A synthetic approach to the actinophyllic acid molecular architecture

Compounds 3a and 3b with the 1-azabicyclo[4.2.1]nonane ring system present in actinophyllic acid, have been synthesized. The method involves the intramolecular acid induced cyclization of the azafulvene 7 (formed between indole-3-carbaldehyde 5 and the azocan-5-one ethyleneketal 4b) into 3b in 48–60% yield as the key reaction. X-ray analyses of 3a and 3b showed they have the ‘wrong’ stereochemistry (indole-anti to the 7-member ring) for its use as a potential intermediate in an eventual synthesis of actinophyllic acid 1.