Further alkaloids common to ants and frogs: decahydroquinolines and a quinolizidine
1999
Jones, T.H. | Gorman, J.S.T. | Snelling, R.R. | Delabie, J.H.C. | Blum, M.S. | Garraffo, H.M. | Jain, P. | Daly, J.W. | Spande, T.F.
Three alkaloids--two minor decahydroquinolines (DHQs) and a major quinolizidine--were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1-3 with 1 again predominating. The common occurrence of alkaloids 1-3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
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