- Novel Photosensitizers for the E/Z-Isomerization of Trienes. Part 1. Synthesis and Application
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Uranine and its thioxanthene and selenoxanthene analogues, as well as the disodium salts of o-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzenesulphonic acid and its thioxanthene and selenoxanthene analogues, show different photosensitizer properties in the E/Z-isomerization of trienes.This has been verified by applying them to the technically useful conversion of tachysterol into previtamin D.The synthesis of the novel photosensitizers with thioxanthene and selenoxanthene moieties are also described.
- Pfoertner, Karl-Heinz
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p. 523 - 526
(2007/10/02)
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- Bridged-ring steroids. III. The synthesis of bridged steroids with a bicycloheptane ring B system
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Reaction of cholesta-5,7-dien-3β-yl 2-tetrahydropyranyl ether with bromoform and potassium tert-butoxide gave 3',3'-dibromo-3',6β-dihydrocyclopropa-5a-cholest-7-en-3β-yl 2-tetrahydropyranyl ether (1c), which on treatment with lithium aluminium hydride and water gave 5,8α-methano-5α-cholest-6-en-3β-yl 2-tetrahydropyranyl ether (2c).This has been converted to 3β-acetoxy-5,8α-methano-5α-cholestan-6-one (16c) and 3β-acetoxy-5,8α-methano-5α-cholestan-7-one (17c).A preliminary investigation of the photochemistry of 16c and 17c has shown that the incorporation of the bicycloheptan-2-one system in the B ring of a steroid results in photoreactions of this system that are different from those observed in the case of simple bicycloheptan-2-ones.
- Yates, Peter,Winnik, Francoise M.
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p. 2501 - 2506
(2007/10/02)
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