Chiral resolution, determination of absolute configuration, and biological evaluation of (1,2-benzothiazin-4-yl)acetic acid enantiomers as aldose reductase inhibitors

A novel series of (1,2-benzothiazin-4-yl)acetic acid enantiomers was prepared by chiral resolution, and their absolute configurations were determined using the PGME method. The biological evaluation of the racemate and single enantiomers has shown a remarkable difference for the aldose reductase inhibitory activity and selectivity. The (R)-(-)-enantiomer exhibited the strongest aldose reductase activity with an IC₅₀ value of 0.120 μM, which was 35 times more active than the S-(+)-enantiomer. Thus, the stereocenter at the C4 position of this scaffold was shown to have a major impact on the activity and selectivity.