Patent ID: 7265106

Claim:
A method of isolating (R)-tofisopam, substantially free of the (S)-enantiomer of tofisopam, said method comprising: (a) adsorbing a mixture of enantiomers of tofisopam onto a chiral separation medium; (b) passing a solvent system through the chiral separation medium in an amount sufficient to elute the tofisopam enantiomers from the separation medium; (c) isolating the (R)-enantiomer of tofisopam, substantially free of the (S)-enantiomer of tofisopam; wherein said chiral separation medium comprises: (2S)-2-{(1S)[(3,5-dinitrophenyl)carbonylamino]phenylmethyl}-3,3-dimethylbutanoate covalently bound to silica, or an amylose derivative of formula I: wherein each R 1 is a radical of the formula II: wherein R 2 and R 3 are independently selected from the group consisting of chloro and —CH 3 and are substituted on the radical of formula II in a substitution pattern selected from the group consisting of 3,4-dimethyl, 2,5-dimethyl, 3,4-dichloro, 2,5-dichloro, 5-chloro-2-methyl, 2-chloro-5-methyl, 4-chloro-3-methyl, 3-chloro-4-methyl, 3-chloro-2-methyl, 4-chloro-2-methyl, 2-chloro-6-methyl and 2-chloro-4-methyl; and n is an integer from about 10 to about 100; said amylose derivative coated on a porous inorganic carrier or a porous organic carrier.