SYNTHESIS OF BRANCHED AND LINEAR ARABINANS

The ortho-ester method of glycosylation has been applied to the synthesis of polysaccharides by using the tricyclic ortho-ester β-L-arabinofuranose 1,2,5-ortho-benzoate (1). The resulting polysaccharide (50% yield) was examined by hydrolytic, periodate-oxidation, and methylation techniques, and identified as a highly branched L-arabinan containing α-(1→5)- [and a few (1→3)-] linkages, with branch points at position 3. Polymerisation of the 3-acetate of ortho ester 1 was similarly accomplished in the presence of an initiator (1,2,3,4-tetra-O-acetyl-β-D-glucopyranose) to give an L-arabinan having α-(1→5)-, and a few (1→2)-, linkages; the reducing unit of each chain is a D-glucose residue. © 1969.