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Elimination of direct responses and one‐bond modulations in long‐range heteronuclear chemical shift correlation spectra through the use of low‐pass J filters and BIRD pulses
Author(s) -
Salazar Miguel,
Zektzer Andrew S.,
Martin Gary E.
Publication year - 1988
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260260108
Subject(s) - heteronuclear molecule , pulse sequence , chemistry , pulse (music) , decoupling (probability) , spectral line , nuclear magnetic resonance , analytical chemistry (journal) , molecular physics , stereochemistry , nuclear magnetic resonance spectroscopy , physics , organic chemistry , optics , control engineering , astronomy , detector , engineering
Modified long‐range heteronuclear chemical shift correlation pulse sequences which incorporate both BIRD pulses midway through the Δ 2 magnetization transfer delay and low‐pass J filters are described. The BIRD pulse provides the means of decoupling one‐bond modulations of response intensity when magnetization is transferred to protonated carbons. The one‐ and three‐step low‐pass J filters utilized eliminate responses due to directly attached protons over a range of one‐bond coupling constants. Results obtained by long‐range optimization of the conventional heteronuclear chemical shift correlation pulse sequence, the previously reported pulse sequence containing only the BIRD pulse midway through Δ 2 and the two new pulse sequences described in this work are compared using 2,3‐dihydrofuran as a model compound. The low‐pass J filters have no adverse effects on the ability of the BIRD pulse to decouple one‐bond modulations. Modulation decoupling in the modified pulse sequences was confirmed using the 3 J (C‐3, H‐1) coupling pathway of the simple alkaloid norharmane. The response intensities, however, were up to 10% lower with a one‐step low‐pass J filter when compared with the simpler pulse sequence containing only the BIRD pulse midway through Δ 2 .