Eutectic solvents formed by (+)-DTTA and L-menthol as novel chiral recognition and separation media for enantioselective extraction of valsartan enantiomers

The enantioseparation of valsartan enantiomers using chiral eutectic solvents (ESs) as extractants was initially studied. The hydrophobic ESs (LM-DTTA) formed by L-menthol and (+)-Di-p-toluoyl-D-tartaric acid is a suitable chiral medium for the enantioselective extraction of R- and S-valsartan. Four principal parameters affecting chiral extraction, such as phase volume ratio, initial rac -valsartan concentration, extraction temperature, and system pH, were evaluated. The results showed that LM-DTTA has better and higher enantioselectivity levels, and one-step chiral extraction achieved an ee value of S-valsartan up to 91% under the optimized conditions. In addition, this chiral medium can be recycled through simple back-extraction with sodium bicarbonate solution and reused at least five times, giving similar results. This work provides a clear example of enantioseparation of the rac -valsartan via liquid–liquid enantioselective extraction using the LM-DTTA as a novel chiral recognition and separation medium. As a result, the established enantioselective extraction method can efficiently separate the R- and S-enantiomer and promote sustainable development for the production of S-valsartan.