Zektzer, Andrew S.;
John, Boban K.;
Martin, Gary E.
Repression of one‐bond modulations in long‐range heteronuclear 2D NMR spectra using a modified long‐range optimized heteronuclear chemical shift correlation pulse sequence
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Media type:
E-Article
Title:
Repression of one‐bond modulations in long‐range heteronuclear 2D NMR spectra using a modified long‐range optimized heteronuclear chemical shift correlation pulse sequence
Contributor:
Zektzer, Andrew S.;
John, Boban K.;
Martin, Gary E.
Description:
<jats:title>Abstract</jats:title><jats:p>A modified long‐range heteronuclear chemical shift correlation pulse sequence which eliminates modulations of response intensity due to one‐bond proton‐carbon [<jats:sup>1</jats:sup> <jats:italic>J</jats:italic>(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° <jats:sub>x</jats:sub>(<jats:sup>1</jats:sup>H)‐τ‐180° <jats:sub>x</jats:sub>(<jats:sup>1</jats:sup>H)/180° <jats:sub>x</jats:sub>(<jats:sup>13</jats:sup>C)‐τ‐90° <jats:sub>‐x</jats:sub>(<jats:sup>1</jats:sup>H) midway through the second magnetization transfer delay, Δ<jats:sub>2</jats:sub>.</jats:p><jats:p>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.</jats:p><jats:p>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.</jats:p>