Jürgen Brem | University of Oxford (original) (raw)

Papers by Jürgen Brem

Research paper thumbnail of Lipase-catalyzed kinetic resolutions of racemic 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols and their acetates

Tetrahedron: Asymmetry, 2011

The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and... more The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and their acetates via enantioselective methanolysis of the corresponding racemic esters rac 2a-c with lipase B from Candida antarctica (CaL-B) or/and by acylation of the racemic alcohols with the lipase A or lipase B from C. antarctica (CaL-A and CaL-B) is described. The absolute configuration of enantiopure 1-(10-ethyl-10H-phenothiazin-1-yl)ethyl acetate 2a was assigned as (R) by using QM/MM(hf/3-21g:uff) calculations within the CaL-B (1LBT crystal structure) enzymic environment.

Research paper thumbnail of Lipase-catalyzed kinetic resolution of racemic 1-(10-alkyl-10H-phenothiazin-3-yl)ethanols and their butanoates

Tetrahedron: Asymmetry, 2010

The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)e... more The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)ethanol rac-2b, 1-(benzo[b]furan-3-yl)ethanol rac-2c and 1-(benzo[b]thiophen-3-yl)ethanol rac-2d was studied by enantiomer selective acylation catalyzed by a selection of commercially available and in house produced lipases. Alcoholysis of the corresponding racemic acetates rac-3a-d catalyzed by Candida antarctica lipase B (CaLB) was also investigated. Two racemic 1-heteroarylethanols rac-2a,b were prepared by addition of the corresponding lithiated heteroarylic compounds 1a,b to acetaldehyde, whereas two others, rac-2c,d were synthesized by the addition of MeMgI onto the corresponding heteroaryl-carbaldehydes 1c,d. The high enantiomer selectivities of CaLB in the acylation of racemic 1-heteroarylethanols rac-2a-d allowed the determination of the enantiomeric preference of these enzymatic acetylation reactions by QM/MM [pm3/uff or hf(3-21+g**)/uff] calculations. For acetylation of each of the racemic alcohols rac-2a-d, four possible tetrahedral intermediate states were compared and analyzed.

Research paper thumbnail of New chemo-enzymatic approaches for the synthesis of (R)- and (S)-bufuralol

Tetrahedron: Asymmetry, 2014

Both enantiomers of bufuralol are pharmaceutically important molecules. While the (S)-isomer with... more Both enantiomers of bufuralol are pharmaceutically important molecules. While the (S)-isomer with a higher b-blocking activity is recommended for hypertension treatment, the (R)-enantiomer can be used as marker of hepatic activity. In this paper two new alternative approaches are described for their chemoenzymatic synthesis, providing both highly enantiomerically enriched stereoisomers of the target molecule (ee 96-98%). One route is based on the baker's yeast mediated stereoselective biotransformation of a-substituted ketones, and the other one on the lipase mediated kinetic resolution of the racemic bromoethanol.

Research paper thumbnail of The Interaction of Nitrophenylalanines with Wild Type and Mutant 4-Methylideneimidazole-5-one-less Phenylalanine Ammonia Lyase

ChemCatChem, 2013

ABSTRACT Racemic nitrophenylalanines and (E)‐nitrophenylacrylates are synthesized from the corres... more ABSTRACT Racemic nitrophenylalanines and (E)‐nitrophenylacrylates are synthesized from the corresponding aldehydes. Both products are important for the examination of the mechanism of action of phenylalanine ammonia lyase (PAL). For the reaction of the rac‐nitrophenylalanines with both wild type (wt) PAL and an 4‐methylideneimidazole‐5‐one (MIO)‐less mutant, the kinetic constants K m and V max are determined and compared with those of the natural substrate L‐phenylalanine: the K m values for the racemic nitrophenylalanines with wt PAL are up to 9 times higher, however, the V max values are up to 5 times lower. Compared to wt PAL, the catalytic activity of MIO‐less PAL mutant for the deamination of L‐phenylalanine is approximately 400 times, while that for 3‐nitrophenylalanine is approximately 50 times lower. Both wt and MIO‐less PALs are enantioselective for L‐nitrophenylalanines. Thus, enantiopure D‐nitrophenylalanines can be biosynthesized from racemic substrates. The biocatalytic synthesis of the corresponding L‐enantiomers is achieved by the reverse reaction, starting from (E)‐nitrophenylacrylates. Both enantiomeric products obtained with wt and MIO‐less PAL are spectroscopically and chromatographically characterized and their optical rotations measured.

