IMPROVEMENTS IN THE SENSITIVITY OF INVERSE-DETECTED HETERONUCLEAR CORRELATION SPECTRA USING MICRO INVERSE PROBES AND MICRO CELLS - HMQC AND HMBC SPECTRA OF CARIBBEAN CIGUATOXIN - PRELIMINARY STRUCTURAL INFERENCES

Cignatoxins are extremely potent activators of voltage-dependent sodium channels and elicit gastrointestinal and neurologic dysfunction in humans. Because they are present only at extremely low levels, the acquisition of heteronuclear shift correlation nmr spectra has been very difficult Inverse-detected heteronuclear shift correlation experiments (HMQC and HMBC) have greatly increased sensitivity relative to older, heteronuclide-detected experiments. The use of micro inverse-detection probes has afforded a further dramatic increase in sensitivity relative to conventional 5 mm probe technology. Micro inverse-detection probes employed in conjunction with Shigemi micro nmr cells are shown to afford a further significant improvement in sensitivity which was necessary to acquire spectra on a sample of <0.1 mu mole of Caribbean ciguatoxin.