Japanese hop ether

Japanese Hop Ether has been prepared by both an intermolecular and an intramolecular PKR. In Kerr s intramolecular version, it... 

Karahana ether (196), isolated from Japanese hops, is also a 1,1,2,3-tetra-methylcyclohexane derivative, and has been synthesised by Coates and Melvin by a route that they suggest may resemble the biogenetic pathway.Their synthesis consists in cyclising geranyl acetate (194) with benzoyl peroxide in the presence of cupric saltsand hydrolysing the resulting mixture to the corresponding diols, from which the cis-diol (195) is separated and converted to the ether with p-toluenesulphonyl chloride in pyridine at room temperature. 

In a later study, the aroma constituents of a Bavarian (Pilsener) beer brewed in Hallertau, near Munich, which possessed a desirable fine hop aroma, was examined [58]. Neither the terpenes and sesquiterpenes nor the methyl esters characterized in hop oil were detected but fraction IV (Table 13.6), which contained terpenoids and sesquiterpenoids, possessed an intensive pleasant hoppy odour. Noteworthy amongst the identified constituents are the cyclic ethers (80)-(86) first found in Japanese hops, the flowery notes of which contribute to hop aroma, and the sesquiterpenoids derived from humulene such as humulene epoxide I, humulene epoxide II, humulol, and humulenol II. Similar results were found with American beers [60, 86]. Humuladienone (79)... 

Hop ether (136) and karahana ether (139) are monoterpenoid compounds which occur in Japanese hop (Shinshu-wase) 426), while the occurrence of (-h)-matatabi ether (138) and of its isomer (137) is limited to the essential oil of Actinidia polygama Franch. et Sav. (Ternstroemiaceae) 261, 716). 

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