Relayed coherence transfer from a heteronucleus through an extended proton spin system

Heteronuclear relayed coherence transfer X → H → H → ..., involving several proton-proton coherence-transfer steps, is demonstrated. All (or selected parts) of the proton spectrum of a molecule containing a heteronucleus can be obtained by inducing coherence in the X spin system and transferring it, stepwise, throughout the coupled-proton spin system. The method permits the proton spectrum of a molecule which contains an NMR-active label to be obtained selectively in the presence of overwhelming amounts of other protonated material. The influence of nuclear relaxation on "extended" coherence-transfer sequences is discussed.