Stereokontrollierte Synthesen von verbrückten Ethern durch Dominocyclisierungen

Icetexane diterpenoids are a diverse family of natural products sourced from several species of terrestrial plants. Icetexanes exhibit a broad array of biological activities and together with their complex 6‐7‐6 tricyclic scaffolds, they have piqued the interest of synthetic organic chemists, natural products chemists, and biological investigators over the past four decades and were reviewed 13 years ago. This review summarizes icetexane natural products isolated since 2009, provides an overview of new synthetic approaches to the icetexane problem, and proposes an additional classification of icetexanes based on novel structures that are unlike previously isolated materials.

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Total Synthesis of (−)‐Platensimycin by Advancing Oxocarbenium‐ and Iminium‐Mediated Catalytic Methods

Eey

Lear

2014

Chemistry A European J

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(-)-Platensimycin is a potent inhibitor of fatty acid synthase that holds promise in the treatment of metabolic disorders (e.g., diabetes and "fatty liver") and pathogenic infections (e.g., those caused by drug-resistant bacteria). Herein, we describe its total synthesis through a four-step preparation of the aromatic amine fragment and an improved stereocontrolled assembly of the ketolide fragment, (-)-platensic acid. Key synthetic advances include 1) a modified Lieben haloform reaction to directly convert an aryl methyl ketone into its methyl ester within 30 seconds, 2) an experimentally improved dialkylation protocol to form platensic acid, 3) a sterically controlled chemo- and diastereoselective organocatalytic conjugate reduction of a spiro-cyclized cyclohexadienone by using the trifluoroacetic acid salt of α-amino di-tert-butyl malonate, 4) a tetrabutylammonium fluoride promoted spiro-alkylative para dearomatization of a free phenol to assemble the cagelike ketolide core with the moderate leaving-group ability of an early tosylate intermediate, and 5) a bismuth(III)-catalyzed Friedel-Crafts cyclization of a free lactol, with LiClO4 as an additive to liberate a more active oxocarbenium perchlorate species and suppress the Lewis basicity of the sulfonyloxy group. The longest linear sequence is 21 steps with an overall yield of 3.8 % from commercially available eugenol.

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Stereokontrollierte Synthesen von verbrückten Ethern durch Dominocyclisierungen

Abstract: Ringkontraktion eines 3,4‐Epoxyalkohols, Lactolisierung und elektrophiler Angriff sind die Schritte der Dominocyclisierung zu anellierten 8‐Oxabicyclo[3.2.1]octanen [Gl. (a)].

Cited by 6 publications

References 11 publications

A Practical Route to Enantiopure, Highly Functionalized Seven-Membered Carbocycles and Tetrahydrofurans: Concise Synthesis of (+)-Nemorensic Acid

A Practical Route to Enantiopure, Highly Functionalized Seven-Membered Carbocycles and Tetrahydrofurans: Concise Synthesis of (+)-Nemorensic Acid

Recent Developments with Icetexane Natural Products

Total Synthesis of (−)‐Platensimycin by Advancing Oxocarbenium‐ and Iminium‐Mediated Catalytic Methods

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