Synthesis of Homoprotoberberines and 8-Oxoprotoberberines by Sequential Bicyclization of Phenylacetamides

The reaction of phenylacetamides with oxalyl chloride/Lewis acid provides a convergent, high-yield entry to C-homoprotoberberine and 8-oxoprotoberberine alkaloids from available starting materials. This approach was used to synthesize 8-oxopseudopalmatine starting from N-[β-(3′,4′-dimethoxyphenyl)ethyl]-3,4-dimethoxyphenylacetamide. Some C-homoprotoberberines exhibit significant cytotoxicity against human breast carcinoma cells.