Systematic synthesis of rare sugars and stereospecific conversion via photocatalysis

Abstract

Abstract Rare sugars have gained attention as potential raw materials for pharmaceuticals and functional foods. Photocatalysis presents a promising approach for rare sugar synthesis due to its mild reaction conditions and environmental compatibility. While previous photocatalytic methods reported individual routes for specific rare sugars, systematic synthesis through a unified methodology has not been achieved, and control of optical isomers remains insufficiently explored. This study investigated a comprehensive photocatalytic approach for the systematic conversion of monosaccharides with stereochemical configuration preservation. When d-glucose in aqueous solution underwent photocatalytic treatment under UV irradiation, d-arabinose formation was confirmed through HPLC, LCMS, and ¹H NMR analyses. Similarly, d-lyxose, d-ribose, and d-xylose were produced from d-galactose, d-allose, and d-gulose, respectively. Further photocatalytic treatment of these aldopentoses yielded corresponding aldotetroses—d-erythrose from d-ribose and d-arabinose, and d-threose from d-lyxose and d-xylose. This demonstrated successful systematic conversion from aldohexoses to aldopentoses and subsequently to aldotetroses in a single reaction system. Moreover, when l-glucose and l-arabinose were used as starting materials, l-arabinose and l-erythrose were obtained, respectively, confirming stereochemical configuration preservation throughout the conversion process. This method provides a systematic approach for rare sugar synthesis while controlling stereochemical configurations.