13C detected 15N-13C coupling measurements at the natural isotopic abundance

We propose a C-13 detected experiment, the (H)CNMQC pulse sequence for measuring one-bond and longrange N-15-C-13 scalar coupling constants in small organic molecules at the natural isotopic abundance. The previously proposed H-1 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 H-H couplings, unwanted coherence leaks and considerable trnoise. These problems are largely avoided in the (H)CNMQC experiment based on direct C-13 detection. In many cases the new experiment improves the measurement sensitivity and accuracy, not least because the N-15-C-13 couplings are measured in the directly detected dimension enabling one-dimensional measurements. (C) 2017 Elsevier Inc. All rights reserved.