Glycals as Chiral Synthons: Selective Construction of Deoxy and Rare Monosaccharides

Abstract

Glycals, a class of 1,2-unsaturated carbohydrate derivatives, have become valuable chiral building blocks for the stereoselective synthesis of deoxy sugars and structurally rare monosaccharides. This chapter reviews the reactivity and synthetic utility of glycals, emphasizing their role as versatile platforms for selective functionalization. Particular attention is given to hydrofunctionalization (1,2-addition), Ferrier-rearrangements, and radical transformations, which enable efficient formation of C-O, C-N, and C-C bonds with high regio- and stereocontrol. The mechanistic principles underlying these processes are discussed together with recent advances in catalytic activation, including photoredox, electrochemical, noncovalent, organocatalytic, and transition-metal-mediated approaches. Applications of glycal chemistry in rare sugar synthesis, natural product construction, glycodrug development, and the preparation of advanced glycosyl donors are also highlighted. By combining classical carbohydrate chemistry with modern catalytic strategies, glycals continue to provide powerful routes to complex carbohydrate architectures and broaden the synthetic toolbox available for carbohydrate-based molecular design.