Isoleucine biosynthesis and metabolism: stereochemistry of the formation of L-isoleucine and of its conversion into senecic and isatinecic acids in Senecio species

Abstract

Incorporation experiments with isoleucine (1) stereospecifically labelled at C-4, and 2-aminobutanoic acid (10) stereospecifically labelled at C-3, in Senecio species have shown that the ethyl migration step during the biosynthesis of L-isoleucine (1) takes place with retention of configuration at the migrating centre, and that during conversion into necic acids of the senecic acid (4) type, both C₅ units are formed with loss of the C-4pro-S hydrogen atom of L-isoleucine (1) and retention of the C-4 pro-R hydrogen atom.