A 4-cyclopentenone of the formula:
wherein R is a lower alkyl group, a lower alkenyl group or a lower alkynyl group and R' is a hydroxyl group or an aliphatic acyloxy group, provided that in case of the dℓ-form, R' is not a hydroxyl group and also that the substituent R at the 2-position and the methyl group at the 3-position take a cis-configuration in the dℓ-, d- or ℓ-form.
式中 R 为低级烷基、低级烯基或低级炔基,R'为羟基或脂肪酰氧基的 4-
环戊烯酮,但在 dℓ-形式中,R'不是羟基,并且在 dℓ-、d- 或 ℓ-形式中,位于 2 位的取代基 R 和位于 3 位的甲基呈顺式构型。