Switching between X-Pyrano-, X-Furano-, and Anhydro-X-pyranoside Synthesis (X = C, N) under Lewis acid Catalyzed Conditions

A variety of C-glycosides can be obtained from the fluoroarylborane (B(C6F5)(3)) or silylium (R3Si+) catalyzed functionalization of 1-MeO- and per-TMS-sugars with TMS-X reagents. A one-step functionalization with a change as simple as the addition order and/or Lewis acid and TMS-X enables one to afford chiral synthons that are common (C-pyranosides), have few viable synthetic methods (C-furanosides), or are virtually unknown (anhydro-C-pyranosides), which mechanistically arise from whether a direct substitution, isomerization/substitution, or substitution/isomerization occurs, respectively.

Automated summary

A variety of C-glycosides can be synthesized through a one-step functionalization process by changing the addition order, Lewis acid, and TMS-X, resulting in common C-pyranosides, rare C-furanosides, and virtually unknown anhydro-C-pyranosides. These synthons are obtained through different mechanisms such as direct substitution, isomerization/substitution, or substitution/isomerization.