Recent developments in syntheses of the post-secodine indole alkaloids. Part III: Rearranged alkaloid types

Abstract

The third part of a planned review on developments in the field of total and formal total synthesis of the post-secodine indole alkaloids focuses on types of rearranged alkaloids, i.e. on the skeletons with altered connectivities next to the indol(e)ine moiety, especially with a new bond to N-1. It reviews the synthesis of melodane, goniomitine, chippiine/dippinine, lirofoline and tronocarpine alkaloids, as well as alkaloids of secoschizozygane/vallesamidine, schizozygane and isoschizozygane type. It covers the literature from approximately 1991 up to May 2011. A review with 115 references.

Vallesamidine and schizozygane alkaloids: rearranged monoterpene indole alkaloids and synthetic endeavours

“…The model studies paved the route for making hydroxyschizozygine and more dehydration methods could be screened therein to complete the total synthesis of schizozygine 26 (Scheme 23). 67 Therefore, starting from 178 , which was prepared through the same route as 173 , Hájíček and co-workers carried out the reductive rearrangement to 179 in 66% yield. However, ozonolysis of the terminal alkene failed to provide the desired alkene cleaved or cyclised product, probably due to the electron-rich indoline motif.…”

Asymmetric construction of pyrido[1,2-a]-1H-indole derivatives via a gold-catalyzed cycloisomerization

“…Polycycles containing indole units are prevalent ring systems distributed in many bioactive alkaloids and pharmaceuticals. 1 Gold-catalyzed cycloisomerizations of different types of allenyl indoles have contributed greatly to this topic: 2–10 In 2006, Widenhoefer and his group reported the pioneering work on the synthesis of tetrahydrocarbazoles and cyclohepta[ b ]indoles via a 6- and 7- exo cycloisomerization of 2-allenyl indoles ( Scheme 1a ). 4 As for 3-allenyl indoles, the gold-catalyzed 6- endo , 5 6- exo , 6 and 5- endo 7 annulations as well as [2 + 2] cycloaddition 8 successfully furnished the construction of varied indole scaffolds ( Scheme 1b ); however, annulations of N -allenyl indoles have been less explored: 9,10 Toste's group reported the construction of dihydropyrroloindole skeletons via a 5-exo cyclization of N -allenyl indoles ( Scheme 1(c1) ).…”

Selective syntheses of leuconolam, leuconoxine, and mersicarpine alkaloids from a common intermediate through regiocontrolled cyclizations by Staudinger reactions

“…Leuconolam, leuconoxine, and mersicarpine alkaloids showcase the incredible structural diversity of natural products. These monoterpene indole alkaloid families, though sharing the same biogenetic origin, 1 present distinctive skeletons with three completely different polycyclic patterns ( 1–6 , Fig. 1 ).…”