title: Suppressing one-bond homonuclear 13C,13C scalar couplings in the J-HMBC NMR experiment: application to 13C site-specifically labeled oligosaccharides.
abstract: Site-specific (13)C isotope labeling is a useful approach that allows for the measurement of homonuclear (13)C,(13)C coupling constants. For three site-specifically labeled oligosaccharides, it is demonstrated that using the J-HMBC experiment for measuring heteronuclear long-range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant-time element in the pulse sequence, the interference from one-bond (13)C,(13)C scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J-HMBC experiments to site-specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule.
authors.affiliation: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Pendrill
authors.forename: Ole W
authors.initials: OW
authors.lastname: Sørensen
authors.forename: Göran
authors.initials: G
authors.lastname: Widmalm
mesh_terms: D002236:Carbohydrate Conformation; D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D009844:Oligosaccharides / Q000737:chemistry*; D012015:Reference Standards
chemical_list: D002247:Carbon Isotopes; D009844:Oligosaccharides
keywords: 13C; 1H; J-HMBC; NMR; heteronuclear long-range coupling constants; oligosaccharide; site-specific labeling