4-(N,N-dimethylaminosulfonyl)-7-(2-chloroformylpyrrolidin-1-yl)-2,1,3-benzoxadiazole: novel fluorescent chiral derivatization reagents for the resolution of alcohol enantiomers by high-performance liquid chromatography

Abstract

Optically active derivatization reagents, 4-(N,N-dimethylaminosulfonyl)-7-(2-chloroformylpyrrolidin-1-yl)-2,1,3-benzoxadiazole [(R)-(+)-DBD-Pro-COCI and (S)-(–)-DBD-Pro-COCI], were synthesized to permit the separation of alcohol enantiomers by high-performance liquid chromatography. The reagents react with hydroxyl groups in the presence of pyridine, which functions as a catalyst and reacts with hydrogen chloride. The maximum excitation and emission wavelengths of the diastereomers derived from the alcohols and the reagents were approximately 450 and 560 nm, respectively. The emission wavelengths of the derivatives shifted slightly towards the blue with increasing acetonitrile concentration in the medium; however, the excitation wavelengths remained constant. The diastereomers derived from some aliphatic alcohols were efficiently resolved by normal-phase chromatography with hexane-ethyl acetate as the eluent. Incomplete separation was realized with a reversed-phase column with water-acetonitrile as the eluent. When (R)-(+)-DBD-Pro-COCI was used as the derivatization reagent, alcohols corresponding to the R-configuration were eluted faster than those corresponding to the S-configuration. As expected, the elution order of the alcohols was reversed when the diastereomers were prepared with (S)-(-)-DBD-Pro-COCI. The R_s values of diastereomers derived from hydrophobic alcohols are larger than those from hydrophilic alcohols.