1,2-Dimethoxyethane → 7beta-Phenylacetamido-3-methoxy-ceph-2-em-4alpha-carboxylic acid diphenylmethyl ester

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A mixture of 670 mg (1 mmol) of 2-[4-(p-toluenesulphonylthio)-3-phenylacetamido-2-oxoazetidin-1-yl]-3-methoxycrotonic acid diphenylmethyl ester, 6.7 ml of 1,2-dimethoxyethane and 0.22 ml of 1,5-diazabicyclo[5.4.0]undec-5-ene is stirred for 25 minutes at room temperature under a nitrogen atmosphere. The reaction mixture is diluted with toluene, washed successively with 2 N hydrochloric acid, saturated aqueous sodium bicarbonate solution and saturated aqueous sodium chloride solution, dried over sodium sulphate and concentrated by evaporation in vacuo. The residue, after preparative thick layer chromatography on silica gel using toluene/ethyl acetate, 1:1, gives 7β-phenylacetamido-3-methoxy-ceph-2-em-4α-carboxylic acid diphenylmethyl ester of melting point 166°-169° C. (from methylene chloride/hexane), UV spectrum (ethanol): λmax =258 mμ (ε=4,500), IR spectrum (methylene chloride) characteristic bands at 2.93, 5.62, 5.73, 5.93 and 6.66μ, Rf value~0.54 (silica gel; system toluene/ethyl acetate, 1:1), and amorphous 7β-phenylacetamido-3-methoxy-ceph-3-em-4-carboxylic acid diphenylmethyl ester, UV spectrum (ethanol): λmax =258 mμ (ε=6,350), 264 mμ (β=6,350), 282 mμ (ε=5,600) (shoulder), IR spectrum (methylene chloride): characteristic bands at 2.94, 5.63, 5.83, 5.94, 6.26 and 6.66μ, Rf value~0.37 (silica gel; system toluene/ethyl acetate, 1:1), in the ratio of 8:1.

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