Influence of side chain conformation and configuration on glycosyl donor reactivity and selectivity as illustrated by sialic acid donors epimeric at the 7-position.

ABSTRACT: Two N-acetyl 4O,5N-oxazolidinone-protected sialyl thioglycosides epimeric at the 7-position have been synthesized and their reactivity and stereoselectivity in glycosylation reactions have been compared. It is demonstrated that the natural 7S-donor is both more reactive and more α-selective than the unnatural 7R-isomer. The difference in reactivity is attributed to the side chain conformation and specifically to the proximity of O7 to the anomeric center. In the natural 7S-isomer, O7 is closer to the anomeric center than in its unnatural 7R-epimer and, therefore, better able to support incipient positive charge at the locus of reaction. The difference in selectivity is also attributed to the side conformation, which in the unnatural 7R-series is placed perpendicularly above the α-face of t

SUBMITTER: Kancharla PK 

PROVIDER: S-EPMC3917720 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature