Pirlindole Enantiomer Separation via Diastereomeric Crystallization
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Solution Overview
Problem
Current methods for obtaining optically active pirlindole enantiomers are costly, difficult to implement on an industrial scale, and have poor reproducibility due to the necessity of large-scale chromatography for enantiomeric separation.
Innovation Solution
A process involving the crystallization of (rac)-pirlindole with optically active acids in an organic solvent, followed by controlled stirring and purification, allows for the production of enantiomerically pure (R)- and (S)-pirlindole in free base or pharmaceutically acceptable salt forms, avoiding the need for large-scale chromatography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large-scale chromatography is used for enantiomeric separation, then enantiomerically pure pirlindole can be obtained, but the process becomes very costly, difficult to implement and with poor reproducibility
Solution Approach 1:
The patent changes the physical-chemical parameters of the system by using diastereomeric salt formation instead of direct chromatographic separation. This involves converting the enantiomeric mixture into diastereomeric salts through reaction with optically active acids, which have different solubility properties that enable separation by crystallization rather than chromatography
Solution Approach 2:
The patent introduces optically active acids (resolving agents) as intermediaries to convert the enantiomeric mixture into separable diastereomeric salts. These intermediaries enable indirect separation by forming compounds with distinct physical properties, avoiding the need for direct enantiomeric separation by chromatography
2Manufacturing precision
If derivatization technique in conjunction with preparative chromatography is used, then enantiomers can be obtained at laboratory scale, but the process is not viable for industrial or semi-industrial scale
Solution Approach 1:
The patent exploits phase transitions, specifically crystallization from solution, to separate diastereomeric salts. By controlling solubility differences in various solvents and temperatures, the enantiomers can be separated through repeated crystallization cycles, providing a scalable alternative to chromatography
Solution Approach 2:
The method changes the separation mechanism from chromatographic retention to crystallization based on solubility parameters. This allows the process to be scaled up by simply increasing the volume of solution and crystallization vessels, without the complexity constraints of large-scale chromatography systems
3Ease of manufacture
If selective crystallization with optically active acids is attempted, then enantiomers can be separated, but previous attempts failed to achieve successful results
Solution Approach 1:
The patent introduces dynamic control of the crystallization process, including controlled addition of resolving agents, temperature programming, and staged crystallization cycles. This dynamic approach allows optimization of both purity and yield, overcoming the static limitations of previous crystallization attempts
Solution Approach 2:
The method employs periodic crystallization cycles with alternating conditions (temperature changes, solvent additions, filtration-recrystallization steps). These periodic actions progressively enrich the enantiomeric purity with each cycle, achieving high purity that single-step crystallization cannot provide
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
This process enables the production of optically active pirlindole enantiomers in quantities suitable for preclinical and clinical studies, is easily scalable, and eliminates the challenges of high costs and poor reproducibility associated with existing methods.
Implementation Method 1
crystallization with optically active acids
Implementation Method 2
adding the optically active acid and stirring the suspension
Implementation Method 3
dissolving it in an organic solvent selected from the group consisting of: methanol, ethanol, propanol, 1-butanol, 2-butanol, tert-butyl alcohol, 2-butanone, acetone, ethyl methyl ketone, methyl isobutyl ketone, dimethylsulfoxide, 1,2-dichloroethane, diethyl ether, dimethyl ether, dimethylformamide, methyl tert-butyl ether, 2-propanol, pyridine, toluene, xylene or mixtures thereof
Implementation Method 4
stirring the suspension from 15 minutes to 2 hours
Implementation Method 5
adding the optically active acid and stirring the suspension
Data Source
AI summary
The present invention provides a new process for obtaining optically active pirlindole enantiomers, in the form of a free base or in the form of pharmaceutically acceptable salts. The products obtained according to the present invention are enantiomerically pure and are useful in medicine.