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Urease: A highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4-dihydropyridines from the in situ formed ammonia
Urease: A highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4-dihydropyridines from the in situ formed ammonia Fatemeh Tamaddon, Somayeh Ghazi PII: DOI: Reference:
S1566-7367(15)30067-4 doi: 10.1016/j.catcom.2015.09.006 CATCOM 4430
To appear in:
Catalysis Communications
Received date: Revised date: Accepted date:
5 May 2015 9 September 2015 11 September 2015
Please cite this article as: Fatemeh Tamaddon, Somayeh Ghazi, Urease: A highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4dihydropyridines from the in situ formed ammonia, Catalysis Communications (2015), doi: 10.1016/j.catcom.2015.09.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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MA
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ACCEPTED MANUSCRIPT
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Urease: a highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4-dihydropyridines from the in situ formed ammonia Fatemeh Tamaddon, Somayeh Ghazi
Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741, Iran Corresponding author: Fatemeh Tamaddon Department of Chemistry Faculty of Science Yazd University Yazd 89195-741 Iran Tel.: 00983531232666 1
ACCEPTED MANUSCRIPT Fax: 00983538210644
PT
E-mail: [email protected]
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Highlights
Urea is a natural odorless source of nitrogen for synthesis of 1,4-dihydropyridines.
SC
Water-based reaction with urea and urease is highly biocompatible.
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Reactions give excellent yields of products without purification. Urease catalyzes Hantzsch reaction with urea in water more than NH4OAc.
MA
This enzymatic medium is reusable and inhibits by heavy metal cations. __________________________________________________
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Abstract
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Urease is a superior biocompatible catalyst for switching from the Biginelli reaction to
AC CE P
urea-based synthesis of 1,4-dihydropyridines in water, where 100% switching occurs at 0.02 g/mL of enzyme. Hantzsch reaction with ammonium acetate (NH4OAc) is inefficiently catalyzed by urease (70%, 4 h), and heavy metal ions inhibit the ureasecatalyzed reactions with urea or NH4OAc. Promotion of the urea-based Hantzsch reaction by urease and its inhibition with Hg2+ supports specificity of urease for in situ generation of ammonia, whereas the role of urease in further transformations is not so specific. The features of this enzymatic method are reusability, mild reaction conditions, biocompatibility, generality, and high yield of products.
2
ACCEPTED MANUSCRIPT Keywords: Urease; Water-based Hantzcsh reaction; Enzymatic; Biocompatible.
PT
________________________________________________
RI
1. Introduction
SC
Because of their significant specificity in organic reactions, enzymes are the most promising catalysts for eco-environmental water-based biotransformations.1 Although
NU
very low loading of enzymes promotes various sequential reactions in living cells and
MA
biotechnological processes,2–4 immobilization of enzymes on solid supports improves their reusability, stability, activity, and resistance to chemical attack.5,6 Urease is a well-
D
known Ni-containing hydrolase enzyme7–9 that increases biochemical dissociation of urea
<>
AC CE P
TE
into ammonia by 1014 times (Scheme 1).
The natural sources of urease are soybean,10 Aspergillus niger PTCC5011,11 and Schizosaccharomyces pombe.12 Multicomponent reactions (MCRs) are strategic for the production of complex molecules and growth of combinatorial chemistry.13–19 Hantzsch20 and Biginelli21 reactions are two common MCRs that produce 1,4-dihydropyridines (1,4-DHPs) and 3,4dihydropyrimidin-2(1H)-ones (DHPMs) as calcium channel-stimulating drugs,22–29 in which the former have a structural connection with hydrogenase coenzymes.28 The similarity of components and catalysts in these reactions leads to the competitive formation of 1,4-DHPs in Biginelli’s experiments, where urea dissociates into ammonia.30–33
Recently,
we
have
reported
3
base-catalyzed29
and
shiftable
ACCEPTED MANUSCRIPT Biginelli/Hantzsch reactions of nano-ZnO in water.30,31 Despite the promotion of these MCRs by acid–base catalysts,34 enzymatic biocompatible synthesis of 1,4-DHPs is still in
PT
demand. Because of the presence of a solid in the final stage,6 immobilization of urease
RI
on magnetic nanoparticles, monoliths, or smart polymers may become an alternative to
SC
further improve the implementation of this process (work in progress). Because urease was selected for the in-water dissociation of urea into ammonia,
NU
competition between enzymatic hydrolysis and condensation of urea was postulated to
MA
orient the Hantzsch/Biginelli reactions (Scheme 2).
