Proceedings of the 2nd International Seminar on Chemistry 2011 (pp. 156-159) Jatinangor, 24-25 November 2011 ISBN 978-602-19413-1-7
Synthesis of quinine-N-oxide Aisyah1, Didin Mujahidin2,* 1
Chemistry Study Program, Faculty of Science and Technology, UIN Alauddin Makassar, Jl.Sultan Alauddin No. 36 Samata Gowa Makassar 2 Chemistry Study Program, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No.10 Bandung *Corresponding author:
[email protected] Abstract Quinine has long been used as an antimalarial drug, eventhough some strains of Plasmodium have recently shown resistancy toward quinine. Besides its important bioactivity, quinine also has been applied as the chiral ligands in several catalytic asymmetric reactions. The amine group at N-1 quinuclidine ring of quinine could be oxidized to quinine-N-oxide which could decrease basicity of the amine in the molecule. Quinine-N-oxide have been previously reported as a product from the biotranformation of quinine in Microsporum gypseum and as a unique metabolite isolated from endophytic fungi, Xylaria sp which hosted in Cinchona plant. However, due to its limited supply of quinine-N-oxide isolated from natural plants, its application is rarely investigated. Here we report the synthesis of quinine-N-oxide using a more simple methodology and a milder condition. By this procedure, quinine have been regioselectively oxidized to quinine 1-N-oxide without destroyed the quinine skeletone. Oxidation of quinine by a bubbling of ozone to the solution of quinine in acetone:water (95:5) with a low flow of ozone at temperature -12˚ to 0˚C produced quinine-N-Oxide in 72% yield. All spectroscopic data, including UV-Vis, FTIR, LC-MS, 1H-NMR and 13C-NMR and comparation data with literature indicates that the product is quinine-N-oxide. Keywords: asymmetric synthesis, chiral catalysis, ozone, quinine, quinine-N-oxide
Introduction Cinchona alkaloids have been reported as metabolites of several species of cinchona plants. The two most popular are quinine and quinidine was formerly used as antimalarial and antiarrhythmic drugs. Recently, quinine mainly employed as a bitter additive in food and beverages industry (Song, 2009). Cinchona alkaloids not only function as bioactive compound, but also as catalyst in several asymmetric reactions. Sharples in 1987 introduced an asymmetric dihydroxylation (AD) of olefin by OsO4 and N-methylmorpholine-N-oxide (NMO) using catalysis of quinine derivate. In 1992, AD was improved by using a chiral ligand as a cocatalyst which mimics the natural catalysis of protein binding pocket. This method utilized a class of phtalazine ligands named 1,4-bis(9-Odihydroquinidine-phtalazine (DHQD2PHAL). In addition, many other asymmetric syntheses take the benefit of cinchona alkaloids as the catalyst, such as enone epoxidation (Corey & Zhang, 1999), asymmetric cycloadition (Kagan & Riant, 1992) and ketene-aldehyde cycloadition (Zhu et al., 2004). Quinine which is oxidized at the nitrogen of quinuclidin ring, is also a potential asymmetric catalyst. This metabolite is produced from the biotransformation of quinine in Cinchona Aisyah & Didin Mujahidin
pubescens by endophytic fungi, Xylaria sp (Shibuya et al., 2003). In addition, quinine-N-oxide has been isolated from Microsporum gipseum (Siebers-Wolf et. al., 1993). The problem in preparing this metabolite is the lack of raw material supply. 6
-
O
5
1
N+
2 8
HO
5'
10
4'
6'
H
3 7
9 O
4
11
3' 2'
7' 8'
N
1'
Figure 1 Quinine-N-Oxide Diaz-Arouzo & Cook (1990) synthesized this compound using a low concentration of hydrogen peroxide as the oxidant. Under this condition, the regioselectivity of the reaction is controlled so the oxidation is directed to the nitrogen of quinuclidine ring. However, it takes rather overnights reaction which will not be of efficient to be applied in industrial scale of production. Here, we introduce a simple methodology utilizing a flow of ozone to the quinine solution under a mild condition to oxidize at the desired site of reaction. Moreover, this condition aims to perform a group transformation only despite an olefin breakage. 156
Proceedings of the 2nd International Seminar on Chemistry 2011 (pp. 156-159) Jatinangor, 24-25 November 2011 ISBN 978-602-19413-1-7
Materials and Methods
Characterization
Preparation of quinine solution
The pure product was identified by chromatographic and spectroscopic methods. Thin Layer Chromatography using the mixture of methanol-acetone 1:1 as the mobile phase and silica gel Merck Kieselgel plate , UV-Vis Spectrometer, Shimadzu FTIR 8501, Spectrometer JEOL ECA 500 which operated at range 500 MHz (1H) , 125 Mhz (13C) and ESI-MS.
