Revised structure for the 6-O-methylglucose polysaccharide of Mycobacterium smegmatis.

Abstract

Chem 243, 433243411, permethylation and hydrolysis of the molecule do not yield 2,4,6-tri-O-methylglucose. This suggests that there is no 3-0-monosubstituted glucose unit in the chain.The present study shows that, instead, this glucose unit is doubly substituted in positions 3 and 4 such that it yields 2,6-di-O-methylglucose on methylation.Periodate oxidation of the polysaccharide followed by reduction and acid hydrolysis gives equimolar amounts of 3-O-methylglucose, 6-0-methylglucose, and glucose.Methylation analysis of the oxidized and reduced product gives 2,3,4,6-tetra-O-methylglucose and 2,6-di-O-methylglucose in a 1:2 molar ratio.Methylation with C2H]methyl iodide yields 3-0- and 2,6-di-0-r2H[lrneth-ylglucose in a 1:1:1 molar ratio.Fast atom bombardment mass spectrometry of the underivatized methylglucose polysaccharide showed that it contained 20 hexose units, and similar analysis of amylase-gluco-