4-methoxy-3-methyl-4-oxobut-2-enoate

methyl 2-(4-methyl-5-oxofuran-2-ylidene)acetate

(Z)-4-(methoxycarbonylmethylene)-3-methylbut-2-en-4-olide

(Z)-4-(methoxycarbonylmethylene)-2-methylbut-2-en-4-olide

1-benzyl-3-methylpyrrole-2,5-dione