Method of resolving amlodipine racemate
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example 1
S-(−)-amlodipine D-hemitartrate DMAC Monosolvate
[0037] Aqueous sodium hydroxide (1 N, 530 mL) was added to a stirred suspension of amlodipine besylate (200 g, 0.353 moles) in methyl t-butyl ether (1.3 L). The reaction mixture was stirred for 20-30 minutes after which the aqueous and organic layers were allowed to separate. After removing the aqueous layer, water (220 mL) was added to the organic layer and the mixture was stirred for 20 minutes. The aqueous layer was again removed and the organic layer was concentrated to approximately one-third of its original volume by vacuum distillation. The organic layer was collected and concentrated to approximately one-third of its original volume by distillation. The concentrate was then mixed with N,N-dimethylacetamide (DMAC, 650 ml) and further concentrated by vacuum distillation until the temperature of the concentrate rose by 10-15° C. The concentrate was allowed to equilibrate to room temperature and pressure before it was added to a s...
example 2
S-(−)-amlodipine Free Base
[0038] Aqueous sodium hydroxide (1 N, 220 mL) was added to a stirred suspension of S-(−)-amlodipine D-hemitartrate DMAC monosolvate (81.1 g, 0.142 moles) in methyl t-butyl ether (960 mL). The reaction mixture was stirred for 20-30 minutes after which the aqueous and organic layers were allowed to separate. After removing the aqueous layer, water (220 mL) was added to the organic layer and the mixture was stirred for 20 minutes. The aqueous layer was again removed and the organic layer was concentrated to approximately one-third of its original volume by vacuum distillation. After allowing the concentrate to equilibrate to room temperature and pressure, heptane (320 mL) was added and the resulting slurry was stirred for 1-2 hr. The slurry was then filtered, and the residual crystalline solid was washed with heptane (500 mL). The crystals were dried in vacuo at 40-50° C. for 8-16 h to yield S-(−)-amlodipine free base (49.10 g, 85% yield, 99.96% enantiomeric ...
example 3
S-(−)-amlodipine D-hemitartrate DMAC Monosolvate
[0039] (RS)-amlodipine (24.85 kg, 60.8 moles) and N,N-dimethylacetamide (DMAC, 104 kg) are added to a reactor and stirred at 20 to 25° C. for 15 to 30 minutes. A solution of D-tartaric acid (9.5 kg, 63.2 mol) in N,N-dimethylacetamide (104 kg) is added at 20 to 25° C. The mixture is heated to 68 to 70° C. over about 60 minutes and stirred for about 60 minutes. The solution is cooled to 20 to 23° C. over 2 to 3 hr and the slurry is then held for about 30 to 45 minutes at 20 to 23° C. The slurry is then filtered and the residual crystalline solid is washed successively with N,N-dimethylacetamide (about 50 kg) and methyl t-butyl ether (about 40 kg). The filter cake is dried in vacuo at 40 to 50° C. for 8 to 16 hr to yield, S-(−)-amlodipine D-hemitartrate DMAC monosolvate (14 kg, 40% yield, 99.2% enantiomeric purity, >99% chemical purity).
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