Enantiopure bicyclic piperidinones: stereocontrolled conjugate additions leading to substituted piperidinones.

The conjugate additions of Reformatsky reagents, organocuprate reagents, and hydroxylamines to a [4.3.0]-bicyclic enelactam derived from 6-oxopipecolic acid have been investigated, and found to be efficient, proceeding with excellent exo-stereocontrol, with the exception of N-benzyl-O-benzylhydroxylamine, which gives predominantly the product of endo-addition. These adducts can be readily converted to substituted piperidinones.