Changes in the hemicellulosic polysaccharides of rye-grass with increasing maturity

Reaction of the C-2 mercurated methyl hexopyranoside acetates 1–3 with an excess of iodine resulted in nearly quantitative replacement of mercury by iodine with retention and inversion of configuration at C-2. Similar replacement was observed with 2-acetoxymercuri-3,4,6-tri-O-acetyl-2-deoxy-α-d-glucopyranose (4). In the iodinolysis of 2-acetoxymercuri-1,3,4,6-tetra-O-acetyl-2-deoxy-α-d-glucopyranose (5) in methanol, however, replacement at C-2 was accompanied to a considerable extent by solvolysis of the 1-acetoxyl group, and a mixture of 1,2-trans isomers of methyl 3,4,6-tri-O-acetyl-2-deoxy-2-iodo-hexopyranosides having the d-gluco and d-manno configurations was obtained, together with 1,3,4,6-tetra-O-acetyl-2-deoxy-2-iodo-α-d-mannopyranose.