Studies toward Total Synthesis of Non-aromatic Erythrina Alkaloids.(3). Synthesis of β-Erythroidine Skeleton (β-Erythroidan)

The β-erythroidine skeleton (β-erythroidan) was synthesized as the 8-oxo derivative by two different routes. One is a four-step synthesis starting from 15, 16, 17-trimethoxy-8-oxo-cis-erythrinan (2) via ozonolytic cleavage of the aromatic ring. The other is a five-step synthesis starting from D-furano-8-oxo-cis-erythrinan (13) via oxidative cleavage of the furan ring. The two routes gave the same 14, 17-dihydro-16(15H)-oxaerythrinan-8, 15-dione (1) (8-oxo-β-erythroidan). 8-Oxo-β-erythroidan (1) was not identical with the compound previously reported by Kitahara and Matsui, suggesting that their synthesis is questionable.