dimethyl erythro-2-hydroxy-3-picryloxybutanedioates
Methyl 4-keto-4-(4'-methylphenyl)but-2-enoate
(E)-methyl 4-(4-chlorophenyl)-4-oxobut-2-enoate
dimethyl 2-(2-hydroxyphenyl)-1,3-dioxolane-4,5-dicarboxylate
methyl 2-(4β-acetylthio-2-oxo-3β-phenoxyacetylamino-1-azetidinyl)-2-hydroxy-acetate