methyl 4-hydroxy-4-(4-nitrophenyl)-2-oxobut-3-enoate

methyl 2-oxo-2-(2-oxocyclohexyl)acetate

methyl 2-(4-chloroanilino)-2-oxoacetate

methyl 1-benzyl-4,5-dioxopyrrolidine-3-carboxylate

dimethyl 2-propan-2-yloxypropanedioate