The chemistry of hop constituents. Part XXIX. A synthesis of (±)-isohumulone

Abstract

(±)-Isohumulone has been synthesised by the reaction between 2-hydroxy-2,6-dimethylhept-3-yn-5-enoyl chloride and ethyl 5-methyl-2-oxohexanoate followed by cyclisation to give 4-hydroxy-3-(2-methylbutyryl)-4-(4-methylpent-1-yn-3-enyl)cyclopentane-1,3-dione, reaction of which with 1-bromo-3-methylbut-2-ene under alkaline conditions followed by hydration of the acetylenic group afforded (±)-isohumulone in low overall yield.