Repression of one-bond modulations in long-range heteronuclear 2D NMR spectra using a modified long-range optimized heteronuclear chemical shift correlation pulse sequence

✍ Scribed by Andrew S. Zektzer; Boban K. John; Gary E. Martin

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 487 KB
• Volume: 25
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260250903

✦ Synopsis

A modified long-range heteronuclear chemical shift correlation pulse sequence which eliminates modulations of response intensity due to one-bond proton-carbon I'J(CH)] spin couplings is described. The 'decoupling' of one-bond modulation has been accomplished through the use of a bilinear rotational decoupling (BIRD) pulse of the type 90°,('H)-~-1800,('H)/1800,('3C~.r-900~,('H) midway through the second magnetization transfer delay, A*.

One-bond modulation of response intensities over a range of optimization values is demonstrated for the simple alkaloid norharmane when long-range optimization of the conventional heteronuclear chemical shift correlation pulse sequence is employed. The modified pulse sequence described eliminates one-bond modulations over the same range of optimization values. Slower modulations which arise due to long-range couplings other than that optimized for are present in both experiments.

Removal of the effects of one-bond modulation represents a potentially significant improvement in the utility of long-range heteronuclear chemical shift correlation experiments as a tool in spectral assignments and structure elucidation.