Resolution process development

The resolution process developed by Syntex is almost ideal (Pope Peachy resolution), with an efficient racemization and recycling of the unwanted (R) -enantiomer (yield >95% of (S)-naproxen from the racemate) and the chiral auxiliary (recovery >98%). 

Upon the resolution process development, finding the optimum resolving agent is the first concern for the chemist. Although various attempts have been made by numerous researchers, a useful concrete theory to find a satisfactory resolving agent has not yet been proposed. 

Another classic resolution process developed by Ethyl Corp. for (S)-ibuprofen production uses (S)-(-)-a-methylbenzylamine (MAB) as the chiral base for diastereomeric salt formation 49 The difference in solubility between (S)- and (ft)-ibuprofen MAB salts is so substantial that only half an equivalent of MAB is used for each mole of racemic ibuprofen, and no seeding is needed. The process can also be performed in a wide range of solvents, and the unwanted (ft)-ibuprofen can be recycled conveniently by heating the mother liquor in sodium hydroxide or hydrochloric acid. Other designer amines have been developed for resolution of ibuprofen with good stereoselectivities,50 but these chiral amines were prepared specifically for ibuprofen resolution and are thus unlikely to be economical for industrial production. 

Resolution The development of Quality Management processes starts with a comprehensive review of existing systems and a careful review of the needs the processes must meet. Showing this process should help reassure the manager that all issues will be covered. You should also indicate what staff are likely to be involved in these processes and ask whether there are any others that should be included. 

An excellent example for an enzymatic resolution process is reported for production of Pregabalin. This drug was approved by the US Food and Drug Administration (FDA) in 2004 against neurophatic pain associated with diabetic peripheral neuropathy and postherpetic neuralgia. Several different routes have been developed based on asymmetric hydrogenation, crystallization and biocatalytic resolutions [16-20]. The most powerful and currently applied process is based on a lipase resolution, shown in Figure 14.3. This process is one of the very few... 

May O., Verseck, S., Bommarius, A. and Drauz, K. (2002) Development of dynamic kinetic resolution processes for biocatalytic production of natural and nonnatural L-amino acids. Organic Process Research Development, 6 (4), 452-457. 

During the early stages of process development it is very unlikely that relevant impurities will have been synthesized in sufficient quantities that a thorough analysis of their eutectic behaviour can be performed. Eutectics should be investigated when possible and are particularly relevant in the purification of stereo-isomers and in classical resolution using diastereomeric salts [5, 24, 25]. 

The first steps include holding scientific workshops with key stakeholders, re-examining and clarifying the scope and interpretation of Part 11 (see Section 9.6.3), developing technical dispute resolution processes, and harmonizing inconsistencies between the different centers of the FDA. 

Dynamic kinetic resolution (DKR) is a process in which the resolution process is coupled with in situ racemization of unreacted substrate. This has been shown to be a potential and feasible method to produce 100 % theoretical yield. We have developed a chemo-enzymatic DKR to obtain higher desired yield for (5)-ibuprofen. The combined base catalyst with lipase has resulted in high conversion and excellent ee of the product. 

The Lab Chip instruments/methods currently commercially available generally have less resolution and are less sensitive compared to conventional CE-SDS methods. However, the high throughput of the Lab Chip technique makes it attractive for in-process monitoring during process development. The Lab Chip method is generally used for process development activities such as clone selection, cell culture process development, and optimization of the downstream purification process. 

Other similar lipase/esterase resolution processes have been developed such as the use of Bacillus that esterase to produce the substituted propanoic acids that are precursors of non-steroidal anti-inflammatory drags, snch as naproxen and ibuprofen etc., and the formation of chiral amines by Celgene. Other methods start from prochiral precursors and have the advantage that enantioselective synthesis allows the production of particular isomers in yields approaching 100%, rather than the 50% yields characteristic of resolution processes. For instance Hoechst have patented the production of enantiomers using Pseudomonas fluorescens lipase to either acylate diols or hydrolyse diacetate esters. 

Around 70% of the pharmaceuticals on the market are chiral, and approximately one third of these are chiral amines [1], This represents a substantial number of achve drug substances that are typically manufactured at a scale of 1-100 l y . The three main manufacturing processes used to introduce these homochiral centers are from optically active starting materials (the so-called Chiral Pool approach), by asymmetric synthesis and by resolution. The last technique is widely practiced but results in waste of the undesired enantiomer. This chapter deals with developments in asymmetric transformations, that is to say methods for augmenting the yield of amine resolution processes to theory 100%, resulting in an alternative to asymmetric synthesis and a practical Green Chemistry solution to the synthesis of optically active amines. Figure 13.1 shows different approaches to the asymmetric transformation that will be discussed in the chapter. 

For the preparation of the (S)-enantiomer an enzymatic racemic resolution process using Aspergillus oryzae protease was developed by Sepracor ... 

If nonconformances or deviations to the project plan or IQ protocol are encountered during the software IQ testing, these must be documented, analyzed, resolved, reviewed, and approved. The resolution process must indicate what additional actions must be taken to provide a conforming product (e.g., return the program to development for error analysis and correction, and re-execute the test script after correction the nonconformance was due to an inaccuracy in the test script, review and update the test script, etc.). After the successful resolution of the nonconformance has been obtained, the original test, the nonconformance information, and the retest must all be retained, approved, and reviewed by the appropriate personal. 

A highly stereoselective kinetic resolution process for Rh-catalyzed enyne cycloisomerization has also been developed by Zhang et al. [41]. This transformation has enabled the highly enantioselective synthesis of polyfunctionalized tetrahydrofurans and lactones with two or three adjacent stereocenters and it is regarded as a major breakthrough in enynes cycloisomerization and in kinetic resolution (Scheme 7). 

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