Synthesis and calcium channel antagonist activity of dialkyl 1,4-dihydro-2,6-dimethyl-4-[3-(1-methoxy-carbonyl-4-substituted-1,4- dihydro-pyridyl)]-3,5-pyridinedicarboxylates.

A novel class of dialkyl 1,4-dihydro-2,6-dimethyl-4-(3-[1- methoxycarbonyl-4-(H, Me, n-Bu or Ph)-1,4-dihydropyridyl])-3,5-pyridinedicarboxylates (3-29) were synthesized and evaluated as calcium channel antagonists using the muscarinic receptor mediated Ca2+ dependent contraction of guinea pig ileal longitudinal smooth muscle (GPILSM). The differences in activity among members of this new class of compounds was less than one log unit (IC50 range of 8.25 x 10(-6) to 4.36 x 10(-7) M), relative to the reference drug nifedipine (IC50 = 1.43 x 10(-8) M). Compounds possessing symmetrical C-3(5) diethoxycarbonyl ester substituents generally exhibited optimum activity. The R3 substituent (H, Me, n-Bu, Ph) at the 4-position of the 4-[3-(1-methoxycarbonyl-1,4-dihydropyridyl)] moiety was a determinant of activity. In symmetrical diester compounds, a R3 H substituent provided optimum activity for Me, i-Bu and t-Bu dialkyl ester analogues, whereas a R3 Ph substituent provided optimum activity for Et and i-Pr symmetrical diesters. The test results indicate the 4-[3-(1-methoxycarbonyl-4-substituted-1,4-dihydropyridyl)] substituent in this new class of compounds is bioisosteric with a 4-(3-nitrophenyl), or a 4-(3-pyridyl) substituent in classical 1,4-dihydropyridine antagonists. Compounds possessing large symmetrical dialkyl ester substituents (i-Bu, t-Bu), in conjunction with a 4-[3-(1-methoxycarbonyl-4-methyl-1,4-dihydropyridyl)] substituent, permanently inhibited recovery of the KCl-induced response in GPILSM.