20 アブシシン酸の電気化学 : 陰極反応の解析

概要

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Abscisic acid has an elelctrophilic side chain that might be involved in binding to receptor proteins. However, the electrochemical property of ABA remains unknown. We investigated the cathodic reaction of ABA and its methyl ester. In a buffer solution of pH 3,ABA was reduced at controlled potential to give a new cyclopropyl derivative, 4-(1-hydroxy-2,2,6-trimethyl-4-oxo-bicyclo[4.1.0]hept-7-yl)-3-methyl-but-3-enoic acid (1), in a high yield. Compound 1 would be formed by the following mechanism; an electron adds to the side chain, the electron localizes at C-5,and then C-5 attacks C-2' to form 1. Calculation by B3LYP method for ABA anion radical showed that C-5 had the highest Mulliken charge and spin density, being coincident with the above reaction mechanism. Compound 1 formed also at pH 7,but, at pH 10,1 was not formed, and one of products was 1'-deoxy-ABA. ABA methyl ester was reduced to 1 methyl ester at pH 3 and 7 as well as ABA. At pH 10,ABA methyl ester gave another major product, 3-methyl-5-(1,3,3-trimethyl-2,5-dioxo-cyclohexyl)-pent-3-enoic acid methyl ester. This dioxo compound would be derived from 1 methyl ester by migration of the side chain to C-2' under an alkaline condition. These elelctrochemical properties are characteristic of an ABA molecule.
植物化学調節学会の論文
2002-10-31