Diazomethane → benzhydryl 2-(benzothiazol-2-yldithio)-alpha-(isopropenyl)-4-oxo-3-[(phenoxyacetyl)amino]azetidine-1-acetate

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Reaction Steps

A distilled solution of diazomethane in ether (containing 1.3 mM of diazomethane) is added to a solution of crude 2-[4-(benzthiazol-2-yldithio)-3-phenoxyacetamido-2-oxo-azetidin-1-yl]-3-hydroxy-crotonic acid diphenylmethyl ester, obtained by ozonisation of 681 mg (1.0 mM) of 2-[4-(benzthiazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-methylene-butyric acid diphenylmethyl ester, in 5 ml of methylene chloride at 0° C. The mixture is stirred for one hour at 0° C. and washed with water, and the organic layer is dried over sodium sulphate. The solvents are removed in vacuo and the residue is chromatographed on 35 g of acid-washed silica gel, using toluene/ethyl acetate, 2:1. An isomer mixture consisting of 2-[4-(benzthiazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-methoxy-crotonic acid diphenylmethyl ester and the corresponding isocrotonic acid diphenylmethyl ester is obtained. IR spectrum (in CH2Cl2): 5.60, 5.88, 6.67, 9.15 and 9.92 μ.

Provenance & Evidence