Microwave assisted facile synthesis of 5-Aryl-5, 6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-ones and docking for anti-inflammatory activity

 

Siddhartha Marupati¹, Laxminarayana Eppakayala²*, Ramesh Malothu³,

Ramchander Merugu⁴,Venkat Reddy Pendyala²

¹Vardhaman College of Engineering, Shamshabad, Hyderabad 500 018, Telangana, India.

²Sreenidhi Institute of Science and Technology (Autonomous) Yamnampet, Ghatkesar, Hyderabad- 501301, Telangana, India

³Jawaharlal Nehru Technological University, Kakinada-533 003, Andhra Pradesh, India

⁴University College of Science, Mahatma Gandhi University, Nalgonda-508254, Telangana, India

*Corresponding Author E-mail: elxnkits@yahoo.co.in

5-Aryl-5,6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-ones (2a-e) were synthesized by the condensation of 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide with different aldehydes using microwave irradiation. All title compounds were characterized by ¹H NMR and massspectra. Molecular docking of 5cox with ligand showed that the title compound was a potent anti-inflammatory compound.

 

 

 

 

INTRODUCTION:

Microwave heating refers to the use of certain frequency of electromagnetic waves ranges (0.01m to 1m) to generate heat in the material. These lie in the region between I.R and radio wave. Microwave assisted Synthesis is considered to be superior to other methods of synthesis Microwave Assisted Organic Synthesis (MAOS), has emerged as a new “lead” in organic synthesis. Synthesis through this method is simple, clean, fast, efficient, and economical. The major advantage of microwave assisted organic reaction is highly accelerated rate of the reaction and reduction in reaction time with enhanced yield and quality of the product.

 

This technique is an important step towards green chemistry, due to ecofriendly nature. Conventional method of organic synthesis needs longer heating time and the excessive use of solvents /reagents lead to environmental pollution. The process involves less production of less by products and less energy intensive. Rapid increase in temperature leads to the increased thermal conductivity due to which faster reaction takes place. In recent years naturally occurring and synthetic heterocyclic compounds are of interest in pharmaceutical and pesticide research.¹

 

Pyrimidines, in particular, cover the considerable position among compounds exhibiting diverse biological activities.^2-6 On the other hand, compounds with the linkage of carbamate or urea are cited to show cytotoxic,^7-12 antimicrobial and insecticidal¹³ or fatty acid amide hydrolase inhibitory¹⁴ activity. There are some recent examples of biologically active pyrimidine-based carbamates and ureas.^15,16 In view of the biological importance of title compounds we have developed a simple method for the 5-Aryl-5,6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-ones.

 

 

Scheme-I

 

Ar = 2-Chlorophenyl, 4-chlorophenyl, 3-flurophenyl,

4-flurophenyl, 2-Methoxyphenyl

 

Experimental Section:

¹H NMR spectra were recorded on a Unity Varian INOVA spectrometer at 400 MHz. Chemical shifts (δ) are reported in ppm relative to TMS. Mass spectrum on a Hewelett Packard mass spectrometer operating at 70ev. The reactions and purity of compounds was controlled by tlc on Silica gel 60 F254 plates (MERCK, Germany). All solvents were dried and distilled before use.

 

In the present study, the X-ray crystal structure of 5cox was obtained from Protein Data Bank¹⁷. Docking calculations were carried out using Docking Server. Docking calculations were carried out on 5cox and title compound. The description of a protein three dimensional structure as a network of hydrogen bonding interactions (HB plot)¹⁸ was introduced as a tool for exploring protein structure and function.

 

General procedure for synthesis of 5-Aryl-5,6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-ones

0.01 m moles of compound 1, 0.01 moles of aromatic aldehyde, were refluxed by adding a drop of H₂SO₄for 2-3 hrs. After completion of the reaction as indicated by T.L.C. The residue was poured into chilled dilute hydrochloric acid to neutralize the reaction mixture. The precipitated solid was collected by filtration and re-crystallized from ethanol.