Research paper thumbnail of Sequential enzymatic procedure for the preparation of enantiomerically pure 2-heteroaryl-2-hydroxyacetic acids

Tetrahedron: Asymmetry, 2012

Starting from the racemic 2-benzofuranyl-and 2-benzo[b]thiophenyl-2-hydroxyacetic acid ethyl este... more Starting from the racemic 2-benzofuranyl-and 2-benzo[b]thiophenyl-2-hydroxyacetic acid ethyl esters as substrates, a general method was developed for the efficient synthesis of the corresponding highly enantiomerically enriched (ee up to 99%) (R)-and (S)-2-heteroaryl-2-hydroxyacetic acids.

Research paper thumbnail of Heterocycles 32. Efficient kinetic resolution of 1-(2-arylthiazol-4-yl)ethanols and their acetates using lipase B from Candida antarctica

Journal of Molecular Catalysis B: Enzymatic, 2013

Research paper thumbnail of Chemoenzymatic Preparation of 1-Heteroarylethanamines of Low Solubility

European Journal of Organic Chemistry, 2012

Both enantiomers of biologically and pharmaceutically interesting benzofuran-, benzothiophen-, an... more Both enantiomers of biologically and pharmaceutically interesting benzofuran-, benzothiophen-, and phenylfuran-based 1-heteroarylethanamines were prepared at close to theoretical yields by using Candida antarctica lipase B (Novozym 435) catalyzed (R)-selective N-acylation with isopropyl butanoate (enantiomeric ratio E Ͼ 200). The use of N-methyl-2pyrrolidinone (NMP) as a cosolvent (1:30) in isopropyl butanoate solved the problem of low solubility of the com-[a]

Research paper thumbnail of 2-Amino-3-(5-phenylfuran-2-yl)propionic Acids and 5-Phenylfuran-2-ylacrylic Acids are Novel Substrates of Phenylalanine Ammonia-Lyase

HETEROCYCLES, 2010

Racemic furanylalanines (III) and phenylfuranylacrylic acids (V) are employed as substrates of re... more Racemic furanylalanines (III) and phenylfuranylacrylic acids (V) are employed as substrates of recombinant phenylalanine ammonia-lyase. When about half of the amount of the racemic furanylalanines (III) are converted into the corresponding acrylates, the (D)-enantiomers (R)-(-)-(III) can be isolated. (L)-Enantiomers (S)-(+)-(III) are obtained from acrylates (V) when the enzyme reaction is reversed in the presence of ammonia. -(PAIZS, C.; TOSA, M. I.; BENCZE, L. C.; BREM, J.; IRIMIE, F. D.; RETEY*, J.; Heterocycles 82 (2011) 2, 1217-1228, http://dx.doi.org/10.3987/com-10-s(e)60 ; Inst. Org. Chem., Univ. Karlsruhe, D-76128 Karlsruhe, Germany; Eng.) -H. Hoennerscheid 30-100

Research paper thumbnail of Enzyme-catalyzed synthesis of (R)- and (S)-3-heteroaryl-3-hydroxy-propanoic acids and their derivatives

Tetrahedron: Asymmetry, 2009

Starting from the racemic 3-benzofuranyl- and 3-benzo[b]thiophenyl-3-hydroxypropanoic acid ethyl ... more Starting from the racemic 3-benzofuranyl- and 3-benzo[b]thiophenyl-3-hydroxypropanoic acid ethyl esters as substrates, various multistep enzymatic procedures were developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids.

Research paper thumbnail of Immobilization to improve the properties of Pseudomonas fluorescens lipase for the kinetic resolution of 3-aryl-3-hydroxy esters

Process Biochemistry, 2012

Lipase AK "Amano" 20 from Pseudomonas fluorescens (PFL) was immobilized using diverse immobilizat... more Lipase AK "Amano" 20 from Pseudomonas fluorescens (PFL) was immobilized using diverse immobilization techniques. The methods developed, especially the optimized sol-gel procedure, enabled the fine tuning of enzymatic activity and enantioselectivity for the kinetic resolution of racemic ethyl 3-aryl-3hydroxypropanoates. The aryl moieties of the racemates include furan-2 and 3-yl, thiophen-2 and 3-yl, benzofuran-2-yl, benzo[b]thiophen-2-yl, as well as phenyl and 4-chloro-and 4-methoxyphenyl groups. The optimized PFL sol-gel preparation (encapsulation from the aqueous solution of PFL, sucrose and Celite in situ) was shown to be efficiently reusable in ten cycles and highly enantioselective with E > 200 to all other substrates except furan-2 and 3-yl and thiophen-2 and 3-yl substituted compounds with E 108-184.

