Maria Misiak, W. Koźmiński, J. Wójcik
Mar 1, 2019
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Steroids
Abstract
HIGHLIGHTSThe 3D NMR experiments were applied for structural study of 3‐(25‐hydroxycholest‐5‐enyl) acetate.The DFT calculation supported experimental NMR results.The configuration of C20 was unambiguously determined. ABSTRACT The application of 3D NMR experiments and DFT calculations enabled the structure investigation of C‐17 epimer of 3‐(25‐hydroxycholest‐5‐enyl) acetate is presented. The H‐17 and H‐20 protons features the same values of 1H chemical shift, what causes that the structure elucidation require additional resolution enabled by 3D NMR experiments. The NMR experiments and theoretical calculations allowed for: the resonance assignment (3D COSY‐HMBC and 3D TOCSY‐HSQC techniques), the prediction of spatial structure (3D NOESY‐HSQC and 3D ROESY‐HSQC experiments), and the precise measurement of heteronuclear coupling constants (3D HSQC‐TOCSY spectra with E.COSY‐type multiplets).