A short stereoselective synthesis of cecropia juvenile hormone

A very short synthesis of the racemic cecropia hormone has been realized, utilizing a Claisen reaction. Methyl 6-hydroxy-3-methyl-7-methylene-2-trans-nonenoate, on treatment with the dimethyl ketal of 3-chloro-3-methyl-2-pentanone and a catalytic amount of 2,4-dinitrophenol, is transformed directly into methyl 11-chloro-3,11-dimethyl-7-ethyl-10-oxo-2-trans, 6-trans-tridecadienoate. Selective reduction gives a mixture of diastereoisomeric chlorohydrins separable by chromatography. The predominant threo-chlorohydrin is transformed into the juvenile hormone.