Patent ID: 6916942

Claim:
A process for preparing a compound of formula I, wherein: R is phenyl, isopropyl, or tert butyl; R 1 is —C(O)R Z in which R Z is (CH 3 ) 3 CO—, (CH 3 ) 3 CCH 2 —, CH 3 (CH 2 ) 3 O—, cyclobutyl-, cyclohexyloxy, or (2-furyl); and R 2 is CH 3 C(O)O—, comprising the steps of: (a) reacting a compound of formula II, wherein R 2 is as defined hereinabove, and R 4 is a hydroxy protecting group, with a beta-lactam of formula IV, wherein R 1 and R are as defined hereinabove, and R 3 is a hydroxy protecting group, in presence of a base to produce the compound of formula III, wherein R, R 1 , R 2 , R 3 and R 4 are as defined hereinabove; and (b) deprotecting the hydroxy protecting groups R 3 and R 4 of the compound of formula III to provide the compound of formula I.