Synthesis of fused triazole-piperidinoses: a free radical cyclization approach

A new strategy has been reported for the synthesis of fused triazole-piperidinoses featuring an unprecedented 6-exo–trig free radical cyclization onto conveniently functionalized 1,2,3-triazoles contained in sugar templates. These compounds are potential key intermediates for the synthesis of azole-glycosidase inhibitors. Radical precursors have been prepared by standard methodologies from 1,2:5,6-di-O-isopropylidene-α-d-allofuranose. The key 6-exo–trig free radical cyclizations using tris(trimethylsilyl)silane/AIBN in toluene, yielded the desired aza-annulated sugars in moderate yields.