Enantioselective enzymatic hydrolysis

Deussen, H.-J., Zundel, M., Valdois, M. et al. (2003) Process Development on the Enantioselective Enzymatic Hydrolysis of S-Ethyl 2-Ethoxy-3-(4-hydroxyphenyl)Propanoate. Organic Process Research Development, 7, 82-87. 

The stereogenic center at C20 is introduced by enantioselective enzymatic hydrolysis of MOM-protected malonic acid dimethyl ester derivative 60 (Scheme 10) with pig liver esterase (PLE). The asymmetric compound 61 is obtained in 90 % yield and 98 % ee. Amide formation with Mu-... 

This collection begins with a series of three procedures illustrating important new methods for preparation of enantiomerically pure substances via asymmetric catalysis. The preparation of 3-[(1S)-1,2-DIHYDROXYETHYL]-1,5-DIHYDRO-3H-2.4-BENZODIOXEPINE describes, in detail, the use of dihydroquinidine 9-0-(9 -phenanthryl) ether as a chiral ligand in the asymmetric dihydroxylation reaction which is broadly applicable for the preparation of chiral dlols from monosubstituted olefins. The product, an acetal of (S)-glyceralcfehyde, is itself a potentially valuable synthetic intermediate. The assembly of a chiral rhodium catalyst from methyl 2-pyrrolidone 5(R)-carboxylate and its use in the intramolecular asymmetric cyclopropanation of an allyl diazoacetate is illustrated in the preparation of (1R.5S)-()-6,6-DIMETHYL-3-OXABICYCLO[3.1. OJHEXAN-2-ONE. Another important general method for asymmetric synthesis involves the desymmetrization of bifunctional meso compounds as is described for the enantioselective enzymatic hydrolysis of cis-3,5-diacetoxycyclopentene to (1R,4S)-(+)-4-HYDROXY-2-CYCLOPENTENYL ACETATE. This intermediate is especially valuable as a precursor of both antipodes (4R) (+)- and (4S)-(-)-tert-BUTYLDIMETHYLSILOXY-2-CYCLOPENTEN-1-ONE, important intermediates in the synthesis of enantiomerically pure prostanoid derivatives and other classes of natural substances, whose preparation is detailed in accompanying procedures. 

Whilst ring opening of epoxides (Volume 6, Chapter 1.3) is really beyond the scope of this review, two recent papers are noteworthy poorly nucleophilic amines can be reacted very cleanly as their di-ethylaluminum derivatives,and a start has been made on chiral induction of opening of epoxides (e.g. cyclohexene oxides).Amino alcohols have been resolved by enantioselective enzymatic hydrolysis of their acetates. Ring opening of phthalimidoaziridines has bwn achieved with water, phenol and tosic acid, amongst other nucleophiles,giving products of formal N—O addition to the double bond. 

Also, in Andeno s diltiazem synthesis (Scheme 27), an early enantioselective enzymatic hydrolysis of an epoxy ester by a lipase is the key step, creating the necessary optically active intermediate 44 [106]. 

The resolution of ( )-Z/77 7 o-mcthylphcnidate (10) free base by enantioselective enzymatic hydrolysis was first reported by us (Novartis) (Scheme 9).[ ] a-Chy-motrypsin and subtilisin carlsberg exhibited selectivity towards the hydrolysis of the (2/ ,2 / )-enantiomer. 

As remikiren was selected for dinical development, bulk quantities had to be prepared. One building block of remikiren, acid (S)-3, was prepared by an enantioselective enzymatic hydrolysis (Fig. 3) as one of the key steps [4, 5], This chapter describes the development of this enzymatic step from the lab- to pilot-scale. Process research for the enzymatic step started in March 1989 and the first batches were piloted in February 1992 on the 120-150 kg scale in a campaign for the production of 150 kg of remikiren. 

Considerable attention has also been given to enantioselective enzymatic hydrolysis of esters of a-amino acids. This is of particular importance as a means of preparing enantiopure samples of unusual (non-proteinaceous) a-amino acids. The readily available proteases a-chymotrypsin (from bovine pancreas) and subtilisin (from Bacillus lichenformis) selectively hydrolyze the L-esters, leaving D-esters unreacted. These enzymatic hydrolysis reactions can be applied to V-protected amino acid esters, such as those containing r-Boc and Cbz protecting groups. 

In an alternate process for the preparation of the C-13 paclitaxel side chain, the enantioselective enzymatic hydrolysis of racemic acetate ci5 -3-(acetyloxy)-4-phenyl-2-azetidinone 38 (Eignre 16.10B), to the corresponding (S)-alcohol 39 and the nnreacted desired (l )-acetate 38 was demonstrated [63] nsing lipase PS-30 from Pseudomonas cepacia (Amano International Enzyme Company) and BMS lipase (extracellnlar lipase derived from the fermentation of Pseudomonas sp. SC 13856). Reaction yields of more than 48% (theoretical maximnm yield 50%) with EEs greater than 99.5% were obtained for the (R)-38. BMS lipase and lipase PS-30 were immobilized on Accnrel polypropylene (PP), and the immobilized lipases were reused (10 cycles) without loss of enzyme activity, productivity, or the EE of the product (R)-38. The enzymatic process was scaled up to 250 L (2.5 kg substrate input) using immobilized BMS lipase and lipase PS-30. Prom each reaction batch, R-acetate 38 was isolated in 45 mol% yield (theoretical maximum yield 50%) and 99.5% EE. The (R)-acetate was chemically converted to (R)-alcohol 39. The C-13 paclitaxel side-chain synthon (2R,3S-37 or R-39) produced by either the reductive or resolution process could be coupled to bacattin III 34 after protection and deprotection to prepare paclitaxel by a semisynthetic process [64]. 

