posted on 2014-11-07, 00:00authored byVerena 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.