Detalle de: Dissecting Tin-Based Activation and Anomerization Pathways in Carbohydrate Chemistry

Tin-based Lewis acids are widely used in glycosylation chemistry, but their precise mechanistic role is still not fully understood. In this study, we combine 119 Sn NMR spectroscopy and density functional theory (DFT) calculations to investigate how Sn-(IV) promoters interact with glycosyl donors and influence anomerization. Our results indicate that glycosyl oxocarbenium ions can form stable ion pairs with tin-based counterions, underscoring the relevance of these species in glycosylation processes. The agreement between experimental and computed 119 Sn chemical shifts provides structural insights into the coordination environment of the tin species. For anomerization, DFT energy profiles support a mechanism involving endocyclic C-O bond cleavage, rotation, and subsequent ring closure. These findings refine our understanding of tin-mediated transformations and offer a framework for rational design of Lewis acid promoters in glycochemistry.