Structural study of 8-azole derivatives of protoberberine alkaloids: experimental and quantum chemical approach |
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| Authors: | Lukáš Maier Matej Pipíška Marek Ne?as |
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| Institution: | a National Center for Biomolecular Research, Masaryk University, Kamenice 5/A4, CZ-62500 Brno, Czech Republic
b Department of Chemistry, Masaryk University, Kamenice 5, CZ-62500 Brno, Czech Republic |
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| Abstract: | New derivatives of protoberberine alkaloids were prepared by nucleophilic addition of some azoles (differing in bulkiness) to the iminium functionality of the quaternary protoberberine alkaloids. Compounds were structurally characterized mainly by 1H and 13C NMR spectroscopy, and the structure of 8-carbazol-1-yl-7,8-dihydroberberine was determined using single-crystal X-ray diffraction. Additionally, conformational behaviors of five derivatives varying in bulkiness of the azole moiety have been investigated by low temperature NMR spectroscopy and quantum chemical calculations. Ring current effects of pyrrole and carbazole moieties on selected 1H NMR resonances have been characterized, visualized, and discussed. |
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| Keywords: | Barrier to rotation Berberine Low-temperature NMR spectroscopy Nucleus-independent chemical shift Palmatine Theoretical calculations |
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