ラジカルカスケード反応を用いるフェナンスロインドリジジン骨格の簡便構築法

抄録

Phenanthroindolizidine skeleton bearing angular methyl group 5 was constructed by treatment of bromo alkene 3 with Bu₃SnH in the presence of ACN (azobiscyclohexanecarbonitrile) in boiling toluene. This process involved continuous 6-endo-trig cyclization of aryl radical and 5-endo-trig cyclization of the resulting &alpha-amidoyl radical. Compound 7 which was reported as hypoestestatin 1 was obtained by reduction of 5 with lithium aluminum hydride. However, spectral data of 7 were not in accord with those of hypoestestatin 1. Then, we assumed that the real structure of hypoestestatin 1 was 8, and we synthesized 8 by the radical cascade reaction of 4 giving 6, followed by reduction of 6. Unfortunately, spectral data of compound 8 were not again in accord with those reported for hypoestestatin 1.

fig.1