Quinine in this experiment was from PT. Kimia Farma Bandung Indonesia. Quinine base 0.9733 g (3 mmol) was dissolved in 20 ml of 95:5 acetone/water (v/v) to a concentration of 0.15 M. (Sciaffo & Dussault, 2008) Oxidation of quinine
Results and Discussion A set of an apparatus was assembled as shown on Figure 2.
In this experiment, quinine-N-Oxide was prepared by a simple oxidation process utilizing a low flow of ozone to the quinine solution. Ozone was favored because it is less toxic and tends to easily leave the reaction mixture by flowing oxygen or nitrogen. Ozone is a powerful oxidant with a redox potential of 2.07 V. It is higher than that of hydrogen peroxide, chlorine and molecular oxygen (Gunten, 2003). The reaction mechanism predominantly goes through a direct oxidation due to the basicity of the quinine solution. By using a mixture of acetone/water as the solvent, hydroxyl radicals from water initiate the chain reaction and deliver more radical species (Gunten, 2003). Oxidation of quinine may occur at several active sites. It can be at the vinyl group, hydroxyl group or at the nitrogen in the quinoline and quinuclidine ring (Song, 2009). However, the condition of reaction can be regulated to perform the oxidation at a certain active site. The oxidation was performed at 12˚ to 0˚C so that the reaction went through milder reaction and favored to oxidize the nitrogen in quinuclidine ring. After purification, a yellow thick product was obtained in 72% yield. The product was subsequently identified by TLC using eluent of methanol-acetone 1:1. A single spot was detected from the product which has a lower Rf (Rf value = 0.3) than that of the quinine (Rf value = 0.5). This indicates that a more polar product had been synthesized. Furthermore, the melting point of the product was 133-134˚C corresponding to quinine-noxide.
ozone input
ice bath
KI traps
Figure 2 The illustration of the oxidation equipment. The quinine solution was placed in a round bottom flask where the reaction temperature was kept at 12˚ to 0˚C using a mixture of ice bath and sufficient Sodium chloride. In addition, 15% of potassium iodide solution with small amount of starch was used to trap the excess of ozone. Ozone was bubbled to the quinine solution with a rate of 0.06 mmol/minute for two hours. The reaction was stopped as the quinine solution turned to pale yellow solution. Subsequently, nitrogen was streamed to the reaction mixture to omit the remaining ozone. Purification The reaction mixture was diluted in 25 mL of water and then extracted with 3 times of 30 mL of CH2Cl2. The organic phase was collected and dried over MgSO4. The residue was then rotary evaporated to obtain yellow foam.
-
N
O
H
HO O
N
aseton 95% 95% acetone dalam air in water -12°-0°C -12 - 0°C
H
HO
O3/O2
N+
O
N
Figure 3 Oxidation of quinine to quinine-N-oxide Aisyah & Didin Mujahidin
157
Proceedings of the 2nd International Seminar on Chemistry 2011 (pp. 156-159) Jatinangor, 24-25 November 2011 ISBN 978-602-19413-1-7
Table 1 NMR spectroscopic data of the product (CDCl3), a : chemical shift of product, quinine-oxide isolated from Xylaria sp.(Shibuya et al., 2003). 1 H-NMRa 500 MHz (ppm)
Position
1 H-NMRb 500 MHz (ppm)
1
-
-
b
: chemical shift of
13
C-NMRa 125 MHz (ppm) -
2a
3.21 (1H; ddd; J= 3.05; 6.1; 12.2)
3.21 (1H; ddd; J= 3.1; 6.6; 12.7)
2b
