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Unusual temperature dependence of enantioselectivity in asymmetric reductions by chiral NADH models.
Org Lett
; 8(10): 2067-70, 2006 May 11.
Artículo
en Inglés
| MEDLINE
| ID: mdl-16671783
RESUMEN
[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 plots demonstrate that the entropy term controls the enantiodifferentiating step, accounting for the observed unique temperature dependencies.