Enantioselective Total Syntheses of Pallambins A–D

Abstract

The first enantioselective total syntheses of (−)‐pallambins A–D have been achieved in 15 or 16 steps from a known chiral cyclohexenone. Salient features of the syntheses include a palladium‐catalyzed oxidative cyclization to assemble the [3.2.1]bicyclic moiety, an Eschenmoser–Claisen rearrangement/lactone formation sequence to construct the C ring, an intramolecular Wittig reaction to form the D ring, and individual transformations of pallambins C and D to generate pallambins A and B. The described synthesis avoids protecting‐group manipulations through the design of highly chemo‐ and stereoselective transformations. During the course of this work, a palladium‐catalyzed method for the dehydrobromination of α‐bromoketones was developed, and the scope of this transformation was also investigated.

The Total Synthesis of Diquinane‐Containing Natural Products

“…In 2012, Lou group, who isolated and elucidated pallambins A-D, reported the photoinducedi nterconversion of Ca nd Dt o Aa nd Br espectively through ad iradical pathway,i nw hich the cyclic enone and the terminal alkene underwent as keletal rearrangement to produce the all-carbon skeleton containing the diquinane and the cyclopropane moieties (Scheme 22 a). [59] Recently,J ia group took advantage of this transformation to the total syntheses of pallambinsAand Bf rom Ca nd D. [60] Starting from the known chiral cyclohexenone 121,facial selective conjugate addition with vinyl cuprateg eneratedi ntermediate 122 and as ubsequentP d-catalyzed oxidative cyclization deliveredt he bicyclo[3.2.1]octane 123.U pon completion of the total syntheses of pallambins Ca nd Dt hrough as eries of transformations from carbon framework 123,i nterconversion of them to pallambins Aa nd Bt hrough Lou's bioinspired photo-induced skeletal rearrangementw ere succeeded, [59] culminatingi nt he first enantioselective total syntheses of pallambins Aand B( Scheme22b).…”

Al−Air Batteries for Seasonal/Annual Energy Storage: Progress beyond Materials

“…To solve these obstacles, Al−air batteries have been extensively studied in the past decades, but mainly from the materials aspects, [12] including cathode catalysts for oxygen reduction reactions, [13–15] doped Al metal anode to suppress self‐corrosion, [16–20] and electrolytes additives for more protective electrolyte/electrodes interphase, [21–25] which have been systematically reviewed in previous literature [12] . However, little attention has been placed on factors beyond materials, actually affecting the energy density delivered by Al−air batteries, particularly the RTE of an APCS.…”

Total Synthesis of (−)‐Glaucocalyxin A

“…[3d,i, 5] Furthermore, it is difficult to introduce the C14-OH by employing the previously reported strategies. [5,6] In the course of our investigation on the total synthesis of structurally complex diterpenoids, [10] we were also intrigued by the intricate molecular architecture of these 14oxygenated diterpenoids. We conceived an opposite sequence for the formation of the ring system to the previously reported approaches: in our design the 14-oxygenated bicyclo-[3.2.1]octane system is formed at the early stage.…”