Beilstein J. Org. Chem.2024,20, 1320–1326, doi:10.3762/bjoc.20.115
., Davis, CA 95616, USA Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India Whitney Laboratory for Marine Bioscience, University of Florida, 9505 N Ocean Shore Blvd., St. Augustine, FL 32080, USA 10.3762/bjoc.20.115 Abstract Eunicellane diterpenoids are a unique family of
-eunicellane skeletons, respectively. Although the structures of these diterpenes only differed in their configuration at a single position, C1, they displayed distinct chemical and thermal reactivities. Here, we used a combination of quantum chemical calculations and chemical transformations to probe their
intrinsic properties, which result in protonation-initiated cyclization, Cope rearrangement, and atropisomerism. Finally, we exploited the reactivity of the trans-eunicellane skeleton to generate a series of 6/6/6 gersemiane-type diterpenes via electrophilic cyclization.
Keywords: atropisomer; Cope
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Graphical Abstract
Figure 1:
Eunicellane diterpenoids and their biosyntheses. (A) The 6/10-bicyclic hydrocarbon framework is con...
Beilstein J. Org. Chem.2018,14, 2461–2467, doi:10.3762/bjoc.14.222
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
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.
Keywords: conformational analysis; low valent titanium; marine natural products; pinacol coupling; ten-membered rings; Introduction
Eunicellane-type diterpenoids share