(E)-4-methoxy-3-methyl-4-oxobut-2-enoic acid

methyl 4-hydroxy-3-methylbut-2-enoate

methyl 4-bromo-3-methyl-2-butenoate

3-methyl-4-(4-methylphenyl)sulfonylbut-2-en-1-ol

(E)-Methyl-4-(p-tolylsulfonyl)-2-butensaeure-methylester