Ethyl -4-chloro-3 -hydroxybutanoate

The strategy described here explains the different possibilities of enzymatic ammonolysis and aminolysis reaction for resolution of esters or preparation of enantiomerically pure amides, which are important synthons in organic chemistry. This methodology has been also applied for the synthesis of pyrrolidinol derivatives that can be prepared via enzymatic ammonolysis of a polyfunctional ester, such as ethyl ( )-4-chloro-3-hydroxybutanoate [30]. In addition, it is possible in the resolution of chiral axe instead of a stereogenic carbon atom. An interesting enzymatic aminolysis of this class of reaction has been recently reported by Aoyagi et al. [31[. The side chain of binaphthyl moiety plays an important role in the enantiodis-crimination of the process (Scheme 7.14). 

S. Takahashi, M. Wada, M. Kataoka, and S. Shimizu, Synthesis of optically active ethyl 4-chloro-3-hydroxybutanoate by microbial reduction, Appl. Microbiol. Biotechnol. 1999, 53, 847-51. 

Fig. 9. Chemicoenzymatic route for the synthesis of L-carnitine. CAAE, ethyl 4-chloroacetoacetate CHBE, ethyl 4-chloro-3-hydroxybutanoate...

Fig. 11. Priniciple of stereospecific reduction of carbonyl compounds coupled with cofacter regeneration (a) and outline of the stereospecific reduction of ethyl 4-chloroacetoacetate (CAAE) by Sporobolomyces aldehyde reductase (AR) with glucose dehydrogenase (GDH) as a cofactor regenerator in a water-organic solvent two-phasic system (b). CHBE, ethyl 4-chloro-3-hydroxybutanoate...

Shimizu, S., Kataoka, M., Morishita, A., Katoh, M., Morikawa, T., Miyoshi, T., and Yamada, H. 1990b. Microbial asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to optically active ethyl 4-chloro-3-hydroxybutanoate. Biotechnol. Lett., 72,593-596. 

Figure 9.2 Biocatalytic production of optically active ethyl 4-chloro-3-hydroxybutanoate with...

Figure 13.1 Ethyl 4-chloro-3-hydroxybutanoate (CHBE) as key Intermediate in API synthesis.

Lactobacillus kefir was also employed as the whole-cell biocatalyst for the asymmetric reduction of ethyl 4-chloroacetoacetate to ethyl (.S )-4-chloro-3-hydroxybutanoate, the chiral... 

Two interesting yeast carbonyl reductases, one from Candida magnoliae (CMCR) [33,54] and the other from Sporobolomyces salmonicolor (SSCR) [55], were found to catalyze the reduction of ethyl 4-chloro-3-oxobutanoate to give ethyl (5)-4-chloro-3-hydroxybutanoate, a useful chiral building block. In an effort to search for carbonyl reductases with anti-Prelog enantioselectivity, the activity and enantioselectivity of CMCR and SSCR have been evaluated toward the reduction of various ketones, including a- and /3-ketoesters, and their application potential in the synthesis of pharmaceutically important chiral alcohol intermediates have been explored [56-58]. 

Amidjojo, M. and Weuster-Botz, D. (2005) Asymmetric synthesis of the chiral synthon ethyl (S)-4-chloro-3-hydroxybutanoate using Lactobacillus kefir. Tetrahedron Asymmetry, 16 (4), 899-901. 

Yamamoto, H., Matsuyama, A. and Kobayashi, Y. (2002) Synthesis of ethyl (R)-4-chloro-3-hydroxybutanoate with recombinant Escherichia coli cells expressing (S)-specific secondary alcohol dehydrogenase. Bioscience Biotechnology and Biochemistry, 66 (2), 4814-83. 

The mixture of products was separated by column chromatography on a silica gel column with hexane/ethyl acetate (7 3) as the eluent. (5)-4-Chloro-3-hydroxybutanoate eluted first from the column followed by (5)-4-cyano-3-hydroxybutanoate. 

Production of Chiral 4-Chloro-3-Hydroxybutanoate Ethyl Ester by Microbial Asymmetric Reduction of 4-Chloroacetoacetate... 

CHBE 4-chloro-3-hydroxybutanoate ethyl ester CHBN 4-chloro-3-hydroxybutyronitrile... 

Recently, this two-phase reaction was improved by using an Esherichia coli transformant expressing both genes for aldehyde reductase and glucose dehydrogenase as the catalyst. When the E. coli transformant cells were incubated in a two-phase system, 300 mg/ml of the substrate was almost stoichiometrically converted to ethyl (R)-4-chloro-3-hydroxybutanoate (92% e.e.) in 16 h [114]. 

Bottlenecks for Bioreduction of Prochiral Carbonyl Compounds by Microbial Cells for Industrial Use Production of (fl)-4-Chloro-3-Hydroxybutanoate Ethyl Ester... 

Fig. 31.23. Synthesis of Ethyl (3S)-4-chloro-3-hydroxybutanoate (ECHB) from Ethyl-4-chloroacetoacetate through whole cell microbial reduction.

Fig. 3.50 Preparation of ethyl (R)-4-chloro-3-hydroxybutanoate by using alcohol dehdyrogenase from Candida parapsilosis.

When the enantioselective reduction of ethyl 4-chloroacetoacetate was carried out with alcohol dehydrogenase from Candida parapsilosis, the other enantiomer was produced ethyl (P)-4-chloro-3-hydroxybutanoate [134]. This product is a key intermediate in a synthesis of (R)-carnitine. In this case a substrate coupled approach was chosen. The enzyme also has a strong oxidation activity for 2-propanol, which was therefore selected as the cosubstrate. The situation is depicted in Fig. 3.50. Under optimized conditions, the yield of (R)-ethyl-4-chloro-3-hydroxy-butanoate reached 36.6 g L-1 (> 99% ee, 95% yield) on a 30 L scale. 

Preparation of Ethyl (R)-4-Chloro-3-hydroxybutanoate (ECHB) by Recombinant E. coli Cells Expressing CpSADH... 

In another application, recombinant E. coli produced 36.6 g/L ethyl-(R)-4-chloro-3-hydroxybutanoate (99% ee) from 40 g/L ethyl-4-chloro-3-oxo-butanoate[210). Here, the secondary alcohol dehydrogenase served as both synthetic (asymmetric reduction) and regenerating (NADH-regeneration via isopropanol oxidation) enzyme (Fig. 16.2-49). 

Ethyl (5) and (/ )-4-chloro-3-hydroxybutanoates (see Tables 6 and 7) are promising chiral building blocks for L-carnitine (R-form), 3-hydroxy-3-methylglutaryl (HMG)-CoA-reduc-tase inhibitors and 1,4-dihydropyridine-type (3-blockers (5-form). 

These compounds are L-dopa (13-tyrosinase) D-p-hydroxyphenylglycine, D-phenylglycine (hydantoinase) ethyl (R)-4-chloro-3-hydroxybutanoate (aldehyde reductase) acrylamide, nicotinamide (nitrile hydratase) acrylic acid, nicotinic acid (nitrilase) 6-hydroxynicotinic acid (hydroxylase) D-malic acid (maleate hydratase) D-pantoic acid (aldonolactonase) and theobromine (oxygenase). 

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