Synthesis of water‐soluble branched polysaccharides and their antitumor activity, 1. Branched polysaccharides from cellulose acetate

Branched polysaccharides of cellulose having β‐glycosidically linked D‐glucose branches were synthesized by condensation of 3,4,6‐tri‐O‐acetyl‐(1,2‐O‐ethylorthoacetyl)‐α‐D‐glucopyranose with activated cellulose acetates (DS ≈ 2) in boiling chlorobenzene in the presence of a catalytic amount of 2,6‐dimethylpyridinium perchlorate. The branched polysaccharides were converted into water‐soluble polysaccharides by saponification and then tested for their antitumor activity. Synthetic, branched polysaccharides with 30% or more branching were found to be completely soluble in water. The structure of branched polysaccharides was determined by methylation analysis, and it was found that branching occurred preferentially at the Cxyh6 positions by β‐glucosidic linkages. The antitumor activity for Sarcoma 180 transplanted to mice was high for polysaccharides with a high DP. Cellulose did not react with acetyl glucose orthoester even after activation.