We report the enantioselective total syntheses of zeylenol (+)‐1, as well as its congeners (−)‐7 and 16, and of 3‐O‐debenzoylzeylenone 28. To this end, a new variant of the Kornblum–DeLaMare rearrangement, which utilises neighbouring‐group participation to impart regioselectivity, has been developed. The approach employs photooxygenation of building blocks derived from a microbial arene oxidation product.
(+)-Grandifloracin was synthesized from sodium benzoate by means of a dearomatizing dihydroxylation that proceeds with unusual regioselectivity. Iron diene complexes formed from the arene oxidation product permit the use of otherwise inaccessible transformations. The synthetic material was shown to be antipodal to the natural product, thus determining the absolute configuration of grandifloracin for the first time.
Substituted furfuryl alcohols are extraordinarily versatile starting materials in synthesis. They are precursors to furanoxonium ion intermediates which are implicated in the Piancatelli reaction (leading to 2-cyclopentenones) and in the synthesis of novel dihydrofuran-based exo enol ether/cyclic ketal natural products. They are also intermediates in a recently discovered (4+3) cycloaddition reaction with 1,3-dienes leading to furan ring-fused cycloheptenes. Here we provide a perspective on recent developments in these areas of synthesis, alongside recent applications of the Achmatowicz reaction and [5+2] cycloaddition reactions of the resulting oxidopyrylium ions.
Covering: up to May 2018The verticillene family of 6,12-membered ring-fused diterpenes are found in plants, liverworts, corals and insects. Carbocations derived from verticillene hydrocarbons are central intermediates in the biosynthesis of the taxane and the phomactin families of polycyclic natural products. This perspective delineates these unique biosynthetic interrelationships, which are reinforced by recent biomimetic synthesis investigations, alongside quantum chemical calculations and targeted engineering studies of the taxadiene synthase (TXS) cascade.
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