The Sarpagine Group

The stereochemistry of the ethylidene group could not be decided from these experiments but it came from the results of the X-ray work carried out on the correlated compounds (Chart IV), macusine A (28) and akuammidine (27). 

The ethylidene moiety in these alkaloids does not hydrogenate readily in alcohols if platinum is used, but goes well in the presence of acetic acid, hydrogen usually coming in such a way as to end up with the ethyl in the isoajmaline configuration (20, 23, 63). However, with palladium as a catalyst in alcohol, sarpagine has apparently given only the alternative dihydro product (16, 62). 

Some of the transformations indicated in Chart IV can be regarded as mimicking a plausible biosynthetic route (Chart I) and the only important 

Upon hydrogenation (30) of voachalotine, the ethyl formed is in the same configuration as in ajmaline, which stands in contrast to the course of the(hydrogenation evinced by deoxysarpagine itself. The nature of the iV-methyl in voachalotine has been thoroughly studied by physical methods and compared with many model compounds (64). 

The structures of the simple analogs of sarpagine shown in Table III were deduced as a natural consequence of a proper analysis of the spectral data routinely measured today. Even so, occasional problems are caused 

Alkaloid Ri R-2 Other Melting point (°C) [a]o (CHCla) Source (structure  

In the case of peraksine [RP-5 (27)] it was shown to have the formula C19H22N2O2, a fact not readily derived from combustion analysis since the free base crystallized from alcohol in a hydrated form (27). It has also been observed that this water of solvation could be displaced by chloroform (20). Peraksine has UV-absorption typical of a 2,3-disub-stituted indole and reacted with benzoyl chloride to form an 0-benzoyl derivative. The second oxygen was apparently present as a cyclic ether when it was found that although peraksine did not react with hydrazine derivatives, it was reducible with sodium borohydride to furnish a diol (mp 290°-291° [a]j) - -41° in Py diacetate, mp 103°-105°). This diol readily lost the elements of water upon acid treatment to afford a new ether, deoxyperaksine, 230° change in crystalline form (mp 255°-257°). Because of these properties peraksine was considered to possess a cyclic hemiacetal moiety. 

The mass spectrum of peraksine shows peaks m/e 182, 169, 168, and 156 characteristic of tetrahydro-j3-carbolines. These peaks as well as an intense peak at m/e 309 (M-1) suggested a sarpagine-like structure. 

The NMR-spectrum of peraksine showed that there were no olefinic bonds to which protons were attached and no ethyl group could be detected instead there seemed to be a terminal methyl (doublet cent. d at 1.28 ppm) of the type CHa-CHX (X = 0 or N) and a multiplet i .0 ppm) thought to be due to —CH2O—. 

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This alkaloid is a member of the sarpagine group, and its structure was readily derived by simple transformations (58) which, among others,... 

For unexplained reasons the formulae intended for page 122 (Table II) in our recent review "The Sarpagine Group of Indole Alkaloids" in Vol. 32 of the present series were accidently replaced by the formulae intended for page 123, and which were thus presented twice. The correct page 122 is reproduced below (next page). 

In Chapter 2, Lounasmaa, Hanhinen, and Westersund present an extensive review of the isolation, spectroscopic characterization, and syntheses that have been conducted in the past 30 years on the sarpagine group of alkaloids. Revised concepts regarding the biogenesis of these alkaloids are discussed. 

Another route to the 16,21-seco system, apart from the reductive cleavage of catharanthine derivatives (27), lies in the use of a fragmentation reaction originally applied in alkaloid chemistry to the sarpagine group (32). Voacanginol 0-tosylate (Via) (mp 135°-140°) decomposed... 

Shukla K, Narain JP, Puri P, Gupta A, Bijiani RL, Mahapatra SC, Karmarkar MG (1991) Glycaemic response to maize, bajra and barley. Indian J Physiol Pharmacol 35 249 54 Sheludko Y, Gerasimenko 1, Kolshom H, Stockigt J (2002) New alkaloids of the sarpagine group from Rauvolfta serpentina hairy root culture. J Nat Prod 65 1006-1010... 

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