Anogeissus leiocarpus gum. Part IV. Exterior chains of leiocarpan A

Abstract

Methylation of leiocarpan A followed by reduction and hydrolysis furnishes a complex mixture of sugars including 2,3,4-tri-O-methyl-D-xylose, 2,3,5-tri-, 2,3-, and 2,5-di-O-methyl-L-arabinose, 2,3,4,6-tetra-, 2,4,6-tri, and-2,4-di-, and 2-O-methyl-D-galactose, 3,4,6-tri-, 3,4-di-, and 4-O-methyl-D-mannose, and 2,3-di-O-methyl-D-glucose. Degradation of periodate-oxidised carboxy-reduced leiocarpan A affords 2-O-α-D-mannopyranosyl-D-erythritol and a degraded polysaccharide from which fragments of lower molecular weight are obtained on further degradation. The structure of leiocarpan A is discussed in the light of these and previous experiments.