Stereochemical Control In Microbial Reduction Research Articles

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 16. Stereochemical Control in Diastereoselective Reduction with Bakers′ Yeast.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Stereochemical Control of Microbial Reduction. Part 17. A Method for Controlling the Enantioselectivity of Reductions with Bakers′ Yeast.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 31. Reduction of Alkyl 2‐Oxo‐4‐arylbutyrates by Baker′s Yeast under Selected Reaction Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereochemical control in microbial reduction. Part 31: Reduction of alkyl 2-oxo-4-arylbutyrates by baker's yeast under selected reaction conditions

Treatment of baker's yeast with phenacyl chloride in an aqueous–organic solvent has been proven to be an effective method of inhibiting the enzymes that afford ( S)-enantiomers of α-hydroxy esters in the reduction of α-keto esters. The procedure is effective for the whole-cell system to produce the ( R)-product with high chemical yield and high enantiomeric excess.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 30. Reduction of Alkyl 2‐Oxo‐4‐phenylbutyrate as Precursors of Angiotensin Converting Enzyme (ACE) Inhibitors.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereochemical Control in Microbial Reduction. 30. Reduction of Alkyl 2-Oxo-4-phenylbutyrate as Precursors of Angiotensin Converting Enzyme (ACE) Inhibitors

Abstract Alkyl 2-oxo-4-phenylbutyrates are reduced to the corresponding alkyl (R)-2-hydroxy-4-phenylbutyrates, versatile chiral building blocks in organic synthesis, in high chemical yield (80—90%) with excellent stereoselectivity ( > 90%ee). The reaction has been run in aqueous diethyl ether at 30 °C for 24 h under the catalysis of bakers’ yeast (Saccharomyces cerevisiae) which was preincubated for 6 h in the presence of phenacyl chloride. The amount of water in the medium should be controlled strictly not to exceed 0.8 mL (g yeast)−1.

Stereochemical Control in Microbial Reduction. XXIX. Mechanism of Stereochemical Control with an Additive in the Diastereoselective Reduction byGeotrichum candidum

The reduction of ethyl 2-methyl-3-oxobutanoate with Geotrichum candidum yields approximately equal amounts of the corresponding syn-(2R,3S)- and anti-(2S,3S)-3-hydroxy esters. When the microbe is incubated with methyl vinyl ketone (MVK) or chloroacetone before it is subjected to the reduction, the corresponding anti-(2S,3S)-hydroxy ester is obtained with exclusive enantio- as well as diastereoselectivity. In order to obtain more insight into the mechanism of this stereochemical control in microbial reduction, β-keto ester reductases were isolated and purified from the cells of G. candidum. Three dominantly competing enzymes were purified. One of them affords the anti-(2S,3S)-hydroxy ester selectively, whereas the others give the syn-(2R,3S)-hydroxy ester selectively. The rates of enzymatic reductions were measured in the presence and absence of an additive. Chloroacetone and MVK are competitive and suicide substrates, respectively, for the syn-enzymes, whereas they hardly affect the activity of the anti-e...

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 28. Asymmetric Reduction of α,β‐Unsaturated Ketones with Bakers′ Yeast.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereochemical Control in Microbial Reduction. XXVIII. Asymmetric Reduction of α,β-Unsaturated Ketones with Bakers’ Yeast

Abstract Bakers’ yeast reduction of α,β-unsaturated ketones affords optically active saturated ketones contaminated by allylic and saturated alcohols as minor components. Stereoselectivity of the reduction of carbon–carbon double bond strongly depends on the structure of β-aryl substituent. The bakers’ yeast reduction of β-phenyl enones gives saturated ketones in moderate stereoselectivity. Stereoselectivity is not altered by substitution at the para-position, whereas introduction of a substituent at the ortho- or meta-position drastically improves the stereoselectivity. Deuterium-labeling experiments reveal that the enzymatic reduction of carbon–carbon double bond proceeds with formal trans-addition of hydrogens regardless the efficiency of stereoselectivity. The resulting optically active ketone was converted to the precursor of (S)-iopanoic acid, an inhibitor of thyroxine 5′-deiodinase that is a thyroid hormone-converting enzyme and an oral cholecystographic agent.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 27. Asymmetric Reduction of α,β‐Unsaturated Ketones with Bakers′ Yeast.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 25. Additives Controlling Diastereoselectivity in a Microbial Reduction of Ethyl 2‐ Methyl‐3‐oxobutanoate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 23. Thermal Treatment of Baker′s Yeast for Controlling the Stereoselectivity of Reductions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Mechanistic study for stereochemical control of microbial reduction of α-keto esters in an organic solvent

