n-Pentenyl glycoside based methodology for determining the relative reactivities of variously protected pairs of glycosides

Article abstract of DOI:10.1021/jo00107a008

The relative rate of hydrolysis of an α/β anomeric pair of glycosides is generally considered to provide insight into various factors that influence anomeric reactivity. However the fact that such hydrolyses are usually carried out with aqueous acids severely limits the range of substrates that can studied. This limitation is overcome with n-pentenyl glycosides (NPGs) which are hydrolyzed under neutral, oxidative conditions. A procedure is described in which a pair (e.g. α₁/β₁, α₁/β₂, β₁/β₂,etc.) of NPGs is made to compete for an insufficient amount of N-bromosuccinimide, the relative rates of reaction being determined from HPLC peak heights of the unreacted starting materials. Some commonly used acid labile protecting groups, e.g. cyclic acetals and acetyl, are shown to exert profound effects upon relative and absolute rates of anomeric activation.