A quantum chemistry study of Qinghaosu

The powerful anti-malarial drug, Qinghaosu (Artemisinin), has been studied using ab initio methods. The DFT B3LYP method with the 6-31G∗ basis set gives an excellent geometry compared to experiments, especially for the OO bond length and the 1,2,4-Trioxane ring subsystem. The R(OO) bond length predicted at this level is 1.460 Å, only 0.018 Å shorter than the experimental measurement. The vibrational analysis shows that the OO stretching mode is combined with the OC vibration mode, having the character of an OOC entity. The OO vibrational band at 722 cm−1 suggested in the experimental studies has been assigned as 1,2,4-trioxane ring breathing.