Apremilast Enantiomeric Resolution via Chiral Salt Formation
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Solution Overview
Problem
The existing methods for preparing apremilast often result in a racemic mixture of 2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine, making it difficult to obtain the desired S enantiomeric form, which is essential for its pharmaceutical applications.
Innovation Solution
A process involving the dissolution of a racemic mixture in an organic solvent followed by the addition of L-phenylalanine p-toluene sulfonamide or di-p-toluoyl-L-tartaric acid to form chiral salts, allowing for the isolation and purification of the S enantiomer, which can then be converted into apremilast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to prepare 2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine, then the synthesis process is simple, but a racemic mixture is produced instead of the desired S enantiomeric form
Solution Approach 1:
Chiral resolving agents (L-phenylalanine p-toluene sulfonamide or di-p-toluoyl-L-tartaric acid) are introduced as intermediaries to differentiate between enantiomers. These agents form diastereomeric salts with the racemic mixture, allowing the S-enantiomer to be isolated through selective crystallization, thereby achieving high chiral purity without complex chiral catalysts or enzymes.
Solution Approach 2:
The patent changes the physical-chemical parameters of the system by adjusting solvent types (methanol, ethanol, isopropanol), temperatures (reflux conditions, cooling rates), and stoichiometric ratios during the resolution process. These parameter optimizations enable efficient separation of enantiomers while maintaining process simplicity and high productivity.
2Manufacturing precision
If chiral resolving agents are added to resolve the racemic mixture, then high chiral purity of the S enantiomer is achieved, but additional steps and reagents are required
Solution Approach 1:
The patent employs commercially available, inexpensive chiral resolving agents (L-phenylalanine p-toluene sulfonamide or di-p-toluoyl-L-tartaric acid) that can be easily obtained and used in a single-use manner. These agents form crystalline salts that are filtered and discarded after one use, eliminating the need for expensive chiral catalysts or complex recycling processes, thus maintaining ease of manufacture while achieving high chiral purity.
3Manufacturing precision
If the resolution process is performed thoroughly to obtain high enantiomeric excess, then the desired S enantiomer is obtained, but the process time increases
Solution Approach 1:
The patent exploits phase transitions (solubility changes with temperature) to accelerate the resolution process. By heating the racemic mixture to reflux with the chiral resolving agent and then cooling the solution, the S-enantiomer salt crystallizes rapidly in high purity form. This temperature-driven phase transition enables quick separation with minimal processing time while achieving high enantiomeric excess.
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 method effectively resolves the racemic mixture, achieving high chiral purity of the S enantiomer and enabling the efficient production of apremilast, a phosphodiesterase 4 inhibitor useful for treating severe plaque psoriasis and psoriatic arthritis.
Implementation Method 1
adding L-phenylalanine p-toluene sulfonamide or di-p-toluoyl-L-tartaric acid to the solution; and isolating a chiral salt of (S)-2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine
Data Source
AI summary
A process for the resolution of racemic 2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine using novel chiral salts is disclosed. An L-phenylalanine p-toluene-sulfonamide salt of (S)-2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine and a di-p-toluoyl-L-tartaric acid salt of (S)-2-(3-ethoxy-4-methoxyphenyl)-1-(methylsulphonyl)-eth-2-ylamine are also provided.