Abstract
15N can almost be considered a “forgotten” nuclide because of its low natural abundance, low γ, and the historical difficulty of direct observation NMR experiments. Indirect detection methods, however, have made the utilization of 15N a facile undertaking and there is a rapidly growing body of literature based on the utilization of long-range 1H–15N heteronuclear shift correlation methods. Probe considerations followed by experiment and parameter optimization are discussed. The impact of 15N chemical shift and correlation data on computer-assisted structure elucidation (CASE) methods is discussed next, followed by examples from various classes of molecules where the elucidation of the structure in question is greatly facilitated by the availability of long-range 1H15N heteronuclear shift correlation data. Examples include pyrazines and N-oxides. Using 15N as means of assembling natural product structural components and the differentiation of isomers is considered next, followed by the relatively new area of unsymmetrical indirect covariance processing that can be used to generate 13C15N heteronuclear shift correlation plots. Keywords: 1H15N GHSQC; 1H15N HMQC; 1H15N GHMBC; INEPT; 1H15N IMPEACH-MBC; 1H15N CIGAR-HMBC; computer-assisted structure elucidation; pyrazine; N-oxide; alkaloids; indoloquinoline; strychnine; isomer differentiation; unsymmetrical indirect covariance
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