1H-Detected IPAP DEPT-INADEQUATE and IPAP RINEPT-INADEQUATE for the measurement of long-range carbon–carbon coupling constants

• DOI: 10.1016/j.jmr.2007.10.016
• Publication Date: 2007-11-14T15:42:28Z
• Authors: Lan Jin; Katalin E. Kövér; Marc R. Lenoir; Dušan Uhrín
• Keywords: Binding Sites; Magnetic Resonance Spectroscopy; Természettudományok; Glycosides; Protons; Kémiai tudományok; 01 natural sciences; Algorithms; Carbon; 0104 chemical sciences

The sensitivity of cryoprobes, which are rapidly becoming available, have brought about the possibility of measurement of (13)C, (13)C coupling constants at the natural abundance of (13)C using tens rather than hundreds of milligrams of compounds. This relatively recent development lays the foundation for a more routine use of the (13)C, (13)C long-range coupling constants in the conformational analysis of molecules. We have designed novel (1)H-detected INADEQUATE experiments optimized for long-range (13)C, (13)C correlations and the measurement of long-range coupling constants. These experiments incorporate refocusing of (1)J(CH) coupling constants prior to the formation of DQ coherences and (1)H-decoupling during the long carbon-carbon evolution intervals. Such modifications significantly enhance their performance over (1)H-detected INADEQUATE experiments currently in use for mapping the one-bond (13)C, (13)C correlations. (1)H or (13)C polarization is used a starting point in long-range correlation (1)H-detected IPAP DEPT-INADEQUATE or RINEPT-INADEQUATE experiments. These correlation experiments were modified yielding in-phase (IP) or antiphase (AP) (13)C, (13)C doublets in F(1). Procedures were developed for their editing yielding accurate values of small (13)C, (13)C coupling constants. The methods are illustrated using mono- and disaccharide samples and compared with related (13)C-detected experiments by means of the measurement of interglycosidic (13)C, (13)C coupling constants of a disaccharide.