NEW MATERIAL:A 5-substituted alkyl-1,3,4-thiadiazol-thiol expressed by formulaI[R is di-substituted alkyl (the amino group may be protected) substituted by two amino groups or one amino group and carboxyl group respectively].

EXAMPLE: 5-(1,5-Diaminopentayl)-1,3,4-thiadiazole-2-thiol.

USE: An intermediate for medicines, e.g. an intermediate for cephalosporin antibiotic substances substituted at the 3- or 7-position.

PROCESS: A compound expressed by formula II[R' is H2N(CH2)nC(NH2)H-, etc.]is esterified to give a compound expressed by formula III (R" is methyl, ethyl or benzyl), which is then converted into a hydrazide to give a compound expressed by formula IV. The resultant hydrazide compound expressed by formula IV is then reacted with carbon bisulfide in the presence of a base, e.g. KOH, to afford a compound expressed by formula V, which is finally cyclized in the presence of a condensing agent to give the compound expressed by formulaI.