Patent ID: 8436188

Claim:
A method for separation of S-(−)-amlodipine from a racemic amlodipine, comprising: 1) reacting an amlodipine racemate with L-tartaric acid in a dimethylacetamide (DMAC) solvent and filtering off a precipitate [R-(+)-amlodipine-hemi-L-tartrate-DMAC solvate], 2) adding methylene chloride and n-hexane to filtrate remaining from step 1) to afford an S-(−)-amlodipine-hemi-L-tartrate-DMAC solvate, and 3) purifying the S-(−)-amlodipine-hemi-L-tartrate-DMAC solvate with methanol, followed by treatment with a base, wherein the methylene chloride and n-hexane in step 2) are used in volumetric amounts (mL) 1 to 3 and 10 to 30 times as much as weight (g) of the racemic amlodipine, respectively.