- Effects of the terminal-methyl position and of the length of the conjugated chain on the cis isomers produced by photo-isomerization: Analysis by HPLC and configurational determination by 1H-NMR spectroscopy of isomeric analogues of retinal and β-apo-12′-carotenal
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An analogue of retinal (β-apo-12′-carotenal), its terminal-methyl group being shifted from the 13 to 14 (from 13′ to 14′) position, was subjected to direct (iodine-sensitized) photo-isomerization. The configurations of five (seven) isomers of the retinal (β-apo-12β-carotenal) analogue were determined by 1H-NMR spectroscopy to be all-trans, 7-, 9- and 11-mono-cis and 9,11-di-cis (all-trans, 9-, 13- and 13′-mono-cis and 9,13-, 9,13′- and 13,13′-di-cis). Comparative direct photo-isomerization in acetonitrile of the above parent and analogue aldehydes showed that the kinds and the amounts of cis isomer produced in the stationary-state mixtures are drastically affected by the terminal-methyl position and by the length of the conjugated chain. The results are discussed in terms of enhanced polarization upon excitation in the terminal C=O and the neighbouring C=C bonds in the conjugated chain.
- Hu, Ying,Okumura, Akio,Koyama, Yasushi,Yamano, Yumiko,Ito, Masayoshi
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- Retinoids and Related Compounds. Part 14. A Novel Synthesis of Conjugated 4-Alkylidenebutenolides and Their Spectral Characterization
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A novel synthesis (the sulfone method) of carotenoidal alkylidenebutenolides is described together with spectral characterization of the latter.
- Ito, Masayoshi,Katsuta, Yuko,Yamano, Yumiko,Tsukida, Kiyoshi
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p. 987 - 994
(2007/10/02)
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- Retinoids and Carotenoids, V.- Synthesis of Modified Retinals
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The syntheses of 13-demethyl-13-ethyl-, 13-demethyl-13-propyl-, 13-demethyl-, 13-demethyl-14-methyl-, and 14-methylretinal are described.The UV spectra of some geometric isomers of these compounds are discussed.
- Bestmann, Hans Juergen,Ermann, Peter,Rueppel, Hartmann,Sperling, Walter
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p. 479 - 498
(2007/10/02)
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