The constituents of Californian redwood: the constitution, absolute stereochemistry, and chemistry of sequirin-B and sequirin-C

Abstract

Two new natural phenols have been isolated from Sequoia sempervirens heartwood. By spectroscopic and chemical methods, one, sequirin-B, is shown to be (2R,4S,5S)-4-(3,4-dihydroxyphenyl)-5-hydroxy-2-(4-hydroxy-phenyl)tetrahydropyran (I; R = H). The second, sequirin-C, was isolated as its methyl ether; it is shown to be (2S,3S)-(E)-3-(3,4-dimethoxyphenyl)-5-(4-methoxyphenyl)pent-4-ene-1,2-diol (V).

Three rearrangements are described. Sequirin-B on acid treatment gives isosequirin, (1S,1′S)-1-(1,2-dihydroxyethyl)-3-(4-hydroxyphenyl)indane-5,6-diol (IX; R¹= R²= OH). Trimethylsequirin-B tosylate on acetolysis gives (2R,4S,5S)-acetoxy-5-(3,4-dimethoxyphenyl-2-(4-methoxyphenyl)tetrahydropyran (XIX; R = Ac). The latter on treatment with acetic and hydrochloric acids affords (1R,2S,4R)-2-acetoxy-1-acetoxy-methyl-6,7-dimethoxy-4S-(4-methoxyphenyl)tetralin (XXXI; R = Ac). The structures of these products are demonstrated and the mechanisms of their formation are discussed.