Research paper thumbnail of Lipase mediated sequential resolution of aromatic β-hydroxy esters using fatty acid derivatives

Tetrahedron: Asymmetry, 2011

The lipase-catalyzed kinetic resolution of a series of aromatic b-hydroxy esters in organic media... more The lipase-catalyzed kinetic resolution of a series of aromatic b-hydroxy esters in organic media has been investigated. Decanoic acid and its esters were successfully used as acyl donors for selective O-acylation. The regio-and enantioselective enzymatic hydrolysis of the decanoate moiety of the diesters was also investigated. The effects of water, reaction temperature, and solvent type, and also the influence of substrates structure on the catalytic behavior of potential commercially available lipases were studied. A novel procedure was developed for the efficient and highly stereoselective synthesis of both enantiomers of both novel and known target compounds.

Research paper thumbnail of Lipase-catalyzed kinetic resolution of racemic 1-heteroarylethanols--experimental and QM/MM study

Tetrahedron: …, 2008

The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)e... more The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)ethanol rac-2b, 1-(benzo[b]furan-3-yl)ethanol rac-2c and 1-(benzo[b]thiophen-3-yl)ethanol rac-2d was studied by enantiomer selective acylation catalyzed by a selection of commercially available and in house produced lipases. Alcoholysis of the corresponding racemic acetates rac-3a-d catalyzed by Candida antarctica lipase B (CaLB) was also investigated. Two racemic 1-heteroarylethanols rac-2a,b were prepared by addition of the corresponding lithiated heteroarylic compounds 1a,b to acetaldehyde, whereas two others, rac-2c,d were synthesized by the addition of MeMgI onto the corresponding heteroaryl-carbaldehydes 1c,d. The high enantiomer selectivities of CaLB in the acylation of racemic 1-heteroarylethanols rac-2a-d allowed the determination of the enantiomeric preference of these enzymatic acetylation reactions by QM/MM [pm3/uff or hf(3-21+g**)/uff] calculations. For acetylation of each of the racemic alcohols rac-2a-d, four possible tetrahedral intermediate states were compared and analyzed.

Research paper thumbnail of Enzyme-catalyzed synthesis of (R)- and (S)-3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoic acids

Tetrahedron: Asymmetry, 2010

Starting from the racemic ethyl 3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoates as substr... more Starting from the racemic ethyl 3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoates as substrates, a multienzymatic procedure was developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids.

Research paper thumbnail of Lipases A and B from Candida antarctica in the enantioselective acylation of ethyl 3-heteroaryl-3-hydroxypropanoates: aspects on the preparation and enantiopreference

Tetrahedron: Asymmetry, 2011

The preparative scale kinetic resolution of racemic ethyl 2-and 3-furyl-and 2-and 3-thienyl-3-hyd... more The preparative scale kinetic resolution of racemic ethyl 2-and 3-furyl-and 2-and 3-thienyl-3-hydroxypropanoates has been performed by Candida antarctica lipases A and B with vinyl esters. A study based on the present work together with the literature has been carried out in terms of lipase enantiopreference and substrate structure. We also discuss the excellent behavior of the lipase A in O-acylations of secondary alcohols with respect to enantiopreference. Tetrahedron: Asymmetry j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t e t a s y 4.3.2.1. Ethyl 3-acetoxy-3-(thiophen-2-yl)propanoate rac-3a (R 1 = Me). Yield: 91%; 1 H NMR: (300 MHz, CDCl 3 ): d = 1.23 (t, J = 7.2 Hz, 3H); 2.03 (s, 3H); 2.96 (ddd, J = 5.4 Hz, J = 8.7 Hz, J = 15.6 Hz, 2H); 4.15 (q, J = 6.9 Hz, 2H); 6.47 (dd, J = 5.4 Hz, J = 8.7 Hz, 1H); 6.94-6.97 (m, 1H); 7.09 (d, J = 3,3 Hz, 1H); 7.27 (d, J = 5,1 Hz, 1H); 13 C NMR: (75 MHz, CDCl 3 ): d = -oxo-1-(thiophen-2-yl)propyl butyrate rac-3a (R 1 = Pr). Yield: 87%; semisolid; 1 H NMR: (300 MHz, CDCl 3 ): d = 0.91 (t, J = 7.5 Hz, 3H); 1.24 (t, J = 7.0 Hz, 3H); 1.63 (overlapped tq, J 1 $ J 2 $ 7.5 Hz, 2H); 2.28 (t, J = 7.5 Hz, 2H); 2.97 (ddd, J = 5.4 Hz, J = 9 Hz, J = 16.2 Hz, 2H); 4.14 (q, J = 7.2 Hz, 2H); 6.49 (dd, J = 5.4 Hz, J = 9 Hz, 1H); 6.94-6.97 (m, 1H); 7.08-7.11 (m, 1H); 7.26-7.29 (m, 1H); 13 C NMR: (75 MHz, CDCl 3 ): d = 13293.0818.

