Stereoselective cross aldol condensation of bicyclo[3.2.0]alkanones

Abstract

A cross aldol reaction between [(S)-(−)] or [(R)-(+)]-benzyloxypropanal and silyl enol ethers derived from bicyclo[3.2.0]alkanones was carried out in the presence of TiCl₄, leading with total stereoselectivity to a 1 : 1 mixture of enantiomerically pure diastereomers isolated in 81% overall yield. Thus, 5 stereogenic centers could be created starting from one. Furthermore, an efficient access to an enantiomerically pure tricyclo[5.3.0.0^2,6]decane scaffold was possible via a 4 step reaction sequence.