Fast 19F Magic Angle Spinning NMR Crystallography for Structural Characterization of Fluorine-Containing Pharmaceutical Compounds

Anal Chem. 2021 Jun 15;93(23):8210-8218. doi: 10.1021/acs.analchem.1c00784. Epub 2021 Jun 3.

Abstract

Fluorine-containing compounds comprise 20 to 30 percent of all commercial drugs, and the proportion of fluorinated pharmaceuticals is rapidly growing. While magic angle spinning (MAS) NMR spectroscopy is a popular technique for analysis of solid pharmaceutical compounds, fluorine has been underutilized as a structural probe so far. Here, we report a fast (40-60 kHz) MAS 19F NMR approach for structural characterization of fluorine-containing crystalline pharmaceutical compounds at natural abundance, using the antimalarial fluorine-containing drug mefloquine as an example. We demonstrate the utility of 2D 19F-13C and 19F-19F dipolar-coupling-based correlation experiments for 19F and 13C resonance frequency assignment, which permit identification of crystallographically inequivalent sites. The efficiency of 19F-13C cross-polarization and the effect of 1H and 19F decoupling on spectral resolution and sensitivity were evaluated in a broad range of experimental conditions. We further demonstrate a protocol for measuring accurate interfluorine distances based on 1D DANTE-RFDR experiments combined with multispin numerical simulations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallography
  • Fluorine*
  • Magnetic Resonance Imaging
  • Magnetic Resonance Spectroscopy
  • Pharmaceutical Preparations*

Substances

  • Pharmaceutical Preparations
  • Fluorine