Promiscuous enzyme-catalyzed Michael addition: synthesis of warfarin and derivatives

BACKGROUND: Biocatalytic promiscuity has attracted much attention from chemists and biochemists in recent years. Warfarin, one of the most effective anticoagulants, has been introduced for clinical use as a racemate for more than half a century. Although some different chemical strategies towards the synthesis of optically active warfarin have been reported, biocatalytic preparation of warfarin remains unexploited. RESULTS: Lipase from porcine pancreas (PPL) was used as a biocatalyst to catalyze the Michael addition of 4-hydroxycoumarin to α,β-unsaturated enones in organic medium in the presence of water to synthesize warfarin and derivatives. The products were obtained in moderate to high yields (up to 95%) with none or low enantioselectivities (up to 28% ee). The influence of reaction conditions including solvents, temperature and molar ratio of substrates was systematically investigated. CONCLUSION: Among the many reported lipase-catalyzed Michael additions, only a few showed enantioselectivity. Therefore, this Michael addition activity of, for example, PPL is a valuable case of enantioselective lipase catalytic promiscuity. In addition, it was the first time warfarin and derivatives were prepared using a biocatalyst. Copyright © 2012 Society of Chemical Industry