Preparation and Purification of Hop Acids and Their Derivatives. Patrick Lu-ping Ting and Henry Goldstein, Miller Brewing Company, 3939 West Highland Blvd., Milwaukee, WI 53208. J. Am. Soc. Brew. Chem. 54(2):103-109. Accepted September 28, 1995.

Pure individual analogs and stereoisomers of the major alpha-acids, beta-acids, cis and trans-iso-alpha-acids, cis and trans-rho-iso-alpha-acids, tetrahydrodesoxy-alpha-acids, tetrahydro-alpha-acids, and cis and trans-tetrahydroiso-alpha-acids have been prepared and isolated using fractional recrystallization, complexation, pH partitioning, and various chromatographic techniques (including preparative normal phase and reverse phase). Their structures were determined by elemental analysis, (^1)H and (^13)C NMR, chirooptical methods, gas chromatography-mass spectrometry (MS), MS, UV, and high-performance liquid chromatography. The configurations of cis and trans-iso-alpha-acids were characterized to help establish the mechanism for the formation of rho-iso-alpha-acids. The stereochemistry of tetrahydroiso-alpha-acids, prepared from alpha-acids and beta-acids, has been clarified. The availability of these pure standards simplifies the analytical procedures, allowing the brewer to take full advantage of the various bittering agents. Keywords: Bittering compounds, Chiral separation, Hops, Hop acids, Hop derivatives.