Process for the preparation of [S(-) amlodipine - L (+)- hemitartarate]

Abstract

The present invention relates to a process for the preparation of [S(−)amlodipine-L(+)-hemi taratarte] from RS amlodipine base using L(+) tartaric acid in the presence of dimethyl sulfoxide.

We claim:  
     
         1 . A process for the preparation of [S(−)amlodipine-L(+)-hemi tartarte which comprises reacting RS amlodipine base with L(+)tartaric acid in an organic solvent at a temperature ranging from 20-35° C. for the period ranging from 16 to 24 hours, separating the solid [R(=)amlodipin-L(+)-hemi tartarate] by filtration, seeding the filtrate to obtain solid [S(−)amlodipin-L(+)-hemi tartarate] by precipitation, filtering the solid and basifying to obtain [S(−)amlodipine-L(+)-hemi tartarte.  
     
     
         2 . A process claimed in  claim 1  wherein the solvent is DMSO  
     
     
         3 . A process claimed in  claim 1  wherein the solvent to amlodipine ratio is 5-6 ml/gm of amlodipine.  
     
     
         4 . A process claimed in  claim 1  wherein L-tartaric acid employed is about 0.5 mole per mole of amlodipine.  
     
     
         5 . A process claimed in  claim 1  wherein the solvate precipitated is S(−)smlodipine hemi L(+)-tartarate mono DMSO solvate.  
     
     
         6 . A process claimed in  claim 1  wherein a stirred solution of RS Amlodipine in DMSO was added to a solution of L(+)Tartaric acid in DMSO, the solid obtained separated by filtration, washed with acetone, dried to give R(+) MeOH), the filtrate seeded with S(−)amlodipine hemi L(+)tartarate salt, the solid so obtained filtered off and washed with acetone and dried to give S(−)amlodipine-hemi L(+)-tartarate mono DMSO solvate.