作者:Ana-Rae de Jong、Bas Hagen、Vincent van der Ark、Herman S. Overkleeft、Jeroen D. C. Codée、Gijsbert A. Van der Marel
DOI:10.1021/jo201586r
日期:2012.1.6
The relative reactivity of glucuronic acid esters was established in a series of competition experiments, in which two thioglucoside and/or thioglucuronic acid ester donors competed for a limited amount of activator (NIS-TfOH). Although glucuronic add esters are often considered to be of very low reactivity, the series of competition reactions revealed that the reactivity of the glucuronic acid esters studied is sufficient to provide productive glycosylation reactions. The latter is illustrated in the synthesis of two Streptococcus pneumoniae trisaccharides, in which the applicability of the two similarly protected frame-shifted thiociisaccharide donors, Glc-GlcA and GlcA-Glc, were compared. The Glc-GlcA disaccharide, featuring the glucuronic acid donor moiety, proved to be the most productive in the assembly of a protected S. pneumoniae trisaccharide.