Manchester NMR Methodology Group

Summary:
FESTA (Fluorine-Edited Selective TOCSY Acquisition) is a new 1D NMR method for efficient structure elucidation in mixtures of fluorine-containing species. It allows simplified ¹H spectra to be obtained that show only those protons that are in a spin system coupled to fluorine of interest.

Pulse sequence diagram:
The basic FESTA pulse sequence of generates ¹H spectra showing only those protons that are in a spin system containing a chosen fluorine. At the beginning, the favorable high equilibrium polarization and excellent chemical shift dispersion of ¹⁹F are exploited in the initial excitation of a fluorine resonance of interest. The resultant coherence is transferred to its proton coupling partner or partners, giving anti-phase magnetization in a doubly selective reverse INEPT (SRI) sequence element. A ¹H selective modulated echo (SME) then refocuses the ¹H-¹⁹F coupling to provide in-phase magnetization at the starting point of the final TOCSY transfer. The complete pulse sequence is thus a ¹⁹F-decoupled doubly selective ¹⁹F → ¹H refocused INEPT-TOCSY.

Downloads:
Bruker pulse program:
SRI-FESTA (right click and chose 'save ... as')
Selective fluorine reverse INEPT (SRI) (right click and chose 'save ... as')

Bruker pulse program for QNP probes:
SRI-FESTA_QNP (right click and chose 'save ... as')
SRI_QNP (right click and chose 'save ... as')

Experimental data:
Mixture of four pharmaceuticals: fluticasone propionate, rosuvastatin calcium and its precursor BEM, and fluconazole

Reference:
FESTA: an efficient NMR approach for the structural analysis of mixtures containing fluorinated species, L. Castañar, P. Moutzouri, T. Barbosa, C. Tormena, R. Rittner, A. Phillips, S. Coombes, M. Nilsson, G. A. Morris. Analytical Chemistry, 2018. DOI: 10.1021/acs.analchem.8b00753

Please note that copyright restrictions prevent us from placing the pdf files on our website, however, this article is open access and the pdf can be downloaded from ACS.