D
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2.1. General
TE
2. Experimental
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Infrared (IR), 1H nuclear magnetic resonance (NMR) (500 MHz), and 13C NMR (125 MHz) spectra were recorded on Fourier transform infrared (FTIR) spectrometer, Bruker Equinox 55, and Bruker AC 500, respectively. Urease (from jack bean) lyophilized 5 U/mg and art no 1.08489.0005 was purchased from Merck. 2.2. General procedure for the synthesis of 1,4-DHPs Urease (0.05 g) was added to a mixture of aldehyde (5 mmol), 1,3-dicarbonyl (5 mmol), and urea (15 mmol), and the mixture was stirred at 70 °C in water, till the product was precipitated. After completion of the reaction (thin-layer chromatography (TLC) monitoring, hexane:EtOAc (70:30)), cold water was added and the product was filtered to give the pure 1,4-DHP product. 2.3. Reusability of the reaction medium
4
ACCEPTED MANUSCRIPT The practical reusability of the reaction medium after three further runs confirmed the unchanged activity of urease under reaction conditions (Figure 1).
PT
<
S1566-7367(15)30067-4 doi: 10.1016/j.catcom.2015.09.006 CATCOM 4430
To appear in:
Catalysis Communications
Received date: Revised date: Accepted date:
5 May 2015 9 September 2015 11 September 2015
Please cite this article as: Fatemeh Tamaddon, Somayeh Ghazi, Urease: A highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4dihydropyridines from the in situ formed ammonia, Catalysis Communications (2015), doi: 10.1016/j.catcom.2015.09.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
TE
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC CE P
Urease: a highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4-dihydropyridines from the in situ formed ammonia Fatemeh Tamaddon, Somayeh Ghazi
Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741, Iran Corresponding author: Fatemeh Tamaddon Department of Chemistry Faculty of Science Yazd University Yazd 89195-741 Iran Tel.: 00983531232666 1
ACCEPTED MANUSCRIPT Fax: 00983538210644
PT
E-mail: [email protected]
RI
Highlights
Urea is a natural odorless source of nitrogen for synthesis of 1,4-dihydropyridines.
SC
Water-based reaction with urea and urease is highly biocompatible.
NU
Reactions give excellent yields of products without purification. Urease catalyzes Hantzsch reaction with urea in water more than NH4OAc.
MA
This enzymatic medium is reusable and inhibits by heavy metal cations. __________________________________________________
D
Abstract
TE
Urease is a superior biocompatible catalyst for switching from the Biginelli reaction to
AC CE P
urea-based synthesis of 1,4-dihydropyridines in water, where 100% switching occurs at 0.02 g/mL of enzyme. Hantzsch reaction with ammonium acetate (NH4OAc) is inefficiently catalyzed by urease (70%, 4 h), and heavy metal ions inhibit the ureasecatalyzed reactions with urea or NH4OAc. Promotion of the urea-based Hantzsch reaction by urease and its inhibition with Hg2+ supports specificity of urease for in situ generation of ammonia, whereas the role of urease in further transformations is not so specific. The features of this enzymatic method are reusability, mild reaction conditions, biocompatibility, generality, and high yield of products.
2
ACCEPTED MANUSCRIPT Keywords: Urease; Water-based Hantzcsh reaction; Enzymatic; Biocompatible.
