The Anti-Iso-α-Acids: Concept and Review of Current Research. Leo De Taeye, Denis De Keukeleire, and Maurice Verzele, Laboratory of Organic Chemistry, State University of Ghent, Krijgslaan, 271 (S.4), B-9000 GENT (Belgium). J. Am. Soc. Brew. Chem. 39:0024, 1981.

Anti-iso-α-acids are positional isomers of iso-α-acids. They are formed in isomerization reaction mixtures of hop α-acids. The anti-isohumulones, 5-(3-methylbutanoyl)-2-(3-methyl-2-butenyl)-4-hydroxy-4-(4-methyl-3-pentenoyl)-cyclopentane-1,3-diones, and some of their derivatives were isolated from isomerization reaction mixtures of humulone. Total yield of the new compounds belonging to the antiseries exceeds 10%. Utilization of the antimembers in the brewing process is high. The anti-iso-α-acids are the most bitter-tasting hop acids known today.

Keywords: Anti-iso-α-acids, Deacylated anti-iso-α-acids, Hop α-acids, Iso-α-acids, Isomerization