CRYSTAL STRUCTURE AND ABSOLUTE CONFIGURATION OF QINGHAOSU

Qinghaosu is an active principle of Artemisia annua L. Its crystal belongs to orthorhombicsystem, space group D-P222.Four molecules are contained in each unit cell. Cell parameters area = 24.077（6）, b = 9.443（3）, c = 6.356（1）A. Intensity data are collected on a four circle diffrac-tometer PW-1100, using CuKradiation. The structure is resolved by the symbolic addition proce-dure and refined by full-matrix least-square method to a final R index of 0.085 for 1553 reflections,0.074 for 1299 observed reflections.The absolute configuration is established by direct measurementof fifteen enantiomer-sensitive Bijvoet reflection pairs.Five oxygen atoms crowd on one side ofthe molecule.O-O bond length is 1.478A. Variation in carbon-oxygen bond types is discussed.