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Ascorbigen A—NMR identification

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    SYSNO ASEP0507455
    Document TypeJ - Journal Article
    R&D Document TypeJournal Article
    Subsidiary JČlánek ve WOS
    TitleAscorbigen A—NMR identification
    Author(s) Sychrovský, Vladimír (UOCHB-X) RID, ORCID
    Šaman, David (UOCHB-X) RID, ORCID
    Fiala, R. (CZ)
    Humpa, O. (CZ)
    Sýkora, Jan (UCHP-M) RID, ORCID, SAI
    Kessler, P. (DE)
    Blechta, Vratislav (UCHP-M) RID, ORCID, SAI
    Dobrev, Petre (UEB-Q) RID, ORCID
    Schraml, Jan (UCHP-M) RID, SAI
    Source TitleMagnetic Resonance in Chemistry - ISSN 0749-1581
    Roč. 57, č. 12 (2019), s. 1084-1096
    Number of pages13 s.
    Languageeng - English
    CountryGB - United Kingdom
    Keywords13C NMR ; 13C–13C coupling constants ; 13C–1H coupling constants ; 1H NMR ; 1H–1H coupling constants ; natural product ; NMR ; NOE ; rotamers ; stereochemistry
    Subject RIVCF - Physical ; Theoretical Chemistry
    OBOR OECDPhysical chemistry
    Subject RIV - cooperationInstitute of Chemical Process Fundamentals - Physical ; Theoretical Chemistry
    R&D ProjectsGA15-12719S GA ČR - Czech Science Foundation (CSF)
    GA16-10948S GA ČR - Czech Science Foundation (CSF)
    GA19-13436S GA ČR - Czech Science Foundation (CSF)
    Způsob publikováníOmezený přístup
    Institutional supportUOCHB-X - RVO:61388963 ; UCHP-M - RVO:67985858 ; UEB-Q - RVO:61389030
    UT WOS000473987100001
    EID SCOPUS85068378971
    AnnotationThe connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one‐bond 13C–13C coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The 13C–13C coupling in one of the pairs was proved by a modification of standard INADEQUATE, however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C–C pairs was confirmed by a combination of COSY and gHSQC, the latter experiment also identified all C–H bonds. The proton nuclear magnetic resonance (1H NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3‐((1H‐indol‐3‐yl)methyl)‐3,3a,6‐trihydroxytetrahydrofuro[3,2‐b]furan‐2(5H)‐one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured 3J(H6–H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2′ proton of the indole and the H6a proton of the tetrahydrofuro[3,2‐b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2‐b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model.
    WorkplaceInstitute of Organic Chemistry and Biochemistry
    ContactMarie Odehnalová, Tel.: 220 183 418 ; Viktorie Chládková,, Tel.: 232 002 434
    Year of Publishing2020
    Electronic address
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