Assignment of the absolute configuration of zwitterionic and neutral macropodumines by means of TDDFT CD calculations |
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| Authors: | Guo Yue-Wei Kurtán Tibor Krohn Karsten Pescitelli Gennaro Zhang Wen |
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| Affiliation: | State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences,Shanghai, People's Republic of China. |
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| Abstract: | Macropodumines B and C (1, 2) are fused pentacyclic alkaloids previously isolated from the Chinese medicinal plant Daphniphyllum macropodum. Macropodumine B (1) possesses an amazing structural feature of a cyclopentadienyl carbanion, stabilized as a zwitterion by an internal iminium cation, which was confirmed by X-ray diffraction analysis. On the basis of the X-ray geometry, the absolute configuration of 1 was determined by employing the solid-state CD/TDDFT approach. The absolute configuration of 2 was instead determined by using TDDFT CD calculations on DFT-optimized geometries, in comparison with CD spectra recorded in solution. |
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| Keywords: | Daphniphyllum alkaloids cyclopentadienyl carbanion X-ray diffraction analysis solid-state CD/TDDFT approach solution vs. solid-state CD |
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