Diels capnellene

In the laboratory of K. Fukumoto, the stereoselective total synthesis of (+)-A -capnellene was carried out using an intramolecular Diels-Alder reaction to obtain a tricyclic 5-5-6 system. Since the target molecule was a triquinane, the six-membered ring had to be converted to a five-membered one, a transformation achieved by a Wolff rearrangement. The required a-diazo ketone was prepared via a deformylative diazo transfer reaction and was photolyzed in methanol. The ring-contracted methyl ester was isolated as a 3 1 mixture of separable isomers favoring the a-isomer. 

A stereoselective total synthesis of ( )-A -capnellene via the intramolecular Diels-Alder approach. /. Chem. Soc. Chem. Commun., 646-647. 

---