Asymmetric Synthesis of (R)-Nilvadipine and (S)-NB 818 via Regioselective Bromination of Chiral 1, 4-Dihydropyridines as a Key Step and Enzymatic Resolution of Racemic 2-Hydroxymethyl-1, 4-dihydropyridine Derivatives

Abstract

Optically active 2-hydroxymethyl-1, 4-dihydropyridines were obtained by lipase-catalyzed hydrolysis or transesterification of racemic materials. Chiral NB 818 and nilvadipine have been synthesized from chiral 2-hydroxymethyl-1, 4-dihydropyridine. On the other hand, chiral 1, 4-dihydropyridines obtained from prochiral substrates have been converted into (S)-NB 818 and (R)-nilvadipine via regioselective bromination of methyl groups under mild conditions.