High resolution-HMBC (HR-HMBC), a new method for measuring heteronuclear long-range coupling constants.
A useful pulse sequence for measuring long-range C--H coupling constants (J(C-H)) named high resolution-HMBC (HR-HMBC) has been developed. In this pulse sequence, the J-scaling pulse [(nt(1))/2-180 degrees (H/C) - (nt(1))/2] is incorporated after the spin evolution period, and then followed by an (1)H 180 degrees pulse to reverse the magnetization of J(C-H) couplings. As a result, splittings of the cross peaks due to the long-range J(C-H) are realigned with separations of nJ(C-H) along the F(1) dimension, and thus even the small long-range J(C--H) values can easily be determined. The efficiency of measuring the long-range J(C--H) using the proposed pulse sequences has been demonstrated in application to the complicated natural product, portmicin.
Furihata
Kazuo
K
Division of Agriculture and Agricultural Life Sciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. furihata@iam.u-tokyo.ac.jp
Tashiro
Mitsuru
M
Seto
Haruo
H
D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008968:Molecular Conformation; D011758:Pyrroles / Q000737:chemistry; D012015:Reference Standards
D011758:Pyrroles; C052322:portmicin