Isolation and characterization by NMR spectroscopy of three monosubstituted 4-sulfobutyl ether derivatives of cyclomaltoheptaose (β-cyclodextrin)

Abstract

The substitution profile of 4-sulfobutyl ether derivatives of cyclomaltoheptaose (β-cyclodextrin) (SBE-β-CD) prepared in our laboratories has been previously described. However, in those studies, no attempt was made to characterize the positional or regional isomers of this material. SBE-β-CD derivatives with degrees of substitution of two or higher represent a large number of possible isomers dependent on this positional and regional substitution. The monosubstituted SBE derivative, however, cannot have regional isomers and, therefore, has only three possible substitution products related to the 2-, 3-, and 6-hydroxyl groups of a glucose unit. In this study the isomers were fractionated by preparative anion-exchange chromatography with the progress of the elution being followed by a capillary electrophoretic (CE) method that resolved these isomers. The eluent containing the isomers was processed, and the pure materials were characterized by nuclear magnetic resonance spectroscopy ( 1H NMR, DEPT, HETCOR, HOHAHA). Through this analysis the assignment of the positional isomers was made. Three isomeric monosubstituted 4-sulfobutyl ether derivatives of cyclomaltoheptaose (β-cyclodextrin) were separated by anion-exchange chromatography and characterized by 2D NMR spectroscopy.