Humulinic acid dehydrated

Fig. 68. Structural formulae of dehydrohumulinic acid (26), cyclized dehydrohumulinic acid (144,145), dehydrated humulinic acid (146) and dehydrated cohumulinic acid (147).

Upon prolonged boiling of humulone or of the humulinic acids in NaOH 2 N (3 to 8 h) dehydrated humulinic acid or 2-(3-methylbutanoyl)-5-(3-methyl-2-butenylidene)-3-hydroxy-2-cyclopentenone (146, Fig. 68) is formed (30%). The melting point is 87°C and the UV absorption maxima are situated at 355 nm in acidic methanol, at 272 nm and 322 nm in alkaline methanol. Compound 146 has a distribution coefficient of 0.36 in the two-phase system iso-octane aqueous buffer pH 7.6. The pK value in 60%... 

Humulone (3.62 g 1 x 10 mol) or humulinic acid (2.66 g 1 x lor mol) is dissolved in a minimum amount of MeOH and added to warm NaOH 2 N (125 ml). The solution is refluxed during 3 to 8 h, cooled, acidified with HCI 6 N and extracted with hexane. The crystalline residue, after evaporation of the solvent, is separated by CCD in the two-phase system iso-octane aqueous buffer pH 7.6. The K value of dehydrated humulinic acid (30%) is 0.36 and the melting point is 87°C. 

Upon hydrogenolysis of the humulinic acids in acidic medium and subsequent GC-MS analysis (see 8.4.3.2.) 2-(3-methylbutyl)-5-(3-methylbutylidene)-3-hydroxy-2-cyclopentenone (141, Fig. 66) is detected (51). This compound is in fact the dehydrated dihydrodeoxohumulinic acid. The double bond should be in the exo... 

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