Fluorinating the Sugar and the Nucleotide: Exploring Fluorination Within GDP-Mannose Probes Using Chemoenzymatic Synthesis.

Fluorinated glycans offer a prime opportunity to study the intricacies of their associated binding events with proteins, invoke resistance toward enzymatic hydrolysis, and modulate carbohydrate physicochemical properties. Sugar nucleotides are the key building blocks used by glycosyltransferases and associated enzymes to assemble glycans and, as such, represent a considerable landscape of opportunity to develop fluorinated motifs and enable structure-to-function understanding. Herein, we target the isosteric inclusion of fluorine within the nucleoside diphosphate sugar framework of GDP-mannose using a chemoenzymatic approach. Utilizing chemical synthesis to incorporate bespoke fluorine modifications and a promiscuous pyrophosphorylase, to assemble the sugar nucleotide, enables first-in-class access to GDP-mannoses containing fluorine within the nucleotide alongside double fluorination, within both the pyranose and nucleotide. These materials are utilized to probe a guanosine diphosphate mannose dehydrogenase critical to mucoid alginate biosynthesis. This work provides an exemplar framework for incorporating fluorine within the nucleotide of derived sugar nucleotides and thus the capability to study glycosyltransferesase utilizing GDP-mannose more broadly.