CHEMISTRY OF HOP CONSTITUENTS XI*. SOME OBSERVATIONS ON THE ISOMERIZATION OF HUMULONE

It is suggested that the bitter bacteriostatic principles in beer which are derived from humulone, cohumulone and adhumulone should be termed isohumulone A, isocohumulone A and isoadhumulone A respectively. These materials have been isolated from beer and some of their characteristics are described. The product obtained when humulone is boiled in alcoholic alkaline solution is shown to be a complex mixture. Relatively pure isohumulone A can, however, be obtained by treating humulone either with hot aqueous alkali or with cold potassium tertiary butoxide in tertiary butanol. The racemization of humulone by heat and its behaviour towards acid have been investigated.