SYNTHESIS OF QINGHAOSU ANALOGUES VIA OZONIZATION

This paper reports some synthetic efforts on the preparation of qinghaosu analogues from relay intermediate by means of ozonization, α, β-unsaturated ketonic acid Ⅱ, a degradation product from qinghaosu, was treated with methyl Grignard reagent at low temperature to afford an allylic lactone Ⅲ, which on ozonization was converted to a stable ozonide Ⅴ. Reduction of Ⅲ by lithium aluminium hydride, followed by ozonization, gave a 1, 2, 4-trioxan compound Ⅺ, which could not be converted to a similar tetracyclic compound as qinghaosu. However, hydrolysis of Ⅲ, followed by ozonization, yielded a mixture, from which only, an analogue of deoxyqinghaosu was obtained.