Strychnane alkaloids

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... 

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 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. 

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. 

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