3.72 (1H; dd; J= 11.0; 12.8)
3.72 (1H; dd; J= 11.0; 12.7)
3
2.95 (1H; qi; J= 8.5)
13
C-NMRb 125 MHz (ppm) -
71.27
71.08
2.96 (1H; m)
42.47
42.38
4
1.95 (1H; br s)
1.95 (1H; m)
27.74
28.77
5a
2.02 (1H; m)
2.03 (1H; m)
28.86
27.64
5b
2.41 (1H; m)
2.39 (1H; m)
6a
3.45 (1H; dd; J = 5.5; 11.0)
3.43 (1H; m)
60.12
59.98
6b
4.15 (1H; m)
4.17 (1H; m)
7a
1.71 (1H; td; J= 2.4; 11.0)
1.71 (1H; m)
21.0
21.00
7b
2.41 (1H; m)
2.43 (1H; m)
8
-
3.46 (1H; dd, J= 5.5; 11.0)
75.10
74.9
9
6.63 (1H; s)
6.23 (1H; br s)
64.24
64.14
10
5.78 (1H; ddd; J= 7.3; 10.4; 17.1)
5.79 (1H; ddd; J= 7.0; 10.3; 17.2)
139.61
139.54
11a
5.02 (1H; dd; J= 1.2; 17.1)
5.02 (1H; dd; J= 0.9; 10.3)
116.89
116.85
11b
5.09 (1H;dd; J= 1.2; 10.4)
5.08 (1H;dd; J= 0.9; 17.2)
1’
-
-
-
-
2’
8.67 (1H; d; J= 4.2)
8.68 (1H; d; J= 4.6)
148.17
148.09
3’
7.78 (1H; d; J= 4.9)
7.78 (1H; d; J= 4.6)
120.18
120.09
4’
-
-
149.48
149.48
4a’
7.83 (1H; d; J= 3.1)
7.83 (1H; d; J= 2.7)
127.66
127.56
5’
-
103.03
102.9
6’
-
-
159.97
159.88
7’
7.39 (1H; dd; J= 3.1; 9.7)
7.40 (1H; dd; J= 2.7; 9.2)
123.69
123.57
8’
7.92 (1H; d; J= 9.2)
7.93 (1H; d; J= 9.2)
131.32
131.23
8a’
-
-
144.65
144.55
3.94 (3H; br s)
56.66
56.54
6’OCH3 3.92 (3H; s)
100 %T
20
4500 4000 quinin1
Figure 4 UV-Vis spectrometer results of the product sample (methanol)
Aisyah & Didin Mujahidin
3500
1 6 2 2 .1 3
2 9 6 2 .6 6
3 0 0 7 .0 2
3000
5 9 0 .2 2
4 6 6 .7 7 4 3 5 .9 1
5 4 7 .7 8 5 3 0 .4 2
7 8 1 .1 7
6 8 0 .8 7 7 2 5 .2 3
6 3 8 .4 4
9 9 3 .3 4
4 0 1 .1 9
8 6 4 .1 1
9 2 7 .7 6
8 3 3 .2 5 8 1 0 .1 0
1 1 3 8 .0 0 1 1 0 9 .0 7 1 2 3 8 .3 0
3 3 2 7 .2 1 3 3 1 1 .7 8 3 2 8 8 .6 3
30
3 2 7 3 .2 0 3 2 5 5 .8 4 3 0 7 8 .3 9
40
1 5 0 8 .3 3
1 4 6 9 .7 6
50
1 0 2 4 .2 0
1 5 9 3 .2 0
60
1 3 6 3 .6 7
1 4 3 6 .9 7
70
1 3 0 5 .8 1
3 6 5 3 .1 8
80
1 0 7 4 .3 5
2 3 7 4 .3 7
90
2500
2000
1750
1500
1250
1000
750
Figure 5 The FTIR result of the product sample (KBr)
158
500 1/cm
Proceedings of the 2nd International Seminar on Chemistry 2011 (pp. 156-159) Jatinangor, 24-25 November 2011 ISBN 978-602-19413-1-7
The next analysis was performed by UV-Vis chromatography. The result is shown on Figure 4. The result of the UV-Vis spectrum showed two main peaks at wavelength 235 nm and 334 nm. These are specific for an aromatic resonance of quinoline and forbidden transition of a lone pair of electrons of tertiary nitrogen. The FTIR spectrum is shown in Figure 5 which interestingly identifies a nitrogen oxide stretch at the wavenumber of 1238 cm-1. The rest signals corresponded to unconjugated alkene (1622 cm-1), hydroxyl group (3200-3300 cm-1), aromatic C-H (3078 cm-1), aliphatic C-H (2962 cm-1) and ether group (1508 cm-1) were observed. The ESI-MS of the product showed a molecular ion at m/z 340.1865, consistent with molecular formula C20H25N2O3. The formation of oxide was deduced from a loss of fragment of mass 16, which is undoubtedly oxygen. As mentioned formerly, oxidation may perform in several active sites of quinine. It could be at the nitrogen of quiniclidine and quinoline ring which will produce a nitrogen oxide derivate or at the vinyl group which will deliver epoxidation or ozonolysis. The NMR data of Table 1 exhibited typical structural units that could be identified as the units of quinine-N-oxide. Five aromatic signals appeared at 7.39, 7.78, 7.92, 7.83 and 8.67 ppm are signals for quinoline ring unit. Vinyl