Convenient Preparation of 3,6-Anhydro Sugars via Intramolecular Cyclization of 6‑O‑Tosyl Pyranosides Promoted by a Catalytic Amount of TBAF

Abstract

3,6-Anhydro sugars are one of most common anhydro sugars in bioactive compounds and natural products. Herein, a high-yielding, mild, and environmentally friendly synthetic approach for 3,6-anhydro sugars was established via the intramolecular cyclization of 6-O-tosyl pyranosides, promoted by a catalytic amount of tetrabutylammonium fluoride (TBAF) and Na₂CO₃ as a cocatalyst. The advantages include avoidance of protection at the 2,4-positions, free of strong bases, minimization of excessive TBAF usage, and extensive substrate applicability, contributing to its efficiency and versatility especially for large-scale preparations.