ISSN:
1434-193X
Keywords:
Carbohydrates
;
Glycoproteins
;
Mannose
;
Glycosylation
;
Mixed acetals
;
Intramulecular aglycon delivery
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
-We have previously developed a novel method for the stereocontrolled synthesis of β-manno-glycoside. Starting from 2-O-PMB (p-methoxybenzyl)-protected mannosyl donor 1, conversion into the mixed acetal 3 under oxidative conditions followed by the activation of the anomeric position affords β-manno-glycoside as a single stereoisomer. Although the utility of this method has been further demonstrated in the synthesis of the core structure of Asn-linked glycan chains, there remained uncertainty with respect to the stereochemistry of the mixed acetal. In order to make a stereochemical assignment of this intermediate, diastereomeric acetals 14a, 15a and 14b, 15b were prepared from 9 + 10/7 and 11 + 12/13, respectively. Investigations by means of NMR and a computational approach using DADAS 90 for quantifying steric hindrance, resulted in the conclusion that 14a/15a derived from 2-O-PMB-protected 9 has an (S) configuration and 14b/15b derived from 2-O-unprotected 11 has an (R) configuration. Based on the characteristic 1H-NMR patterns inherent to the (S) isomers, 4,6-O-benzylidene-protected 30-35, derived from thiomannosides 5, 23, 24, 26, 27, were also revealed to have the (S) configuration.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
