Enantioselective syntheses and calcium channel modulating effects of (+)- and (-)-3-isopropyl 5-(4-methylphenethyll) 1,4-dihydro-2,6-dimethyl-4-(2-pyridyl)-3,5-pyridinedicarboxylates.

The (+)- and (-)-enantiomers of 3-isopropyl 5-(4-methylphenethyl) 1,4-dihydro-2,6-dimethyl-4-(2-pyridyl)-3,5-pyridinedicarboxylate were synthesized using an efficient highly enantioselective (ee > or = to 96%) variant of the Hantzsch dihydropyridine synthesis. The key step in this procedure involved the asymmetric Michael addition of a metalated chiral aminocrotonate, derived from D-valine or L-valine, respectively, to the Knoevenagel acceptor (Z)-2-isopropoxycarbonyl-1-(2-pyridyl)-but-1-en-3-one. Both enantiomers exhibited a dual cardioselective partial calcium channel agonist (positive inotropic)/smooth muscle selective calcium channel antagonist effect. The relative in vitro smooth muscle calcium channel antagonist activities of the (-):(+) enantiomers was 26:1. In contrast, the (+)-enantiomer exhibited a greater in vitro positive inotropic effect on guinea pig left atrium where the contractile force was maximally increased by 14.8% at a concentration of 1.63 x 10(-8)M.