Control of Phosphoryl Migratory Transesterifications Allows Regioselecive Access to Sugar Phosphates

Phosphate esters in polyhydroxylated systems are normally blighted by uncontrolled migration under a variety of reaction conditions. Cesium fluoride is demonstrated as a reagent to control migration of primary phosphates during transesterifications. This allows easy exchange of phosphoryl protecting groups enabling enhanced synthetic strategic flexibility and regioselective phosphate installation. Mechanistic analysis suggests that a fluoride-induced extended solvent sphere modulates steric bulk at phosphorus to favor the primary position.