反应详情

A solution of 0.54 g (0.7 mmol) of 2-[4-(p-toluenesulphonylthio)-3-(α-tert.butoxycarbonylamino-α-phenylacetylamino)-2-oxoazetidin-1-yl]-3-hydroxy-crotonic acid diphenylmethyl ester in 20 ml of methylene chloride/methanol, 1:1, is stirred for 15 minutes with an excess of a solution of diazomethane in ether at 0° C. and is then concentrated by evaporation in vacuo. Preparative layer chromatography of the residue on silica gel, using toluene/ethyl acetate, 1:1, as the running agent, and elution of the zone which is visible in UV light gives 2-[4-(p-toluenesulphonylthio)-3-(α-tert.butoxycarbonylamino-α-phenylacetylamino)-2-oxoazetidin-1-yl]-3-methoxy-crotonic acid diphenylmethyl ester, which is recrystallised from methylene chloride/diethyl ether/hexane. Melting point 204°-206° C.; UV spectrum (ethanol): λmax =259 mμ (ε=16,000); IR spectrum (Nujol): characteristic bands at 2.93, 5.58, 5.80, 5.84, 5.93, 6.24 and 6.57μ; thin layer chromatogram: Rf value~0.33 (silica gel; toluene/ethyl acetate, 1:1).

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