Stereoselective Reduction Of Prochiral Carbonyl Compounds By Photo-biocatalysis With Microalgae

Chiral alcohols are the key building blocks for single enantiopure pharmaceuticals and other fine chemicals. Therefore, it is important to develop an efficient, environment-friendly and energy-saving technique to produce these chiral alcohols. It is an environmental-friendly, energy-saving and sustainable development synthesis technique to produce chiral alcohols with microalgae cell, since microalgae can utilize solar energy to regenerate the co-factor by photosynthesis.In this paper, the stereoselective reduction of aromatic ketone,β-carbonyl ester and straight-chain aliphatic ketone (using acetophenone, ethyl acetoacetate and 2-octone as the model substrate, respectively) by Scenedesmus obliquus, Chlorella vulgaris, Anabaena flosaquae Spirulina platensis were investigated. The former two microalgae are eukaryotic green algae, and the last two is prokaryotic cyanobacteria. We hope to develop a novel chiral alcohols producing technique.Two microalgaes from cyanophyta(Anabaene flosaquae & Spirulina platensis ) have better ability in stereoselective reduction of acetoacetate. Both of their products are (S)-phenyl ethanol, and reach the yield of 40% and above. The products e.e.(e.e., enantiometric excess) both can reach 80% and above. Especially Anabaena flosaquae, its e.e. can reach 100% in proper reaction condition. Both of the two microalgae did not have stereoselective reduction abilities in anaerobic environment(micro-oxygen) or dark conditions.The other two microalgaes from Chlorophyta(Scenedesmus obliquus & Chlorella vulgaris) have better ability in stereoselective reduction of ethyl acetoacetate. Product from Scenedesmus obliquus reach the yield of 70%, and the e.e. can reach 80% and above. The Chlorella vulgaris'catalytic efficiency is lower than Scenedesmus obliquus, only about 30%, but the e.e. can reach 90% and above. The catalytic efficiency of both microalgae in anaerobic environment(micro-oxygen) are lower than normal reaction condition, but the stereoselective catalytic ability of both microalgae is higer. The two kinds of microalgae did ont have stereoselective reduction abilities in dark conditions.In the stereoselective reduction of 2-octanone, the target product did not be detected. The experiment result shows that the microalgaes in laboratory can not stereoselectively reduct long-chain aliphatic ketones.This reasch gives new choice for the stereoselective reduction of chiral alcohols, and new technical route for the production of chiral alcohols.