Assignment of the absolute configuration of zwitterionic and neutral macropodumines by means of TDDFT CD calculations.
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.
Guo
Yue-Wei
YW
State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences,Shanghai, People's Republic of China.
Kurtán
Tibor
T
Krohn
Karsten
K
Pescitelli
Gennaro
G
Zhang
Wen
W
D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D011083:Polycyclic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013997:Time Factors
D011083:Polycyclic Compounds; C520040:macropodumine B; C520039:macropodumine C