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Selective COSY‐ J ‐resolved‐HMBC, a new method for improving sensitivity of cross peaks of methine proton signals attached to a methyl group
Author(s) -
Furihata Kazuo,
Tashiro Mitsuru
Publication year - 2012
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.3816
Subject(s) - chemistry , pulse sequence , multiplet , proton , vicinal , coupling constant , methyl group , analytical chemistry (journal) , pulse (music) , nuclear magnetic resonance , stereochemistry , spectral line , group (periodic table) , physics , chromatography , organic chemistry , quantum mechanics , astronomy , particle physics , detector , optics
Improved pulse sequences for measuring long‐range C‐H coupling constants ( n J C‐H ), named selective COSY‐ J ‐resolved HMBC‐1 and −2, have been developed. In the spin systems, such as ‐CH C ‐CH A (CH 3 )‐CH B ‐, a methine proton H A splits into a multiplet owing to several vicinal couplings with protons, resulting in attenuation of its cross‐peak intensity. Therefore, the measurements of n J C‐H with H A are generally difficult in the J ‐resolved HMBC or selective J ‐resolved HMBC spectrum. With the aim of accurate measurements of n J C‐H in such a spin system, we have developed new pulse sequences, which transfer the magnetization of a methyl group to its adjacent methine proton. The proposed pulse sequences successfully enable to enhance the sensitivity of H A cross peak in comparison with the selective J ‐resolved HMBC pulse sequence. Copyright © 2012 John Wiley & Sons, Ltd.