# Dissecting Tin-Based Activation and Anomerization Pathways in Carbohydrate Chemistry

## TL;DR

This paper explores how tin-based catalysts work in carbohydrate chemistry, revealing new insights into their role in glycosylation and anomerization processes.

## Contribution

The study provides a detailed mechanistic understanding of tin-based activation and anomerization using NMR and DFT.

## Key findings

- Glycosyl oxocarbenium ions form stable ion pairs with tin-based counterions.
- DFT calculations support anomerization via endocyclic C–O bond cleavage and ring closure.
- 119Sn NMR data align with computed chemical shifts, revealing tin coordination environments.

## Abstract

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 119Sn 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 119Sn 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.