title: Selective COSY-J-resolved-HMBC, a new method for improving sensitivity of cross peaks of methine proton signals attached to a methyl group.
abstract: 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.
authors.affiliation: Division of Agriculture and Agricultural Life Sciences, The University of Tokyo, Tokyo, Japan. afuriha@mail.ecc.u-tokyo.ac.jp
authors.forename: Kazuo
authors.initials: K
authors.lastname: Furihata
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Tashiro
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D008697:Methane; D008956:Models, Chemical; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011522:Protons; D011758:Pyrroles / Q000737:chemistry; D012680:Sensitivity and Specificity; D013113:Spin Labels; D013237:Stereoisomerism
chemical_list: D001555:Benzene Derivatives; D011522:Protons; D011758:Pyrroles; D013113:Spin Labels; C052322:portmicin; C004912:ethylbenzene; D008697:Methane