Production of 2-azetidinone derivative

PURPOSE:To produce the subject compound as a raw material of a carbapenem- based antibiotic in a high yield from a readily available 2-(phthalimidemethyl) acetoacetic acid ester as the raw material without a complicated separation- purification according to a series of processes. CONSTITUTION:A 2-(phthalimidemethyl)acetoacetic acid ester of formula I (R is methyl or ethyl) as the raw material is catalytically reduced in the presence of an asymmetric hydrogenation catalyst so as to obtain a (2S, 3R)-3- hydroxy-2-(phthalimidemethyl)acetic acid ester of formula II. t-Butyldimethylsilyl chloride is then reacted therewith and the resultant compound of formula III is subsequently reacted with hydrazine to obtain (2S,3R)-2-aminomethyl-3-(t-butyl- dimethylsiloxy) butyric acid ester of formula IV. A Grignard reagent is finally reacted therewith so as to open the ring. Thereby, the objective (1 R, 3S)-3-(1'-t- butyldimethylsiloxyethyl)azetidin-2-one of formula V is obtained. The compound of formula V has a steric configuration suitable for a raw material of a carbapenem antibiotic.