STUDIES ON CIRCULAR DICHROISM OF SOME REACTIONAL INTERMEDIATES OF ARTEMISININ AND ARTEMISININ B

This paper reports circular dichroism, sector and the olefin octant projection of 6- pair synthetic intermediates of Qinghaosu (artemisinin) and Qinghaosu B (artemisinin B):γ-lactone ( compounds 1～4, 7～10 ), δ-lactone (compounds 5～6 ) and endo -α,β-unsaturated-γ-lactone (compounds 11～ 12 ). The relationship between double bond in the ring A and Cotton effect signs of diffrent lactone chromophore has been studied. By using lactone sector rule, the olefin octant rule, allylic oxygen rule and Beecham rule with C = C-C-O and C = C -C=O chromophore, their absolute configurations were assigned. The results show that the Cotton effect signs of lactone chromophore of compounds 2,4,6, and 12 should be inverted while compounds 8 and 10 are independent on the double bond in ring A.