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Unusual Temperature Dependence of Enantioselectivity in Asymmetric Reductions by Chiral NADH Models

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journal contribution
posted on 11.05.2006, 00:00 by Ryota Saito, Shoichiro Naruse, Koji Takano, Keiko Fukuda, Akira Katoh, Yoshihisa Inoue
Unusual stereoselectivity changes, i.e., enhancement and inversion of enantioselectivity with increasing temperature, were observed in the asymmetric reduction of methyl benzoylformate with chiral 1,4-dihydropyridines possessing amino acid residues as ligating chiral auxiliaries. The differential activation parameters, ΔΔHS-R and ΔΔSS-R, obtained from the Eyring plots demonstrate that the entropy term controls the enantiodifferentiating step, accounting for the observed unique temperature dependencies.