Direct measurement of heteronuclear long-range coupling constants from phase-sensitive HMBC spectra

A simple pulse sequence in inverse-detection mode is proposed for the detection of heteronuclear long-range couplings. In the resulting 2D heteronuclear multiple-bond correlation (HMBC) spectra, pure-absorptive peak patterns are obtained along both frequency dimensions. Since the heteronuclear couplings result in anti-phase splittings over the proton homonuclear multiplets along the ω2-dimension, the phase-sensitive HMBC experiment can be provided as an easy and direct means for the measurement of heteronuclear long-range coupling constants.