Some More Alkaloids Having Diverse Skeletal Patterns

Abstract

Alkaloids are structurally most diversified natural products. They offer simple (e.g., in Chaps. 16– 22) to very complex structural patterns (e.g., in Chaps. 27 and 28). Their biological activities claim a special attention for drug discovery (Chap. 33). Some representative members of a few different classes of alkaloids have been included and discussed in Chaps. 15– 29. To illustrate further structural diversifications several examples of alkaloids (Fig. 30.1) not included in earlier Chapters are cited in this chapter with references. The stereostructures of these alkaloids have been settled in the usual way by suitable combinations of the following: degradation, spectral analysis, synthesis, chemical correlations, applications of some rules (e.g., Prelog’s rule, Bredt’s rule, etc.), and occasionally by ORD studies and X-ray crystallography. A plethora of alkaloids with diversified structural patterns belonging to different classes appearing in the literature during 1960s [1] and till 1988 [2] have been compiled with some leading references concerning their isolation/structure/stereochemistry/synthesis. Quite a number of review articles on the uses of heterocycles in the synthesis of alkaloids have collectively appeared in an edited book in 2011 [3]. They display wide structural variations of alkaloids.