SYNTHESIS AND BIOLOGICAL-ACTIVITIES OF FLUORINATED PLANT-GROWTH REGULATORS, 4,4,4-TRIFLUORO-3-(3-INDOLYL)BUTYRIC ACIDS AND 4,4,4-TRIFLUORO-3-(2-INDOLYL)BUTYRIC ACID BEARING A METHYL-GROUP ON THE INDOLE NUCLEUS

Four methyl-substituted 4,4,4-trifluoro-3-(3-indolyl)butyric acids (Me -TFIBAs, 1a, 1c, 1e, 1f) and 4,4,4-trifluoro-3-(3-methyl-2-indolyl)but acid (3-Me-TFIBA-2, 1g) were synthesized as fluorinated plant growth regulators respectively from methyl-substituted indoles and trifluoroa cetaldehyde ethyl hemiacetal via methyl-substituted 2,2,2-trifluoro-1- (3-indolyl)ethanols and 2,2,2-trifluoro-1-(3-methyl-2-indolyl)ethanol. Their biological activities were compared with those of TFIBA (1), 2- Me-TFIBA (1b) and 5-Me-TFIBA (1d). The 4-Me-, 6-Me-TFIBAs and 3-Me-TFI BA-2 had marked root growth-promoting activity for Chinese cabbage and lettuce, and their activities were close to those of the 5-Me-TFIBA. The 4-Me- and 6-Me-TFIBAs had promoting activity for rice plants equiv alent to that of 5-Me-TFIBA. 3-Me-TFIBA-2 had the strongest root growt h-promoting activity (about 4.3-fold the control value). For all three plants, however, the root growth-promoting activity of 1-Me-TFIBA (1a ), was lower than that of TFIBA, the original non-substituted compound .