The benzathine salt of atorvastatin (Form B) was synthesized by preparing a stock solution of the free acid of atorvastatin (U.S. Pat. No. 5,273,995) in acetonitrile (1 g in 40 mL of ACN). A solution of N,N′-bis(phenylmethyl-1,2-ethanediamine (benzathine) was prepared by dissolving 220.64 mg (0.5 equivalents) in acetonitrile (80 mL) and water (20 mL). The stock solution of atorvastatin free acid was added to the counterion solution with stirring. After 2 days of stirring at ambient temperature, the solids were isolated by vacuum filtration using a Buchner funnel fitted with a paper filter (#2 Whatman). The solids were rinsed with acetonitrile (75 mL) to afford atorvastatin benzathine Form B. Note that this procedure is the same as above except that the sample was not oven dried.
