RESUMEN
The size and shape of the chiral cavity of a macrocyclic receptor were tuned by the alteration of the binaphthyl moiety to improve the chiral recognition/discrimination ability. For example, host 3 with the 3,5-bis(trifluoromethyl)phenyl group at the 3,3'-positions showed improved enantioselectivity for small molecules such as 2-chloropropionic acid and methyl lactate as evaluated by the binding constants. This host 3 also had an excellent ability as an NMR chiral solvating agent.
Asunto(s)
Compuestos Macrocíclicos/química , Modelos Moleculares , Conformación Molecular , Naftalenos/química , Estereoisomerismo , Especificidad por Sustrato , TermodinámicaRESUMEN
Chiral macrocycles with the hydrogen bond donor/acceptor sites in the cavity were synthesized and covalently bonded to silica gel to give chiral stationary phases (CSPs), which showed excellent abilities to resolve various chiral compounds, such as benzoin and Co(acac)3, in HPLC. Various organic solvents could be used as the mobile phase to optimize the resolution efficiency of CSPs, and in some cases, even MeCN, MeOH, and CO(2) could be used for the complete resolution of enantiomers.
Asunto(s)
Compuestos Macrocíclicos/síntesis química , Benzoína/química , Cromatografía Líquida de Alta Presión/métodos , Enlace de Hidrógeno , Compuestos Macrocíclicos/química , Estructura Molecular , EstereoisomerismoRESUMEN
Trifunctional organocatalysts and mimicking the active site of serine hydrolases showed high catalytic activity with up to a 3,700,000-fold acceleration for the acyl-transfer reactions from vinyl trifluoroacetate to alcohol.
Asunto(s)
Alcoholes/síntesis química , Materiales Biomiméticos/química , Biomimética , Ésteres/química , Piridinas/química , Tiourea/química , Compuestos de Vinilo/química , Alcoholes/química , Sitios de Unión , Materiales Biomiméticos/síntesis química , Catálisis , Enlace de Hidrógeno , Conformación Molecular , Piridinas/síntesis química , Factores de TiempoRESUMEN
Bifunctional macrocycles 1-4 and diamide 5 were designed and synthesized. NMR studies demonstrated that, among them, receptor 1 functions as the best chiral solvating agent (shift reagent), which is effective for a wide range of chiral compounds having a carboxylic acid, oxazolidinone, carbonate, lactone, alcohol, sulfoxide, sulfoximine, sulfinamide, isocyanate, or epoxide functionality. The addition of only 5 mol % (69 microg, 0.15 mM) of 1 splits the enantiomeric signals of sulfoxide 13. The excellent performance of 1 as a chiral solvating agent, such as versatility, signal sharpness, high splitting ability, high sensitivity, wide detection window, and synthetic accessibility, is reported. NMR studies revealed that the principal binding site of 1 is the two amide NH groups of the lower segment and that the additional binding site is the pyridyl nitrogen. The V-shaped arrangement of the two 2,6-diacylaminopyridine moieties as constructed in 1 was found to be much more effective for binding a variety of compounds than the parallel alignment of the two binding motifs as constructed in 4. The NO2 group in 1 enhanced not only the binding ability but also the degree of enantioselectivity. Unexpectedly, the comparisons between 1 and 3 enabled us to find the importance of the relative orientation of the binaphthyl moiety; the orthogonal disposition of the binaphthyl moiety in 1 most effectively brings about the differential ring-current effect on the chiral guest molecule bound, which leads to the high degree of chiral discrimination in NMR.
RESUMEN
[structure: see text] Bifunctional macrocycle 1 with C2 symmetry was newly synthesized. NMR studies demonstrated that receptor 1 functions as a chiral shift reagent (solvating agent) that is highly effective for a wide range of chiral compounds having a carboxylic acid, oxazolidinone, lactone, alcohol, sulfoxide, sulfoximine, isocyanate, or epoxide functionality. Binding constants were determined to investigate the binding behavior of 1.