PT
________________________________________________
RI
1. Introduction
SC
Because of their significant specificity in organic reactions, enzymes are the most promising catalysts for eco-environmental water-based biotransformations.1 Although
NU
very low loading of enzymes promotes various sequential reactions in living cells and
MA
biotechnological processes,2–4 immobilization of enzymes on solid supports improves their reusability, stability, activity, and resistance to chemical attack.5,6 Urease is a well-
D
known Ni-containing hydrolase enzyme7–9 that increases biochemical dissociation of urea
<
AC CE P
TE
into ammonia by 1014 times (Scheme 1).
The natural sources of urease are soybean,10 Aspergillus niger PTCC5011,11 and Schizosaccharomyces pombe.12 Multicomponent reactions (MCRs) are strategic for the production of complex molecules and growth of combinatorial chemistry.13–19 Hantzsch20 and Biginelli21 reactions are two common MCRs that produce 1,4-dihydropyridines (1,4-DHPs) and 3,4dihydropyrimidin-2(1H)-ones (DHPMs) as calcium channel-stimulating drugs,22–29 in which the former have a structural connection with hydrogenase coenzymes.28 The similarity of components and catalysts in these reactions leads to the competitive formation of 1,4-DHPs in Biginelli’s experiments, where urea dissociates into ammonia.30–33
Recently,
we
have
reported
3
base-catalyzed29
and
shiftable
ACCEPTED MANUSCRIPT Biginelli/Hantzsch reactions of nano-ZnO in water.30,31 Despite the promotion of these MCRs by acid–base catalysts,34 enzymatic biocompatible synthesis of 1,4-DHPs is still in
PT
demand. Because of the presence of a solid in the final stage,6 immobilization of urease
RI
on magnetic nanoparticles, monoliths, or smart polymers may become an alternative to
SC
further improve the implementation of this process (work in progress). Because urease was selected for the in-water dissociation of urea into ammonia,
NU
competition between enzymatic hydrolysis and condensation of urea was postulated to
MA
orient the Hantzsch/Biginelli reactions (Scheme 2).
D
<
2.1. General
TE
2. Experimental
AC CE P
Infrared (IR), 1H nuclear magnetic resonance (NMR) (500 MHz), and 13C NMR (125 MHz) spectra were recorded on Fourier transform infrared (FTIR) spectrometer, Bruker Equinox 55, and Bruker AC 500, respectively. Urease (from jack bean) lyophilized 5 U/mg and art no 1.08489.0005 was purchased from Merck. 2.2. General procedure for the synthesis of 1,4-DHPs Urease (0.05 g) was added to a mixture of aldehyde (5 mmol), 1,3-dicarbonyl (5 mmol), and urea (15 mmol), and the mixture was stirred at 70 °C in water, till the product was precipitated. After completion of the reaction (thin-layer chromatography (TLC) monitoring, hexane:EtOAc (70:30)), cold water was added and the product was filtered to give the pure 1,4-DHP product. 2.3. Reusability of the reaction medium
4
ACCEPTED MANUSCRIPT The practical reusability of the reaction medium after three further runs confirmed the unchanged activity of urease under reaction conditions (Figure 1).
