New pyrimido[5,4-c]cinnolines with antiplatelet activities.

Twenty one new pyrimido[5,4-c]cinnolines containing different lipophilic moieties (viz. phenyl, 4-methoxyphenyl, 2-furanyl, 2-thienyl) in position 2 and additional basic groups (e.g., alkylaminopropyl, dialkylaminopropyl and cyclohexylaminopropyl) in position 4 of the title ring system have been prepared and investigated for antiplatelet effects (Born test). Ten of them inhibited the platelet aggregation induced by collagen with an IC(50) below 10 micromol/L (6a, 6b, 6c, 6g, 6h, 6i, 6k, 6m, 6q, 6u). A closer inspection of the antiplatelet effect with other inducers showed antagonism against adrenaline (6m), ADP antagonist (6i) and PAF antagonist activities (6m, 6i, 6u) in nanomolar (IC(50)) concentration ranges.