Effect of substitution pattern on H-1, C-13 NMR chemical shifts and (1)J(CH) coupling constants in heparin derivatives

H-1, C-13 NMR chemical shifts and (1)J(CH),, coupling constants were measur ed for derivatives of heparin containing various sulfation patterns. H-1 an d C-13 chemical shifts varied considerably after introducing electronegativ e sulfate groups. Chemical shifts of protons linked to carbons changed by u p to 1 ppm on substitution with O- and N-sulfate or acetyl groups. Differen ces up to 10 ppm were detected for C-13 chemical shifts in substituted gluc osamine, but a less clear dependence was found in iduronate. (1)J(CH) value s formed two groups, corresponding to either sulfation or non-sulfation at positions 2 and 3 of glucosamine. O-sulfation caused increases up to 6 Hz i n (1)J(CH) and N-sulfation decreases up to 4 Hz. N-acetylation gave similar (1)J(CH) values to N-sulfation. At positions 2 and 3 of iduronate the tren d was less marked; (1)J(CH) for O-sulfated positions usually increasing. In troduction of sulfate groups influences chemical shift and (1)J(CH) values at the position of substitution, but also at more remote positions. (1)J(CH ) at the glycosidic linkage positions varied between free-amino and N-sulfa ted compounds, by up to 9 Hz. These results and changes in chemical shift v alues suggest that iduronate residues and the glycosidic linkages are affec ted, indicating overall conformational change. This may have important impl ications for biological activities. (C) 2000 Elsevier Science Ltd. All righ ts reserved.