Synthesis of Enantiomerically Pure Cyclopentene Building Blocks

Abstract An efficient synthesis of the enantiomerically pure CIS-annulated cyclopentenes 2 and ENT-2 was established by the use of an enzymatic transesterification and hydrolysis, respectively, followed by an S N 2-type substitution with a benzyloxymethyl cuprate and a sigmatropic rearrangement. The advantage of this approach is the short sequence combined with an excellent overall yield and an enantiomeric excess of 99%.