Optically active 1,4-dihydropyridine compounds and the microbial process for the stereoselection thereof

A process for preparing an optically active (4R)-1,4-dihydro-2,6-dimethyl-4-(nitrophenyl)pyridine-3,5-dicarboxylic acid mono-ester derivative which comprises reacting a compound of formula (I) below:

• ##STR10## wherein R represents a lower alkanoyl group, a heterocyclic carbonyl group, a halo-substituted acetyl group, an alkoxyacetyl group, an aryloxyacetyl group, a substituted or unsubstituted phenyl-lower alkanoyl group, a phenyl-substituted or unsubstituted lower alkenoyl group, an alkoxy or alkenyloxycarbonyl group, an aralkyloxycarbonyl group or an organic sulfonyl group;
• and n represents an integer of 2 to 4, or a salt thereof with a microorganism capable of asymmetric hydrolysis and belonging to the genus Streptomyces, the genus Paecilomyces, the genus Botryodioplodia or the genus Alternaria with lyophilized, dried or immobilized cells of said microorganism, or with a concentrate or dried powder of a culture broth of said microorganism, and collecting the resulting optically active 1,4-dihydropyridine compound of formula (II) below:
• ##STR11## wherein R and n have the same significance as defined above, or a salt thereof.