X-ray and DFT Study of Glaucocalyxin A Compound with Cytotoxic Activity
Wang, Fu-dong（Chinese Acad Sci, Lanzhou Inst Chem Phys）
Wang, Tao（ Xiamen Univ, Coll Phys & Mech Elect Engn）
Ding, Lan（NW Normal Univ, Coll Life Sci）
Wang, Han-qing（Chinese Acad Sci, Lanzhou Inst Chem Phys）
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The title compound glaucocalyxin A (1) (7 alpha,14 beta-dihydroxy-ent-kaur-16-en-3,15-dione) isolated from the leaves of isodon excisoides was characterized by IR, H-1 NMR C-13 NMR, H-1-H-1 COSY, HMQC, HMBC, and EIMS, and its crystal structure was determined by single-crystal X-ray diffraction. The X-ray crystal structure revealed that the molecular backbone of the chosen crystal is a tetracyclic system, including three six-membered rings and a five-membered ring, and the three six-membered rings are in a chair-like conformation. The five-membered ring adopts a twisted envelope-like conformation, and its geometrical parameters were compared with theoretical calculations at the B3LYP and HF level of theory. The molecules form extensive networks through the intra- and intermolecular hydrogen bonds. The experimental NMR data were interpreted with the aid of magnetic shielding constant calculations, by means of the GIAO (gauge-Including atomic orbitals) method. Calculated kind experimental results were compared with a satisfactory level of agreement. Molecular electrostatic potential map was used in an attempt to identify key features of the diterpenoid glaucocalyxin A that is necessary for its activity. Calculations of molecular electrostatic potential and stabilization energies suggest that the protonation of glaucocalyxin A will be able to occur on carbonyl oxygen atoms.
CitationCHINESE JOURNAL OF CHEMICAL PHYSICS，2009,22（3）：275-284