The reaction of methyl hydrazine (I) and methyl isothiocyanate (II) in either ethanol or THF afforded 2,4-dimethylthiosemicarbazide (III). Acylation of (III) with 3-fluorobenzoyl chloride in either pyridine or THF/N(Et)3 yielded 1-(3-fluorobenzoyl)-2,4-dimethylthiosemicarbazide (IV), which was easily cyclized to MDL 26,479 by warming in 1 M aqueous NaOH.