Unusual Temperature Dependence of Enantioselectivity in Asymmetric Reductions by Chiral NADH Models
作者:Ryota Saito、Shoichiro Naruse、Koji Takano、Keiko Fukuda、Akira Katoh、Yoshihisa Inoue
DOI:10.1021/ol060475g
日期:2006.5.1
[reaction: see text] 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, DeltaDeltaH(S-R) and DeltaDeltaS(S-R), obtained from the Eyring
[反应:见正文]在具有手性的1,4-二氢吡啶的手性1,4-二氢吡啶与连接的手性助剂不对称还原苯甲酰甲酸酯的过程中,观察到了不寻常的立体选择性变化,即对映选择性随温度升高而增强和反转。从Eyring曲线获得的差分激活参数DeltaDeltaH(SR)和DeltaDeltaS(SR)表明,熵项控制了对映微分步骤,这说明了观察到的独特温度依赖性。