3.98 g of trityl chloride were slowly added under an inert atmosphere to a mixture of 3.16 g of the product of Step A, 6 ml of dimethylformamide, 12 ml of methylene chloride and 1.89 ml of triethylamine cooled to -15° C. and the mixture stood at 10° C. for 30 minutes and then 3 hours at room temperature. 13 ml of N hydrochloric acid were added to the mixture which was stirred and decanted. The organic phase was washed with N hydrochloric acid, then with water and was extracted with methylene chloride. The extracts were dried and evaporated to dryness to obtain 7.89 g of raw ethyl 2-(2-tritylamino-4-thiazolyl)-2-ethoxyiminoacetate having a syn configuration.
