THE PHASE TEST INTERMEDIATE AND THE ALLOMERIZATION OF CHLOROPHYLL a

Publisher Website
Google Scholar
Abstract
The phase test intermediate of methyl chlorophyllide a is generated in organic solvents by alkoxyl and hydroxyl ions. The intermediate is oxidized by oxygen and such oxidants as iodine, p-benzoquinone, and potassium permanganate. Different products are obtained depending on the solvent, the base used to generate the intermediate, and the oxidant. Three fractions are obtained from methanol containing oxygen and traces of magnesium methoxide. These are (1) Mg-purpurin 7-trimethyl ester, (2) Mg-purpurin 7-lactone-methyl ether-dimethyl ester, and (3) Mg-10-oxy-methyl pheophorbide a. The first and third fractions each make up 10-15% of the total oxidized pigment. Mg-"unstable" chlorin diester is obtained by oxidation with potassium permanganate of the phase test intermediate generated in pyridine by aqueous potassium hydroxide. Mg-10-methoxy-methyl pheophorbide a is obtained by oxidation with iodine of the phase test intermediate generated in methanol by magnesium methoxide (ca. 7%, w/v). It is concluded that allomerization of chlorophyll in alcoholic solution is due to oxidation by oxygen of traces of phase test intermediate. The visible and infrared absorption spectra of the allomerized derivatives are presented and discussed.