Chemistry of Some Amino Acid Derivatives of Phenoxyalkylbutyric Acids

Abstract

HIS paper reports on the synthesis and properties of 38 new herbiT cides, amino acid derivatives of 4-(2,4-dichlorophenoxy)and 4-(2-methyl-4-chlorophenoxy)butyric acids. The biological evaluation of the compounds as selective herbicides is being conducted by other investigators and will be published later. In the past 18 years major advances have been made in the regulation of plant growth by use of synthetic organic compounds. Many of these new synthetics have reached commercial production and are widely utilized as herbicides. The most prominent among these have been the variously substituted phenoxyalkylcarboxylic acids. The literature abounds with reports on their structural configuration in relation to mode of action, growth-regulating properties and selective herbicidal properties. These researchers were stimulated by the early work on 2,4-dichlorophenoxyacetic acid and other related compounds triggered by such preparative contributions as Pokorny's (7) in 1941. Shaw and Gentner (9) in their paper on the selective herbicidal properties of substituted phenoxyalkylcarboxylic acids have briefly reviewed the literature on some of the most significant contributions concerning the biological activity of these acids. Preliminary investigations 2,3 have shown that the chemical attachment of an amino acid through amide linkage to variously substituted phenoxycarboxylic acids affects the selective herbicidal properties of the latter. The effect seems to depend upon the type of amino acid and its optical configuration. The optimum effect observed so far has been with an amino acid phenoxy-cx-propionic acid series.4 Preliminary screening tests5 (3, 4, 5) designed to measure growth-regulating activity of these compounds have been in close agreement with herbicidal evaluation data.4 Activity tests have shown, for instance, a wide difference in the behavior pattern of compounds made from D-, Land DLoptical forms of amino acids. This difference was greater in the cc-propionic acid4 (3) than in the