Evaluation of pulse sequences combining 13 C‐ 1 H shift correlation and heteronuclear J spectroscopy with full 1 H‐ 1 H decoupling

Three different two‐dimensional 13 C‐ 1 H shift‐correlation sequences which detect 1 H chemical shifts and one bond 13 C‐ 1 H[J(CH)] couplings in f 1 with full 1 H‐ 1 H decoupling are described and evaluated. They are particularly useful for detecting small differences in 1 J(CH) for non‐equivalent methlene groups in natural products and other complex organic molecules. The best of the three allows determination of 1 J(CH) and 1 H chemical shifts to a precision better than 1 Hz, with sensitivity comparable to previous shift‐correlation and J‐resolved pulse sequences. 1 J(CH) Values for a typical alkaloid suggest that these parameters are a useful probe of conformational, electronic and ring size effects in natural products.