Coupling of carboxylic acid (II) to the 7-aminocephem derivative (I) using POCl3 and pyridine produced the corresponding amide (III). Displacement of the chloro group of (III) with triphenyl phosphine furnished the phosphonium salt (IV), which was subjected to a Wittig reaction with chloroacetaldehyde (V), yielding the Z-propenyl chloride (VI). Subsequent reaction of allyl chloride (VI) with 4-amino-2-mercapto-6-methylpyrimidine (VII) in the presence of NaI produced the E-propenyl sulfide (VIII). The N-trityl group and the p-methoxybenzyl ester of (VIII) were finally cleaved by treatment with trifluoroacetic acid in anisole to furnish the title compound.