Influence of Levulinoyl Protecting Groups on Glycosylation Stereoselectivity and Glycosyl Cation Structure

作者：Niklas Geue, Kim Greis, Sabrina Omoregbee‐Leichnitz, Carla Kirschbaum, Chun‐Wei Chang, Gerard Meijer, Gert von Helden, Peter H. Seeberger, Kevin Pagel · 发表于：European Journal of Organic Chemistry · 年份：2025 · DOI：10.1002/ejoc.202500732 · 被引用次数：12 · 研究领域：Carbohydrate Chemistry and Synthesis、Glycosylation and Glycoproteins Research、Microbial Metabolites in Food Biotechnology

The stereoselective synthesis of 1,2‐ cis glycosidic bonds is historically challenging, and a common synthetic approach is based on the participation of remote protecting ester groups. Common intermediates of glycosylation reactions are glycosyl cations, whose structures are difficult to characterize. Here, the glycosylation reactions and structure of the glycosyl cations of galactose and mannose are investigated when protected with levulinic acid (Lev) at C4 and/or C6, respectively. The glycosyl cations can be assigned to rearranged structures as a consequence of ring opening, as well as dioxolenium ions that suggest remote participation. Some evidence for the long‐range interaction of the Lev keto group is found as previously proposed, which could explain unusual solution‐phase stereoselectivities observed.