Enantioselective Extraction of Borate Complexed- Diol Racemates

The use of liquid-liquid extraction for enantioseparation has been known since 1959, although the first articles in the English literature appeared in the late 1960s. Enantioselective liquid-liquid extraction (ELLE) is an attractive alternative for chromatography and resolution by crystallization, although judged from the scientific literature, commercialization of ELLE has not been achieved to date. This study reports ELLE of racemates with diol or those capable of having diol type of structure. Such compounds are borate complexed followed by extraction into non polar phase using a chiral quaternary ammonium salt. Ion pair formed by the chiral quaternary ammonium salt with borate complexed diol type racemate exhibit differential transportation behavior. Selectively extracted ion-pair is labile under acidic pH. Hence, one of the two enantiomer is recovered in larger excess as compared with another one from organic phase.