Ajmalan

Ajmalan is a parent hydride used in the IUPAC nomenclature of natural products and also in CAS nomenclature.International Union of Pure and Applied Chemistry (1999). " [http://old.iupac.org/publications/pac/1999/pdf/7104x0587.pdf Revised Section F: Natural Products and Related Compounds (IUPAC Recommendations 1999).] " "Pure Appl. Chem." 71: 587–643.] It is a 20-carbon alkaloid with six rings and seven chiral centres.

The name is derived from ajmaline, an antiarrhythmic alkaloid isolated from the roots of "Rauwolfia serpentina" [Siddiqui, S.; Siddiqui, R. H. (1931). "J. Indian Chem. Soc." 8: 667–80.] which is formally a dihydroxy-derivative of ajmalan. The –an ending indicates that ajmalan is partially saturated. Ajmaline itself is named after Hakim Ajmal Khan, a distinguished practitioner of the Unani school of traditional medicine in South Asia. [Ahmed Nasim Sandilvi (2003). " [http://www.dawn.com/weekly/science/archive/030412/science5.htm Salimuzzaman Siddiqui: pioneer of scientific research in Pakistan.] " "Daily Dawn", 2003-04-12. Retrieved on 2007-07-19.]

The absolute configuration of the seven chiral carbon atoms in ajmalan is defined by convention, as is the numbering system. The stereochemistry is the same as that in naturally-occurring ajmaline, and corresponds to (2"R",3"S",5"S",7"S",15"S",16"R",20"S") using conventional numbering.

Ajmalan can be systematically named as:(1"S",4"S",5"S",7"S",8"R",16"S",17"R")-4-ethyl-9-methyl-2,9-diazahexacyclo [14.2.1.0^2,7.0^5,18.0^8,16.0^10,15] nonadeca-10,12,14-trieneor as:(2"S",3"S",5"S",6a"S",11a"R",11b"S",12"R")-4"H",11"H"-3-ethyl-11-methyl-1,2,3,5,6,6a,11a,11b-octahydro-2,5,6a-(epiethane [1,1,2] triyl)indolo [2,3-"c"] quinolizine.Note that the numbering of the atoms in the systematic names is different from the conventional numbering of ajmalan. [The numbering is also different between the von Baeyer name and the fusion name, given the different conventions which apply to the two methods of nomenclature.]

The ajmalan skeleton is similar to those of certain other alkaloids, and ajmalan could also be given the following semisystematic names::(2β,5β,16"R",20β)-1-methyl-1,2,19,20-tetrahydro-5,16-cyclo-16a-homo-17-norakuammilan;:(2β,5β,7β,16"R",20β)-1-methyl-2,7-dihydro-5,16:7,17-dicyclocorynan;:(2β,7β,16"R",20β)-1-methyl-2,7,19,20-tetrahydro-7,17-cyclosarpagan;:(2β,3α,7β,20β)-1-methyl-2,7,19,20-tetrahydro-3,4:7,17-dicyclo-22-norvobasan;:(2β,5β,7β,16"R",20β)-1-methyl-2,7-dihydro-5,16:7,17-dicyclo-17-secoyohimban.However, the relative complexity even of these names justifies the use of ajmalan as a defined parent hydride in alkaloid nomenclature.

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