Yield:-

Reaction Conditions:

Stage #1:(+/-)-humulone with trans-4-cyclohexene-1,2-diamine in isopropyl alcoholResolution of racemate;
Stage #2: with sulfuric acid in hexanes;water

Steps:

13.2B
Step 2B: Purification of (+)-humulone ((+)-IV) from racemic (+/-)-humulone (III); Solutions of racemic (+/-)-humulone (III) in methanol (10%, w/v) and 1S,2S-4-cyclohexene-1,2-diamine in methanol (10%, w/v) are formulated respectively. Both are mixed in equimolar amounts (approximately 3:1 by volume), methanol is evaporated, and the residue is re-dissolved in a minimal amount of 2-propanole (other solvents can be used, as for example t-butyl methyl ether, acetonitrile, ethyl acetate, or benzene). Crystals will form, consisting of the amine salt of (+)-humulone ((+)-IV), while the (-)-humulone ((-)-IV) salt will remain in solution. The crystals are filtered, dried, than mixed with hexanes and aq. sulfuric acid to liberate the free acid of (+)-humulone ((+)-IV). The hexane layer is separated, washed with brine, dried with sodium sulfate and evaporated to yield (+)-humulone ((+)-IV) as indicated by chiral HPLC.

References:

Carroll, Brian J.;Darland, Gary;Desai, Anuradha;Konda, Veera;Dahlberg, Clinton J.;Urban, Jan US2012/108671, 2012, A1 Location in patent:Page/Page column 18