96.3 mg of the dry Mg salt of (+)-cis isohumulone ((+)-VIII) was dissolved in 1 mL of methanol. 3.1 mg (0.3 eq) of MgO was added, and the reaction mixture was stirred for five minutes. 30 mg of 10% Pd/C was added to the solution, and stirring was resumed. A hydrogen atmosphere was introduced by bubbling hydrogen gas into the solution. After 45 minutes the reaction was judged to be complete by HPLC, the stirring was stopped, and the hydrogen atmosphere was removed by opening the vial. 1 equivalent of sulfuric acid was added to the reaction mixture (pH˜1), and the reaction was filtered through a 0.2 mm syringe filter. The reaction vessel and filter were washed 2 times successively with ethyl acetate. The filtrate was concentrated in vacuo, redissolved in hexanes, dried over Na2SO4, filtered via a cotton pipette, and concentrated in vacuo and dried overnight at 0.070 mbar. 58.1 mg of (+)-KDT-500 was produced. Further purification was carried out via chromatography and crystallization.
