5) Conclusion

We have now established a novel synthetic route for lactones via a combination of thiyl radical addition-cyclization and the subsequent hydrolysis of the hydroximates which have proved to be a new and promising functional group in the synthetic organic chemistry. This thiyl radical addition-cyclization of the hydroximate was successfully applied to the practical synthesis of (±)-oxo-parabenzlactone and the related lignans, and evaluation of their biological activities is now in progress.


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