Synthesis of water‐soluble branched polysaccharides and their antitumor activity, 3. Branched polysaccharides from ivorynut mannan, ivorynut mannan acetate and konjak glucomannan

Abstract Branched polysaccharides of ivorynut mannan (β‐(1→4)‐D‐mannopyranan) and konjak glucomannan (β‐(1→4)‐linked copolymer of D‐mannopyranose and D‐glucopyranose with side chains) having β‐glycosidically linked D‐glucose branches were synthesized by condensation of 3,4,6‐tri‐ O ‐acetyl‐(1,2‐ O ‐ethylorthoacetyl)‐β‐D‐glucopyranose with activated ivorynut mannan, ivorynut mannan acetate and konjak glucomannan. When ivorynut mannan was used as main chain polymer, a branched polysaccharide with 11% degree of branching was obtained and found to be 50% soluble in water. Branched polysaccharides from ivorynut mannan did not lead to completely water‐soluble products, even if the condensation reaction was repeated or the acetyl derivative was used as a starting polymer. A branched polysaccharide with 5−10% degree of branching obtained from konjak glucomannan was completely soluble in water with out starting from the acetylated polymer. The structure of these branched polysaccharides was determined by methylation analysis, and it was found that branching of both water‐soluble polysaccharides obtained from ivorynut mannan and konjak glucomannan occurred preferentially at the C‐6 positions. The antitumor activity of these polymers was low as compared to that of branched polysaccharides obtained from cellulose and curdlan.