group signals appeared at 5.02 ppm and 5.08 ppm for geminal proton and 5.81 ppm for methyne proton. This methyne signal was multiplet due to cis and trans coupling from its two proton neighbor. There were four deshielding methylene signals, 3.21; 3.45; 3.72 and 4.15 ppm that showed inductive effect from oxygen. This indicates that quinine was oxidized at the tertiary nitrogen of quinuclidine ring. Similar with 1H-NMR spectrum, 13C-NMR spectrum also disclosed inductive effect of oxygen to quinuclidine ring. Three alkyl carbon signals appear more deshielding at 60.1, 71.1 and 75.1 ppm. Carbon chemical shifts of quinoline ring were assigned at 103.0; 120.2; 123.7; 127.6; 131.3; 144.6; 148.2 and 159.9 ppm. Meanwhile, signals of vinyl groups are seen at 116.8 and 139.7 ppm. Finally, all spectroscopic data, including UVVis, FTIR, ESI-MS, 1H-NMR and 13C-NMR and comparation data with literature revealed that the product is quinine-N-oxide.
Conclusions In conclusion, quinine-N-oxide had been successfully synthesized utilizing flows of ozone as the oxidant. Reaction was performed under a mild condition which provides a more simple methodology and high-yield product.
Aisyah & Didin Mujahidin
Acknowledgements This work is financially supported by BPPS scholarship from Kemendiknas RI. We also wish to thank Mr. Ahmad from Puspitek LIPI Serpong for his contribution in NMR analysis.
References Corey, E. J. & F. Y. Zhang. 1999. Mechanism and conditions for highly enantioselective epoxidation of alpha, beta-enones using charge-accelerated catalysis by a rigid quaternary ammonium salt. Org. Lett. 1: 1287-1290. Diaz-Arauzo, H. & J. M. Cook. 1990. Synthesis of 10,11-dihydroxydihydroquinidinen-oxide, A new metabolite of quinidine. Preparation and H-NMR spectroscopy of the metabolites of quinine and quinidine and conformational analysis via 2D COSY NMR spectroscopy. J. Nat. Prod. 53:112-124. Gunten, O.V. 2003. Ozonation of drinking water: Part I. Oxidation kinetics and product formation. Water Res. 37:1443-1467. Kagan, H.B. & O. Riant. 1999. Catalytic asymmetric Diels Alder reactions. Chem. Rev. 92:1007–1019. Schiaffo, C. E. & P.H. Dussault. 2008. Ozonolysis in Solvent/Water Mixtures: Direct Conversion of Alkenes to Aldehydes and Ketones. J. Org. Chem. 73: 4688-44690. Sharpless, K.B., W. Amberg. Y. L. Bennani, G. A. Crispino. J. Hartung. K. S. Jeong, H. L. Kwong. K. Morikawa. Z-M. Wang. D. Xu & X. L. Zhang. 1992. The osmiumcatalyzed asymmetric dihydroxylation: a new ligand class and a process improvement. J. Org. Chem. 57:2768-2771. Shibuya, H., C. Kitamura. S. Maehara. M. Nagahata. H. Winarno. P. Simanjuntak. H-S. Kim. Y. Wataya, & K. Ohashi. 2003. Transformation of Cinchona alkaloids into 1-N-Oxide derivatives by endophytic Xylaria sp. isolated from Cinchona pubescens, Chem. Pharm. Bull. 51:71-74. Siebers-Wolf, S., W. R. Abraham & K. Kieslich. 1993. Microbiological hydroxylation and Noxidation of Cinchona alkaloids. Biocatalysts Biotransform. 8:47-58. Song, C.E., (Editor). 2009. Cinchona Alkaloids in Synthesis and Catalysis: Ligand, Immobilization and Organocatalyst, WileyVCH. Verlag GmbH. Zhu, C., X. Shen & S.G. Nelson. 2004. Cinchona alkaloid-Lewis acid catalyst systems for enantioselective ketene−aldehyde cyclo additions. J. Am. Chem. Soc. 126:5352– 5353.
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