| 摘要 |
A process for preparing an optically active 2-substituted or unsubstituted-4-hydroxy-2-cyclopentenone of the formula: <IMAGE> wherein R is a hydrogen atom, an allyl group or a propargyl group, which comprises reacting the corresponding 2-substituted or unsubstituted-4-hydroxy-2-cyclopentenone of the formula: <IMAGE> wherein R is defined above with a lactone chosen from (1R,5S)-6,6-dimethyl-4-hydroxy-3-oxabicyc lo[3.1.0]hexan-2-one or (1S,5R)-6,6-dimethyl-4-hydroxy-3-oxabicyclo[3.1.0]hexan-2-one in a molar ratio of 1.5 - 2:1 in the presence of p-toluenesulfonic acid or benzenesulfonic acid in the coexistence of an organic solvent under elimination of water as an azeotropic mixture with the organic solvent to obtain a reaction mixture comprising (1R,5S)-6,6-dimethyl-3-oxa-4(R)-[1(R)-4-oxo-2-substituted or unsubstituted-2-cyclopentenyloxy]bicyclo[3.1.0]hexan-2-one or (1S,5R)-6,6-dimethyl-3-oxa-4(S)-[1(S)-4-oxo-2-substituted or unsubstituted-2-cyclopentenyloxy]bicyclo[3.1.0]hexan-2-one of the formula: <IMAGE> wherein R is as defined above, of which either one isomer is contained in a considerably larger amount than the other isomer, separating the isom er having the larger content from the reaction mix ture and hydrolyzing the separated isomer to give the optically active 2-substituted or unsubstituted-4-hydrox y-2-cyclopentenone.
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