Strychnan

According to KisakQrek and Hesse (4), eight of these types are named vin-cosan, vallesiachotaman, corynanthean, strychnan aspidospermatan (all these... 

No vincosan alkaloids were found in Tabemaemontana species, and only a few examples of vallesiachotaman, strychnan, aspidospermatan ebuman, and tacaman alkaloids have been detected. 

The intramolecular version of the Heck reaction has been extremely fruitful, enabling elegant synthesis of many complex molecules [68, 69]. The Mori-Ban indole synthesis (Section 1.10, vide infra) is a good example of such method. In addition, Rawal et al. carried out an intramolecular Heck cyclization of pentacyclic lactam 55 with a pendant vinyl iodide moiety [70]. Employing Jeffery s ligand-free conditions, 55 was converted to a hexacyclic strychnan alkaloid precursor 56 with complete stereochemical control... 

An elegant and efficient stereocontrolled total synthesis of strychnine has been achieved by applying intramolecular Diels Alder and Heck reations as key reactions [47]. An unusual exo-Diels-Alder reaction of 102 afforded 103, which was converted to the vinyl iodide 104. The Heck reaction of 104 using Pd(OAc)2 gave the hexacyclic strychnan system 105 smoothly in 74% yield. Hydrolysis of 105 afforded isostrychnine, which was isomerized to strychnine (106) under basic conditions. 

The subsequent steps from geissoschizine to form the Strychnos alkaloids, the secodines, the Aspidosperma alkaloids and the iboga alkaloids remain speculative, based on low levels of incorporation of early precursors or alkaloid time course studies. Joining C-2 and C-16 while moving C-3 to C-7, yields the strychnan skeleton... 

Kuehne, M.E., and Xu, F., Syntheses of strychnan- and aspidospermatan-type alkaloids. Part 10. An enantioselective synthesis of (-)-strychnine through the Wieland-Gumhch aldehyde, 7. Org. Chem., 63, 9427, 1998. 

Mitraphylline IP (strychnan) Mitrgyna rotundifolia Weak depressant, hypotensive... 

Strychnine ip (strychnan, dimer ) Strychnos toxifera Skeletal muscle relaxant... 

Gan C-Y, Low YY, Etoh T, Hayashi M, Kraniyama K, Kam TS. Leuconiocines A-G and ( )-ebumamaline, biologically active strychnan and ebuman alkaloids from Leu-conotis. Prod 2009 72(12) 2098-103. 

C = corynanthean-type of alkaloid I = ibogan-type of alkaloid S = strychnan-type of alkaloid... 

Kuehne ME, Xu F. Total synthesis of strychnan and aspido-spermatan alkaloids. 3. The total synthesis of ( )-strychnine. J. Org. Chem. 1993 58(26) 7490-7497. 

The quasidimer longicaudatine (8), with a corynanthean-strychnan skeleton, is present in a variety of African and Asian Strychnos species and has now been found for the first time in an American species, S. trinervis (Table 1.4). Its structure is based largely on interpretation of its NMR spectra, especially the spectrum, which is very similar to those of the relevant parts of geissoschizine and strychnine. The compound is presumed to be derived via an enamine coupling between Wieland-Gumlich aldehyde and geissoschizal (475, 479). 

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