1,6-ANHYDRO-BETA-D-GLUCOPYRANOSE DERIVATIVES AS GLYCOSYL DONORS FOR THIOGLYCOSIDATION REACTIONS

1,6-Anhydro derivatives of D-glucopyranose, maltose, and maltotriose reacted at room temperature with trimethylsilylated benzenethiol (2) and cyclohexanethiol (3) in the presence of zinc iodide (Znl2) or trimethylsilyl triflate (TMSOTf), giving the corresponding thioglycosides with predominance of one anomer in high yield. 1,6-Anhydro-2,3,4-tri-O-benzyl-β-D-glucopyranose (1) condensed with a more complex thiol derivative, methyl 2,3,6-tri-O-benzyl-4-thio-4-S-trimethylsilyl-α-D-glucopyranoside (19), to give the 4-thiomaltose derivative (20), whereas no condensation took place between the 1,6-anhydro disaccharide homologue (21) and thiol derivative (19). The difference in reactivity between 1,6-anhydro mono- and di-saccharides was utilized for a specific cross-coupling reaction.