Synthesis of Optically Pure 1,4-Dihydropyridine Derivatives by Means of Diastereoisomeric Separation of the Hantzsch Intermediates Bearing (R)-1-Phenylethylamino Group

Hantzsch intermediates, which were obtained by Michael addition reaction of benzylideneacetoacetates with the enamino esters bearing (R)-1-phenylethylamino group as a chiral auxiliary, were separated into two diastereoisomeric mixtures. Each of them underwent cyclization reaction to give optically pure 1,4-dihydropyridine derivatives.