Research paper thumbnail of Rhodanine hydrolysis leads to potent thioenolate mediated metallo-β-lactamase inhibition

Nature chemistry, 2014

The use of β-lactam antibiotics is compromised by resistance, which is provided by β-lactamases b... more The use of β-lactam antibiotics is compromised by resistance, which is provided by β-lactamases belonging to both metallo (MBL)- and serine (SBL)-β-lactamase subfamilies. The rhodanines are one of very few compound classes that inhibit penicillin-binding proteins (PBPs), SBLs and, as recently reported, MBLs. Here, we describe crystallographic analyses of the mechanism of inhibition of the clinically relevant VIM-2 MBL by a rhodanine, which reveal that the rhodanine ring undergoes hydrolysis to give a thioenolate. The thioenolate is found to bind via di-zinc chelation, mimicking the binding of intermediates in β-lactam hydrolysis. Crystallization of VIM-2 in the presence of the intact rhodanine led to observation of a ternary complex of MBL, a thioenolate fragment and rhodanine. The crystallographic observations are supported by kinetic and biophysical studies, including (19)F NMR analyses, which reveal the rhodanine-derived thioenolate to be a potent broad-spectrum MBL inhibitor and...

Research paper thumbnail of Biochemical characterization of New Delhi metallo- -lactamase variants reveals differences in protein stability

Journal of Antimicrobial Chemotherapy, 2014

Objectives: Metallo-b-lactamase (MBL)-based resistance is a threat to the use of most b-lactam an... more Objectives: Metallo-b-lactamase (MBL)-based resistance is a threat to the use of most b-lactam antibiotics. Multiple variants of the New Delhi MBL (NDM) have recently been reported. Previous reports indicate that the substitutions affect NDM activity despite being located outside the active site. This study compares the biochemical properties of seven clinically reported NDM variants.

Research paper thumbnail of Chromophore-Linked Substrate (CLS405): Probing Metallo-β-Lactamase Activity and Inhibition

ChemMedChem, 2013

Serine- and metallo-β-lactamases present a threat to the clinical use of nearly all β-lactam anti... more Serine- and metallo-β-lactamases present a threat to the clinical use of nearly all β-lactam antibiotics, including penicillins, cephalosporins, and carbapenems. Efforts to develop metallo-β-lactamase (MBL) inhibitors require suitable screening platforms to allow the rapid determination of β-lactamase activity and efficient inhibition. Unfortunately, the platforms currently available are not ideal for this purpose. Further progress in MBL inhibitor identification requires inexpensive and widely applicable assays. Herein the identification of an inexpensive and stable chromogenic substrate suitable for use in assays of clinically relevant MBLs is described. (6R,7R)-3-((4-Nitrophenoxy)methyl)-8-oxo-7-(2-phenylacetamido)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 5,5-dioxide (CLS405) was synthesised in a three-step protocol. CLS405 was then characterised spectroscopically, and its stability and kinetic properties evaluated. With a Δλmax value of 100 nm between the parent and hydrolysis product, a higher analytical accuracy is possible with CLS405 than with commonly used chromogenic substrates. The use of CLS405 in assays was validated by MBL activity measurements and inhibitor screening that resulted in the identification of N-hydroxythiazoles as new inhibitor scaffolds for MBLs. Further evaluation of the identified N-hydroxythiazoles against a panel of clinically relevant MBLs showed that they possess inhibitory activities in the mid- to low-micromolar range. The findings of this study provide both a useful tool compound for further inhibitor identification, and novel scaffolds for the design of improved MBL inhibitors with potential as antibiotics against resistant strains of bacteria.

Research paper thumbnail of Lipase-catalyzed kinetic resolutions of racemic 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols and their acetates

Tetrahedron: Asymmetry, 2011

The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and... more The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and their acetates via enantioselective methanolysis of the corresponding racemic esters rac 2a-c with lipase B from Candida antarctica (CaL-B) or/and by acylation of the racemic alcohols with the lipase A or lipase B from C. antarctica (CaL-A and CaL-B) is described. The absolute configuration of enantiopure 1-(10-ethyl-10H-phenothiazin-1-yl)ethyl acetate 2a was assigned as (R) by using QM/MM(hf/3-21g:uff) calculations within the CaL-B (1LBT crystal structure) enzymic environment.

