4-环戊酮-1,2-二甲酸

2,3,4-tris(ethoxycarbonyl)cyclopentanone

5-methylenetetrahydrocyclopenta[c]furan-1,3-dione

(+)-(1S,2R)-4-methylene-2-[(2E)-3-phenyl-2-propenyloxycarbonyl]cyclopentanecarboxylic acid