金丝桃蒽酮结构变化的理论研究

Theoretical Study on Structure Change of Hypericin

用MMX和AMI方法对金丝桃蒽酮(HYP)结构变化过程的生成热进行了计算.发现:1.HYP1,2位OH可越过20kJ/mol左右的势垒,绕C—O键旋转而形成分子内氢键,并估算出键能约为10kJ/mol;2.HYP其他四个OH也可进行类似的构象变化,势垒在26kJ/mol左右,相应分子内氢键键能约为20kJ/mol;3.HYP分子内氢传递产生的异构体在能量上不稳定.进而在此基础上探讨了1,2位OH分子内氢键的形成对HYP光敏活性的影响.

MMX and AMI methods were employed to calculate heat of formation of hypericin(HYP) in the process of structure change. It was found that (i) Hydroxyls of HYP at position 1,2 could form intramolecular hydrogen bond(IHB) through crossing a barrier of about 20kJ/mol and rotating around C-0 bond, and the hydrogen bond energy was estimated to be approximately 10kJ/mol. (ii) By rotating other four hydroxyls, the conformation of HYP could be changed in similar processes. The barriers were about 26kJ/mol, and the corresponding hydrogen bond energies were about 20kJ/mol. (iii) Isomers of HYP generated through intramolecular hydrogen transfer were not thermally stable. In addition, the influences of forming IHB between hydroxyls at position 1,2 on photosensitivity of HYP were investigated as well.