Atenolol → Atenolol p-toluate

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Reaction Steps

The atenolol having low optical purity (1 mole) and p-toluic acid (1 mole) are dissolved in acetone (5 to 50 liters) with heating and the mixture is stirred at 0° to 15° C. for 5 to 24 hours. The precipitated crystals are removed by filtration, and the mother liquor is concentrated to give an optically active atenolol p-toluate with having higher optical purity, for example a salt having an optical purity of 98% ee or more from a salt having an optical purity of 91% ee in a yield of 50to 80%. In this method, when benzoic acid is used instead of p-toluic acid and chloroform is used instead of acetone, similar result is obtained. When p-t-butylbenzoic acid is used instead of p-toluic acid in the above method, the produced salt is hardly soluble in a solvent, and hence, it is necessary to use a solvent having higher solubility such as ethanol or 2-propanol instead of acetone.

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