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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. [ABSTRACT FROM AUTHOR]

The sesquiterpene nanaimoal was synthesized in 21% overall yield and in a biomimetic manner. As a key step, the acid- catalyzed cyclization of farnesal under zeolite NaY confine- ment conditions was used. The intrazeolite cyclization of farnesal affords as major product a double-bond isomer of nanaimoal, via a novel diastereoselective tandem I ,5-diene cyclization/Prins-type reaction. [ABSTRACT FROM AUTHOR]

A general preparation method of the all-(E)-polyprenols 12 has been developed from readily available geranyl sulfone by the chain-extension process utilizing the C5 unit 5 and the chain-termination process utilizing the C5 unit 10 together with the chemoselective reductive desulfonylation. The polyprenols 12 were converted to compounds 3 containing two consecutive prenyl sulfone moieties at the tail end, which underwent the controlled electrophilic cyclization only at the carbon-carbon double bonds that were remote from the flat and rigid benzenesulfonyl groups. [ABSTRACT FROM AUTHOR]

The article provides insights in structural biology and chemistry of the terpenoid cyclases. Terpenoid cyclases catalyze the most complex chemical reactions occuring in the environment. They generate a unique hydrocarbon product with remarkable structural and stereochemical precision. The article also discusses monototerpene cyclases, diterpene cyclases, triterpene cyclases and antibody catalysis of cationic cyclization reactions.

The article reports on the potential of cycloalkane skeleta of terpenoids for the potential of combining polyepoxide cyclizations with biomimetric polyene cyclizations. The viabilities of the cyclization processes for durgamone and nakorone are tested via diepoxide cyclizations terminated by carbon nucleophiles.