Specification of the stereospecificity of some oxido-reductases by diamond lattice sections

Abstract

Our work on the stereospecificity of microbiological reductions of alicyclic ketones led us to take an active interest in the stereospecificity ofthe enzymic reduction of carbonyl compounds and the enzymic oxidation of alcohols. Some micro-organisms, e.g. Curvularia falcata, reduce a great nurober of mono-, bi-and tri-cyclic ketones, of widely varying structures, to the corresponding alcoholsl. If such a microbiological reduction engenders a new asymmetric carbon atom, then often only one of the two possible epimeric products is formed. W e call this type of stereospecificity "product stereospecificity", thus distinguishing it from "substrate stereospecificity", a term reserved for the selectivity ofthe enzyme for enantiomeric or diastereomeric substrates.Such highly stereospecific microbiological reductions of racemic or meso carbonyl compounds Iead to mixtures of optically active diastereomeric alcohols which can be separated by chromatography. Figure 1 shows the Ö)-cQ+ct) ~ OH ct) OH 0 0 0 ct)-cQ 0 0 cQ I o ~-cP o f OH Figure 1. Absolute configuration of the products obtained by the microbial reduction of Stereoisomerie decalin-1, 4-diones by Curvulariafalcata

Enantioselective reduction of acetyldimethylphenylsilane by Trigonopsis variabilis (DSM 70714)

“…It is of interest to see whether the stereochemistry of these biotransformations is in agreement with Prelog's rule (Prelog 1964). Furthermore, we are studying other microbial and enzymatic reaction types with regard to their applicability on elementorganic substrates, such as esterase (Syldatk et al 1986).…”

Access to Enantiopure α‐Alkyl‐β‐hydroxy Esters through Dynamic Kinetic Resolutions Employing Purified/Overexpressed Alcohol Dehydrogenases

“…While the first two ADHs were used in a purified form, the last one was employed as a lyophilised E. coli preparation containing the overexpressed enzyme. [19] These enzymes present in general an excellent Prelog selectivity, [20] and while the first two are highly active toward methyl alkyl or aryl ketones, [16,17,21] the last one can also accept ethynyl ketones and ethynyl ketoesters. [18,22] Furthermore, all of them have demonstrated tolerance against organic solvents, and therefore they can be used in a 'coupled-substrate' approach employing an excess of 2-propanol (5% v v -1 ) to recycle the cofactor.…”

Dynamic Reductive Kinetic Resolution of Benzyl Ketones using Alcohol Dehydrogenases and Anion Exchange Resins

“…10 Identical results were achieved using the DOWEX-MWA-1 and the Amberlite IRA-440C (data not shown) in comparison with the previous kinetic resolution experiments (Table 2). Aiming for a higher racemization rate, the dynamic process was tested at higher pHs (9)(10). Unfortunately, only a slight racemization was found when using the IRA-440C resin at pH 9 (data not shown).…”