Thio-click reaction of 2-deoxy- exo -glycals towards new glycomimetics: stereoselective synthesis of C -2-deoxy- d -glycopyranosyl compounds

A series of 2-deoxy-glycopyranosyl cyanides with d - arabino , d - lyxo , d - erythro , and d - threo configurations was synthesized from the corresponding glycals via 2-deoxy-glycopyranosyl acetates. The cyanides were transformed to anhydro-aldose tosylhydrazones by reduction with NaH 2 PO 2 /Ra-Ni in the presence of tosylhydrazine. The tosylhydrazones furnished 2-deoxy- exo -glycals under modified Bamford–Stevens conditions. Photoinitiated thiol–ene additions of these exo -glycals resulted in the corresponding C -(2-deoxy- d -glycopyranosyl)methyl sulfides in medium to good yields with exclusive regio- and stereoselectivities in most cases. Several disaccharide mimics with a C–S moiety in place of the glycosidic oxygen were also obtained.