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S. Schenone et al. / Bioorg. Med. Chem. 9 (2001) 2149–2153
role in determining the antalgic activity. This fact could
also account for the prevailing antiphlogistic feature of
2c in comparison with that of its homologue 2h bearing
a more lipophilic CH3 group (p=+0.56) on the aryl-
sulphonyl substituent.
Pharmacology
The tested compounds were administered orally by
gavage in 1% methylcellulose suspension, using a dose
of 50 mg/kg (ꢃ140 mmol/kg). Indomethacin was inclu-
ded and used as reference drug in all the tests for com-
parison purposes at the dose of 5 mg/kg (14 mmol/kg).
The estimation of ED50 and LD50 values was afforded
using the Litchfield and Wilcoxon I formula, by means
of the computer program PHARM-PCS [7].11
In conclusion, these thiadiazolone derivatives, with a
sulphonyl side chain, seem to be promising and suscep-
tible to development as peripheral antinociceptive
agents. Moreover, a comparison of our results to those of
some close related substituted thiazolidine-2,4-diones,10
points out better antiphlogistic and antipain properties
for the present thiadiazolo-2(3H)one derivatives.
The following experimental procedures were employed.
Anti-inflammatory activity
The paw edema inhibition test was used on rats.12
Groups of five rats of both sexes (body weight 220–280
g), pregnant females excluded, were given a dose of the
test compound. Thirty minutes later, 0.2 mL of 1%
carrageenan suspension in 0.9% NaCl solution was
injected subcutaneously into the plantar aponeurosis of
the hind paw. The paw volume was measured by a water
plethysmometer (Socrel) and then measured again 1,
2, 3, and 4 h later. The mean variation of the paw
volume at each time interval was compared to that of
the control group at the same time intervals and per-
centage inhibition values were calculated. The experi-
mental results at the first and fourth hour are listed in
Table 5.
Experimental
Chemistry
Starting materials were purchased from Aldrich-Italia
(Milan). Melting points were determined with a Buchi
530 apparatus and are uncorrected. IR spectra were
measured in KBr with a Perkin-Elmer 398 spectro-
photometer. 1H NMR spectra were recorded in (CD3)2SO
solution on a Varian Gemini 200 (200 MHz) instrument,
chemical shifts are reported as d (ppm) relative to TMS
1
as internal standard; J in Hz. H patterns are described
using the following abbreviations: s=singlet, d=doub-
let, t=triplet, q=quartet, m=multiplet, br=broad.
All compounds were tested for purity by TLC (Merck,
Silica gel 60 F254, CHCl3 as eluant).
Analgesic activity
The acetic acid writhing test was used on mice.13
Groups of 10 mice (weight 20–25 g) of both sexes,
pregnant females excluded, were given a dose of the test
compound. Thirty minutes later the animals were injec-
ted intraperitoneally with 0.25 mL/mouse of 0.5% ace-
tic acid solution and writhes were counted during the
following 25 min. The mean number of writhes for each
experimental group and percentage inhibition compared
to the control group were calculated. The experimental
results are listed in Table 6.
Analyses for C, H, Nwere within ꢂ0.3% of the theoretical
value.
General procedure for thiosemicarbazides (3a–l). A solu-
tion of the suitable isothiocyanate (21 mmol) in anhy-
drous tetrahydrofuran (THF) (10 mL) was added
dropwise to a suspension of benzenesulphonyl or p-
toluenesulphonyl hydrazide (20 mmol) in anhydrous
THF (40 mL). The mixture was continuously stirred for
over three days and kept at room temperature to com-
plete the reaction (TLC monitored), the solvent was
evaporated under reduced pressure and the residue
treated with water (50 mL). The white solid which was
obtained was filtered and crystallized from dry ethanol
(Tables 1 and 2).
Microanalyses of compounds 2a–l
Compound
% Calculated/found
H
C
N
General procedure for 1,3,4-thiadiazol-2(3H)-ones (2a–l).
A phosgene solution (20% in toluene, 12 mL, ꢃ24
mmol) was added dropwise by cooling to a suspension
of each thiosemicarbazide 3a–l (20 mmol) and anhy-
drous sodium acetate (4.1 g, 50 mmol) in anhydrous
THF (50 mL). The reaction mixture was stirred over-
night at room temperature, the solvent was evaporated
under reduced pressure and the residue treated with
water (50 mL). The resulting suspension was extracted
with CHCl3 (3ꢄ40 mL) and dried (MgSO4). After
removal of the solvent, the residue was purified by col-
umn chromatography (Florisil1 60–100 mesh, CHCl3
as eluant) to give a solid residue which was crystallized
from Et2O petroleum ether (1:1) (Tables 3 and 4).
2a
2b
2c
2d
2e
2f
50.44
50.16
51.86
51.72
49.58
49.51
47.86
48.17
45.72
45.71
51.86
52.09
53.17
52.93
3.33
3.35
3.77
3.78
3.61
3.66
2.87
2.96
2.74
2.66
3.77
3.74
4.18
4.23
12.60
12.63
12.13
12.15
11.56
11.46
11.96
11.80
11.42
11.28
12.10
12.24
11.63
11.65
2g
Schenone, Silvia
