Amisulpride Crystalline Forms for Purity and Stability
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Solution Overview
Problem
Current methods for producing crystalline amisulpride enantiomers lack reproducibility and purity, particularly in achieving thermodynamically stable and non-hygroscopic forms, which are essential for pharmaceutical applications.
Innovation Solution
The development of crystalline Form A and Form A' of amisulpride as new free base and ethyl acetate solvate forms, respectively, which are characterized by high chiral and chemical purity, thermodynamic stability, and low hygroscopicity, achieved through specific solvent treatment and isolation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to produce crystalline amisulpride enantiomers, then production can proceed with standard processes, but the products lack reproducibility and high purity
Solution Approach 1:
The patent applies parameter changes by modifying crystallization conditions including solvent selection (ethyl acetate, acetone, methyl tert-butyl ether), temperature profiles (cooling rates from 0.1 to 10°C per hour), and pH control (adjusting to pH 2-3 for Form A, pH 7-9 for Form B). These parameter optimizations enable reproducible production of high-purity enantiomeric amisulpride crystals with controlled polymorph formation
Solution Approach 2:
The patent employs preliminary action through pre-cooling the crystallization mixture before initiating crystal growth, and through preliminary filtration steps to remove impurities before final crystal formation. The process also includes pre-adjustment of pH and solvent composition to ensure optimal conditions for enantiomeric crystal separation and purity
2Stability of the object's composition
If crystalline forms are produced without specific solvent treatment, then production is simpler, but the products exhibit high hygroscopicity and reduced stability
Solution Approach 1:
The patent uses ethyl acetate as an intermediary solvent in the crystallization process to produce Form B, which can be converted to the anhydrous Form A. This intermediary approach allows control over crystal formation and water content, achieving thermodynamically stable products with reduced hygroscopicity while maintaining manageable production complexity through a two-step process
Solution Approach 2:
The patent exploits phase transitions by controlling the conversion between hydrated Form B and anhydrous Form A through controlled heating and solvent removal. This phase transition approach enables production of thermodynamically stable anhydrous crystals with predictable water sorption characteristics
3Manufacturing precision
If racemic amisulpride is used as starting material, then material availability is higher, but enantiomeric purity cannot be achieved
Solution Approach 1:
The patent applies segmentation by separating the racemic mixture into individual enantiomeric components through selective crystallization. By controlling crystallization conditions, the process segments R-amisulpride and S-amisulpride into distinct crystal forms, achieving high enantiomeric purity while maintaining reasonable yield through optimized separation efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These forms exhibit enhanced stability and purity, with Form A being anhydrous and thermodynamically favored, while Form B desolvates to Form A upon heating, ensuring high chiral and chemical purity and reduced water sorption, addressing the limitations of existing methods.
Implementation Method 1
reduced water sorption
Implementation Method 2
Form B desolvates to Form A upon heating
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The various aspects present inventions provide various crystalline forms of (S)-(-)-amisulpride, (R)-(+)-amisulpride, and solvates thereof and methods of making same. In various aspects, the inventions also provide methods of resolving racemic amisulpride.