Research paper thumbnail of Lipase-catalyzed kinetic resolutions of racemic 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols and their acetates

Tetrahedron: Asymmetry, 2011

The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and... more The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and their acetates via enantioselective methanolysis of the corresponding racemic esters rac 2a-c with lipase B from Candida antarctica (CaL-B) or/and by acylation of the racemic alcohols with the lipase A or lipase B from C. antarctica (CaL-A and CaL-B) is described. The absolute configuration of enantiopure 1-(10-ethyl-10H-phenothiazin-1-yl)ethyl acetate 2a was assigned as (R) by using QM/MM(hf/3-21g:uff) calculations within the CaL-B (1LBT crystal structure) enzymic environment.

Research paper thumbnail of Lipase-catalyzed kinetic resolution of racemic 1-(10-alkyl-10H-phenothiazin-3-yl)ethanols and their butanoates

Tetrahedron: Asymmetry, 2010

The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)e... more The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)ethanol rac-2b, 1-(benzo[b]furan-3-yl)ethanol rac-2c and 1-(benzo[b]thiophen-3-yl)ethanol rac-2d was studied by enantiomer selective acylation catalyzed by a selection of commercially available and in house produced lipases. Alcoholysis of the corresponding racemic acetates rac-3a-d catalyzed by Candida antarctica lipase B (CaLB) was also investigated. Two racemic 1-heteroarylethanols rac-2a,b were prepared by addition of the corresponding lithiated heteroarylic compounds 1a,b to acetaldehyde, whereas two others, rac-2c,d were synthesized by the addition of MeMgI onto the corresponding heteroaryl-carbaldehydes 1c,d. The high enantiomer selectivities of CaLB in the acylation of racemic 1-heteroarylethanols rac-2a-d allowed the determination of the enantiomeric preference of these enzymatic acetylation reactions by QM/MM [pm3/uff or hf(3-21+g**)/uff] calculations. For acetylation of each of the racemic alcohols rac-2a-d, four possible tetrahedral intermediate states were compared and analyzed.

Research paper thumbnail of New chemo-enzymatic approaches for the synthesis of (R)- and (S)-bufuralol

Tetrahedron: Asymmetry, 2014

Both enantiomers of bufuralol are pharmaceutically important molecules. While the (S)-isomer with... more Both enantiomers of bufuralol are pharmaceutically important molecules. While the (S)-isomer with a higher b-blocking activity is recommended for hypertension treatment, the (R)-enantiomer can be used as marker of hepatic activity. In this paper two new alternative approaches are described for their chemoenzymatic synthesis, providing both highly enantiomerically enriched stereoisomers of the target molecule (ee 96-98%). One route is based on the baker's yeast mediated stereoselective biotransformation of a-substituted ketones, and the other one on the lipase mediated kinetic resolution of the racemic bromoethanol.

Research paper thumbnail of The Interaction of Nitrophenylalanines with Wild Type and Mutant 4-Methylideneimidazole-5-one-less Phenylalanine Ammonia Lyase

ChemCatChem, 2013

ABSTRACT Racemic nitrophenylalanines and (E)‐nitrophenylacrylates are synthesized from the corres... more ABSTRACT Racemic nitrophenylalanines and (E)‐nitrophenylacrylates are synthesized from the corresponding aldehydes. Both products are important for the examination of the mechanism of action of phenylalanine ammonia lyase (PAL). For the reaction of the rac‐nitrophenylalanines with both wild type (wt) PAL and an 4‐methylideneimidazole‐5‐one (MIO)‐less mutant, the kinetic constants K m and V max are determined and compared with those of the natural substrate L‐phenylalanine: the K m values for the racemic nitrophenylalanines with wt PAL are up to 9 times higher, however, the V max values are up to 5 times lower. Compared to wt PAL, the catalytic activity of MIO‐less PAL mutant for the deamination of L‐phenylalanine is approximately 400 times, while that for 3‐nitrophenylalanine is approximately 50 times lower. Both wt and MIO‐less PALs are enantioselective for L‐nitrophenylalanines. Thus, enantiopure D‐nitrophenylalanines can be biosynthesized from racemic substrates. The biocatalytic synthesis of the corresponding L‐enantiomers is achieved by the reverse reaction, starting from (E)‐nitrophenylacrylates. Both enantiomeric products obtained with wt and MIO‐less PAL are spectroscopically and chromatographically characterized and their optical rotations measured.

