Design of the substrate for oxidative phenol coupling. An efficient synthesis of the C-homoerythrinan skeleton

Abstract

Attention is drawn to the importance of conformational interactions in the cyclisation step of intramolecular phenolic coupling reactions. Careful design of the substrate molecule to minimise these interactions should result in better yields for this important strategy of natural product synthesis. The hypothesis is supported by the contrast in the behaviour of the 1-phenethylquinoline (5) and the 1-phenylacetamidoquinoline (8): when these diphenols were oxidised under identical conditions, (5) gave a complex intractable mixture whereas (8) gave in 67% yield the dienone (23) with the C-homoerythrinan skeleton.