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Issue 10, 2013
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Conformation and reactivity in dibenzocyclooctadienes (DBCOD). A general approach to the total synthesis of fully substituted DBCOD lignans via borostannylative cyclization of α,ω-diynes

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Abstract

Dibenzocyclooctadienes (DBCOD) are a class of plant-derived natural products that exhibit a broad range of biological activities. These include cytotoxicity, anti-hepatitis-B activity, inhibition of HIV replication and of NO production and activity. None of the fully substituted DBCODs have been prepared before. 2,2′-Dipropargylbiphenyls undergo highly regio- and atropselective cyclizations mediated by a [B-Sn]-reagent, 1-trimethylstannyl-2,5-diazaborolidine (Me3Sn–B[–N(Me)CH2CH2(Me)N–], in the presence of Pd(II)-catalysts, to give highly functionalized DBCOD precursors. The configuration of the newly created, axially chiral, 1,2-bis-alkylidene moiety is controlled by the resident chirality of the starting biphenyls and the configurations of the benzylic positions. New chemistry of the bis-alkylidenes described in this paper enables the first total syntheses of a wide variety of DBCOD natural products, fully functionalized at the cyclooctadiene ring. These include ananolignans B, C, D, F, interiotherin C, kadsuralignan B, tiegusanin D and schizanrin F. Revision of the structure of a key natural product, ananolignan B, is also reported. Key steps in the syntheses exploits the conformational features of the various DBCOD intermediates as revealed by NMR spectroscopy and X-ray crystallography.

Graphical abstract: Conformation and reactivity in dibenzocyclooctadienes (DBCOD). A general approach to the total synthesis of fully substituted DBCOD lignans via borostannylative cyclization of α,ω-diynes

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Publication details

The article was received on 23 Jun 2013, accepted on 16 Jul 2013 and first published on 17 Jul 2013


Article type: Edge Article
DOI: 10.1039/C3SC51751A
Citation: Chem. Sci., 2013,4, 3979-3985

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    Conformation and reactivity in dibenzocyclooctadienes (DBCOD). A general approach to the total synthesis of fully substituted DBCOD lignans via borostannylative cyclization of α,ω-diynes

    W. Gong and T. V. RajanBabu, Chem. Sci., 2013, 4, 3979
    DOI: 10.1039/C3SC51751A

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