Research paper thumbnail of Sequential enzymatic procedure for the preparation of enantiomerically pure 2-heteroaryl-2-hydroxyacetic acids

Tetrahedron: Asymmetry, 2012

Starting from the racemic 2-benzofuranyl-and 2-benzo[b]thiophenyl-2-hydroxyacetic acid ethyl este... more Starting from the racemic 2-benzofuranyl-and 2-benzo[b]thiophenyl-2-hydroxyacetic acid ethyl esters as substrates, a general method was developed for the efficient synthesis of the corresponding highly enantiomerically enriched (ee up to 99%) (R)-and (S)-2-heteroaryl-2-hydroxyacetic acids.

Research paper thumbnail of Heterocycles 32. Efficient kinetic resolution of 1-(2-arylthiazol-4-yl)ethanols and their acetates using lipase B from Candida antarctica

Journal of Molecular Catalysis B: Enzymatic, 2013

Research paper thumbnail of Chemoenzymatic Preparation of 1-Heteroarylethanamines of Low Solubility

European Journal of Organic Chemistry, 2012

Both enantiomers of biologically and pharmaceutically interesting benzofuran-, benzothiophen-, an... more Both enantiomers of biologically and pharmaceutically interesting benzofuran-, benzothiophen-, and phenylfuran-based 1-heteroarylethanamines were prepared at close to theoretical yields by using Candida antarctica lipase B (Novozym 435) catalyzed (R)-selective N-acylation with isopropyl butanoate (enantiomeric ratio E Ͼ 200). The use of N-methyl-2pyrrolidinone (NMP) as a cosolvent (1:30) in isopropyl butanoate solved the problem of low solubility of the com-[a]

Research paper thumbnail of 2-Amino-3-(5-phenylfuran-2-yl)propionic Acids and 5-Phenylfuran-2-ylacrylic Acids are Novel Substrates of Phenylalanine Ammonia-Lyase

HETEROCYCLES, 2010

Racemic furanylalanines (III) and phenylfuranylacrylic acids (V) are employed as substrates of re... more Racemic furanylalanines (III) and phenylfuranylacrylic acids (V) are employed as substrates of recombinant phenylalanine ammonia-lyase. When about half of the amount of the racemic furanylalanines (III) are converted into the corresponding acrylates, the (D)-enantiomers (R)-(-)-(III) can be isolated. (L)-Enantiomers (S)-(+)-(III) are obtained from acrylates (V) when the enzyme reaction is reversed in the presence of ammonia. -(PAIZS, C.; TOSA, M. I.; BENCZE, L. C.; BREM, J.; IRIMIE, F. D.; RETEY*, J.; Heterocycles 82 (2011) 2, 1217-1228, http://dx.doi.org/10.3987/com-10-s(e)60 ; Inst. Org. Chem., Univ. Karlsruhe, D-76128 Karlsruhe, Germany; Eng.) -H. Hoennerscheid 30-100

Research paper thumbnail of Enzyme-catalyzed synthesis of (R)- and (S)-3-heteroaryl-3-hydroxy-propanoic acids and their derivatives

Tetrahedron: Asymmetry, 2009

Starting from the racemic 3-benzofuranyl- and 3-benzo[b]thiophenyl-3-hydroxypropanoic acid ethyl ... more Starting from the racemic 3-benzofuranyl- and 3-benzo[b]thiophenyl-3-hydroxypropanoic acid ethyl esters as substrates, various multistep enzymatic procedures were developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids.

Research paper thumbnail of Immobilization to improve the properties of Pseudomonas fluorescens lipase for the kinetic resolution of 3-aryl-3-hydroxy esters

Process Biochemistry, 2012

Lipase AK "Amano" 20 from Pseudomonas fluorescens (PFL) was immobilized using diverse immobilizat... more Lipase AK "Amano" 20 from Pseudomonas fluorescens (PFL) was immobilized using diverse immobilization techniques. The methods developed, especially the optimized sol-gel procedure, enabled the fine tuning of enzymatic activity and enantioselectivity for the kinetic resolution of racemic ethyl 3-aryl-3hydroxypropanoates. The aryl moieties of the racemates include furan-2 and 3-yl, thiophen-2 and 3-yl, benzofuran-2-yl, benzo[b]thiophen-2-yl, as well as phenyl and 4-chloro-and 4-methoxyphenyl groups. The optimized PFL sol-gel preparation (encapsulation from the aqueous solution of PFL, sucrose and Celite in situ) was shown to be efficiently reusable in ten cycles and highly enantioselective with E > 200 to all other substrates except furan-2 and 3-yl and thiophen-2 and 3-yl substituted compounds with E 108-184.

