HEPARIN-LIKE COMPOUNDS PREPARED BY CHEMICAL MODIFICATION OF CAPSULAR POLYSACCHARIDE FROM ESCHERICHIA-COLI K5

O-Sulfation of sulfaminoheparosan SAH, a glycosaminoglucuronan with the structure -->4)-beta-D-GlcA(1-->4)-beta-D-GlcNSO(3)(-)-(1-->, obtained by N-deacetylation and N-sulfation of the capsular polysaccharide from E. coli K5, was investigated in order to characterize the sulfation pattern eliciting heparin-like activities. SAH was reacted (as the tributylammonium salt in N,N-dimethylformamide) with pyridine-sulfur trioxide under systematically different experimental conditions. The structure of O-sulfated products (SAHS), as determined by mono- and two-dimensional H-1 and C-13 NMR, varied with variation of reaction parameters. Sulfation of SAH preferentially occurred at O-6 of the GlcNSO(3)(-) residues. Further sulfation occurred either at O-3 or at O-2 of the GlcA residues, depending on the experimental conditions. Products with significantly high affinity for antithrombin and antifactor Xa activity were obtained under well-defined conditions. These products contained the trisulfated aminosugar GlcNSO(3)(-)3,6SO(3)(-), which is a marker component of the pentasaccharide sequence through which heparin binds to antithrombin.