Biosynthesis of valine and isoleucine: synthesis and biological activity of (2S)-α-acetolactic acid (2-hydroxy-2-methyl-3-oxobutanoic acid), and (2R)- and (2S)-α-acetohydroxybutyric acid (2-ethyl-2-hydroxy-3-oxobutanoic acid)

Stereoisomers of the two substrates for the enzyme reductoisomerase of the valine-isoleucine pathway of biosynthesis have been synthesised in optically pure form. These compounds are (2S)-α-acetolactate (2-hydroxy-2-methyl-3-oxobutanoate) and (2R)- and (2S)-α-acetohydroxybutyrate (2-ethyl-2-hydroxy-3-oxobutanoate). The synthesis of (2S)-α-acetolactate represents the first synthesis in optically pure form of the substrate of the enzyme in the valine pathway. Only the (2S)-isomers of these compounds acted as substrates for the reductoisomerase of Salmonella typhimurium.