Studies on Abscisic Acid

Part I. Syntheses of Keto-ionylideneacetic Acids

Abstract

Methyl α-ionylideneacetates were oxidized with selenium dioxide to a mixture of methyl 3'-keto-β-ionylideneacetates and a small amount of methyl 4'-keto-α-ionylidene-acetates followed by treatment with active manganese dioxide. By a similar oxidation methyl 3'-keto-β-ionylideneacetates were prepared from methyl β-ionylidene acetates. Methyl 4';-keto-α-ionylideneacetates were obtained by oxidation of methyl α-ionylideneacetates with tert-butyl chromate. Dehydrobromination of methyl bromoionylideneacetate, obtained by bromination of methyl 2-trans-α-ionylideneacetate with N-bromosuccinimide, gave a mixture of methyl 2-trans-dehydro-β-ionylideneacetate and methyl 2-cis-dehydro-β-ionylideneacetate. The growth inhibitory activities of these sesquiterpene carboxylic acids and keto esters on rice seedlings were tested.