Chiral synthesis and stomatal closure activities of γ-pseudo- and dihydro-abscisic acids

Analogues of abscisic acid (ABA) were prepared from chiral cyclohexanone building blocks. Synthetic (1'R, 3'S)-1',3'-gamma-dihydroxy-gamma-ionylideneacetic acid and (R)-1'-hydroxy-3'-oxo-gamma-ionylideneacetic acid (tentatively named gamma-pseudo-ABA) provided authentic data for new metabolities isolated from Cercospora cruenta. Both enantiomers of 2', 3'-dihydroABA were also prepared. Only the (1'S, 2'S)-isomer of 2', 3'-dihydroABA induced substantial closure of stomata on the epidermal strips of Commelina communis.