Asymmetric total synthesis of structurally intriguing and highly oxygenated lancifodilactone G acetate (7) has been achieved for the first time in 28 steps from a cheap commodity chemical, 2-(triisopropylsiloxy)-1,3-butadiene.
Complex natural products are a proven and rich source of disease-modulating drugs and of efficient tools for the study of chemical biology and drug discovery. The architectures of complex natural products are generally considered to represent significant barriers to efficient chemical synthesis. Here we describe a concise and efficient asymmetric synthesis of 19-dehydroxyl arisandilactone A—which belongs to a family of architecturally unique, highly oxygenated nortriterpenoids isolated from the medicinal plant Schisandra arisanensis. This synthesis takes place by means of a homo-Michael reaction, a tandem retro-Michael/Michael reaction, and Cu-catalysed intramolecular cyclopropanation as key steps. The proposed mechanisms for the homo-Michael and tandem retro-Michael/Michael reactions are supported by density functional theory (DFT) calculation. The developed chemistry may find application for the synthesis of its other family members of Schisandraceae nortriterpenoids.
Pre-schisanartanin C belongs to the family of Schisandra nortriterpenoids with potent antihepatitis, antitumor,
and anti-HIV
activities. This paper presents the enantioselective total synthesis
of pre-schisanartanin C (1). An important step in the
total synthesis of 1 is gold-catalyzed intramolecular
cyclopropanation of a 1,8-enyne substrate bearing a secondary ester
group at the propargylic position to prepare a bicyclo[6.1.0]nonane
core. Additional highlights include (i) an asymmetric Diels–Alder
reaction to install the initial C5 stereogenic center of 1 and (ii) a sequential Pd-catalyzed Stille coupling, regio- and stereoselective
Sharpless asymmetric dihydroxylation, and a subsequent intramolecular
lactonization to construct the side chain of 1. The developed
chemistry paves the way for the total syntheses of other family members
bearing highly rigid bicyclo[6.1.0]nonane cores.
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