Synthesis and Biological Activity of 2′,3′-iso-Aryl-abscisic Acid Analogs

2′,3′-iso-Benzoabscisic acid (iso-PhABA), an excellent selective abscisic acid (ABA) analog, was developed in our previous work. In order to find its more structure-activity information, some structural modifications were completed in this paper, including the substitution of phenyl ring and replacing the ring with heterocycles. Thus, 16 novel analogs of iso-PhABA were synthesized and screened with three bioassays, Arabidopsis and lettuce seed germination and rice seedling elongation. Some of them, i.e., 2′,3′-iso-pyridoabscisic acid (iso-PyABA) and 2′,3′-iso-franoabscisic acid (iso-FrABA), displayed good bioactivities that closed to iso-PhABA and natural (+)-ABA. Some others, for instance, substituted-iso-PhABA, exhibited certain selectivity to different physiological process when compared to iso-PhABA or (+)-ABA. These analogs not only provided new candidates of ABA-like synthetic plant growth regulators (PGRs) for practical application, but also new potential selective agonist/antagonist for probing the specific function of ABA receptors.