American Chemical Society
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Variants of the Prins Cyclization for the Synthesis of Terpenoid Spiroethers and Oxabicyclo[3.3.1]Nonane Derivatives

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journal contribution
posted on 2014-11-07, 00:00 authored by Verena Weidmann, Jasper Ploog, Serge Kliewer, Mathias Schaffrath, Wolfgang Maison
Terpenoid spiroethers are abundant natural flavors with significant impact, particularly in the food industry. We present in this article the synthesis of new derivatives of the well-known flavors theaspirane and vitispirane using a variant of the Prins cyclization starting from α,β-unsaturated or heterocyclic ketones. When aromatic ketones were used as the starting materials for Lewis acid-mediated cyclizations, an alternative pathway involving a domino sequence of Prins cyclization, followed by an intramolecular Friedel–Crafts alkylation, gave benzoannelated oxabicyclo[3.3.1]­nonane derivatives. Different reaction pathways may be triggered by the reaction temperature to give with good selectivity either tetrahydropyran derivatives as conventional Prins products or oxabicyclo[3.3.1]­nonane derivatives.