Total Synthesis of Tiacumicin B: Implementing Hydrogen Bond Directed Acceptor Delivery for Highly Selective β‐Glycosylations
Résumé
We report a total synthesis of tiacumicin B, a natural macrolide whose remarkable antibiotic properties are used to treat severe intestinal infections. The strategy is in part based on our experience of the synthesis of the tiacumicin B aglycone, and on the decisive use of sulfoxides as anomeric leaving-groups in H-bond-mediated Aglycone Delivery (HAD). This new HAD variant permitted highly b-selective rhamnosylation and noviosylation. To increase convergence, the rhamnosylated C1-C3 fragment thus obtained was anchored to the C4-C19 aglycone fragment by adapting the reliable Suzuki-Miyaura cross-coupling used for the aglycone synthesis. Ring-size selective macrolactonization provided a compound engaged directly in the noviolysation step with a virtually total b-selectivity. The final efficient removal of all the protective groups (PGs) provided synthetic tiacumicin B.
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