A Concise, Efficient and Production-Scale Synthesis of a Protected l-Lyxonolactone Derivative:  An Important Aldonolactone Core

A multikilogram-scale synthesis of l-lyxonolactone-2,3-O-isopropylidene is reported. It proceeds efficiently from an optimized, large-scale, aqueous bromine oxidation of d-ribose to d-ribonolactone including a one-pot isopropylidene formation, and subsequent conversion of the d-ribonolactone-2,3-O-isopropylidene to l-lyxonolactone-2,3-O-isopropylidene via the derived C5-mesylate and intramolecular relactonization of the product of aqueous potassium hydroxide cleavage of the d-ribonolactone ring. The inversion of configuration at the C4-chiral center is understood in terms of an intermediating C4−C5-epoxide. The overall process is noteworthy for its operational simplicity, stereochemical integrity, and use of inexpensive chemicals.