合成路线1

The epoxidation of alpha-(3beta-benzamido-4beta-allyloxy-2-oxoazetidin-1-yl)-alpha-isopropylilideneacetic acid diphenylmethyl ester (I) with a peracid gives the corresponding epoxide in the allyl group (II), which is chlorinated with tert-butyl hypochlorite affording the chloro epoxide (III). The methoxylation of (III) with lithium methoxide yields the 3beta-benzamido-3alpha-methoxy derivative (IV), which is condensed with lithium 1-methyltetrazol-5-ylmercaptide (V) to afford the tetrazol derivative (VI). The oxidation of (VI) with CrO3 affords the ketonic compound (VII), which is debenzoylated by treatment with PCl5, MeOH and triethylamine giving alpha-[3beta-amino-3alpha-methoxy-4beta-[3-(1-methyltetrazol-5-yl)thiomethyl-2-oxopropoxy]-2-oxoazetidine-1-yl]-alpha-isopropylidieneacetic acid diphenylmethyl ester (VIII). The condensation of (VIII) with alpha-(p-benzyloxyphenyl)-alpha-(benzyloxycarbonyl)acetyl chloride (IX) by means of triethylamine affords the 3beta-[alpha-(benzyloxyphenyl)-alpha-(benzyloxycarbonyl)acetamido] derivative (XX).