Preparation and structural characterization of a sulfated octasaccharide with heparin-like anticoagulant activity

Heparins are sulfated polysaccharides with a heterogeneous mixture derived from animal tissues, subject to supply limitations and the risk of animal virus residues. Patients using heparin also face the risks of spontaneous bleeding and thrombocytopenia. Here we reported an efficient riclinoctaose-based approach for rapid chemical synthesis of a structurally defined heparin-like anticoagulant sulfated octasaccharide (SRO). We used sulfur trioxide-pyridine, sulfur trioxide-trimethylamine, and sulfur trioxide-triethylamine complexes as solvents for one-pot O-sulfation and determined the optimal conditions for synthesizing SRO. Sulfur trioxide-trimethylamine provided reasonable control over the degree of substitution between 1.85 and 1.88, revealing a single molecule with a theoretical molecular weight of 2952.96 g/mol. The structural features of the SRO were carried out by Fourier transform infrared spectroscopy and one- and two- dimensional ¹H and ¹³C NMR analysis, revealing sulfation repeatedly present at the fixed positions of C-6/C-2/C-3 and reducing terminals. The anticoagulant activity of SRO was demonstrated by efficiently blocking coagulation in the blood of mice and human. SRO dose-dependently decreased ferric chloride-induced experimental thrombosis in mice. Like heparin, SRO specifically inhibits coagulation factor Xa, but significantly reduces the risk of bleeding compared to heparin. Therefore, we named it octaparin. These results support that octaparin is expected to replace animal-sourced heparin.