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DOI: 10.1055/s-0036-1589810
Synthesis of (±)-Atropurpuran
Publication History
Publication Date:
19 December 2016 (online)
Key words
diterpenes - atropurpuran - oxidative dearomatization - samarium - ketyl–olefin cyclization![](https://www.thieme-connect.de/media/synfacts/201701/i_c072_s1_10-1055_s-0036-1589810.gif)
Significance
(±)-Atropurpuran belongs to the arcutane diterpenes and was isolated from Aconitum hemsleyanumvar. atropurpureum.Its complex structure features a tetracyclo[5.3.3.04,9.04,12]tridecane core embedding two quaternary centers and four additional stereocenters. Qin and co-workers disclose the first total synthesis relying on an oxidative dearomatization/intramolecular Diels–Alder cascade to build the bicyclo[2.2.2.]octane ring, a reductive Knoevenagel condensation, and a ketyl–olefin cyclization.
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Comment
Oxidative dearomatization of B using phenyliodine diacetate (C) in methanol followed by heating at 150 °C in xylene afforded tricycle E in 72% yield. Opening of the lactone and oxidation followed by a reductive Knoevenagel condensation and an aldol addition reaction furnished key intermediate J. Samarium-mediated ketyl–olefin cyclization afforded the (±)-atropurpuran core K in 95% yield. The total synthesis of (±)-atropurpuran was completed in a total of 25 linear steps and 0.4% overall yield.
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![](https://www.thieme-connect.de/media/synfacts/201701/i_c072_s1_10-1055_s-0036-1589810.gif)