Synthesis from a by-product of artemisinin production
As a starting point, the chemists use artemisinic acid a substance produced as a hitherto unused by-product from the isolation of artemisinin from sweet wormwood, which is produced in volumes ten times greater than the active ingredient itself. Moreover, artemisinic acid can easily be produced in genetically modified yeast as it has a much simpler structure. "We convert the artemisinic acid into artemisinin in a single step," says Peter Seeberger. "And we have developed a simple apparatus for this process, which enables the production of large volumes of the substance under very controlled conditions." The only reaction sequence known up to now required several steps, following each of which the intermediate products had to be isolated laboriously a method that was far too expensive to offer as a viable alternative to the production of the drug from plants.
The striking simplification of artemisinin synthesis required not only a keen sense for an elegant combination of the correct partial reactions to enable the process to take place in a single step; it also took a degree of courage, as the chemists departed from the paths typically taken by industry up to now. The effect of the molecule, which not only targets malaria but possibly also other infections and even breast cancer, is due to, among other things, a very reactive chemical group formed by two neighbouring oxygen atoms which chemists refer to as an endoperoxide. Peter Seeberger and Franois Lvesque use photochemistry to incorporate this structural element into the artemisinic acid. Ultraviolet light converts oxygen into a form that can r
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