Acetylation of β-Cyclodextrin Surface-Functionalized Cellulose Dialysis Membranes with Enhanced Chiral Separation

The enhanced enantiomeric separation of racemic phenylalanine solution has been demonstrated by the membrane-based chiral resolution method using an acetylated β-cyclodextrin-immobilized cellulose dialysis membrane. β-Cyclodextrin (CD) was first immobilized onto the surface of commercial cellulose d...

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Bibliographic Details
Published in:Langmuir 2007-12, Vol.23 (26), p.12990-12996
Main Authors: Xiao, Youchang, Lim, Hui Miang, Chung, Tai Shung, Rajagopalan, Raj
Format: Article
Language:English
Subjects:
Acetylation
beta-Cyclodextrins - chemistry
Cellulose - chemistry
Chemistry
Colloidal state and disperse state
Dialysis
Exact sciences and technology
General and physical chemistry
Membranes
Membranes, Artificial
Models, Molecular
Porous materials
Stereoisomerism
Surface physical chemistry
Surface Properties
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Summary:The enhanced enantiomeric separation of racemic phenylalanine solution has been demonstrated by the membrane-based chiral resolution method using an acetylated β-cyclodextrin-immobilized cellulose dialysis membrane. β-Cyclodextrin (CD) was first immobilized onto the surface of commercial cellulose dialysis membranes, followed by the acetylation reaction through the treatment of the membranes with acetic anhydride to form the chiral selective acetylated β-cyclodextrin-immobilized cellulose dialysis membrane. The acetylated CD-immobilized membrane exhibits enantioselectivity in the range of 1.26−1.33 depending on the acetylation time. The improvement in enantioselectivity after acetylation was mainly attributed to the better discrimination ability of acetylated CD and the decrease in membrane pore size. Molecular modeling simulations indicate that the acetylation of hydroxyl groups would result in a CD conformation with torus distortions and would create higher steric hindrance for penetrants. As a result, compared to the original CD, the acetylated CD may have less effective binding but better discrimination of enantiomers. The energy drop is only 3 kcal/mol between different enantiomers before and after the binding of phenylalanine with an unmodified CD. The energy drop increases to 10 kcal/mol if acetylated CD is employed as the chiral selector, showing stronger characteristics for chiral selection.
ISSN:0743-7463
1520-5827
DOI:10.1021/la7026384