dimethyl 4-carboxy-3,5-dihydroxyhomophthalate

dimethyl 2,6-dimethyl-4-oxopiperidine-3,5-dicarboxylate

dimethyl 3-[(2,4-dinitrophenyl)hydrazinylidene]pentanedioate

methyl 5-(2-amino-2-oxoethyl)-2H-triazole-4-carboxylate