摘要
采用单晶x射线衍射技术对化合物的晶体结构进行了研究．研究结果表明，Glaucocalyxin A分子含3个六元环和1个五元环，其中六元环均为椅式构象，五元环为扭曲信封式构象．Glaucocalyxin A晶体结构属正交晶系．采用密度函数理论和Hartree—Fock方法对该化合物晶体的键长、键角和两面角进行计算，并与X衍射测定值进行比较，结果表明理论值与实验值符合相当好．应用规范不变原子轨道，分别在不同水平上，计算了GlaucocalyxinA的^1 H和^13 C NMR化学位移，并对理论计算值的误差进行了统计分析，结果表明计算值与实验值的符合是令人满意的．通过对该分了的三维分子表面静电位的研究，提出了该分子抗癌活性的可能部位．
The title compound glaucocalyxin A （1） （Ta,14β-dihydroxy-ent-kaur-16-en-3,15-dione） iso- lated from the leaves of isodon excisoides was characterized by IR, 1H NMR, 13C NMR, 1H-1H COSY, HMQC, HMBC, and EIMS, and its crystal structure was determined by singlecrystal 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 param- eters 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 and 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 po- tential and stabilization energies suggest that the protonation of glaucocalyxin A will be able to occur on carbonyl oxygen atoms.
