An advanced pentacyclic intermediate, amenable to further elaboration into the target molecules simalikalactone D and quassimarin, has been synthesized from (S)-(+)-carvone in 21 steps and with an overall yield of 12 %. The synthesis is efficient, stereocontrolled, enantiospecific, and chirality productive, creating eight new chiral centres in pentacycle, and should provide opportunities for rapid access to simalikalactone D analogues and other bioactive quassinoids. The reaction sequence involves a regioselective bishydroxylmethylation, a stereocontrolled epoxidation, an epoxymethano-bridge formation, a 1,3-sigmatropic rearrangement and an intramolecular Diels-Alder reaction as the key steps.
Terpenes Terpenes U 0200 Studies Towards Simalikalactone D (Ia) and Quassimarin (Ib): Construction of an Advanced Pentacyclic Intermediate (II). -(SHING*, T. K. M.; ZHU, X. Y.; YEUNG, Y. Y.; Chem. Eur.
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