2,2'-Dithio-bis-5-methyl-1,3,4-thiadiazole (48.09 g) and (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid (23.38 g) were suspended in tetrahydrofuran (297 ml) and triphenylphosphine (48.09) was added at 20°-25° C. This mixture was stirred for half an hour to generate 2-mercapto-5-methyl-1,3,4-thiadiazolyl-(Z)-2-(2-aminothiazol-4-yl)-2-methoxyimino acetate in solution. Thereafter, the reaction mixture was cooled to 3°-5° C., diluted with N,N-dimethylacetamide (46.8 ml), water (297 ml) and 7-aminocephalosporanic acid (27.2 g) was added, followed by triethylamine addition in 20 min. The reaction was continued for 3-4 hours at 3°-5° C. Thereafter, acetic acid (18 g) and water (100 ml) were added and the aqueous layer was thoroughly extracted with methylene chloride to remove tetrahydrofuran and other by-products. The aqueous phase containing triethylamine salt of cefotaxime acid was mixed with excess isopropyl alcohol (250 ml) and acidified to pH 2.80 at 0°-5°° C. with hydrochloric acid to precipitate cefotaxime acid. The mixture was then filtered, the solids washed with water, isopropyl alcohol and dried to obtain cefotaxime acid.
