POLYFUNCTIONAL (R)-2-HYDROXYCARBOXYLIC ACIDS BY REDUCTION OF 2-OXO ACIDS WITH HYDROGEN GAS OR FORMATE AND RESTING CELLS OF PROTEUS-VULGARIS

Various (R)-2-hydroxy acids such as (R)-2-hydroxy-3-enoic-, 3,5-dienoic-, 4-oxo-, (R,S)-3-hydroxy and some others were prepared on a scale up to 0.12 mol by biocatalytic reduction of the corresponding 2-oxo acids with P. vulgaris and hydrogen gas and/or formate as electron donors. With the exception of the 2-hydroxy-4-oxo acids it could be proved that the enantiomeric excess is > 97%. For the 4-oxo derivatives this enantiomeric excess can be assumed. The yields of isolated products are high because they were isolated from rather small amounts of biocatalyst and low buffer concentrations. Product concentrations in the range of 0.1-0.24 M were obtained. For 1 mmol of product formation in 15-20 h about 20-40 mg (dry weight) of P. vulgaris cells are necessary.