[Synthesis and pharmacological properties of alkyl esters of various DL-omega-phenylamino acids].

: The synthesis of some branched-chain and n-alkyl ester hydrochlorides of DL-2-phenylglycine, DL-3-phenyl-3-aminopropionic acid, DL-4-phenyl-4-aminobutyric acid, DL-phenylalanine and DL-4-phenyl-2-aminobutyric acid is described. For 28 alkyl esters of these DL-amino acids, the pharmacological data about the antagonism against spasms induced by barium chloride, histamine and acetylcholine in the guinea-pig ileum in vitro, as well as about the acute toxicity of intraperitoneally administered doses in the mouse, are reported. Empirical structure-activity relationships established for 36 compounds of this group of substances are discussed. It was found that the maxima of the four actions mentioned depended upon the length of the carbon chain in the molecule. In contrast, no clear-cut branching effect was observed. With reference to toxicity, DL-4-phenyl-2-aminobutyric acid n-octyl ester hydrochloride has been found to be the most favourable spasmolytic agent among the compounds under investigation.