mg/kg was administered orally as refer-
ence drug for comparison. The test compounds at two dose lev-
els (10, 20 mg/kg) were administered orally. The reaction time
was recorded at 30 min, 1, 2, and 3 h after the treatment, and
cut-off time was 10 sec. The percent analgesic activity (PAA) was
calculated by the following formula
3-Amino-2-mercapto-5,6,7,8-tetrahydro-3H-
benzo[4,5]thieno[2,3-d]pyrimidin-4-one 3
A solution of 2 (3.15 g, 0.01 mol) in ethanol 30 mL was treated
with hydrazine hydrate (4.3 g, 0.01 mol, 99%) and refluxed on a
water bath until the methylmercaptan evolution ceased (8 h).
After cooling, the solid obtained was filtered, dried, and recrys-
tallized from ethanol-acetone mixture. Yield = 75%, mp. 251–
2528C. IR: 3300, 3200 (NH2), 2550 (SH), 1680 cm– 1 (C=O). 1H-NMR
(CDCl3): d 1.5–1.9 (m, 8H, (CH2)4), 3.2 (s, 1H, SH), 5.4 (s, 2H, NH2,
D2O exchangeable); MS (m/z): 253 [M+]; Anal. calcd. for
C10H11N3OS2: C, 47.47; H, 4.38; N, 16.68. Found: C, 47.40; H, 4.33;
N, 16.66.
ꢀ
ꢁ
T2 ꢀ T1
10 ꢀ T1
PAA ¼
6100
where T1 is the reaction time (s) before treatment, and T2 is the
reaction time (s) after treatment.
Anti-inflammatory activity
3-Amino-2-methylsulfanyl-5,6,7,8-tetrahydro-3H-
benzo[4,5]thieno[2,3-d]pyrimidin-4-one 4
To an ice-cold solution of 3 (2.53 g, 0.01 mol) in dimethyl forma-
mide (50 mL), sodium hydroxide (0.4 g, 0.01 mol) was added and
the mixture was stirred for 1 h. To this dimethyl sulphate
(1.25 g, 0.01 mol) was added dropwise with constant stirring.
Anti-inflammatory activity was evaluated by carrageenan-
induced paw oedema test in rats [18]. Diclofenac sodium 10,
20 mg/kg was administered as a standard drug for comparison.
The test compounds were administered at two dose levels (10
and 20 mg/kg). The paw volumes were measured using the mer-
cury displacement technique with the help of a plethysmograph
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