Single-isomer sulfated alpha-cyclodextrins for capillary electrophoresis: hexakis(2,3-di-O-methyl-6-O-sulfo)-alpha-cyclodextrin, synthesis, analytical characterization, and initial screening tests

The third, concluding member of the family of single-isomer, fully sulfated alpha-cyclodextrins, the sodium salt of hexakis(2,3-di-O-methyl-6-O-sulfo)-alpha-cyclodextrin (HxDMS), has been synthesized on the kilogram scale, completing the nine-member array of the single-isomer, 6-O-sulfo CDs now available. HxDMS was tested for the capillary electrophoretic (CE) resolution of the enantiomers of nonelectrolyte, weak acid and weak base analytes contained in our CD screening kit. HxDMS complexed differently with many of the analytes tested than either its larger-ring analogs, heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS) and octakis(2,3-di-O-methyl-6-O-sulfo)-gamma-CD (ODMS) or its same-ring, but differently substituted analogs, hexakis(6-O-sulfo)-alpha-CD (HxS) and hexakis(2,3-di-O-acetyl-6-O-sulfo)-alpha-CD (HxDAS). For all analytes, the effective mobilities and separation selectivities as a function of the background electrolyte concentration of HxDMS followed the trends that were found for the other single-isomer, 6-O-sulfo CDs.