Development of Transesterification Catalyzed by Tetranuclear Zinc Cluster -Application for Highly Chemoselective O-Acylation of Aminoalcohol-

摘要

Esterification is one of the most general and widely used reactions in organic synthesis, and wide varieties of methods have been developed. Common routes to ester are condensation reaction of a carboxylic acid with an alcohol and the reaction using hyper reactive acylating reagents such as acyl halides and acid anhydrides. However, when these reaction was applied to amino alcohols, N-acylation took place exclusively due to the much higher reactivity of amino groups and higher thermodynamic stability of amides compared to esters (Scheme 1, path a). As a result, the common strategy for the selective acylation of hydroxyl groups in the presence of an amino group involves the protection of an amino group by its conversion into the corresponding amide or carbamate, followed by the acylation of the hydroxyl functionality, and selective N-deprotection (Scheme 1 ,path c). In terms of atom-economy, direct O-selective acylation in the presence of unprotected primary and secondary alkyl amines is highly desirable, there is no example, however, except lipase mediates this reaction.