Understanding the NMR properties and conformational behavior of indole vs. azaindole group in protoberberines: NICS and NCS analysis
| Authors | |
|---|---|
| Year of publication | 2012 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Molecular Structure |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1016/j.molstruc.2012.06.034 |
| Doi | http://dx.doi.org/10.1016/j.molstruc.2012.06.034 |
| Field | Physical chemistry and theoretical chemistry |
| Keywords | Density-functional theory; Nuclear magnetic shielding; Conformational analysis; Nucleus-independent chemical shift; Localized molecular orbitals; Berberine |
| Attached files | |
| Description | We report here the preparation and the structural investigation into a series of 8-(indol-1-yl)-7,8-dihydroprotoberberine derivatives derived from berberine, palmatine, and coptisine. Structures of these new compounds were characterized mainly by 2D NMR spectroscopy and the conformational behavior was investigated by using methods of density-functional theory (DFT). PBE0/6-311+G** calculated NMR chemical shifts for selected derivatives correlate excellently with the experimental NMR data and support the structural conclusions drawn from the NMR experiments. An interesting role of the nitrogen atom in position N7' of the indole moiety in 8-(7-azaindol-1-yl)-7,8-dihydroprotoberberines as compared to other 8-indolyl derivatives is investigated in detail. The experimentally observed trends in NMR chemical shifts are rationalized by DFT calculations and analysis based on the nucleus-independent chemical shifts (NICS) and natural localized molecular orbitals (NLMOs). |
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