Pyridyl ester containing 1,4-dihydropyridine derivatives and salts thereof and pharmaceutical composition containing the same

A 1,4-dihydropyridine represented by the formula (I) or a pharmaceutically acceptable salt thereof:

• ##STR38## wherein R.sup.1 and R.sup.5, which may be the same or different, represent lower alkyl groups, R.sup.2 represents a pyridyl group;
• R.sup.3 represents a phenyl group or a phenyl group substituted by at least one substituent selected from the group consisting of halogen atoms and nitro, cyano, azido, lower alkyl, lower alkoxy, trihalo-lower alkyl, lower alkanesulfonyl, benzyl, phenethyl, methylbenzyl, chlorobenzyl, methoxybenzyl, phenyl, naphthyl, benzyloxy, phenethyloxy, p-chlorobenzyloxy, p-methoxybenzyloxy, phenoxy, naphthoxy, p-methylphenoxy, lower alkythio, phenylthio, naphthylthio, p-methylphenylthio, benzylthio, phenethylthio, p-chlorobenzylthio, p-methoxybenzylthio and lower alkoxycarbonyl groups;
• R.sup.4 represents a carboxyl group esterified with a group selected from the group consisting of lower alkyl, lower alkoxy-lower alkyl, lower alkylthio-lower alkyl, N,N-di(lower alkyl)amino-lower alkyl, N-benzyl-N-lower alkylamino-lower alkyl, N-(4-chlorobenzyl)-N-lower alkylamino-lower alkyl, N-phenyl-N-lower alkylamino-lower alkyl and N,N-dibenzylamino-lower alkyl;
• A represents an alkylene group;
• B represents an alkenylene group;
• X represents an oxygen atom;
• Y represents a vinylene group;
• and Z represents an alkylene group.