Synthesis and Reactions of 3, 7-Cycloerythrinan : Skeletal Rearrangement of 2, 7, 8-Trioxoerythrinans to 4-Oxo-4H-pyrido[2, 1, -a]isoquinolines

Treatment of 2, 7, 8-trioxoerythrinan derivatives with anhydrous phosphoric acid or Lewis acids gave 3, 7-cycloerythrinan derivaties via an intramolclar aldol condensation. The structures of the products were established by spectroscopic and chemical means. Further treatment of the 3, 7-cycloerythrinans with anhydrous phosphoric acid resulted in skeletal rearrangement to yield 6, 7-dihydro-4-oxo-4H-pyrido[2, 1-a]isoquinolines, whose structures were also determined mainly by spectroscopic means.