| abstract |
Disclosed are (±)-2,6-dimethyl-4-(3-nitrophanyl)-1,4-dihydropyridine-3.5-dicarboxylic acid-3-(1-benzyl-3-piperidyl) ester-5-methyl ester, the melting point of the hydrochloride of which is 196 to 202°C (referred to as (±)-α-form], from among the diastereomers of 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydrapyridine-3,5-dicarboxylic acid-3-(1-benzyl-3-piperidyll ester-5-methyl ester represented by the formula:n and an optical isomer having an optical rotation degree of (+) from among (±)-α-form or a salt thereof. |