Process for the preparation of low molecular weight heparin

A process for the preparation of Enoxaparin sodium, comprising the steps of:

• a) salifying heparin sodium with benzethonium chloride to form benzethonium heparinate,
• b) reacting the benzethonium heparinate obtained in step (a) with benzyl chloride in an inert solvent to form a crude heparin benzyl ester,
• c) adding water to the reaction mixture containing the crude heparin benzyl ester obtained in step (b) at a temperature of 0° C. to room temperature to obtain a precipitate of heparin benzyl ester,
• d) adding an alcoholic solution of sodium acetate to the reaction mixture containing the precipitate of heparin benzyl ester obtained in step (c) to isolate the heparin benzyl ester sodium salt,
• e) depolymerizing the heparin benzyl ester sodium salt obtained in step (d) with sodium hydroxide to produce crude Enoxaparin sodium,
• f) bleaching the crude Enoxaparin sodium obtained in step (e) at a pH of about 9-10 to obtain a decolorized Enoxaparin sodium, and
• g) purifying the decolorized Enoxaparin sodium.