Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

Autor: Alex Frichert, Peter G. Jones, Thomas Lindel
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Beilstein Journal of Organic Chemistry, Vol 14, Iss 1, Pp 2461-2467 (2018)
Druh dokumentu: article
ISSN: 1860-5397
DOI: 10.3762/bjoc.14.222
Popis: The first synthesis of diterpenoid eunicellane skeletons incorporating a 1,3-cyclohexadiene moiety is presented. Key step is a low-valent titanium-induced pinacol cyclization that proved to be perfectly diastereoselective. Determination of the relative configuration of the diol was aided by the conversion to the diastereomer by oxidation and reduction. Conformational analysis of some of the resulting diols obtained under McMurry conditions was complicated by the presence of several conformers of similar energy. The pinacol coupling appears to start at the ketone, as indicated by the selective reduction of non-cyclizing cyclohexane systems that were synthesized from limonene oxide. The title compounds and their synthetic precursors are prone to aromatization on contact with air oxygen. Attempted synthesis of cyclohexene-containing eunicellane bicycles by elimination of water from tertiary alkynyl carbinols afforded novel allene systems. Our study may be of help towards the total synthesis of solenopodin or klysimplexin derivatives.
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