Oral anticoagulant Warfarin (4-hydroxy-3-(3-oxo-1-phenyl butyl)-2H-1- benzopyran-2-one) is synthesized in optically active form starting from 4- hydroxycoumarin via formation of optically active enamines followed by Michael addition reaction with benzyliden acetone at low temperature. Different amines gave 17-68% ee and the chemical yield was 22-71%, depending on the reaction conditions and the structure of chiral amines.