NMR Research Today is a free monthly online journal that collates and summarizes the latest research about NMR, including details on nuclear magnetic resonance, structural determination, techniques.

NMR characterization of an S-linked glucuronide metabolite of the potent, novel, nonsteroidal progesterone agonist tanaproget.

Keating KA, McConnell O, Zhang Y, Shen L, Demaio W, Mallis L, Elmarakby S, Chandrasekaran A

Roy J. Carver Metabolomics Center, University of Illinois Urbana-Champaign, 601 S. Goodwin Avenue M/C 110, Urbana, IL 61801, USA. kkeating@uiuc.edu

Tanaproget is a first-in-class nonsteroidal progesterone receptor agonist that is being investigated for use in contraception. A major in vitro and in vivo metabolite of tanaproget formed in humans was initially characterized as a glucuronide of tanaproget. However, whether the glucuronide was linked to the nitrogen or sulfur of the benzoxazine-2-thione group in tanaproget could not be determined by liquid chromatography/mass spectrometry (LC/MS) and LC-tandem mass spectrometry analysis. To obtain additional structural details for this metabolite, additional quantities were generated from rat liver microsomal incubations and purified by high-performance liquid chromatography (HPLC) for NMR analysis. The NMR data for the metabolite confirmed that the glucuronide was covalently bound to either the sulfur or the nitrogen of the benzoxazine-2-thione moiety. The lack of key through-bond (scalar) and through-space (dipolar) one-dimensional (1D) and two-dimensional (2D) NMR couplings and correlations in the metabolite spectra (due primarily to low sample concentration) precluded an unambiguous structure elucidation. Subsequent synthesis of the S- and N-glucuronides of tanaproget from tanaproget facilitated the unambiguous regio- and stereochemical assignment of the metabolite by comparison of 1D NMR chemical shifts and scalar coupling constants, 2D NMR correlations, and HPLC and LC/MS characteristics between the synthetic compounds and the metabolite. From extensive comparison of the spectral and chromatographic data of the microsomally derived metabolite and the synthetic compounds, the metabolite has been determined to be the S-(beta)-D-glucuronide of tanaproget.

Published 18 July 2006 in Drug Metab Dispos, 34(8): 1283-7.
Full-text of this article is available online (may require subscription).

© 2005-2008 NMR Research Today. All Rights Reserved.