Enantioselective Total Syntheses of Pallambins A–D

Abstract

The first enantioselective total syntheses of (À)pallambins A-D have been achieved in 15 or 16 steps from aknownchiral cyclohexenone.Salient features of the syntheses include ap alladium-catalyzed oxidative cyclization to assemble the [3.2.1]bicyclic moiety,a nE schenmoser-Claisen rearrangement/lactone formation sequence to construct the Cring, an intramolecular Wittig reaction to form the Dring, and individual transformations of pallambins Cand Dtogenerate pallambins Aa nd B. The described synthesis avoids protecting-group manipulations through the design of highly chemoand stereoselective transformations.D uring the course of this work, ap alladium-catalyzed method for the dehydrobromination of a-bromoketones was developed, and the scope of this transformation was also investigated.

seco‐Labdanes: A Study of Terpenoid Structural Diversity Resulting from Biosynthetic C−C Bond Cleavage

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The Total Synthesis of Diquinane‐Containing Natural Products

“…In 2012, Lou group, who isolated and elucidated pallambins A–D, reported the photoinduced interconversion of C and D to A and B respectively through a diradical pathway, in which the cyclic enone and the terminal alkene underwent a skeletal rearrangement to produce the all‐carbon skeleton containing the diquinane and the cyclopropane moieties (Scheme 22 a). [59] Recently, Jia group took advantage of this transformation to the total syntheses of pallambins A and B from C and D [60] . Starting from the known chiral cyclohexenone 121 , facial selective conjugate addition with vinyl cuprate generated intermediate 122 and a subsequent Pd‐catalyzed oxidative cyclization delivered the bicyclo[3.2.1]octane 123 .…”

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