A novel approach to angular triquinanes via intramolecular 1,3-dipolar cycloaddition of nitrile oxide
摘要:
The framework of angular triquinane sesquiterpenes was stereoselectively constructed via the intramolecular 1,3-dipolar cycloaddition of nitrile oxide precursors. Optically active indandione 9 was converted into olefinic oximes 18A and 18B through two successive alkylations, followed by ring contraction. Oxidation of the mixture 18A and 18B with sodium hypochlorite gave rise to tetracyclic isoxazolines 21A and 21B, which were transformed into tricyclo[6.3.0.0(4,8)]undecanes 28 and 29.