Synthesis of β-sulfenyl endoperoxides 9 was achieved by a four component sequential free radical reaction based on the application of the thiol-olefin-co-oxygenation reaction to monoterpenes, followed by in situ treatment with triphenylphosphine. β-Sulfenyl endoperoxides 9 were oxidized with m-CPBA to β-sulfonyl endoperoxides 10. This process provides an efficient method for the preparation of peroxides containing the 2,3-dioxabicyclo[3.3.1]nonane system (2) characteristic of antimalarial agents of the yingzhaosu A (3) family. A simple NMR diagnostic tool for the identification of stereoisomers is described.
Bibliographical noteFunding Information:
This research was supported by grant No. 94-102 from the United States—Israel Binational Science Foundation (BSF), Jerusalem, Israel. E. E. K. and L. K. are grateful to the Israel Ministry of Absorption for financial support. R. H. thanks the Swiss Society of the Friends of the Weizmann Institute of Science for a generous fellowship. We gratefully acknowledge Dr L. Shimon for X-ray analysis.
- Antimalarial peroxides
- Free radicals
- Multi-component reaction
- Sequential reactions
- Thiol olefin co-oxygenation reaction