Homodecoupled 1,1- and 1,n-ADEQUATE: Pivotal NMR Experiments for the Structure Revision of Cryptospirolepine

Cryptospirolepine is the most structurally complex alkaloid discovered and characterized thus far from any Cryptolepis specie. Characterization of several degradants of the original, sealed NMR sample a decade after the initial report called the validity of the originally proposed structure in question. We now report the development of improved, homodecoupled variants of the 1,1‐ and 1,n‐ADEQUATE (HD‐ADEQUATE) NMR experiments; utilization of these techniques was critical to successfully resolving long‐standing structural questions associated with crytospirolepine. Taking a second look: Development of an improved, homodecoupled 1,1‐ and 1,n‐ADEQUATE (HD‐ADEQUATE) technique is reported and applied to the revision of the structure of a 700 μg sample of the complex, spiro nonacyclic alkaloid cryptospirolepine whose structure was first reported in 1993.