Abstract
Two dibenzazecine derivatives (8 and 9) were readily prepared as a mixture by a photochemical reaction of the bromophenolic compound (6). Reduction of the mixture (8 and 9) with diborane followed by column chromatography on silica gel gave the secondary amine (11), which was converted into the diene derivative (12) by Birch reduction. Treatment of 12 with 5% hydrochloric acid, followed by O-methylation with diazomethane provided the homoerythrina base (1) in 21% yield.On the other hand, the base (1) was also prepared via Birch reduction of the amine (9). The mixture of the amides (8 and 9) was reduced directly with sodium in liquid ammonia and subjected to fractional crystallization to yield 13. On treatment with 5% hydrochloric acid, 13 produced the homoerythrina derivative (14), which was methylated with diazomethane to afford 15. Finally, the homoerythrina base (1) was obtained by reduction of the amide group in 15.
