Studies of model compounds for the analysis of ester-containing polysaccharides by the reductive-cleavage method.
The four O-propionyl regioisomers of methyl tri-O-methyl-alpha-D-glucopyranoside and the 2- and 3-O-propionyl regioisomers of methyl tri-O-methyl-beta-D-glucopyranoside were subjected to reductive cleavage in the presence of Et3SiH and Me3SiOSO2CF3, BF3.Et2O, or Me3SiOSO2Me-BF3.Et2O. The O-propionyl group was stable when either Me3SiOSO2CF3 or BF3.Et2O was the catalyst, but was slowly reduced to the (1-propyl) ether when Me3SiOSO2Me-BF3.Et2O was the catalyst. Reductive cleavages catalyzed by Me3SiOSO2CF3 were complete in 6 h, those catalyzed by BF3.Et2O required at least 24 h, and those catalyzed by Me3SiOSO2Me-BF3.Et2O required 30 min or less. In the alpha-series, the rate of reductive cleavage decreased in the order 6-O-propionyl greater than 4-O-propionyl greater than 3-O-propionyl much greater than 2-O-propionyl. The reductive cleavage of beta anomers was faster than that of the corresponding alpha anomers. This effect was particularly striking for the alpha and beta anomers of the 2-O-propionyl regioisomer, as would be expected on the basis of a participation reaction.
Sherman
J S
JS
Department of Chemistry, University of Minnesota, Minneapolis 55455.
Gray
G R
GR
D002236:Carbohydrate Conformation; D004952:Esters; D006868:Hydrolysis; D007202:Indicators and Reagents; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D009005:Monosaccharides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry*; D013329:Structure-Activity Relationship
D004952:Esters; D007202:Indicators and Reagents; D009005:Monosaccharides; D011134:Polysaccharides