3-(2-Phenylacetamido)-2-azetidinone (750 mg.) and benzyl 2-bromo-2-(4-benzyloxyphenyl)acetate (1.51 g.) was added to anhydrous N,N-dimethylformamide (10 ml.), and disdolved in it by warming for a while. The solution was cooled in an ice-water bath, and to the solution was added all at once sodium hydride (50% oily) (178 mg.) under stirring. After removing the cooling bath, the reaction mixture was stirred for 30 minutes to which ethyl acetate was added. The reaction mixture was filtered and the filtrate was washed with water, 2% hydrochloric acid and water respectively, and then dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure to give an oily material (1.98 g.), which was subjected to column chromatography using silica.gel (40 g.). The fractions, eluted with a mixture of benzene and chloroform were subjected to thin layer chromatography using silica.gel, and the thin layer was developed with a mixture of chloroform and acetone to give two isomers of 1-(α-benzyloxycarbonyl-4-benzyloxybenzyl)-3-(2-phenylacetamido)-2-azetidinone. The isomer A was recrystallized from a mixture of chloroform and ether. Yield: 90 mg. Mp: 129° to 130° C. (dec.). The isomer B is oily material. Yield: 120 mg. The isomer A (90 mg.) obtained above was dissolved in methanol (7 ml.), and to the solution was added 10% palladium carbon (30 mg.). The mixture was reacted in hydrogen atmosphere at ordinary temperature and ordinary atm. until the absorption of hydrogen gas was completed. The catalyst was filtered off from the fraction mixture, and the filtrate was concentrated under reduced pressure. The residue obtained was crystallized from a mixture of ethyl acetate and ether to give crystals of 3-(2-phenylacetamido)lactacillanic acid. The product was identified by comparing an I.R. absorption spectrum and a N.M.R. absorption spectrum and a melting point with an authentic sample synthesized by another method from 3-aminolactacillanic acid.
