SYNTHESIS OF THE ALL-CIS-PERHYDRONAPHTHO[ 1,8-BC]FURAN SYSTEM BY PHOTOCYCLIZATION

The diketone 3 was reduced to the diol which then was transformed to t he tetracyclic diketal 5 by treatment with sodium in ethanol. Protecti on of the remaining hydroxy group was followed by hydrolysis of the di methylketal. The resulting ketone 7 was stereoselectively converted to the tertiary alcohol by methyl magnesium chloride. Acidic retrograde aldol reaction of the tertiary alcohol led to the decalindione 10, whi ch was partially dehydrogenated by cupric chloride under basic conditi ons. The resulting endione 1 cyclized by light induced hydrogen abstra ction and collapse of the resulting diradical to the perhydronaphtho[1 ,8-bc]furan derivative.