Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride
This study aims to demonstrate the coordination of oxygen regarding the hemophore HasApf expressed by Escherichia coli cells, which appears to create an unlikely oxygen-activating system in HasA due to the already-coordinated iron. In the asymmetric oxidation of rac-1-(6-methoxynaphthalen-2-yl)ethan...
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doaj-7d9981227b394ea79aa0497f6a8a913f2020-11-25T00:55:12ZengMDPI AGCatalysts2073-43442016-03-01633810.3390/catal6030038catal6030038Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium BorohydrideHiroyuki Nagaoka0Sanyo Shokuhin Co., Ltd. R & D, 555-4 Asakura, Maebashi, Gunma 371-0811, JapanThis study aims to demonstrate the coordination of oxygen regarding the hemophore HasApf expressed by Escherichia coli cells, which appears to create an unlikely oxygen-activating system in HasA due to the already-coordinated iron. In the asymmetric oxidation of rac-1-(6-methoxynaphthalen-2-yl)ethanol (rac-1) using dissolved oxygen, the signals at g-values of 2.8, 2.22, and 1.72 in the electron spin resonance (ESR) spectra disappeared in conjunction with the promotion of oxoferric (FeIII−O–O−) species in the distal site. These results suggest that the iron of porphyrin/Fe may be oxidized in water, leading to exhibition of greater asymmetric oxidation activity in the promotion of oxoferryl (FeIV=O) species. A ketone (~50% chemical yield) produced from (R)-(−)-sec-alcohol can be desymmetrized by NaBH4 in aqueous medium at 40 °C (>99% enantiomer excess, ee, >90% chemical yield) in the absence of NAD(P). Therefore, HasA can be regenerated via successive asymmetric catalytic events through an incorporated iron electron-transfer system in the presence of oxygen: FeII + O2 → FeIII−O–O− → FeIV=O (oxidizing rac-1) → FeII + H2O. This process is similar to a Fenton reaction. The use of a HasA-catalytic system with an incorporated redox cofactor for asymmetric oxidation overcomes the apparent difficulties in working with pure dehydrogenase enzyme/redox cofactor systems for biotransformations.http://www.mdpi.com/2073-4344/6/3/38enantioselective oxidationhemophore HasAheterogeneous enzyme catalysisiron electron-transfer systemiron porphyrin |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Hiroyuki Nagaoka |
spellingShingle |
Hiroyuki Nagaoka Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride Catalysts enantioselective oxidation hemophore HasA heterogeneous enzyme catalysis iron electron-transfer system iron porphyrin |
author_facet |
Hiroyuki Nagaoka |
author_sort |
Hiroyuki Nagaoka |
title |
Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride |
title_short |
Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride |
title_full |
Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride |
title_fullStr |
Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride |
title_full_unstemmed |
Heterogeneous Asymmetric Oxidation Catalysis Using Hemophore HasApf. Application in the Chemoenzymatic Deracemization of sec-Alcohols with Sodium Borohydride |
title_sort |
heterogeneous asymmetric oxidation catalysis using hemophore hasapf. application in the chemoenzymatic deracemization of sec-alcohols with sodium borohydride |
publisher |
MDPI AG |
series |
Catalysts |
issn |
2073-4344 |
publishDate |
2016-03-01 |
description |
This study aims to demonstrate the coordination of oxygen regarding the hemophore HasApf expressed by Escherichia coli cells, which appears to create an unlikely oxygen-activating system in HasA due to the already-coordinated iron. In the asymmetric oxidation of rac-1-(6-methoxynaphthalen-2-yl)ethanol (rac-1) using dissolved oxygen, the signals at g-values of 2.8, 2.22, and 1.72 in the electron spin resonance (ESR) spectra disappeared in conjunction with the promotion of oxoferric (FeIII−O–O−) species in the distal site. These results suggest that the iron of porphyrin/Fe may be oxidized in water, leading to exhibition of greater asymmetric oxidation activity in the promotion of oxoferryl (FeIV=O) species. A ketone (~50% chemical yield) produced from (R)-(−)-sec-alcohol can be desymmetrized by NaBH4 in aqueous medium at 40 °C (>99% enantiomer excess, ee, >90% chemical yield) in the absence of NAD(P). Therefore, HasA can be regenerated via successive asymmetric catalytic events through an incorporated iron electron-transfer system in the presence of oxygen: FeII + O2 → FeIII−O–O− → FeIV=O (oxidizing rac-1) → FeII + H2O. This process is similar to a Fenton reaction. The use of a HasA-catalytic system with an incorporated redox cofactor for asymmetric oxidation overcomes the apparent difficulties in working with pure dehydrogenase enzyme/redox cofactor systems for biotransformations. |
topic |
enantioselective oxidation hemophore HasA heterogeneous enzyme catalysis iron electron-transfer system iron porphyrin |
url |
http://www.mdpi.com/2073-4344/6/3/38 |
work_keys_str_mv |
AT hiroyukinagaoka heterogeneousasymmetricoxidationcatalysisusinghemophorehasapfapplicationinthechemoenzymaticderacemizationofsecalcoholswithsodiumborohydride |
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