4- chloro-3-oxobutanoate

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]. 

Wada, M., Kataoka, M., Kawabata, H. et al. (1998) Purification and characterization of NADPH-dependent carbonyl reductase, involved in stereoselective reduction of ethyl 4-chloro-3-oxobutanoate, from Candida magnoliae. Bioscience Biotechnology and Biochemistry, 62 (2), 280-285. 

Several interesting reactions have been described for quinolizine-3-diazonium tetrafluoroborate 121. Thus, its treatment with secondary amines gave the corresponding triazenes 122 <2004ZNB380>, while its reaction with 1,3-dicarbonyl compounds gave the corresponding hydrazones. In the case of alkyl 4-chloro-3-oxobutanoates, the intermediate hydrazone 123 furnished a pyrazole derivative 124, as shown in Scheme 17 <2002H(57)2091>. 

M. Wada, K. Kita, H. Yanase, and S. Shimizu, Stereoselective reduction of of ethyl 4-chloro-3-oxobutanoate by Escherichia coli transformant cells coexpressing the aldehyde reductase and glucose dehydrogenase genes, Appl. Microbiol. Biotechnol. 1999, 53, 486-490. 

CR carbonyl reductase GDH glucose dehydrogenase COBE ethyl 4-chloro-3-oxobutanoate BA butyl acetate. 

Organisms Lactobacillus kefir DSM 20587, Saccharomyces cerevisiae, Candida magnoliae, Bacillus megaterium, Thermoanaerobium brockii, Clostridium beijerinckii, Thermoanaerobacter ethanolicus, Rhodococcus ruber DSM 44541. Solvents ace = acetone iPr = i-PrOH. Substrates WM Wieland-Miescher ketone 4-Me-HP 4-methyl Hajos-Parrish ketone COBE ethyl 4-chloro-3-oxobutanoate. 

Wada M, Kawabata H et al (1999) Occurrence of multiple ethyl 4-chloro-3-oxobutanoate-reducing enzymes in Candida magnoliae. J Biosci Bioeng 87 144-148... 

Recently, we [67] have described the reduction of the methyl ester of 4-chloro-3-oxobutanoic acid (39) to the methyl ester of S-( )-4-chloro-3-hydroxy-butanoic acid (40) (Fig. 13) by cell suspensions of Geotrichum candidum SC 5469., S ( )-(40) is a key chiral intermediate in the total chemical synthesis of a cholesterol antagonist (SQ 33600), which acts by inhibiting hydroxymethylglu-taryl CoA (HMG CoA) reductase. In the biotransformation process, a reaction... 

Figure 13 Synthesis of chiral synthon for anticholesterol drug SQ 33600 stereoselective microbial reduction of 4-chloro-3-oxobutanoic acid methyl ester (39).

Glucose-grown cells of G. candidum SC 5469 have also catalyzed the stereoselective reduction of ethyl-, isopropyl-, and tertiary-butyl esters of 4-chloro-3-oxobutanoic acid and methyl and ethyl esters of 4-bromo-3-oxobutanoic acid. A reaction yield of >85% and e.e. of >94% were obtained. NAD+-depen-dent oxido-reductase responsible for the stereoselective reduction of P-keto esters of 4-chloro- and 4-bromo-3-oxobutanoic acid was purified 100-fold. The molecular weight of purified enzyme is 950,000. The purified oxido-reductase was immobilized on Eupergit C and used to catalyze the reduction of (39) to S-( - )-(40). The cofactor NAD+ required for the reduction reaction was regenerated by glucose dehydrogenase. 

In another study, screening was carried out for reduction of substituted benzazepin-2,3-dione 23 to a 3-hydroxy derivative 24 (Scheme 19.14). This was accomplished by a bacterial strain of Rhodococcus fascians ATCC 12975 (Norcardia salmonicolor SC 6310) with a conversion of 97% and an optical purity of >99.9%. This reaction product 24 is a key intermediate in the synthesis of the calcium antagonist SQ 31,765 (25).104 105 The Bristol-Myers Squibb group has also shown the selective reduction of the (3-keto ester, methyl-4-chloro-3-oxobutanoate, by the fungus Geotrichum candidum SC 5469 to the corresponding (,S )-hydroxy ester.106... 

Shimizu, S., Kataoka, M., Katoh, M., Morikawa, T., Miyoshi, T., and Yamada, H. 1990a. Stereoselective reduction of ethyl 4-chloro-3-oxobutanoate by a microbial aldehyde reductase in an organic solvent-water diphasic system. Appl. Environ. Microbiol, 56, 2374-2377. 

Fig. 42 Stereospecific reduction of 4-chloro-3-oxobutanoate ester (COBE) to (K) and (S)-4-chloro-3-hydroxybutanoate ester (CHBE) by aldehyde reductase from Sporobolomyces salmonicolor and carbonyl reductase from Candida magnoliae, respectively...

Cyclopropyl isocyanates react effectively with various nucleophilic reagents. Ammonia and amines yield urea derivatives, " alcohols and phenols afford carbama-tg5,i5 5,164,181,184,185 )V )y-dimethylhydrazine gives a semicarbazide derivative, whereas cyclo-propylammonium chlorides are obtained in refluxing hydrochloric acid. The yields are usually very good. When more highly functionalized nucleophiles are employed, such as the enolate from ethyl 4-chloro-3-oxobutanoate, more complex molecules can be obtained, e.g. the formation of furanone derivative 15. ... 

The enantioselectivity of a biocatalytic reduction can be controlled by modifying the substrate because the enantioselectivity of the reduction reaction is profoundly affected by the structure of substrates. For example, in the reduction of 4-chloro-3-oxobutanoate by bakers yeast, the ester moiety can be used to control the stereochemical course of the reduction 161 531. When the ester moiety was smaller than a butyl group, then (Sj-alcohols were obtained, and when it was larger than a pentyl group then (R)-alcohols were obtained as shown in Fig. 15-9. 

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