[1-methyl-2-[(1-oxoallyl)oxy]ethyl] hydrogen maleate

2-Butenedioic acid (2Z)-, mono1-methyl-2-(1-oxo-2-propenyl)oxyethyl ester

(Z)-2-Butenedioic acid hydrogen 1-[1-methyl-2-[(1-oxo-2-propenyl)oxy]ethyl] ester