0.228 g of tosyl chloride were added to a mixture of 0.806 g of the syn isomer of 2-(2-tritylamino-4-thiazolyl)-2-trityloxyimino-acetic acid, 5 ml of acetone and 0.17 ml of triethylamine and the mixture was stirred for one hour. A solution of 0.155 g of 4-fluoromethyl-3-amino-2-oxo-azetidine hydrochloride in 5 ml of methylene chloride and 0.31 ml of triethylamine was added to the mixture which was stirred for 20 minutes and added to methylene chloride. The mixture was stirred for 90 minutes and was evaporated to dryness. The residue was added to methylene chloride and water with stirring and the decanted organic phase was dried and evaporated to dryness. The residue was chromatographed over silica gel and was eluted with ether to obtain 0.598 g of racemate of the syn isomer of cis 4-fluoromethyl-3-[2-(2-tritylamino-4-thiazolyl)-2-trityloxyimino-acetamido]-2-oxo-azetidine.
