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.