title: NASCA-HMBC, a new NMR methodology for the resolution of severely overlapping signals: application to the study of agathisflavone.
abstract: BACKGROUND
  Standard NMR 2D heteronuclear HMBC spectra have a low resolution in the indirect carbon dimension, making it very difficult to assign signals to individual carbons when their chemical shifts are < 0.3 ppm apart.
  
  
  OBJECTIVE
  To establish spectral aliasing for HMBC experiments to improve the resolution in the carbon dimension without increasing the total experimental time and avoiding ambiguities in the observed chemical shifts.
  
  
  METHODS
  The NASCA-HMBC (Non-ambiguous Assignment by Superposition of Coupled Aliased HMBC) methodology combines a pair of HMBC spectra recorded with slightly different carbon windows to provide typically one order of magnitude increase in the resolution and unambiguous chemical shifts.
  
  
  RESULTS
  The application of this methodology to a biflavonoid found in Ouratea gilgiana resulted in spectra with a sufficiently high resolution to make the assignment straightforward and report, for the first time, the full assignment of agathisflavone.
  
  
  CONCLUSIONS
  The methodology should find many applications in dimeric and oligomeric compounds such as peptides, carbohydrates, polyketides and other cases where signal clustering is expected.
authors: Section of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Quai E. Ansermet 30, CH-1211 Geneva 4, Switzerland.
authors: Gaétan Bayiha Ba
authors: GB
authors: Njock
authors: Trixie Ann
authors: TA
authors: Bartholomeusz
authors: Mohammadali
authors: M
authors: Foroozandeh
authors: Dieudonné Emmanuel
authors: DE
authors: Pegnyemb
authors: Philippe
authors: P
authors: Christen
authors: Damien
authors: D
authors: Jeannerat