Spiroligozymes for transesterifications: design and relationship of structure to activity.
J Am Chem Soc
; 134(44): 18345-53, 2012 Nov 07.
Article
en En
| MEDLINE
| ID: mdl-22992057
ABSTRACT
Transesterification catalysts based on stereochemically defined, modular, functionalized ladder-molecules (named spiroligozymes) were designed, using the "inside-out" design strategy, and mutated synthetically to improve catalysis. A series of stereochemically and regiochemically diverse bifunctional spiroligozymes were first synthesized to identify the best arrangement of a pyridine as a general base catalyst and an alcohol nucleophile to accelerate attack on vinyl trifluoroacetate as an electrophile. The best bifunctional spiroligozyme reacted with vinyl trifluoroacetate to form an acyl-spiroligozyme conjugate 2.7 × 10(3)-fold faster than the background reaction with a benzyl alcohol. Two trifunctional spiroligozymes were then synthesized that combined a urea with the pyridine and alcohol to act as an oxyanion hole and activate the bound acyl-spiroligozyme intermediate to enable acyl-transfer to methanol. The best trifunctional spiroligozyme carries out multiple turnovers and acts as a transesterification catalyst with k(1)/k(uncat) of 2.2 × 10(3) and k(2)/k(uncat) of 1.3 × 10(2). Quantum mechanical calculations identified the four transition states of the catalytic cycle and provided a detailed view of every stage of the transesterification reaction.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Piridinas
/
Compuestos de Vinilo
/
Materiales Biomiméticos
/
Alcoholes
Idioma:
En
Revista:
J Am Chem Soc
Año:
2012
Tipo del documento:
Article
País de afiliación:
Estados Unidos