A versatile method of synthesis of the quaternary benzo [c] phenanthridine alkaloid (1), having a tertiary benzo [c] phenanthridine skeleton, from the norbase (3) is described. Treatment of the norbase (3) with sodium borohydride in formic or in acetic acid gave the N-methyl-(5) or the N-ethyl-(7) dihydrobase, respectively, in good yield. The N-methyldihydrobase (5) could also be prepared by treatment of the norbase (3) with sodium borohydride and dimethyl sulfate in hexamethylphosphoric triamide. The dihydrobases (5 and 7) were readily convertible to the corresponding quaternary benzo [c] phenanthridine alkaloids by oxidation with Jones reagent or with 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone (DDQ) in good yields. In addition, we found that the air-oxidation of the carbanions derived from the ψ-cyanides (11) of the quaternary bases (1) gave the corresponding oxybases (10) in excellent yields.
本文介绍了一种从
硼酸基(3)合成具有三级
苯并[c]菲啶骨架的四级
苯并[c]菲啶生物碱(1)的通用方法。用
硼氢化钠在
甲酸或
乙酸中处理去甲基 (3),可分别得到 N-甲基-(5)或 N-乙基-(7)二氢化酶,收率很高。在六甲基
磷酸三酰胺中用
硼氢化钠和
硫酸二甲酯处理
硼氢化钠碱(3),也可以制备出 N-甲基二氢化酶(5)。用琼斯试剂或 2,3-二
氯-5,6-二
氰基-1,4-苯醌(
DDQ)进行氧化,二氢化酶(5 和 7)很容易转化为相应的季
苯并[c]菲啶生物碱,而且收率很高。此外,我们还发现,通过空气氧化从季
铵盐碱(1)的ψ-
氰化物(11)中得到的碳离子,可以得到相应的氧碱(10),而且收率极高。