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.

Citation

Spande, T.F.; Jain, P.; Garraffo, H.M.; Pannell, L.K.; Yeh, H.J.C.; Daly, J.W.; Fukumoto, S.; Imamura, K.; Torres, J.A.; Snelling, R.R.; Jones, T.H. 1999. Occurrence and significance of decahydroquinolines from dendrobatid poison frogs and a Myrmicine ant: Use of 1H and 13C NMR in their conformational analysis. Journal of Natural Products. 62:5-21.