Synthesis of ethyl α-nitro-β-trifluoromethyl acrylate and β-trifluoromethyl-substituted tryptophan analogs and their plant growth regulating activity

Abstract

Ethyl α-nitro-β-trifluoromethyl acrylate was synthesized by nucleophile-catalyzed reaction of ethyl nitroacetate with excess trifluoroacetaldehyde methyl hemiacetal and subsequent dehydration of the intermediate alcohol with P₂O₅. The synthesized nitro olefin regioselectively reacts with the substituted indoles to give fluorinated 3-indolyl-2-nitrobutyrates, which were converted into the corresponding β-trifluoromethyl-substituted tryptophan analogs via the nitro group reduction followed by saponification of the ethoxycarbonyl group. In the step of synthesis of amino ester, the 2-methylindole derivative was resolved into diastereomers, which were transformed to the corresponding acids separately. It was found that the synthesized β-trifluoromethyltryptophans have plant-growth regulating activity apparently attributable to their metabolic transformations into substituted α-trifluoromethylindol-3-ylacetic acids.