Synthesis and Immunostimulatory Activity of Xanthone C‑β-Glucosides

Xanthone C-glycosides are widely distributed in various plants and exhibit a broad spectrum of biological activities. However, existing synthetic strategies have been restricted to general applicability to structurally diverse xanthone C-glycosides. To address this limitation, we developed a versatile synthetic method based on nucleophilic addition of brominated xanthene to a glycosyl lactone to construct the C–C glycosidic bond. Using this strategy, four novel xanthone C-β-glucosides (20a–d) were synthesized. Xanthone 4-C-β-glucoside 20a exhibited preliminary immunostimulatory activity by promoting dendritic cell maturation and activation. This strategy enables preparation of a variety of xanthone C-β-glucosides, facilitating structural diversification and subsequent biological evaluation.