Longe-distance Controle in Stereoselective Reduction of 3-[3-(4"-Bromo[1, 1"-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one - Relative Configuration of Prevailing Diastereomer and Absolute Configuration of its Enantiomers (CROSBI ID 77546)
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Podaci o odgovornosti
Avdagić, Amir ; Cotarca, Livius ; Hameršak, Zdenko ; Hollosi, Miklos ; Ljubović, Edina ; Šuste, Andreja ; Šunjić, Vitomir
engleski
Longe-distance Controle in Stereoselective Reduction of 3-[3-(4"-Bromo[1, 1"-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one - Relative Configuration of Prevailing Diastereomer and Absolute Configuration of its Enantiomers
Depending on the reducing agent and reaction conditions, diastereoselective reduction of 3‐[3‐(4′‐bromo[1, 1′‐biphenyl]‐4‐yl)‐3‐keto‐1‐phenylpropyl]‐4‐hydroxy‐2H‐1‐benzopyran‐2‐one (2) proceeds with different stereoselectivity ; a surprisingly high, approximately 90% d.e. of 4A is achieved with NaBH4 in MeOH at low temperature. Resulting diastereomeric racemates 4A and 4B are separated and their respective syn and anti configurations are assigned on the bases of mechanic considerations, supported by the 1H‐NMR spectra and conformational analysis based on MM2 calculations. The syn diastereomer 7A, 4‐OMe derivative of 4A, was partially resolved by acylation at C(3)‐OH with S‐(−)‐camphanic acid to camphanyl ester 12 of (−)‐7A, leaving (+)‐enantiomer 7A. The assignment of absolute 1R, 3S‐configuration to (−)‐7A is based on comparison of its CD spectrum with those of the model compounds S‐14 and R‐15, which represent partial chromophores 4‐hydroxy‐2H‐1‐benzopyran‐2‐one (4‐hydroxycoumarin) A, and 4′‐bromo‐1, 1′‐biphenyl B ; their exciton coupling in (−)‐7A is suggested.
stereoselective reduction
Special Issue: Special Commemorative Issue Honoring Chirality Medal Winner
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Podaci o izdanju
9 (5-6)
1997.
512-522
objavljeno
0899-0042
1520-636X
10.1002/(SICI)1520-636X(1997)9:5/6<512::AID-CHIR18>3.0.CO;2-R