New oxadiazole derivatives showing partly antiplatelet, antithrombotic and serotonin antagonistic properties

Ten new 1, 2, 4-oxadiazole- and six new 1, 3, 4-oxadiazole-carboxamides containing different lipophilic moieties (i.e. 4-biphenyl-, 1-naphthyl, phenylpropyl- and n-hexyl substituents) and additional basic groups which are mainly alkyl- and dialkylaminoalkyl residues have been synthesized and tested for antiplatelet effects in vitro (Born-test) and antithrombotic properties in vivo (laser thrombosis model). If the platelet aggregation was induced by collagen, the inhibitory effects (IC50) were between 58 microM and 300 microM. Using serotonin (5-HT) as an inducer, compound 6a (N-(3-dimethylaminopropyl-5-(biphenyl-4-yl)-1, 3, 4-oxadiazole-2-carboxamide) had an IC50 = 1 microM (12e: (N-3-Dimethylaminopropyl)-3-(1-naphthyl)-1, 2, 4-oxadiazole-5-carboxamide, 6.7 microM). In an in vitro rat tail artery assay 6a and 12e behaved as a competitive 5-HT2A receptor antagonist (6a: pKB = 6.86 +/- 0.04; 12e: pKB = 6.66 +/- 0.05). The antithrombotic effects of some compounds were small but significant (7-10 % inhibition of thrombus formation).