To 70.5 ml of N,N-dimethylformamide are added 7.05 g of methyl 2-(2-tritylamino-4-thiazolyl)-(Z)-2-hydroxyiminoacetate and 3.3 g of potassium carbonate. Then, under ice-cooling and stirring 2.12 g of allyl bromide is added dropwise over a period of 5 minutes. The mixture is further stirred under ice-cooling for 4 hours. To this reaction mixture are added 1.65 g of potassium carbonate and 1.06 g of allyl bromide, and the mixture is stirred for an additional 4 hours. The reaction mixture is diluted with 150 ml of water and extracted three times with 100 ml portions of ether. The ether extract is washed twice with 100 ml portios of aqueous sodium chloride and dried over anhydrous sodium sulfate. The solvent is then distilled off and the residue is purified by column chromatography [silica gel: 300 g; eluent: hexane-ethyl acetate (1:1)] and crystallized from ether-hexane to give 7.0 g of methyl 2-(2-tritylamino-4-thiazolyl)-(Z)-2-allyloxyiminoacetate, m.p. 115°- 116° C.
