Three-bond Couplings Between Hydrogen and Heteronuclei

8 Three-bond Couplings Between Hydrogen and Heteronuclei 

Hennig et have measured a full set of heteronuclear /caHN and /c ca couplings in the protein ubiquitin. The authors suggested a non-Karplus-type dependence of these couplings on the torsional angle of the proceeding residue. Several examples of proteins whose solution structure has been elucidated with the help of heteronuclear couplings are listed in Table 5.4. 

The structures of two new pyrrolidine alkaloids, pandamarilactonine-A and -B isolated from Pandanus amaryllifolius Roxb, have been deduced by Takayama and co-workers with the help of vicinal Jhc and /hh couplings. Girault and co-workers have determined conformations of free and ribosome-bound macrolide antibiotics using NMR and molecular modelling. The authors analysed Vhc and /hh couplings of the proline and sugar part of lincomydn and clindamycin and of the macrocycle as well as desosamine part of HMR 3647 (telithromycin).  

The three-dimensional structure of the antibiotic 6-O-methylerythromycin in water has been determined by Steinmetz et by the use of torsional constraints obtained from proton-proton and proton-carbon vicinal couplings and distance constraints obtained from NOESY, ROESY and GOESY spectra. 

A conformational analysis of naproxen anion and monensin sodium has been performed by the use of the /hc couplings. Especially extensive use of these couplings has been made by the authors in the case of the latter compound. They concluded that the conformation of monoensin in solution is very close to that in crystals. Further examples of the application of vicinal proton-carbon couplings in the conformational analysis of compounds include the NMR and quantum-chemical study of the stereochemistry of spiroepoxides obtained by oxidation of (Z)-3-arylidene-l-thioflavan-4-ones performed by Toth et and the elucidation of the structure of isomalyngamides A and B isolated from a collection of the cyanobacterium Lyngbya majuscula from Hawaiian waters by Kan et 

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