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Cascade Metathesis Reactions for the Synthesis of Taxane and Isotaxane Derivatives
Cong Ma1, Aurélien Letort2, Rémi Aouzal1
1Laboratoire de Synthèse Organique, CNRS UMR 7652, Ecole Polytechnique, DCSO, 91128, Palaiseau, France.
Abstract:
Tricyclic isotaxane and taxane derivatives have been synthesized by a very efficient cascade ring-closing dienyne metathesis (RCDEYM) reaction, which formed the A and B rings in one operation. When the alkyne is present at C13 (with no neighboring gem-dimethyl group), the RCEDYM reaction leads to 14,15-isotaxanes 16 a,b and 18 b with the gem-dimethyl group on the A ring. If the alkyne is at the C11 position (and thus flanked by a gem-dimethyl group), RCEDYM reaction only proceeds in the presence of a trisubstituted olefin at C13, which disfavors the competing diene ring-closing metathesis reaction, to give the tricyclic core of Taxol 44.
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