Occurrence and Significance of Decahydroquinolines from Dendrobatid Poison Frogs and a Myrmicine Ant:  Use of ¹H and ¹³C NMR in Their Conformational Analysis

Abstract

Structures for 2,5-disubstituted decahydroquinolines (DHQs) are reported for the two diastereomeric pairs cis-275B (14) and cis-275B' (15) and 5-epi-trans-269AB (18) and trans-269AB (19), all isolated from skin extracts of dendrobatid frogs, and for 5-epi-cis-275B' (16) and 5-epi-trans-275B (17) found in the extracts of virgin queens of a myrmicine ant [Solenopsis (Diplorhoptrum) azteca]. Detection of such DHQs in an ant, their first reported occurrence, strengthens a dietary hypothesis for the origin of the approximately 30 DHQs that have been detected in extracts of frog skin. NMR data on the two conformers of cis-decahydroquinoline permit assignment of ring conformations and stereochemistry to cis-DHQs of the "N-endo" type or the "N-exo" type. These conformations are also assigned on whether H-8a is equatorial or axial as determined with E-COSY or 1D-HOHAHA spectra.

Biosynthesis and function of polyacetylenes and allied natural products

“…A dietary hypothesis for the origin of poison-dart frog toxins was strengthened during the past decade by identifying the link between myrmicine ants and the accumulation of decahydroquinoline alkaloids in the amphibian's skin [265]. These heterocycles are related to frog-accumulated histrionicotoxin (21A) and gephyrotoxin (21B), which are high-affinity noncompetitive inhibitors of nicotinic acetylcholine receptors (Fig.…”

Bioactive alkaloids of frog skin: Combinatorial bioprospecting reveals that pumiliotoxins have an arthropod source

“…DHQs have been detected in myrmicine ants (13,14,20) including extracts from ants that were microsympatric in Panamá with a dendrobatid frog (D. auratus) that contained the same DHQ 195A as a major alkaloid (14). An extract from ants (Solenopsis sp.…”

Ammonia chemical ionization tandem mass spectrometry in structure determination of alkaloids. I. Pyrrolidines, piperidines, decahydroquinolines, pyrrolizidines, indolizidines, quinolizidines and an azabicyclo[5.3.0]decane

“…1 Alkaloids 253I and 253J were present in extracts from ants as reported. 8 The synthetic alkaloid (À)-1R,4S,10S-4-allyl-1- …”

“…8 While some of these alkaloids are synthetic, all of them represent structures or substructures widely distributed among natural products and, thus, such CI-MS/MS data will be useful in the structural determination of natural products, where the availability of material is scarce.…”