(13)C detected (15)N(13)C coupling measurements at the natural isotopic abundance.

We propose a (13)C detected experiment, the (H)CNMQC pulse sequence for measuring one-bond and long-range (15)N(13)C scalar coupling constants in small organic molecules at the natural isotopic abundance. The previously proposed (1)H detected H(C)NMBC experiment performs poorly in situations where the carbon atom of interest has no attached protons, in the presence of splittings due to the homonuclear HH couplings, unwanted coherence leaks and considerable t1-noise. These problems are largely avoided in the (H)CNMQC experiment based on direct (13)C detection. In many cases the new experiment improves the measurement sensitivity and accuracy, not least because the (15)N(13)C couplings are measured in the directly detected dimension enabling one-dimensional measurements.