Modulating steric effects in diastereoselective Staudinger reaction: Synthesis of optically pure cis-β-lactams

Article abstract of DOI:10.1016/0040-4020(96)00048-8

Diastereoselection in the synthesis of β-lactams (14 and 15) via ketene-imine cycloaddition (Staudinger reaction) using different chiral auxiliaries has been examined. While sterically demanding imines derived from bicyclic aldehyde (1) with a β chiral centre provided excellent selectivity, use of imines derived from bicyclic aldehyde (17) with a γ chiral centre was not effective. Improvement of stereoselectivity was also sought using imines (6 and 7) derived from chiral amines (2d,e) and chiral aldehyde (1). The bicyclic terpenoid skeleton of the chiral auxiliary in 1 was dismantled by ruthenium tetroxide oxidation to given multiply functionalized β-lactams-23a-d in good yield.