1,5-disubstituted 1,2,3-triazolylation at C1, C2, C3, C4, and C6 of pyranosides: a metal-free route to triazolylated monosaccharides and triazole-linked disaccharides

Abstract

A pair of easily accessible vinyl sulfones derived from styrene epoxide and monotosylated glycerol were reacted with six different azidopyranosides having an azido group at C1, C2, C3, C4, C6, and at the terminal position of an exocylic chain attached to C1. The reaction was performed mostly in water at elevated temperature without any metal catalyst to afford regioselectively 1,5-disubstituted triazolylated pyranosides in high yields. Another set of exocyclic vinyl sulfones prepared from 3-O-methylated- and 3-O-benzylated glucofuranosides as well as 3-O-benzylated allofuranoside were also subjected to 1,3-dipolar cycloaddition reactions with six azidopyranosides under similar reaction conditions to generate a series of 1,5-disubstituted triazole-linked disaccharides. The synthesis of all 1,5-disubstituted triazolylated monosaccharides as well as all 1,5-disubstituted triazole linked disaccharides are reported for the first time. Steric bulk around the azido and vinyl sulfone groups plays a significant role in deciding the outcome of the reactions. This powerful and practical route has the potential to be exploited for the synthesis of complex 1,5-disubstituted 1,2,3-triazolylated carbohydrates.