To elucidate the mechanism for stereochemical control of yeast reduction of α-keto esters in organic media, seven enzymes responsible for the reduction have been isolated from bakers' yeast and kinetic parameters for enzymatic reductions have been measured. In yeast reduction of ethyl 3-methyl-2-oxobutanoate ( 1f), enantiomeric excess in the produced ( R)-hydroxy ester increases when an organic solvent is used as the reaction medium in place of water. Difference in K m of the enzymes contributes largely to the stereochemistry of reduction by whole yeast cell. Four enzymes contribute to catalytic reduction of 1f. K m of the ( R)-producing enzyme has been found to be the lowest among those of four enzymes. Stereochemical course of the reduction shifts toward the ( R)-product by lowering the substrate concentrations, because the ( R)-producing enzyme is most active among the enzymes under diluted conditions. In yeast reduction of ethyl 2-oxohexanoate ( 1d), the corresponding ( S)-hydroxy ester is obtained in water, whereas the antipode is given in benzene. Five enzymes participate to the reduction of 1d and the ( R)-producing enzymes have smaller K ms than those of the ( S)-producing enzymes. When the reaction is run in benzene, however, the produced α-hydroxy ester does not undergo further decomposition. The inhibition of enzymatic decomposition in an organic solvent is also accounted for by low concentration of α-hydroxy ester in aqueous phase surrounding the bakers' yeast.

Stereochemical Control in Microbial Reduction. XXV. Additives Controlling Diastereoselectivity in a Microbial Reduction of Ethyl 2-Methyl-3-oxobutanoate

Abstract Stereoselectivity of microbe-catalyzed reduction of ethyl 2-methyl-3-oxobutanoate to optically active 3-hydroxy-2-methylbutanoate can be controlled by the addition of methyl vinyl ketone to the reaction system. The reduction by Geotrichum candidum, Endmyces magnusii, and Mucor javanicus with an appropriate additive affords the corresponding anti-(2S,3S)-hydroxy ester selectively, whereas the reduction by bakers’ yeast and Candidatropicalis with an additive gives the corresponding syn-(2R,3S)-hydroxy ester selectively.

Stereochemical Control in Microbial Reduction. XXIII. Thermal Treatment of Bakers’ Yeast for Controlling the Stereoselectivity of Reductions

Abstract The diastereoselectivity in a bakers’ yeast reduction of various alkyl 2-alkyl-3-oxoalkanoates can be controlled by a thermal treatment of the yeast in the presence of methyl vinyl ketone. Pretreated bakers’ yeast gives the corresponding (2R,3S)-hydroxy esters selectively. Two β-keto ester reductases, named l-enzyme-1 and l-enzyme-2, are actual reductants of intact bakers’ yeast reduction. The thermal stability and inhibition constants of the purified enzymes can dictate the stereochemical outcome of pretreated bakers’ yeast reductions.

Stereochemical Control in Microbial Reduction. XXI. Effect of Organic Solvents on Reduction of α-Keto Esters Mediated by Bakers’ Yeast

Abstract Reduction of α-keto esters mediated by bakers’ yeast takes place in an organic solvent without immobilization of the microbe. Several factors such as water content, pH of the solution, amount of bakers’ yeast, and the property of the organic solvent affect to enantioselectivity of the reduction. In benzene, stereochemistry of the reduction shifts markedly toward preferential production of the (R)-α-hydroxy ester. The stereochemical consequence of the present reaction is accounted for by two factors; 1) the inhibition of enzymatic decomposition of the produced (R)-α-hydroxy ester in benzene and 2) the enhancement of relative activities of dehydrogenases or reductases in producing the (R)-α-hydroxy ester under dilute concentrations of the substrate at the vicinity of enzymes.

ChemInform Abstract: Stereochemical Control in Microbial Reduction. Part 19. Effect of Heat‐ Treatment on the Diastereoselectivity in the Reduction with Bakers′ Yeast.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereochemical control of microbial reduction. 17. A method for controlling the enantioselectivity of reductions with bakers' yeast

Stereochemical control of microbial reduction. 17. A method for controlling the enantioselectivity of reductions with bakers' yeast

Stereochemical control in microbial reduction. 19. Effect of heat-treatment on the diastereoselectivity in the reduction with baker's yeast

Diastereoselectivity in the reduction of 2-alkyl-3-oxobutanoates is controlled by the heat-treatment of bakers' yeast. The heat-treated yeast exerts higher syn-selectivities than the untreated one.

Stereochemical Control in Microbial Reduction. 18. Mechanism of Stereochemical Control in the Diastereoselective Reduction with Baker’s Yeast

Abstract Reduction of a variety of 2-alkyl-3-oxobutanoates with bakers’ yeast yields the corresponding l-(3S)-hydroxy esters with exclusive enantioselectivity, while the diastereoselectivity, syn/anti ratio, varies depending on the structure of the alkoxyl moiety. In order to elucidate the mechanism for this stereochemical control, oxidoreductases that reduce 2-alkyl-3-oxobutanoate have been isolated from the cells of bakers’ yeast and purified. Two dominant competing 2-alkyl-3-hydroxybutanoate oxidoreductases have been obtained: one of them reduces 2-alkyl-3-oxobutanoates stereoselectively yielding the corresponding l-syn-hydroxy esters, whereas the other affords a mixture of l-syn- and l-anti-hydroxy esters. The experimental results on stereoselectivity have nicely been simulated using kinetic parameters elucidated.