NASCA-HMBC, a New NMR Methodology for the Resolution of Severely Overlapping Signals: Application to the Study of Agathisflavone

作者：Njock Gaetan Bayiha Ba; Bartholomeusz Trixie Ann; Foroozandeh Mohammadali; Pegnyemb Dieudonne Emmanuel; Christen Philippe^*; Jeannerat Damien

来源：Phytochemical Analysis, 2012, 23(2): 126-130.

DOI：10.1002/pca.1333

• spectral aliasing
• high-spectral resolution
• NMR
• biflavonoids
• Ouratea gilgiana

Introduction - 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 %26lt;0.3 ppm apart. %26lt;br%26gt;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. %26lt;br%26gt;Methodology - 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. %26lt;br%26gt;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. %26lt;br%26gt;Conclusion - The methodology should find many applications in dimeric and oligomeric compounds such as peptides, carbohydrates, polyketides and other cases where signal clustering is expected.

• 出版日期2012-4