Chemistry of secologanin. Part 7: Chemical fragmentation of secologanin: biomimetic transition from the aliphatic into the aromatic skeleton

2008

Molecules

Strictosidine, the precursor of more than 2,500 indole alkaloids, was isolated from four species of three plant families. By searching the Dictionary of Natural Products on DVD it was found that about 150 indole alkaloids were obtained from the same species (coalkaloids), which is a direct proof of their common origin. On the base of their three-dimensional structure, taxonomic properties and standard reaction mechanisms an extended network was established which involved the four fundamental skeletons, the three types of carbon framework in the secologanin subunit and all major groups of indole alkaloids derived from secologanin and tryptamine (except a few minor groups, in which only less then 10 alkaloids were known). The system was extended to the heterodimer indole alkaloids and the quinoindole alkaloids as well.

Section: The Central Role Of Stemmadenine and Secodine Derivativesmentioning

confidence: 99%

Rigorous Biogenetic Network for a Group of Indole Alkaloids Derived from Strictosidine

2008

Molecules

“…An experimental analog of this bond cleavage was presented earlier. 14 The formation of the melodan alkaloids is the result of a long molecular evolution, as is briefly outlined in Scheme 2. In the coupling reaction of 1 and 2, strictosidine 3 is formed, which, after deglucosylation, affords the large subclass of the type Iα (vincosan) alkaloids, i. e. compounds having C-3 of the secologanin subunit attached to the α position of the indole ring.…”

Section: Genealogy Of the Melodan Alkaloidsmentioning

confidence: 99%

Molecular interrelations in the Melodinus alkaloids

2006

Arkivoc

Structural and chemotaxonomical data as well as consideration of standard organic reaction mechanisms provided a coherent picture about the probable formation of the small but characteristic group of Melodinus alkaloids in the plant family Apocynaceae. All 14 alkaloids could be classified into the melodan skeleton and its rearranged version and derived from 18,19-didehydrotabersonine as parent compound.

“…The rearrangement formally involves the cleavage of the strategic bond C-15-C-16 of strictosidine and reattachment of the C 3 -unit through its C-17 atom either to C-14 or C-20, respectively. This strategic bond could be cleaved also under acidic or basic conditions in secologanin 16 and strictosidine as well as their simple derivatives. However, the details of this point are outside of the subject of the present study.…”

Section: The Systemmentioning

confidence: 99%

“…As it was already mentioned, this strategic bond could be cleaved under acidic or basic conditions even in secologanin, as well as in strictosidine derivatives. 16 Seven close derivatives of 35 were isolated from Apocynaceae species. These structures might be considered as precursors or intermediates on the way toward the formation of the type II and type III, that is, 'rearranged' indole alkaloids.…”

Section: Isomerization and Fragmentations In The Strychnan Skeletonmentioning

confidence: 99%

Reaction mechanism and chemotaxonomy in the formation of the type I indole alkaloids derived from secologanin

J of Physical Organic Chem

2006

The history of biomolecules is written into the structure of their educts and products. The group of indole alkaloids derived from secologanin and tryptamine has more than 2000 individual compounds isolated mainly from the Rubiaceae, Loganiaceae, and Apocynaceae plant families and having strictosidine as a common precursor. To detect their history in its main lines, the compounds isolated from the same or closely related species were ordered as intermediates into reaction sequences according to the principles of basic organic reaction mechanisms. The analysis is restricted to the main lines of the monomeric alkaloids having one un-rearranged secologanin subunit (type I) closed to N-4 atom and one tryptamine subunit in intact or cleaved form. Deglucosylation of strictosidine opens the way for different types of cyclizations. Subsequent key bond-braking and bond-making reactions involve bond C-5-C-6 in the tryptamine subunit, bond C-15-C-16 in the secologanin subunit, and bond C-3-C-7 at the attachment of the two subunits, and indicate the crucial importance of a strong long-range through-bond interaction between the two nitrogen atoms. With a few principles it was possible to interpret such important biogenetic-type steps, as the formation of the akuammidan and akuammilan bridges, the transition from the vincosan into the strychnan and further to the aspidospermatan skeleton, the breaking and transformation of the side-chain of the triptamine subunit and the cleavage of the strategic bond C-15-C-16 toward the formation of the formation of type II and type III alkaloids.