Synthesis, metabolism and biological activity of a deuterated analogue of the plant hormone S-(+)-abscisic acid

The synthesis of a deuterated analogue of the plant hormone S-(+)-abscisic acid (ABA), S-(+)-[7',7', 7', 8', 8', 8', 9', 9', 9']-nonadeuteroabscisic acid [(+)-d(9)-ABA], is described. The biological activity of (+)-d(9)-ABA was compared to that of (+)-ABA in two assays. Analogous to the metabolism of (+)-ABA to (-)-phaseic acid (PA) by maize (Zea mays L. cv Black Mexican Sweet) cell suspension cultures, (+)d(9)-ABA was oxidized but at a slower rate to d(8)-PA at 25 degrees. At low concentrations the deuterated analogue was a more effective inhibitor of cress seed (Lepidium sativum L.) germination than the natural hormone.