A toolbox of HSQC experiments for small molecules at high 13 C‐enrichment. Artifact‐free, fully 13 C‐homodecoupled and J CC ‐encoding pulse sequences

A set of modified HSQC experiments designed for the study of 13 C‐enriched small molecules is introduced. It includes an improved sensitivity‐enhanced HSQC experiment eliminating signal artifacts because of high‐order 13 C magnetization terms generated at high 13 C enrichment. A broadband homonuclear 13 C decoupling sequence based on Zangger and Sterk's method simplifies the complex 13 C– 13 C multiplet structure in the F1 dimension of HSQC. When recording spectra at high resolution, the combination with a multiple‐site modulation of the selective pulse outperforms the constant‐time HSQC in terms of sensitivity and reliability. Finally, two pulse sequences reintroducing selected J CC couplings with selective pulses facilitate their assignments and measurements either in the splitting of the resulting doublets or by modulation of the signal amplitude. A sample of uniformly 92% 13 C‐enriched cholesterol is used as an example. Copyright © 2013 John Wiley & Sons, Ltd.