1-(Dialkylaminomethyl)-azetidin-2-ones. Intermediates in a highly stereoselective preparation of trans-3,4-disubstituted azetidin-2-ones

Abstract

The use of dialkylaminomethyl derivatives as a new β-lactam N—H protecting group is described. The group is stable to basic reagents but is readily removed with dilute aqueous acids. 1-Dialkylaminomethyl derivatives bearing a 4-substituent are converted in good yield and with high stereoselectivity into trans-3,4-disubstituted derivatives via reaction with LDA and subsequent addition of electrophiles. The products of several of these sequences are of interest as intermediates to thienamycin related substances.