“Perfect Echo” HMQC: Sensitivity and resolution enhancement by broadband homonuclear decoupling

Abstract

Homonuclear 1H–1H J-modulation leads to J-multiplets in F1 dimension of 2D 1H–13C HMQC spectra. This hampers unambiguous signal assignment for overcrowded 13C spectra. Broadband homonuclear decoupling has been achieved in the indirect t1 evolution period by incorporating blocks of perfect echo. This method of perfect echo HMQC demonstrates better resolution and sensitivity than conventional HMQC spectra. The results on Cyclosporine demonstrate that the method is very efficient for refocusing geminal couplings in weakly coupled –13CH2 groups. Partial refocusing of vicinal couplings is also observed for –13CH and –13CH3 groups. Interpretation of the result based on product operator formalism is also given. Comparison of pe-HMQC, HMQC and HSQC reveals that the F1 linewidth of pe-HMQC is much narrower than HMQC and very close to that of HSQC for CH2 groups.