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>
RI
2.4. Selected Spectral data
SC
2.4.1. Diethyl 2,6-dimethyl-4-(2-pyridyl)-1,4-dihydropyridine-3,5-dicarboxylate (entry
NU
18)
Pale yellow solid (0.287 g, 87%), mp = 192–194°C, IR (KBr, ʋ
−1
max/cm
): 3174 (NH
MA
stretching), 1688 (C=O) cm−1. 1H NMR (500 MHz, CDCl3): δ = 1.23 (t, J = 7.11 Hz, 6H,
D
2 × CH3–CH2), 2.28 (s, 6H, 2 × CH3), 4.06–4.12 (m, 4H, O–CH2CH3), 5.22 (s, 1H, CH),
TE
7.16 (td, J1 = 4.88, J2 = 0.63 Hz, 1H), 7.43 (d, J = 7.77, 1H), 7.61 (td, J = 7.66, 1.69 Hz, 1H), 8.53 (d, J = 3.98 Hz, 1H), 8.62 (br s, 1H, NH) ppm. 13C NMR (125 MHz, CDCl3): δ
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= 14.71, 19.31, 43.24, 59.96, 102.15, 122.19, 124.71, 136.11, 146.73, 148.65, 165.63, 168.14 ppm. MS (EI): m/z: 330 (M+, 8.5), 307 (8), 285 (7), 252 (100), 239 (7), 224 (10), 196 (18), 170 (7), 106 (5), 78 (7), 51 (5). 2.4.2. Ethyl 1,2,3,4-tetrahydro-4-phenyl-6-methyl-2-thioxopyrimidine-5-carboxylate (Scheme 2) Pale yellow solid (0.08 g, 30%) mp = 203–206°C, IR (KBr, ʋ
−1
max/cm
): 3328, 3186 (NH
stretching), 1665 (C=O), 1200 (C=S) cm−1. 1H NMR (500 MHz, CDCl3): δ = 1.15 (t, J = 7.0 Hz, 3H, CH3), 2.30 (s, 3H, CH3), 4.00 (q, J = 7.0 Hz, 2H, CH2–CH3), 5.21 (s, 1H, CH), 7.20–7.50 (m, 5H, Ph), 9.60 (br s, 1H, NH), 10.41 (br s, 1H, NH) ppm. 3. Results and discussion
5
ACCEPTED MANUSCRIPT In order to check the catalytic performance of urease and optimal conditions, the three-component reaction of urea (1), benzaldehyde (2), and ethyl acetoacetate (3) was
PT
screened as a Biginelli model reaction at various conditions and loadings of the urease
SC
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RI
2.4. Selected Spectral data
SC
2.4.1. Diethyl 2,6-dimethyl-4-(2-pyridyl)-1,4-dihydropyridine-3,5-dicarboxylate (entry
NU
18)
Pale yellow solid (0.287 g, 87%), mp = 192–194°C, IR (KBr, ʋ
−1
max/cm
): 3174 (NH
MA
stretching), 1688 (C=O) cm−1. 1H NMR (500 MHz, CDCl3): δ = 1.23 (t, J = 7.11 Hz, 6H,
D
2 × CH3–CH2), 2.28 (s, 6H, 2 × CH3), 4.06–4.12 (m, 4H, O–CH2CH3), 5.22 (s, 1H, CH),
TE
7.16 (td, J1 = 4.88, J2 = 0.63 Hz, 1H), 7.43 (d, J = 7.77, 1H), 7.61 (td, J = 7.66, 1.69 Hz, 1H), 8.53 (d, J = 3.98 Hz, 1H), 8.62 (br s, 1H, NH) ppm. 13C NMR (125 MHz, CDCl3): δ
AC CE P
= 14.71, 19.31, 43.24, 59.96, 102.15, 122.19, 124.71, 136.11, 146.73, 148.65, 165.63, 168.14 ppm. MS (EI): m/z: 330 (M+, 8.5), 307 (8), 285 (7), 252 (100), 239 (7), 224 (10), 196 (18), 170 (7), 106 (5), 78 (7), 51 (5). 2.4.2. Ethyl 1,2,3,4-tetrahydro-4-phenyl-6-methyl-2-thioxopyrimidine-5-carboxylate (Scheme 2) Pale yellow solid (0.08 g, 30%) mp = 203–206°C, IR (KBr, ʋ
−1
max/cm
): 3328, 3186 (NH
stretching), 1665 (C=O), 1200 (C=S) cm−1. 1H NMR (500 MHz, CDCl3): δ = 1.15 (t, J = 7.0 Hz, 3H, CH3), 2.30 (s, 3H, CH3), 4.00 (q, J = 7.0 Hz, 2H, CH2–CH3), 5.21 (s, 1H, CH), 7.20–7.50 (m, 5H, Ph), 9.60 (br s, 1H, NH), 10.41 (br s, 1H, NH) ppm. 3. Results and discussion
5
ACCEPTED MANUSCRIPT In order to check the catalytic performance of urease and optimal conditions, the three-component reaction of urea (1), benzaldehyde (2), and ethyl acetoacetate (3) was
PT
screened as a Biginelli model reaction at various conditions and loadings of the urease
SC
<