The chemistry of zerumbone. Part 5: Structural transformation of the dimethylamine derivatives

Zerumbone () and its 6,7-epoxide () react with ammonia and dimethylamine regio- and stereospecifically, affording monoamines , , and . All adducts have the same relative configuration at C2 and C3. The conjugate amination is thermodynamically controlled to arrive at a single diastereomer. At 15°C reacts with cyanide to give aminonitrile as the single product, while at 30°C, acyclic aminonitrile is also formed. The reaction with affords at 0°C bicyclic aminonitrile of the asteriscane skeleton, while at 30°C or higher temperature, mixtures of and tricyclic nitriles are obtained. Refluxing of , and in aqueous acetonitrile promotes scission of the zerumbone ring by retro-Mannich reaction to provide acyclic aldehydes , respectively. The dimethylamino group of , and is eliminated stereospecifically by Cope- and base-catalyzed eliminations to regenerate the zerumbone skeleton in the products , and . Cope elimination of results in a mixture of by deaminative transannular etherification.