14.85 ml of N,O-bis(trimethylsilyl)acetamide are added at 30° to 7.4 g of 7-amino-3-[(2,5-dihydro-6-hydroxy-2-methyl-5-oxo-1,2,4-triazin-3-yl)thiomethyl]ceph-3-em-4-carboxylic acid (water content: 3.7%) in 50 ml of dichloromethane. After two hours at 30°, the mixture is cooled to -15°. 8.1 g of 2-(2-amino-4-thiazolyl)-2-oxothioacetic-acid-S-benzothiazol-2-ylester are added, and stirred for six hours at -15°. The preparation is added to 500 ml of ethanol which has been warmed to 50°, then cooled whilst stirring and stirred for one hour at 0°. The deposit is filtered off, washed and dried. 9.1 g of the title compound are obtained as a yellow powder. IR: 3320 NH, 1805 c=o, 1735 c=o, 1690 c=o, 1645 (amide I), 1555 (amide II).