FIGURE 16.10 Preparation of the chiral C-13 paclitaxel side-chain synthon. (A) Enantio-selective microbial reduction of 2-keto-3-(Al-benzoylamino)-3-phenyl propionic acid ethyl ester 36. (B) Enantioselective enzymatic hydrolysis of cw-3-(acetyloxy)-4-phenyl-2-azetid-inone 38. 

Figure 16.11B) was prepared for the semisynthesis of the new orally active taxane 40. The enantioselective enzymatic hydrolysis of racemic c -3-acetyloxy-4-(l,l-dimethylethyl)-2-azetidinone 41 to the corresponding undesired (5)-alcohol... 

FIGURE 16.11 (A) Water-soluble taxane 40. (B) Enantioselective enzymatic hydrolysis of... 

Both chiral compounds have been prepared by enantioselective reduction of ethyl-5-oxohexanoate 71 and 5-oxohexanenitrile 72 by Pichia methanolica SC 16116. Reaction yields of 80%-90% and more than 95% EEs were obtained for each chiral compound. In an alternate approach, the enzymatic resolution of racemic 5-hydroxy-hexane nitrile 73 by enzymatic succinylation was demonstrated using immobilized lipase PS-30 to obtain (S)-5-hydroxyhexanenitrile 69 in 35% yield (maximum yield is 50%). (S)-5-Acetoxy-hexanenitrile 74 was prepared by enantioselective enzymatic hydrolysis of racemic 5-acetoxyhexanenitrile 75 by Candida antarctica lipase. A reaction yield of 42% and an EE of more than 99% were obtained [96]. 

Enantioselective Enzymatic Hydrolysis of Racemic 1 - 2, 3 -Dihydro Benzo[b]furan-4 -yl -1,2-oxirane... 

FIGURE 16.22 (A) Melatonin receptor agonist 93. Enantioselective enzymatic hydrolysis... 

Enantioselective Hydrolysis of Diethyl Methyl-(4-Methoxy-phenyO-Propanedioate. The (5 )-monoester (26) (Fig. 6B) is a key intermediate for the syntheses of 33-receptor agonists. The enantioselective enzymatic hydrolysis of diester (27) to the desired acid ester (26) by pig liver esterase (32) has been demonstrated. In various organic solvents, the reaction yields and e.e. of the monoester (25) were dependent upon the solvent used. High e.e. (>91%) were obtained with methanol, ethanol, and toluene as a cosolvent. Ethanol gave the highest reaction yield (96.7%) and e.e. (96%). 

Fig. 6. (A) Enantioselective hydrolysis of a-methyl phenylalanine amide (24) and a-methyl-4-hy-droxyphenylalanine amide (25) by amidase. (B) Enantioselective enzymatic hydrolysis of methyl-(4-methoxyphenyl)-propanedioic acid ethyl diester (2Z) to (5)-monoester (26).

Fig. 20 Integration of catalytic production of racemic lactates (Sects. 4-6) with an enantioselective enzymatic hydrolysis as proposed by Van Wouwe et al. [167]...

The enantioselective enzymatic hydrolysis of amides is widely studied. These reactions are catalyzed by acylases, amidases and lipases. Some examples are shown in Fig. 10.32. Aspartame, an artificial sweetener, is synthesized by thermo lysin, a protease (Fig. 10.32(a)). 

S.2.2 Routes Employing Late-Stage C-3/N Bond Formation In prior methodological studies, Mariano and coworkers had reported an interesting photochemical conversion of pyridinium perchlorate (438) into meso-4-acetylamino-3,5-acetoxycyclopentene (439), and its desym-metrization by enantioselective enzymatic hydrolysis with electric eel acetylcholinesterase to give (+)-440 in 80% They subsequently reported... 

MCPBA is the reagent most commonly used for alkene epoxidation. Payne oxidation (H O / CUjCN) is a convenient and inexpensive alternative. In the course of a study of the enantioselective enzymatic hydrolysis of 6, Takeshi Sugai of Keio University has described Tetrahedron Lett. 2007, 48, 979) a practical procedure for multigram Payne epoxidation of 5. 

Paclitaxel (Taxol 53, Figure 4.16), a complex, polycyclic diterpene, exhibits a unique mode of action on microtubule proteins responsible for the formation of the spindle during cell division and known to inhibit the depol)nnerization process of microtubulin. Paclitaxel is approved by the FDA for the treatment of ovarian cancer and metastatic breast cancers. (] )-54 side chain was required for the preparation of the Paclitaxel 53 [85-88] by a semisynthetic process. The enantioselective enzymatic hydrolysis of racemic acetate ds-3-(acetyloxy) -phenyl-2-azetidinone 55 to the corresponding (S)-alcohol 56 and the xmreacted desired (] )-acetate 57 was demonstrated [89] using lipase PS-30 from Pseudomonas cepacia (Amano Enz)nne Co.) and BMS lipase (extracellular lipase derived from the fermentation of Pseudomonas sp. SC 13856). Reaction 3delds of >48% (theoretical maximum )deld 50%) with ee of >99.5% were obtained for the (R)-acetate. 

Focus on Enantioselective Enzymatic Hydrolysis of Esters and Amides... 

Figure 23 Synthesis of chiral synthon for calcium channel blocker, diltiazem Enantioselective enzymatic hydrolysis of racemic 76.

Figure 37 Enantioselective enzymatic hydrolysis of iV-acyloxymethyl (3-lactams.

Figure 45 Preparation of chiral synthon for naproxen Enantioselective enzymatic hydrolysis of racemic chloroethyl-2-(6-methoxy-2-naphthyl)propionate 129.

Figure 53 Enantioselective enzymatic hydrolysis of meso-l,3-bis(acetoxymethyl)-2-tran5-alkylcyclopentanes.

---