13C-detected IPAP-INADEQUATE for simultaneous measurement of one-bond and long-range scalar or residual dipolar coupling constants

✍ Scribed by Lan Jin; Dušan Uhrín

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 214 KB
• Volume: 45
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2031

✦ Synopsis

Abstract

The sensitivity of cryoprobes, which are rapidly becoming available, means that the measurement of coupling constants involving ^13^C, ^13^C pairs at the natural abundance of ^13^C can now, in principle, be done by using tens rather then hundreds of milligrams of compounds. However, a robust method that would yield reliable values of small long‐range carbon‐‐carbon coupling constants is still missing. In this Communication, we describe a novel ^13^C–detected incredible natural‐abundance double‐quantum transfer experiment (INADEQUATE) experiment for simultaneous correlation of one‐bond and long‐range ^13^C^13^C pairs and the measurement of both types of coupling constants in ^13^C natural abundance samples. This method yields accurate values of one‐bond and long‐range coupling constants by manipulation of pure phase in‐phase (IP) and antiphase (AP) doublets, and is referred to as ^13^C‐detected IPAP‐INADEQUATE. It is illustrated by the measurement of interglycosidic ^3^J~CCOC~ coupling constants in a disaccharide molecule providing important information about the conformation of the glycosidic linkage. Owing to the simplicity of INADEQUATE spectra the carbon–carbon coupling constants are particularly suitable for studies of partially oriented molecules through the measurement of carbon–carbon residual dipolar couplings (RDCs). An example of this approach is presented. We expect the method to find a variety of applications in the conformational analysis of small molecules, determination of diastereoisomers and enantiomers, and studies of molecules in aligned media. Copyright © 2007 John Wiley & Sons, Ltd.