Y2 cadinene

Highly uMtr-diastereofacial selective cycloaddition of isoprene (2) with 4-isopropyl-2-cyclohexenone allowed a short regiocontrolled and stereocon-trolled synthesis [13] of jS-cadinene and (y2-cadinene, Scheme 3.3). High anti-diastereofacial selectivity also occurs in the Diels-Alder reaction of optically active cyclohexenones 6-9 (Figure 3.2), readily available from the chiral pool, with open chain dienes [14-16]. Their cycloadducts are valuable intermediates in the synthesis of optically active sesquiterpenes in view of the easy conversion of the gem-dimethylcyclopropane and gem-dimethylcyclobutane in a variety of substituents. 

Chromolaenin (108) and 1-acetoxydihydroisochromolaenin (109) are new sesqui-terpenoids which co-occur with eupatene (110) in several Chromolaena species. Experimental details have been provided for the stereospecific total synthesis of (+)- -cadinene (112) and (-)-y2-cadinene (113) from the known enol ether (111)... 

Both (+)- -cadinene (71) and ( )-y2-cadinene (72) have been synthesised from the previously known intermediates (73, R = Et, optically active) and (73, R = Me, racemic). (— )-y2-Cadinene is one example of the relatively small... 

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