SYNTHESIS OF NEW ABSCISIC-ACID (ABA) ANALOGS POSSESSING A GEOMETRICALLY RIGID CYCLIZED SIDE-CHAIN

In a solution, cis-abscisic acid (ABA) isomerizes into the trans-isomer which is physiologically inactive, and this structural instability is regarded as a reason for insuitability of ABA in agricultural applications. The side chain of ABA, the 2-cis-4-trans-3-methyl-2,4-pentadienoic acid moiety, was replaced with various substituted phenyl groups to examine biological effects of the inflexibility of the part. Construction of the phenyl moiety was achieved by cyclizing the ionone derivatives and subsequent aromatization. Some of those new compounds showed ABA-like activity in both seed germination and transpiration assays.