Synthesis of optically pure (R,Z)-5-dec-1-enyloxacyclopentan-2-one, the sex pheromone of the Japanese beetle

Abstract

Optically pure (R,Z)-5-dec-1-enyloxacyclopentan-2-one (1) has been synthesised from methyl 4-oxotetradec-5-ynoate (2) by a chiral reduction with 9-(pinan-3-yl)-9-borabicyclo[3.3.1]nonane (3) which yielded the R-alcohol (4), in 74% enantiomeric excess. This was further purified by recrystallisation of the salt formed from the phthalate ester of compound (4) and (+)-α-methylbenzylamine and then hydrolysed and converted into (R,Z)-(–)-(1).