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Structure and NMR properties of 6‐substituted‐5,6‐dihydrobenzo[ c ]phenanthridine alkaloids
Author(s) -
Kadam Shivaji S.,
Maier Lukáš,
Šolomek Tomáš,
Nečas Marek,
Šmejkal Karel,
Dostál Jiří,
Sklenář Vladimír,
Marek Radek
Publication year - 2013
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3175
Subject(s) - phenanthridine , chemistry , sanguinarine , carbazole , chelerythrine , nuclear magnetic resonance spectroscopy , isoquinoline , carbon 13 nmr , density functional theory , mass spectrometry , computational chemistry , stereochemistry , crystallography , alkaloid , photochemistry , organic chemistry , protein kinase c , chromatography , enzyme
We report a preparation of new 6‐substituted‐5,6‐dihydrobenzo[ c ]phenanthridines by the reaction of azoles with quaternary benzo[ c ]phenanthridine alkaloids sanguinarine and chelerythrine. The prepared compounds have been characterized by NMR spectroscopy, mass spectrometry , and single‐crystal X‐ray diffraction. Conformational behaviors of carbazole derivatives in solution have been investigated by low‐temperature NMR experiments. Barriers to rotation around newly formed C6–N bonds were determined to be 12–13 kcal/mol. Quantum chemical calculations have been used to reproduce the experimental observations. Large structural effects on several 1 H NMR resonances were observed experimentally, analyzed by Density Functional Theory (DFT) calculations at B3LYP/6‐311+G(d,p)/PCM level, and interpreted by ring‐current effects of the benzo[ c ]phenanthridine and carbazole units. Copyright © 2013 John Wiley & Sons, Ltd.