Organocatalytic enantioselective total synthesis of (-)-arboricine.

The tetracyclic indole alkaloid (-)-arboricine has been prepared using an asymmetric organocatalytic Pictet-Spengler reaction as the key step followed by a diastereoselective Pd-catalyzed iodoalkene/enolate cyclization. The absolute stereochemistry was unequivocally proven by X-ray crystallographic analysis and appeared to be opposite to the published structure in the original paper.