英文别名
                        methyl (1S,3aR,4S,6aR)-4-methyl-6-oxo-1,3a,4,5,6,6a-hexahydropentalene-1-carboxylate;methyl (1R,3aR,4S,6aR)-4-methyl-6-oxo-1,3a,4,5,6,6a-hexahydropentalene-1-carboxylate;methyl (1R,3aS,4S,6aS)-4-methyl-6-oxo-1,3a,4,5,6,6a-hexahydropentalene-1-carboxylate;2α-methoxycarbonyl-6β-methyl-cis-bicyclo<3.3.0>oct-3-en-8-one