Unspecific Peroxygenases (UPOs) are increasingly significant enzymes for selective oxygenations as they are stable, highly active and catalyze their reactions at the expense of only hydrogen peroxide ...as the oxidant. Their structural similarity to chloroperoxidase (CPO) means that UPOs can also catalyze halogenation reactions based upon the generation of hypohalous acids from halide and H2O2. Here we show that the halogenation and oxygenation modes of a UPO can be stimulated at different pH values. Using simple aromatic compounds such as thymol, we show that, at a pH of 3.0 and 6.0, either brominated or oxygenated products respectively are produced. Preparative 100 mg scale transformations of substrates were performed with 60–72 % isolated yields of brominated products obtained. A one‐pot bromination‐oxygenation cascade reaction on 4‐ethylanisole, in which the pH was adjusted from 3.0 to 6.0 at the halfway stage, yielded sequentially brominated and oxygenated products 1‐(3‐bromo‐4‐methoxyphenyl)ethyl alcohol and 3‐bromo‐4‐methoxy acetophenone with 82 % combined conversion. These results identify UPOs as an unusual example of a biocatalyst that is tunable for entirely different chemical reactions, dependent upon the reaction conditions.
Heme‐dependent unspecific peroxygenases (UPOs) catalyze the selective oxygenation of organic molecules at pH 6.0 using hydrogen peroxide to form the oxidant Compound I at the active site. Compound I can also be recruited for the oxidation of halide ions in the presence of peroxide at pH 3.0 to generate hypohalous acid for halogenation reactions. Hence, the activity of UPOs towards a substrate such as thymol can be tuned to give oxygenated or halogenated products dependent upon the pH of the reaction.
A lyophilized preparation of an unspecific peroxygenase variant from Agrocybe aegerita (rAaeUPO‐PaDa‐I‐H) is a highly effective catalyst for the oxygenation of a diverse range of N‐heterocyclic ...compounds. Scalable biocatalytic oxygenations (27 preparative examples, ca. 100 mg scale) have been developed across a wide range of substrates, including alkyl pyridines, bicyclic N‐heterocycles and indoles. H2O2 is the only stoichiometric oxidant needed, without auxiliary electron transport proteins, which is key to the practicality of the method. Reaction outcomes can be altered depending on whether hydrogen peroxide was delivered by syringe pump or through in situ generation using an alcohol oxidase from Pichia pastoris (PpAOX) and methanol as a co‐substrate. Good synthetic yields (up to 84 %), regioselectivity and enantioselectivity (up to 99 % ee) were observed in some cases, highlighting the promise of UPOs as practical, versatile and scalable oxygenation biocatalysts.
A lyophilized preparation of an unspecific peroxygenase variant from Agrocybe aegerita (rAaeUPO‐PaDa‐I‐H) is a highly effective catalyst for the oxygenation of a diverse range of N‐heterocyclic compounds. Scalable, high yielding and enantioselective biocatalytic oxygenations have been developed, including 27 preparative examples (ca. 100 mg scale) across a wide range of substrates, including alkyl pyridines, bicyclic N‐heterocycles and indoles.
Biocatalysis: A Pharma Perspective Adams, Joseph P.; Brown, Murray J. B.; Diaz‐Rodriguez, Alba ...
Advanced synthesis & catalysis,
June 6, 2019, Letnik:
361, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Biocatalysis over the past few years has matured into an essential tool for modern, cost effective and sustainable pharmaceutical manufacturing. While some reaction classes are well established, and ...may even be the option of first intent, other more recently discovered enzyme classes are being rapidly developed both in academia and industry. Notwithstanding this, there are further promising enzymes that require further investment and investigation to allow their future industrial use. We here outline GSK's perspective on the current status of biocatalysis for pharmaceutical manufacturing and provide our views on areas of significant potential.
Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible‐light photocatalysis. Here we show that the redox potential of a carbon ...nitride photocatalyst (CN‐OA‐m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo‐chemo‐enzymatic cascades that give either the (S)‐ or the (R)‐enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN‐OA‐m led to the enantioselective hydroxylation of ethylbenzene to (R)‐1‐phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)‐1‐phenylethanol (93 % ee).
Green or blue? The wavelength controls the outcome. Chromoselective activation of a carbon nitride generates electron holes with different oxidation potentials that are used for selective oxidation processes. By coupling the photocatalytic reactions with biocatalysis the (S)‐ or the (R)‐enantiomer of 1‐phenylethanol was synthesized stereoselectively.
A series of enantiopure hydroxy esters and lactones has been synthesized in a chemodivergent manner via alcohol dehydrogenase (ADH) reduction of the corresponding keto esters by means of cascade or ...tandem protocols. Thus, ADH from Rhodococcus ruber (ADH-A) or Lactobacillus brevis (LBADH) afforded both antipodes in a very selective way when dealing with small derivatives. With bulkier substrates, ADH from Ralstonia sp. (RasADH) was successfully employed to achieve the synthesis of enantioenriched γ- or δ-hydroxy esters. To isolate the corresponding lactones, two different approaches were followed: a cascade reaction by spontaneous cyclization of the hydroxy ester intermediate, or a one-pot two-step tandem protocol. Moreover, a chemoenzymatic route was designed to obtain a chiral brominated lactone, which enabled further modifications in a sequential fashion by Pd-catalyzed reactions, affording relevant functionalized lactones.
An efficient methodology to oxidize beta , beta -dihalogenated secondary alcohols employing oxygen was achieved in a biphasic medium using the laccase from Trametes versicolor/TEMPO pair, providing ...the corresponding ketones in a clean fashion under very mild conditions. Moreover, a chemoenzymatic protocol has been applied successfully to deracemize 2,2-dichloro-1-phenylethanol combining this oxidation with an alcohol dehydrogenase-catalyzed bioreduction.
PDF
