Thiosemicarbazones, acyclic

The acyclic C-nucleoside analogues of 1,3,4-thiadiazoles 247 were prepared by the oxidative cyclization of the thiosemicarbazones 248 (X = S) with iron(III) chloride (86JPR1 87BCJ3405). The respective oxadiazole analogues were prepared by the oxidation of the acetate of 248 (X = O) with iodine (72MI1). Both of the aroylhydrazones and thiosemicarbazones... 

Acyclic semicarbazones usually exhibit a band at 1675-1645 cm for C=N. Acyclic thiosemicarbazones display a weak band at 1650-1630 cm the thiosemi-carbazones of seven aldoses did not have this band, and were therefore considered to have a cyclic structure (Holker, 1964). 

Thiosemicarbazone derivatives of glucose, galactose and mannose exist in DMSO solution as tautomeric mixtures of pyranose and acyclic forms, and that of fructose also contains furanose forms. The tbiocarbohydrazone dmivatives of glucose and galactose also exhibit ring-chain... 

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