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Paper | Special issue | Vol 82, No. 1, 2010, pp.603-617
Published online, 21st July, 2010
DOI: 10.3987/COM-10-S(E)33
Diastereoselective Cyclization Reactions of Chiral Proline Auxiliary-Substituted N-Benzoyl-α-dehydro(1-naphthyl)alaninamide Derivatives via Photoinduced Electron Transfer

Yuhki Sato, Yuhta Haruyama, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan


Irradiation of the title 1-naphthylalaninamide derivatives [(Z)-1] bearing N’-substituted (S)-prolinamide auxiliaries in 1,2-dichloroethane and methanol containing triethylamine mainly afforded the corresponding (4S,5S)-4,5-dihydrooxazoles [(4S,5S)-2, diastereomeric excess (de) = 21–84%] and (4R,5R)-2 (de = 18–43%), respectively. Analysis of substituent and solvent effects on the diastereoselective photocyclization of (Z)-1 substantiated that steric bulkiness of the chiral auxiliary, solvent polarity, and intramolecular hydrogen bond are major factors controlling de, while intermolecular hydrogen-bonding and charge-transfer interactions invert the configuration of the dihydrooxazole diastereomer preferentially formed.