Visible-light-induced, photocatalyst-free generation of glycosyl radicals: Emerging routes for glycosylation.

Stereoselective glycosylation remains one of the most powerful strategies for constructing biologically active molecules, yet precise control over anomeric selectivity continues to be a formidable challenge. Recently, visible-light-driven, photocatalyst-free protocols for generating glycosyl radicals have emerged as a reliable and sustainable alternative to stereoselective glycoside synthesis. The introduction of a wide variety of radical precursors has significantly broadened the scope of this chemistry, enabling access to structurally diverse and biologically relevant glycosidic architectures. These methods proceed under mild conditions, display excellent tolerance toward sensitive functional groups, and are inherently aligned with green chemistry principles. In this chapter, we discuss recent progress in photocatalyst-free glycosyl radical generation, with particular attention to innovative radical precursors and their applications in the construction of glycosides.