Total Synthesis of the Highly Oxygenated Quassinoid (+/-)-Klaineanone

Article abstract of DOI:10.1021/ja00198a046

The total synthesis of klaineanone (1), isolated from the seeds of Hannoa klaineana, is described in racemic form.The synthesis commences with the tetracyclic ketone 6, which is transformed into tetracyclic olefinic lactone 23, which possesses the correct configuration at C(9).Incorporation of the ring A 1β-hydroxy-2-oxo-Δ^3,4 olefin unit into tetracyclic olefinic lactone 23, which features a Rubottom epoxidation of silyloxy diene 35 followed by a base-catalyzed tautomerism of the resultant hydroxy ketone 36, provides tetracyclic olefin 37, Epoxidation of the C(11), C(12) olefin in teracyclic compound 37 and subsequent acid-catalyzed ring opening affords dl-klaineanone.