In the space of 10 years, the number of alkaloids isolated from this family has increased from the seven reported by Popelak and Lettenbauer (15) in their earlier brief review to more than 25 bases which have fully characterized structures. Consequently, the present chapter is written as a comprehensive review of the subject through 1979. At present, four different ring systems have been identified. These will be referred to as the mesembrine subgroup, the joubertiamine type, the pyridine-dihydropyridone class, and the tortuosamine subgroup. Representative alkaloids belonging to each of these ring systems are shown in Scheme 1. The mesembrine subgroup is by far the largest, comprising 15 bases with known structures...
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