Enantiospecific synthesis and chiroptical properties of bicyclic enones

The enantiospecific synthesis of several bicyclic enones starting from enantiomerically pure (+)-(1S,5S)-bicyclo[3.3.1]-nonane-2,6-dione (1) was accomplished. The target enones 7-9 were obtained in high yield and purity by using a catalytic amount of benzeneselenic anhydride. (+)-(1S,5R)-bicy-clo[3.3.1]inonane-2,3,6-trione was obtained from diketone 1 by alpha-hydroxylation involving the use of iodine under basic conditions. The reaction included a ring closure/reopening sequence via oxatricyclo[4.3.1.0(3,8)]decane-10-one. It was shown that the latter triketone exists in enone/enol form.