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DOI: 10.1055/s-0035-1556544
Absolute configuration assignment of remotely separated alcohols by the CSSF-TOCSY-INEPT experiment
Natural products containing remotely separated secondary alcohols widely exist in marine and terrestrial organisms. Absolute stereochemistry assignment of these alcohols by NMR spectroscopic methods remains challenging. This is mostly because the severely overlapping resonances flanking the stereocenters invalidate the conventional Mosher analysis. Herein, our recently developed 1D selective NMR experiment, CSSF-TOCSY-INEPT, has provided a convenient solution to the stereochemistry of these alcohols. It is achieved via chemical shift selective (CSS) excitation of the oxygenated methine signals, followed by TOCSY and INEPT transfer to generate the 13C NMR subspectra of all carbon segments subtended at each stereogenic center. 13C subspectra consolidation and the extract of anisotropic shift (Δδ) from (R) and (S)-Mosher esters allow the simultaneous configuration assignment of all alcohols. The new approach is unrestricted by the distance between the remote alcohols and also effective for polyhydroxylated compounds, which make it an attractive and unique tool for structure elucidation of macrolide, acyclic lipids, etc.