Selective Acetylation of Non-anomeric Groups of per--Trimethylsilylated Sugars.

Selective modification of the hydroxyl groups of sugars has been a long-standing challenge due to their proximate relative reactivity. Herein, we report a TMSOTf-catalyzed selective acetylation of the non-anomeric hydroxyl groups of several per--TMS-protected sugar substrates while leaving their anomeric group unaffected. In addition to standing versatile by itself, the anomeric -TMS group left intact can be functionalized to afford key sugar precursors such as imidate donors, which could otherwise be synthesized via a stepwise anomeric deprotection-functionalization procedure.