Abstract: Methods and systems for synthesizing heparin compounds are provided. The chemoenzymatic synthesis of structurally homogeneous low molecular weight heparins that have a reversible anticoagulant activity is provided. Also disclosed are heparin compounds having anticoagulant activity, including a binding affinity to antithrombin and an anti-Xa activity, but no detectable anti-lla activity. Additionally, provided are synthetic, low-molecular weight heparin compounds with reversible anticoagulant activity, where the anticoagulant activity is reversible by protamine.