A short multigram asymmetric synthesis of prostanoid scaffolds

Enantiomerically pure polysubstituted cyclopentanes which can be regarded as prostanoid scaffolds have been prepared by an efficient synthetic sequence readily applicable to the preparation of multigram quantities. The first key reaction is the diastereoselective allylmetallation of oxoamide which is readily prepared from γ-butyrolactone and an enantiomerically pure 2,5-dimethylpyrrolidine. The second key-step is an intramolecular [2+2] cycloaddition of a keteneiminium salt leading to bicylo[3.2.0] heptanones. These intermediates have been easily transformed into a variety of prostanoid scaffolds of high enantiomeric purities.