Synthesis of 3-(α- and β-d-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine Original Research Article

Di-O-isopropylidene- and O-methanesulfonyl-protected 1-C-(6-chloro-1,2,4-triazolo[4,3-b]pyridazin-3-yl)pentitols were prepared in three to four steps from d-galactose, d-glucose, d-mannose, and 2,3:5,6-di-O-isopropylidene-α-d-mannofuranose. Acid-catalysed treatment of (1S)- and (1R)-1-C-(6-chloro-1,2,4-triazolo[4,3-b]-pyridazin-3-yl)-2,3:4,5-di-O-isopropylidene-1-O-methanesulfonyl-d-arabinitols in refluxing 1,2-dimethoxyethane furnished 3-(α- and β-d-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine, respectively. Several structures, including the structure of the 3-(β-d-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine, were also determined by single-crystal X-ray diffraction analysis.