SYNTHESIS AND BIOLOGICAL-ACTIVITIES OF 5,6-DIFLUOROINDOLE-3-ACETIC ACID - A NEW FLUOROINDOLE AUXIN

5,6-Difluoroindole-3-acetic acid (5,6-F-2-IAA, 1), a new fluoroindole auxin synthesized via Fischer's indolization, has much a stronger elon gation activity on At ena coleoptile segments than indole-3-acetic aci d (IAA). Although the optimal concentration of 5,6-F-2-IAA for Avena c oleoptile elongation was much higher than that of 5,6-Cl-2-IAA, the ex tent of elongation was much greater. 5,6-F-2-IAA also induces the form ation and promotes the growth of lateral roots of mung bean seedlings. Of the synthetic monofluoro- and difluoro-IAAs, it had the strongest inhibitory activity on hypocotyl growth of Chinese cabbage. It also is moderately resistant to peroxidase oxidation.