Of dendrobatid alkaloids

Two classes of dendrobatid alkaloids have potential dietary sources. The first are the pyrrolizidine oximes (32), whose carbon skeleton is identical to that of nitropolyzonamine, an alkaloid from a small millipede (33). Indeed, raising the dendrobatid frog D. auratus in Panama on leaf-litter arthropods, gathered weekly, resulted in skin levels of the... 

First Enantioselective Synthesis of Dendrobatid Alkaloids Indolizidine 2091 and 223J 53... 

Extracts from skins of the neotropical frog Dendrobates tricolor from Ecuador have given the alkaloid 8-hydroxy-6-(2-methylhexylidene)azabicyclo[4.3.0]non-ane (4), the structure and absolute configuration of which have been determined by X-ray crystallography of the hydrochloride salt. This alkaloid is the first structurally defined member of the pumiliotoxin A class of dendrobatid alkaloids. Spectroscopic studies (m.s. and n.m.r.) have allowed the formulation of the... 

The indispensable contribution of crystallography has been to establish the molecular formulas, the stereoconfigurations, and the absolute configurations of five quite different toxins representative of the five major classes of dendrobatid alkaloids. Each of the five substances had unexpected and novel chemical bonding. Knowledge of the structures from crystal structure analyses led to reevaluations of the spectral properties of analogs and congeners and to the definitions of the structures of more than 200 dendrobatid alkaloids. 

Most amphibian alkaloids are not as complex in structure as the steroidal batrachotoxins and samandarines. Of the 300 known amphibian alkaloids, most have been characterized from the skin extracts of frogs of the family Dendrobatidae and, hence, have been referred to as dendrobatid alkaloids. The major bicyclic classes of dendrobatid alkaloids are the histrionicotox-ins, decahydroquinolines, and pumiliotoxin-A class. Because of the presence of a piperidine ring in most dendrobatid alkaloids, they also have been referred to as piperidine-based alkaloids. 

Simple 2,5-disubstituted decahydroquinolines do not appear to have been reported to occur in Nature except in certain amphibians. Decahydroquinolines, like histrionicotoxins, occur in a range of dendrobatid frogs. These two classes of dendrobatid alkaloids often occur together in the same species or population. Indeed, the 19-carbon decahydroquinoline 269AB (or 269A and 269B) always appears to accompany the 19-carbon... 

Wrobleski, A., Sahasrabudhe, K., Aube, J. Asymmetric Total Synthesis of Dendrobatid Alkaloid 251F. J. Am. Chem. Soc. 2002,124, 9974-9975. 

Fora review of 7 recent approaches to pumiliotoxih-C [Habermehl (1998), Bach (1998), Comins (1993), Kunz (1999), Mori (2001), Stille (1993), Padwa (20(X))] see Sklenicka, H. M. Hsung, R. P. "Receht Approaches to c/s-Azadecalins Synthesis of Dendrobatid Alkaloid Pumiliotoxin C" Chemtracts-Organic Chemistry 2002, 15, 391-401. 

Wrohleski A, Sahasrabudhe K, Aube J. Asymmetric total synthesis of dendrobatid alkaloids preparation of indolizi-dine 25 IF and its 3-desmethyl analogue using an intramolecular Schmidt reaction strategy. J. Am. Chem. Soc. 2004 126(17) 5475-5481. 

Other Alkaloids. There remain a large number of dendrobatid alkaloids of unknown or poorly defined structures. Many of these are only trace... 

Such a protocol has been used to characterize a large number of dendrobatid alkaloids. Two additional alkaloids of the histrionicotoxin class were detected and characterized. These were histrionicotoxins 235 A and 259 (see Fig. 13). The structure of histrionicotoxin 259 has been confirmed by proton and carbon-13 magnetic resonance spectroscopy (255). Histrionicotoxins as a class are characterized by a major fragment ion (CsHioN) at m/z 96. All form O-acetyl derivatives and all of the eleven... 

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