Planar chromatographic separation of enantiomers and diastereomers with cyclodextrin mobile phase additives

A variety of racemic compounds were resolved using reversed-phase thin-layer chromatography (TLC) with mobile phases containing highly concentration solutions of beta-cyclodextrin (beta-CD). These include the drugs labetalol and mephenytoin, metallocenes, crown ethers, methyl-p-toluenesulfinate, nornicotine derivaties and several dansyl and beta-naphthylamide substituted amino acids. It was possible to resolve some racemates that could not be separated on beta-CD bonded phase liquid chromatography (LC) columns with this technique. Likewise there were some compounds that could be resolved with the LC approach that failed to separate with the present TLC method. In cases of racemates that could be resolved by either approach, it was found that the retention order was exactly opposite for the two methods. Enantiomeric resolution is highly dependent on mobile phase composition. In particular, the type and amount of organic modifier as well as the concentration of beta-CD affect the observed resolution. Possible reasons for the chromatographic behavior are discussed. Several diastereoisomeric compounds were separated as well, including steroid epimers and pharmaceutical compounds.