The C-19 methyl substituted sarpagine-macroline-ajmaline alkaloids: Diversity, occurrence, bioactivity, and synthesis

Abstract The C-19 methyl substituted sarpagine/macroline/ajmaline alkaloids are an emerging group of structurally and biosynthetically related alkaloids. To date, there are more than 70 alkaloids that can be categorized as belonging to this subgroup. About two dozen of these alkaloids have been reported to possess useful and important bioactivity ranging from anti-inflammatory to anticancer, while the rest of the alkaloids remain mostly unexplored. The total synthesis of more than a dozen of these alkaloids has been reported, to date. This chapter is a compilation of the monomeric alkaloids which possess the C-19 methyl substituent (as a part of the core ring system), which belong to either the sarpagine, macroline, or ajmaline alkaloid series reported recently. An up-to-date discussion of their isolation from various plant sources (and corresponding plant morphology), proposed biosynthetic studies, as well as reported biosynthesis are included. In addition, the partial or formal, as well as the total syntheses have also been included.