6-METHOXY-2-(4-SUBSTITUTED PHENYL)BENZOXAZOLES AS FLUORESCENT CHIRAL DERIVATIZATION REAGENTS FOR CARBOXYLIC-ACID ENANTIOMERS

Three chiral derivatization reagents: 2-[4-(L-leucyl)aminophenyl]-6-me thoxybenzoxazole, (D-phenylglycyl)aminophenyl]-6-methoxybenzoxazole, a nd (L-phenylalanyl)aminophenyl]-6-methoxybenzoxazole, have been synthe sized to permit separation of carboxylic acid enantiomers by high-perf ormance liquid chromatography. Enantiomeric carboxylic acids were read ily condensed with the chiral reagents in the presence of 2,2'-dipyrid yl disulfide and triphenylphosphine. The diastereometric amides formed were separated on a normal-phase column, and were sensitively detecte d fluorometrically at 375 nm, with excitation at 330 nm. The detection limit Of L-PheBOX derivative of 2-phenylpropionic acid was 70 fmol at a signal-to-noise ratio of 3.