Research paper thumbnail of Lipase mediated sequential resolution of aromatic β-hydroxy esters using fatty acid derivatives

Tetrahedron: Asymmetry, 2011

The lipase-catalyzed kinetic resolution of a series of aromatic b-hydroxy esters in organic media... more The lipase-catalyzed kinetic resolution of a series of aromatic b-hydroxy esters in organic media has been investigated. Decanoic acid and its esters were successfully used as acyl donors for selective O-acylation. The regio-and enantioselective enzymatic hydrolysis of the decanoate moiety of the diesters was also investigated. The effects of water, reaction temperature, and solvent type, and also the influence of substrates structure on the catalytic behavior of potential commercially available lipases were studied. A novel procedure was developed for the efficient and highly stereoselective synthesis of both enantiomers of both novel and known target compounds.

Research paper thumbnail of Lipase-catalyzed kinetic resolution of racemic 1-heteroarylethanols--experimental and QM/MM study

Tetrahedron: …, 2008

The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)e... more The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)ethanol rac-2b, 1-(benzo[b]furan-3-yl)ethanol rac-2c and 1-(benzo[b]thiophen-3-yl)ethanol rac-2d was studied by enantiomer selective acylation catalyzed by a selection of commercially available and in house produced lipases. Alcoholysis of the corresponding racemic acetates rac-3a-d catalyzed by Candida antarctica lipase B (CaLB) was also investigated. Two racemic 1-heteroarylethanols rac-2a,b were prepared by addition of the corresponding lithiated heteroarylic compounds 1a,b to acetaldehyde, whereas two others, rac-2c,d were synthesized by the addition of MeMgI onto the corresponding heteroaryl-carbaldehydes 1c,d. The high enantiomer selectivities of CaLB in the acylation of racemic 1-heteroarylethanols rac-2a-d allowed the determination of the enantiomeric preference of these enzymatic acetylation reactions by QM/MM [pm3/uff or hf(3-21+g**)/uff] calculations. For acetylation of each of the racemic alcohols rac-2a-d, four possible tetrahedral intermediate states were compared and analyzed.

Research paper thumbnail of Enzyme-catalyzed synthesis of (R)- and (S)-3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoic acids

Tetrahedron: Asymmetry, 2010

Starting from the racemic ethyl 3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoates as substr... more Starting from the racemic ethyl 3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoates as substrates, a multienzymatic procedure was developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids.

Research paper thumbnail of Lipases A and B from Candida antarctica in the enantioselective acylation of ethyl 3-heteroaryl-3-hydroxypropanoates: aspects on the preparation and enantiopreference

Tetrahedron: Asymmetry, 2011

The preparative scale kinetic resolution of racemic ethyl 2-and 3-furyl-and 2-and 3-thienyl-3-hyd... more The preparative scale kinetic resolution of racemic ethyl 2-and 3-furyl-and 2-and 3-thienyl-3-hydroxypropanoates has been performed by Candida antarctica lipases A and B with vinyl esters. A study based on the present work together with the literature has been carried out in terms of lipase enantiopreference and substrate structure. We also discuss the excellent behavior of the lipase A in O-acylations of secondary alcohols with respect to enantiopreference. Tetrahedron: Asymmetry j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t e t a s y 4.3.2.1. Ethyl 3-acetoxy-3-(thiophen-2-yl)propanoate rac-3a (R 1 = Me). Yield: 91%; 1 H NMR: (300 MHz, CDCl 3 ): d = 1.23 (t, J = 7.2 Hz, 3H); 2.03 (s, 3H); 2.96 (ddd, J = 5.4 Hz, J = 8.7 Hz, J = 15.6 Hz, 2H); 4.15 (q, J = 6.9 Hz, 2H); 6.47 (dd, J = 5.4 Hz, J = 8.7 Hz, 1H); 6.94-6.97 (m, 1H); 7.09 (d, J = 3,3 Hz, 1H); 7.27 (d, J = 5,1 Hz, 1H); 13 C NMR: (75 MHz, CDCl 3 ): d = -oxo-1-(thiophen-2-yl)propyl butyrate rac-3a (R 1 = Pr). Yield: 87%; semisolid; 1 H NMR: (300 MHz, CDCl 3 ): d = 0.91 (t, J = 7.5 Hz, 3H); 1.24 (t, J = 7.0 Hz, 3H); 1.63 (overlapped tq, J 1 $ J 2 $ 7.5 Hz, 2H); 2.28 (t, J = 7.5 Hz, 2H); 2.97 (ddd, J = 5.4 Hz, J = 9 Hz, J = 16.2 Hz, 2H); 4.14 (q, J = 7.2 Hz, 2H); 6.49 (dd, J = 5.4 Hz, J = 9 Hz, 1H); 6.94-6.97 (m, 1H); 7.08-7.11 (m, 1H); 7.26-7.29 (m, 1H); 13 C NMR: (75 MHz, CDCl 3 ): d = 13293.0818.

