Investigations on the Chemistry of Heparin

The position of the O-sulfates in heparin was investigated by methylation procedures. Heparin was converted to the acetamido derivative and permethylated with diiethyl sulfate in aqueous alkali. Other methylation methods in organic solvents were also used. The carboxyl groups in the uranic acid moieties were then reduced and the resulting permethylated polysaccharide was hydrolyzed. The products were identified either as crystalline derivatives or by chromatography and specific color reactions. These were characterized as 3-O-methyl-n-glucose, 2,3-di-o-methyl-nglucose, 3-0-methyl-n-glucosamine, glucosamine, and 3,6di-0-methylglucosamine. On the basis of the amounts isolated, it is concluded that about one-third of the glucuronic acid moieties in heparin are sulfated on carbon atom 2 whereas the rest are not sulfated. Most of the glucosamine in heparin contains sulfate ester groups on carbon 6. Glucosamine units which are not sulfated and 3,6-di-O-sulfoglucosamine units are also present in small proportions. It is proposed that the degree of sulfation of the individual units in the heparin polymer is not uniform and that it may vary in different parts of the chain.