| Abstract: | L -Phosphinothricin, the parent α-amino acid of the herbicide glufosinate-ammonium, has been obtained in high enantiomeric purity by three different methods. The stereoselective alkylation of a D -valine-derived bis-lactim ether, followed by the hydrolysis of the heterocyclic intermediate, represents an attractive approach for gram-scale quantities in the laboratory. Another very efficient access to L -phosphinothricin consists of the asymmetric hydrogenation of a prochiral α-acylamido acrylate with a chiral bis-phosphine-rhodium catalyst, while the reaction of chiral pre-built C-4-fragments, like L -vinylglycine or L -2-amino-4-halobutyric acid, which can be obtained from the inexpensive starting materials L -aspartic acid and L -glutamic acid, with (methyl)phosphinic acid derivatives represents a third route which allows the production of nearly enantiomerically pure L -phosphinothricin. |
