Sensitivity- and Gradient-Enhanced Hetero (ω₁) Half-Filtered TOCSY Experiment for Measuring Long-Range Heteronuclear Coupling Constants

An enhanced version of the X(ω₁) half-filtered TOCSY experiment for measurement of long-range heteronuclear coupling constants is proposed which yields high-quality spectra with substantially increased sensitivity and resolution. The modified method features gradient-enhanced X filtering sequences, broadband homonuclear decoupling during t₁, optional ¹J_XII scaling in the F₁ domain, and gradient coherence selection in combination with the sensitivity-enhanced protocol for the TOCSY transfer. These modifications extend the applicability of the method - coupling constants can be measured accurately for natural abundance samples at low concentrations and for compounds yielding complex spectra. Computer-aided analysis of E.COSY-type multiplets is applied for the determination of heteronuclear long-range coupling constants.