Process for preparing optically active 3-hydroxybutanoic acid.

摘要

For preparing an optically active 3-hydroxybutanoic acid of formula: wherein R<1> represents a protective group of carboxylic acid, and R<2> represents hydrogen, C1-4 alkyl which may be substituted with halogen, C1-4 alkoxy or a phenyl or benxyloxy which may each be substituted with a C1-4 alkyl or alkoxy; a 3-oxobutanoic acid ester of formula: wherein R<1> and R<2> are as defined above, preferably in a halogenated hydrocarbon solvent under H2 pressure of 10-150 kg/cm<2> at 15-100 DEG C for 10-40 hours, is asymmetrically hydrogenated in the presence as a catalyst of a ruthenium-optically active phosphine complex, preferably a 'BINAP' tertiary phosphine complex. The compound (I) can be used for synthesizing in 5 steps a 4-acetoxyazetidin-2-one derivative, a useful intermediate for obtaining penem antibiotics. The synthesis of (I) is carried out economically from (II) which is easily prepared from an aceto-acetic ester.