I. Synthetic studies of drimane and labdane-type terpenoids via photo-electrocyclic reaction of trienes involving enolate double bond. Irradiation of β-keto-ester 1 with high pressure mercury lamp in methanol in the presence of 2-molar excess of sodium methoxide gave bicyclic enolate ester by electrocyclic reaction involving triene in a conrotatory manner and subsequent protonation gave highly stereoselectively a key decalone derivative 4. 1). Five stage synthesis of hydroxy lactone 19 accessible to bemarivolide starting from key decalone derivative 4 is described. 2). Six stage synthesis of γ-hydroxy enone 28 accessible to 6-oxogrindelic acid starting from key decalone derivative 4 is described. II. New synthesis of cyclopentenols via intramolecular photo-oxentane formation. Several cyclopentenol derivatives accessible to natural products were synthesized in moderate yield by the irradiation of olefinic β-keto ester derivatives followed by treatment with sodium hydride. III. Photosensitized oxygenation of highly skewed polyenes. Photosensitized oxygenation of cis-β-ionol prepared from trans-β-ionol by photosensitized isomerization of double bond afforded in high yield a mixture of allenic diol and exomethylene diol in the ratio of 1:2.
