Dendrobates auratus

In an effort to identify possible sources of the 16 alkaloids found in the skin of the Panamanian poison frog Dendrobates auratus, ants from a total of 61 terrestrial nests were analyzed [124]. The alate queens of one species of myr-micine ants (Solenopsis (Diplorhoptrum) sp.) collected at Cerro Ancon were found to contain the decahydroquinoline (-)-ds-195A (112) which was also present as a minor alkaloid in the skin of the microsympatric population of D. auratus. Moreover, from wingless ants of two nests collected at Isla Taboga and identified as Megalomyrmex silvestrU the same workers isolated the stereo-isomeric 3,5-disubstituted pyrrolizidines rfs-251 K (117) and trans-251 K (118) in the same ratio 3 1 that was present in the skin of a microsympatric population of D. auratus (Fig. 20) [124]. 

The alkaloid 249H, Fig. (11), was isolated from the skin extracts of the poisonous frog Dendrobates auratus of the Isla Taboga of the Pacific coast of Panama [26]. A sample containing only traces of impurities was obtained by successive column chromatography of the methanolic skin extract. H and C NMR spectroscopy and correlation spectra were only consistent with a branched substituent, the first to be reported for simple indolizidines isolated from frog skin, and an unusual cw-fused trisubstituted indolizidine nucleus. 

Alkaloid profiles of three different populations of Dendrobates auratus were found to be considerably different [716]. Descendents of these frogs did not produce alkaloids unless they were raised on wild-caught insects [716], Thus, environmental factors have a significant role in either initiating or otherwise promoting alkaloid production in dendrobatid frogs. 

A novel approach has been developed towards the total synthesis of (+ )-allopumiliotoxin 339A (112), a minor consituent of skin extracts from the family of Panamanian poison frogs Dendrobates auratus, based on an intramolecular chromium(II)-mediated cyclization. Ketone 107, after a Homer—Emmons condensation, DIBAL reduction, and conversion to the bromide 109, is homologated based on Evans alkylation procedure [45] and transformed through a series of efficient reactions into the iodoolefin 110. 

Biosynthetically, little is known of the origin of these alkaloids. In a preliminary study, radioactive acetate and mevalonate were incorporated into skin steroids of frogs, while incorporation of these potential precursors into skin alkaloids was not detected (750). Neither radioactive cholesterol nor serine was significantly incorporated into the batrachotoxins. Three species, Phyllobates aurotaenia, Dendrobates pumilio and Dendrobates auratus were used in these exploratory biosynthetic studies. 

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