[3,3'-bi-1,3-thiazolidine]-4,4'-dione system. I. Synthesis, conformational analysis and pharmacological activities of 2,2'-diaryl derivatives.

The two configurational isomers, d1, and meso, of some 2,2'-diaryl-[3,3'-bi-1,3-thiazolidine]-4,4'-dione derivatives have been obtained and characterized. The 1H-N.M.R. spectra of both stereoisomers in DMSO-d6 solution are temperature-dependent and their dynamic behaviour has been related to the hindered rotation of the N--N bond. Evidence for an orthogonal disposition of the two heterocyclic rings, in the ground state, is presented. These new bicyclic compounds possess interesting antiinflammatory, analgesic and antipyretic activities as well as low acute toxicity and ulcerogenicity. The antiinflammatory effect, which in some compounds is higher than that of indomethacin and phenylbutazone, appears to be a function of the relative disposition of the substituents at position 2 and 2': generally the meso isomers are more active than the d1 ones. The lipophilicity of the tested compounds was determined by reversed-phase thin-layer chromatography.