Selective COSY‐J‐resolved‐HMBC,a new method for improving sensitivity of cross peaks of methine proton signals attached to a methyl group |
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| Authors: | Kazuo Furihata Mitsuru Tashiro |
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| Affiliation: | 1. Division of Agriculture and Agricultural Life Sciences, The University of Tokyo, , Tokyo, Japan;2. Department of Chemistry, College of Science and Technology, Meisei University, , Tokyo, Japan |
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| Abstract: | Improved pulse sequences for measuring long‐range C‐H coupling constants (nJC‐H), named selective COSY‐J‐resolved HMBC‐1 and ?2, have been developed. In the spin systems, such as ‐CHC‐CHA(CH3)‐CHB‐, a methine proton HA splits into a multiplet owing to several vicinal couplings with protons, resulting in attenuation of its cross‐peak intensity. Therefore, the measurements of nJC‐H with HA are generally difficult in the J‐resolved HMBC or selective J‐resolved HMBC spectrum. With the aim of accurate measurements of nJC‐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 HA cross peak in comparison with the selective J‐resolved HMBC pulse sequence. Copyright © 2012 John Wiley & Sons, Ltd. |
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| Keywords: | selective COSY‐J‐resolved HMBC selective J‐resolved HMBC selective excitation J‐scaling long‐range C‐H coupling constants |
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