Process for resolving DL-Mandelic acid with novel 2-benzylamino-1-butanols

Claim 1

A process for resolving DL-mandelic acid which comprises: (a) reacting about equimolecular amounts of DL-mandelic acid and an optically active 2-benzylamino-1-butanol represented by formula (I), ##STR9## wherein X represents chloro, bromo, fluoro, or nitro, at about 40°-50° C. in a two-phase mother liquor, consisting of a mixture of a water phase and a water immiscible organic phase, said organic phase being a lower alkyl ester of a lower aliphatic carboxylic acid selected from ethyl acetate, n-propyl acetate, isopropyl acetate, ethyl propionate, n-propyl propionate, or isopropyl propionate, or mixtures thereof, to form a mandelate salt represented by formula (II), ##STR10## (b) cooling the reaction mixture to crystallize said mandelate salt; (c) separating the crude mandelate salt from the two-phase mother liquor; (d) recrystallizing or slurrying the crude mandelate salt in a solvent medium selected from water, methanol, ethanol, or isopropanol, or mixtures thereof, to obtain an optically pure mandelate salt; (e) alkalizing the water phase of the two-phase mother liquor obtained in step (c); (f) separating the alkalized water phase from the organic phase; (g) agitating the optically pure mandelate salt from step (d) and the organic phase from step (f) with about 1.05 to 1.10 moles of aqueous sodium or potassium hydroxide per mole of mandelate salt at ambient temperature to hydrolyze said salt and form a clear two-phase liquid mixture consisting of an organic phase containing an optically active compound of formula (I) and an alkalized aqueous phase containing the sodium or potassium salt of an optically active mandelic acid; (h) recovering the aqueous phase from step (g) and reacting said salt of an optically active mandelic acid with about an equimolecular amount of an organic dicarboxylic acid selected from oxalic, tartaric, maleic, malonic, or fumaric acid, at about 25°-40° C. to form a mixture of an optically active mandelic acid and a mono-sodium or potassium salt of said dicarboxylic acid having a low solubility in water; (i) cooling the reaction mixture to ambient temperature and diluting the same with a water-soluble organic liquid solvent selected from the group consisting of acetone, methanol, ethanol, n-propanol, and isopropanol to complete the precipitation of said salt of said dicarboxylic acid; (j) separating said salt of said dicarboxylic acid; (k) removing said water-soluble organic solvent; and (l) recovering D-(-) or L-(+)-mandelic acid from said mother liquor.