for the following products
1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid monomethyl ester | 2,6-Dimethyl-5-methoxycarbonyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3-carboxylic acid and 5-Methoxycarbonyl-2,6-dimethyl-4(3-nitrophenyl)-1,4-dihydropyridine-3-carboxylic acid
