The first enantioselective synthesis of a secalonic acid containing a dimeric tetrahydroxanthenone skeleton is described, using a Wacker-type cyclization of a methoxyphenolic compound to form a chiral chroman with a quaternary carbon stereogenic center with >99% ee. Further steps are a Sharpless dihydroxylation and a Dieckmann condensation to give a tetrahydroxanthenone. A late-stage one-pot palladium-catalyzed Suzuki-dimerization reaction leads to the 2,2'-biphenol linkage to complete the enantioselective total synthesis of secalonic acid E in 18 steps with 8% overall yield.

Of the more than 100 casbane diterpenes knownt o date,o nly the eponymous parent hydrocarbon casbene itself has ever been targeted by chemical synthesis.Outlined herein is ac onceptually new approach that brings not as ingle but avariety of casbane derivatives into reach, especially the more highly oxygenated and arguably more relevant members of this family.T he key design elements are ac atalyst-controlled intramolecular cyclopropanation with or without subsequent equilibration, chain extension of the resulting stereoisomeric cyclopropane building blocks by chemoselective hydroboration/cross-coupling,a nd the efficient closure of the strained macrobicyclic framework by ring-closing alkyne metathesis.A hydroxy-directed catalytic trans-hydrostannation allows for late-stage diversity.These virtues are manifested in the concise total syntheses of depressin, yuexiandajisu A, and ent-pekinenin C. The last compound turned out to be identical to euphorhylonal A, the structure of which had clearly been misassigned.

A convergent, nine‐step (LLS), enantioselective synthesis of α‐cyclopiazonic acid and related natural products is reported. The route features a) an enantioselective aziridination of an imine with a chiral sulfur ylide; b) a bioinspired (3+2)‐cycloaddition of the aziridine onto an alkene; and c) installation of the acetyltetramic acid by an unprecedented tandem carbonylative lactamization/N−O cleavage of a bromoisoxazole.

[Rh2(MEPY)4] is a versatile catalyst for asymmetric synthesis but its preparation requires purification by chromatography on surface‐modified silica. A higher yielding procedure based on a more convenient work‐up is presented herein. Moreover, a much improved method for the preparation of [BiRh(OTfa)4] is described, which makes this heterobimetallic complex readily available. Subsequent exchange of the trifluoroacetate ligands opens access to a so far underappreciated family of (chiral) paddlewheel complexes. While [BiRh] complexes comprising four carboxylate ligands are highly adequate for intermolecular asymmetric cyclopropanation reactions, [BiRh(MEPY)4] as the heterobimetallic cousin of [Rh2(MEPY)4] was found to be surprisingly unreactive; DFT calculations uncover the reasons for this inertia.

Ac onvergent, nine-step (LLS), enantioselective synthesis of a-cyclopiazonic acid and related natural products is reported. The route features a) an enantioselective aziridination of an imine with ac hiral sulfur ylide;b )abioinspired (3+ +2)-cycloaddition of the aziridine onto an alkene;a nd c) installation of the acetyltetramic acid by an unprecedented tandem carbonylative lactamization/NÀOc leavage of ab romoisoxazole.