痂囊腔菌素A分子构型和分子内氢键的理论研究

用半经验量子化学AM1方法对天然苝醌化合物痂囊腔菌素A(EA)的分子构型和分子内氢键进行了研究;从EA可能的64种构型中选择16种进行了计算.结果表明,EA的X射线晶体结构对应的构型是II型左旋(A)a,a型(II-L-A-a,a);小的生成热差值可以使得异构体间的转换容易进行,有利于发生分子内质子传递.尽管采用AM1方法计算得到的EA各种构象的平面性有所差别,但都很接近晶体的平面性.此外,EA分子内氢键键能的平均值为22.9kJ/mol;II型的氢键键能比I型的大,(9,10)位的氢键键能比(3,4)位的大;EA的平面性是由苝醌环上的侧链取代所决定,而与分子内是否存在氢键无关.

Theoretical study on molecular configuration and intramolecular hydrogen bond of Elsinochrome A

The molecular configuration and intra-molecular hydrogen bond of natural perylenequinone elsinochrome A（EA） were examined with semi-empirical quantum chemical method AM1.Sixteen configurations were selected from 64 possible configurations and calculated.Results indicate that the X-ray crystal structure of EA corresponds to type-II left-hand rotation a,a configuration（II-L-A-a,a）.A small difference in formation heat allows easy inter-transformation among various isomers,which facilitates intra-molecular proton transfer.Besides,though the planarities of EA configurations calculated with AM1 method are somewhat different,they are all similar to those of X-ray crystals.Moreover,the average intra-molecular hydrogen bond energy of EA is 22.9 kJ/mol.The hydrogen bond energies of type-II configuration are larger than that of type-I configuration,while hydrogen bond energies at（9,10） positions are greater than that at（3,4） positions.Furthermore,the planarity of EA is determined by side-chain substitution on perylenequinone ring and is not dependent on whether or not intra-molecular hydrogen bond exists.