The reaction of methylhydrazin (I) with potassium thiocyanate (II) gives N-methyl-N-aminothiourea (III), which is cyclized with dimethyl oxalate (IV) by means of sodium methoxide in methanol to afford 2,5-dihydro-6-hydroxy-2-methyl-3-mercapto-5-oxo-1,2,4-triazine (V). The reaction of (V) with 7-aminocephalosporanic acid (VI) in a buffer solution at pH 6.5 gives 7-amino-3,4-[(2,5-dihydro-6-hydroxy-2-methyl-5-oxo-as-triazin-3-yl)thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (VII), which is condensed with 2-(2-chloroacetamido-4-thiazolyl)-2-[(Z)-methoxyimino]acetyl chloride (VIII) at pH 2 yielding 7-]2-(2-chloroacetamido-4-thiazolyl)-2-[(Z)-methoxyimino]acetamido-3-[[(2,5-dihydro-6-hydroxy-2-methyl-5-oxo-as-triazin-3-yl)thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (IX). Finally, this compound is hydrolyzed and treated with sodium hydroxide.