Condensation of 2-amino-5-thio-1,3,4-thiadiazoline with 1-O-acetyl -2,3,5-tri-O-benzoylribofuranose by both fusion and Vorbruggen procedure gave rise to two products, which were isolated and characterized to be positional isomers of amino-thio-thiadiazoline ribofuranoside by elemental analysis, ^1H, ^1^3C NMR and mass spectra. The structures of the products were assigned by crystallographic analysis and ^1H NMR to be 4-(β-D-ribofuranosyl)-2-amino-5-thio-1,3,4 -thiadiazoline and 3-(β-D-ribofuranosyl)-2-imino-5-thio-1,2,4- thiadiazoline.

Key words: C13 NMR SPECTROMETRY, FURAN P, PROTON MAGNETIC RESONANCE SPECTROMETRY, GLYCOSIDE, ISOMER, THIADIAZOLE P, RIBONUCLEOSIDE