The synthesis and biological activity of several ethyl 1-acylindole-3-acetates

Abstract

Several ethyl 1-acylindole-3-acetates have been synthesized and their biological activities in three plant systems ascertained. The 1-dichloroacetyl derivative was as active as the parent ester in the tomato ovary growth assay. The 2-chloropropionyl, 3-chloropropionyl, 4-nitrobenzoyl, and 4-aminobenzoyl derivatives were least active. The acetyl and chloroacetyl derivatives were of intermediate activity. The dichloroacetyl radical increased the activity of the parent ester as measured by delay in abscission of debladed bean petioles. The acetyl, chloroacetyl, and nitrobenzoyl compounds were less active, but more active than the parent compound. The 2-chloropropionyl, 3-chloropropionyl, and 4-aminobenzoyl derivatives were no more active than the parent ester and acid. All of the 1-acyl derivatives, except the acetyl, were as active in the Avena straight growth assay as both indole-3-acetic acid and ethyl indole-3-acetate over the range of concentrations used. Ethyl 1-acetylindole-3-acetate was of equivalent activity only at 1 × 10 −5M. The possible implications of these results in the concepts of structural requirements for auxin activity are discussed.