Abstract
8'-and 9'-Methoxyabscisic acids (methoxy-ABAs) were synthesized as antimetabolic analogs of abscisic acid (ABA). The racemic mixtures were resolved by HPLC. (+)-8'-Methoxy-ABA inhibited the elongation of rice seedlings four times more strongly than (+)-ABA did, and (+)-9'-methoxy-ABA inhibited the germination of lettuce seeds and the induction of α-amylase by gibberellin A3 in barley seeds seven and two times more strongly, respectively. These methoxy-ABAs are the first analogs reported to have higher activity than ABA. (+)-8'-and (+)-9'-Methoxy-ABAs were less active in causing stomatal closure than (+)-ABA. These biological activities and 1H-NMR analysis suggest that the activity of methoxy-ABAs involved delayed metabolism, as was expected. The activity of (-)-isomers of ABA and methoxy-ABAs was also tested.
