First total syntheses of unnatural (−)-14-epi-samaderine E (5) and natural (−)-samaderine Y (2) were accomplished from (S)-(+)-carvone (6) in 18 and 21 steps, respectively. The syntheses are short, efficient (with an average yield of 80 % plus for each transformation), enantiospecific, and produce nine new chiral centers. The crucial points of the syntheses included a regioselective allylic oxidation on ring C, regio- and stereoselective reduction of ketone, a stereocontrolled epoxidation, an epoxymethano-bridge formation, a chemoselective Grignard reaction, an intramolecular Diels–Alder reaction, an intramolecular aldol addition, and a newly developed manganese(III)-catalyzed allylic oxidation on ring A.

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.