Site-Selective Acylation of Pyranosides with Oligopeptide Catalysts

Abstract

Herein, we report the oligopeptide-catalyzed site-selective acylation of partially protected monosaccharides. We identified catalysts that invert site-selectivity compared to <i>N</i>-methylimidazole, which was used to determine the intrinsic reactivity, for 4,6-<i>O</i>-protected glucopyranosides (<i>trans</i>-diols) as well as 4,6-<i>O</i>-protected mannopyranosides (<i>cis</i>-diols). The reaction yields up to 81% of the inherently unfavored 2-<i>O</i>-acetylated products with selectivities up to 15:1 using mild reaction conditions. We also determined the influence of protecting groups on the reaction and demonstrate that our protocol is suitable for one-pot reactions with multiple consecutive protection steps.