Distribution of D-galactosyl groups in guaran and locust-bean gum

Distribution of α-d-galactopyranosyl side-chain groups in two galactomannans, guaran and locust-bean gum, was determined by measurement of the O-acetyl-O-methyl-d-mannitol derivatives obtained from the corresponding primary C-p-tolylsulfonyl polysaccharide derivatives. The O-acetyl-O-methyl-d-mannitol derivatives were produced by β-elimination and methylation, with sodium (methylsulfinyl)methide and methyl iodide, of the primary C-p-toluenesulfinylated galactomannans, followed by sequential acid hydrolysis, reduction, and acetylation of the partially degraded p-tolyl sulfones. The results indicated that side-chain units of guaran are alternately disposed along the d-mannan backbone, whereas those of locust-bean gum are disposed in uniform blocks along the backbone.