Stereoselective synthesis of methyl trans-chrysanthemate and related derivatives

γ-Hydroxyalkenylstannanes, readily available from α,β-unsaturated esters, α,β-unsaturated aldehydes and tri(n-butyl)stannyllithium, react with boron trifluoride etherate to produce vinyl cyclopropane carboxylic esters. An original highly convergent synthesis of chrysanthemic acid is reported.