A QUANTUM-CHEMISTRY STUDY OF QINGHAOSU

The powerful anti-malarial drug, Qinghaosu (Artemisinin), has been stu died using ab initio methods. The DFT B3LYP method with the 6-31G bas is 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 Angstrom, only 0.018 Angstrom shorter than the experimental measurement. The vibrational a nalysis shows that the O-O stretching mode is combined with the O-C vi bration mode, having the character of an O-O-C entity. The O-O vibrati onal band at 722 cm(-1) suggested in the experimental studies has been assigned as 1,2,4-trioxane ring breathing. (C) 1997 Published by Else vier Science B.V.