Catalytic asymmetric synthesis of the Colorado potato beetle pheromone and its enantiomer

An efficient catalytic asymmetric synthesis of the CPB pheromone [(S)-1,3-dihydroxy-3,7-dimethyl-6-octen-2-one] and its enantiomer was accomplished with 99% ee and in gram quantities from geraniol. The key steps in this procedure involve Sharpless asymmetric epoxidation and recrystallization of the 4-bromobenzoate from the CPB pheromone to improve its enantiomeric purity. Furthermore, the absolute configuration of the CPB pheromone enantiomer was confirmed as (R) for the first time by the X-ray crystallographic structure of its benzoate.

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(R)-1,3-Dihydroxy-3,7-dimethyl-6-octen-2-oneC10H18O3Ee = 99%[α]D20=-3.7 (c 1.0, CHCl3)Source of chirality: l-(+)-diethyl tartrateAbsolute configuration: (R)