Synthesis of 7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylates: the olivanic acid ring system

Abstract

The β-lactams prepared from penta-1,4-diene and cyclohexa-1,4-diene by reaction with chlorosulphonyl isocyanate can be readily converted into the 7-oxo-1-azabicyclo[3.2.0]hept-2-ene ring system, using an intramolecular Witting reaction to form the 2,3-double bond.