PROBING THE ROLE OF THE HYDROXYL GROUP OF ABA - ANALOGS WITH A METHYL-ETHER AT C-1'

(+)-(S)- and (-)-(R)-C-1'-O-methyl abscisic acids and their methyleste rs, as well as the methyl ethers of the acetylenic analogue of methyl ABA, were synthesized through an enantioselective route, giving a seri es of optically active, new C-1' substituted analogues with known ster eochemistry. In a wheat embryo germination inhibition assay, (-)-C-1'- O-methyl ABA shows high activity, comparable with(+)- and (-)-ABA, whe reas(+)-C-1'-O-methyl ABA is less active. In a wheat seedling transpir ation assay, both analogues exhibit weak activity although the (+)-ABA -like analogue is more potent than its enantiomer. The anti-transpiran t response increases over time, which may indicate that the analogue i s being metabolized to ABA in vivo.