Chapter 4 Dibenzazonine Alkaloids

Abstract

Publisher Summary This chapter describes the occurrence and classification, structure determination, synthesis, biosynthesis, pharmacological properties, and related alkaloids: dibenzazecines. Dibenzazonines are found in plants of the families Menispermaceae, Leguminosae, Fumariaceae, and Papaveraceae, and only eight naturally occurring dibenzazonines are known. Shamma and Moniot classified dibenzazonines into two groups: type A, which comprises the fully oxygenated bases, and type B, which includes alkaloids that have undergone a net deoxygenation with respect to their biogenetic precursors. The first group is represented by erybidine (1) and crassifolazonine (2), which both have substitutes at C-2 and C-3 but differ in the oxygenation pattern of ring C. Alkaloids of type B are more numerous and include the unusually tetrasubstituted protostephanine (3) and the trisubstituted laurifonine (4), laurifine (5), laurifinine (6), neodihydrothebaine (7), and bractazonine (8). Dibenzazonines have been synthesized by three general approaches: (A) construction of the azonine ring from an appropriately substituted biphenyl derivative, (B) formation of the aryl–aryl bond, and (C) by rearrangement of various types of alkaloids. The alkaloid protostephanine exerts a moderately strong and persistent hypotensive effect. Most of the other compounds show some central nervous activity.