RuO4-promoted syn-oxidative polycyclization of isoprenoid polyenes: a new stereoselective cascade process

Isoprenoid polyenes farnesyl acetate, geranylgeranyl acetate and squalene undergo oxidative polycyclization to bis-, tris-, and penta-tetrahydrofurane products, respectively, in the presence of catalytic amounts of RuO4 (from RuO2·2H2O) and NaIO4 as primary oxidant. The stereochemistry of the bis-cyclization product was established as cis-threo-cis-threo through chemical methods and 2D-NMR experiments, and a cascade mechanism was proposed that explains the reactivity exhibited by all the related polyenes. A similarity with rhenium(VII) chemistry has emerged.