Precise Measurement of Long-Range Heteronuclear Coupling Constants by a Novel Broadband Proton-Proton-Decoupled CPMG-HSQMBC Method

A broadband proton–proton‐decoupled CPMG‐HSQMBC method for the precise and direct measurement of long‐range heteronuclear coupling constants is presented. The Zangger–Sterk‐based homodecoupling scheme reported herein efficiently removes unwanted proton–proton splittings from the heteronuclear multiplets, so that the desired heteronuclear couplings can be determined simply by measuring frequency differences between singlet maxima in the resulting spectra. The proposed pseudo‐1D/2D pulse sequences were tested on nucleotides, a metal complex incorporating P heterocycles, and diglycosyl (di)selenides, as well as on other carbohydrate derivatives, for the extraction of nJ(1H,31P), nJ(1H,77Se), and nJ(1H,13C) values, respectively. Multiplets simplified: A broadband proton–proton‐decoupled CPMG‐HSQMBC method is proposed for the precise and direct measurement of long‐range heteronuclear coupling constants. The broadband homodecoupling scheme incorporated in the experiment efficiently eliminates unwanted proton–proton splittings from the heteronuclear multiplets, so that the heteronuclear couplings of interest can be determined simply by measuring frequency differences between singlet maxima of pure antiphase doublets (see figure).