Tandem Oxidative Dearomatizing Spirocyclizations of Propargyl Guanidines and Ureas

Treatment
of propargyl ureas or guanidines with iodosobenzene diacetate
results in an oxidative tandem amination/etherification dearomatizing
spirocyclization. This transformation leads directly to the complete
framework of the Leucetta alkaloids, spirocalcaridine
A and B.

通过对丙基脲或胍与碘代苯二甲酸乙酯的反应，可实现氧化偶联胺/醚化去芳构化螺环化反应。该转化过程直接导向了Leucetta生物碱的完整结构框架，包括螺卡卡尔丁A和B。