Research paper thumbnail of Rhodanine hydrolysis leads to potent thioenolate mediated metallo-β-lactamase inhibition

Nature chemistry, 2014

The use of β-lactam antibiotics is compromised by resistance, which is provided by β-lactamases b... more The use of β-lactam antibiotics is compromised by resistance, which is provided by β-lactamases belonging to both metallo (MBL)- and serine (SBL)-β-lactamase subfamilies. The rhodanines are one of very few compound classes that inhibit penicillin-binding proteins (PBPs), SBLs and, as recently reported, MBLs. Here, we describe crystallographic analyses of the mechanism of inhibition of the clinically relevant VIM-2 MBL by a rhodanine, which reveal that the rhodanine ring undergoes hydrolysis to give a thioenolate. The thioenolate is found to bind via di-zinc chelation, mimicking the binding of intermediates in β-lactam hydrolysis. Crystallization of VIM-2 in the presence of the intact rhodanine led to observation of a ternary complex of MBL, a thioenolate fragment and rhodanine. The crystallographic observations are supported by kinetic and biophysical studies, including (19)F NMR analyses, which reveal the rhodanine-derived thioenolate to be a potent broad-spectrum MBL inhibitor and...

Research paper thumbnail of Biochemical characterization of New Delhi metallo- -lactamase variants reveals differences in protein stability

Journal of Antimicrobial Chemotherapy, 2014

Objectives: Metallo-b-lactamase (MBL)-based resistance is a threat to the use of most b-lactam an... more Objectives: Metallo-b-lactamase (MBL)-based resistance is a threat to the use of most b-lactam antibiotics. Multiple variants of the New Delhi MBL (NDM) have recently been reported. Previous reports indicate that the substitutions affect NDM activity despite being located outside the active site. This study compares the biochemical properties of seven clinically reported NDM variants.

Research paper thumbnail of Chromophore-Linked Substrate (CLS405): Probing Metallo-β-Lactamase Activity and Inhibition

ChemMedChem, 2013

Serine- and metallo-β-lactamases present a threat to the clinical use of nearly all β-lactam anti... more Serine- and metallo-β-lactamases present a threat to the clinical use of nearly all β-lactam antibiotics, including penicillins, cephalosporins, and carbapenems. Efforts to develop metallo-β-lactamase (MBL) inhibitors require suitable screening platforms to allow the rapid determination of β-lactamase activity and efficient inhibition. Unfortunately, the platforms currently available are not ideal for this purpose. Further progress in MBL inhibitor identification requires inexpensive and widely applicable assays. Herein the identification of an inexpensive and stable chromogenic substrate suitable for use in assays of clinically relevant MBLs is described. (6R,7R)-3-((4-Nitrophenoxy)methyl)-8-oxo-7-(2-phenylacetamido)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 5,5-dioxide (CLS405) was synthesised in a three-step protocol. CLS405 was then characterised spectroscopically, and its stability and kinetic properties evaluated. With a Δλmax value of 100 nm between the parent and hydrolysis product, a higher analytical accuracy is possible with CLS405 than with commonly used chromogenic substrates. The use of CLS405 in assays was validated by MBL activity measurements and inhibitor screening that resulted in the identification of N-hydroxythiazoles as new inhibitor scaffolds for MBLs. Further evaluation of the identified N-hydroxythiazoles against a panel of clinically relevant MBLs showed that they possess inhibitory activities in the mid- to low-micromolar range. The findings of this study provide both a useful tool compound for further inhibitor identification, and novel scaffolds for the design of improved MBL inhibitors with potential as antibiotics against resistant strains of bacteria.

Research paper thumbnail of Lipase-catalyzed kinetic resolutions of racemic 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols and their acetates

Tetrahedron: Asymmetry, 2011

The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and... more The synthesis of both enantiomers of 1-(10-ethyl-10H-phenothiazin-1,2, and 4-yl)ethanols 1a-c and their acetates via enantioselective methanolysis of the corresponding racemic esters rac 2a-c with lipase B from Candida antarctica (CaL-B) or/and by acylation of the racemic alcohols with the lipase A or lipase B from C. antarctica (CaL-A and CaL-B) is described. The absolute configuration of enantiopure 1-(10-ethyl-10H-phenothiazin-1-yl)ethyl acetate 2a was assigned as (R) by using QM/MM(hf/3-21g:uff) calculations within the CaL-B (1LBT crystal structure) enzymic environment.