 

5-(2-Chlorophenyl)-5,6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-one (2a)

¹H NMR (CDCl₃, 400 MHz): δ 8.42 (brs, 1H), 8.39 (brs, 1H), 8.32(m, 4H), 5.55(s, 1H), 4.10(s, 3H), 2.81 (t, 2H), 1.84 (m, 2H), 1.21 (t, 3H); Mass: m/z=259 [M+H]⁺

 

5-(4-Chlorophenyl)-5, 6-dihydro-1-methyl-3-propyl-1H-pyrazolo [4,3-d]pyrimidin-7(4H)-one (2b)

¹H NMR (CDCl₃, 400 MHz): δ 8.62 (brs, 1H), 8.24 (brs, 1H), 8.44 (d, 2H,), 5.78 (s, 1H), 4.22 (s, 3H), 2.81(t, 2H), 1.84(m, 2H), 1.12(t, 3H); Mass: m/z=259 [M+H]⁺

5-(3-flurophenyl)-5, 6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-one (2c)

¹H NMR(CDCl₃, 400 MHz): δ 8.62 (brs, 1H), 8.34 (brs, 1H), 8.24 (d, 2H, J=7.6 Hz), 7.98(d, 2H, J=7.6 Hz), 5.78(s, 1H), 4.21m (s, 3H), 2.80 (t, 2H), 1.83 (m, 2H), 1.10 (t, 3H Mass: m/z=289 [M+H]⁺

 

5-(4-flurophenyl)-5, 6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-one (2d)

¹H NMR (CDCl₃, 400 MHz): δ 8.53 (brs, 1H), 8.34 (brs, 1H), 8.24 (d, 2H), 7.99(d, 2H,), 5.78(s, 1H), 4.24 (brs, 3H), 2.82 (t, 2H), 1.83 (m, 2H), 1.11 (t, 3H);  Mass: m/z=289 [M+H]⁺

 

5-(2-Methoxyphenyl)-5, 6-dihydro-1-methyl-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-7(4H)-one (2e)

¹H NMR (CDCl₃, 400 MHz): δ 8.42 (brs, 1H), 8.36 (brs, 1H), 8.29 (d, 2H), 7.98(d, 2H), 5.88 (s, 1H), 4.12 (brs, 3H), 2.71(t, 2H), 1.83 (m, 2H), 1.12 (t, 3H); Mass: m/z=259.2 [M+H]⁺

 

RESULTS AND DISCUSSION:

Microwave mediated facile synthesis of the title compound was possible within Compound (1), when reacted with different aromatic aldehydes pyrimidine derivatives (2a-e) are obtained. The reaction was very clear in and gave single product, which is an environmentally benign reaction. The reaction time was very less when compared to commercial methods. The yield of the products was also more and does not give other impurities. Molecular docking of 5cox with ligand using docking server, predicted a free energy of -4.92 kcal/mol making the title compound a probable potent anti-inflammatory compound. According to docking server Inhibition constant is 249.12uM which predicts that the ligand is going to inhibits enzyme and result in a clinically relevant drug interaction with a substrate for the enzyme. The interaction between the ligand and the target enzyme are presented in the figure (1). Tables 1 & 2 shows the interaction energies and various bonds involved in the binding of the ligands to the enzymes. The interaction of ligand and protein was generated and is depicted in HB plot (Figure 2).

 

CONCLUSIONS:

Microwave mediated facile synthesis of the title compound was environmentally benign reaction. Molecular docking of 5cox with ligand showed that the title compound was a potent anti-inflammatory compound.

 

 

Table 1: Molecular Docking energy level table

Est. Free Energy of Binding	Est. Inhibition Constant, Ki	vdW +Hbond + desolv Energy	Electrostatic Energy	Total Intermolec. Energy	Frequency	Interact. Surface
-4.92 kcal/mol	249.12 uM	-5.21 kcal/mol	-0.01 kcal/mol	-5.21 kcal/mol	50%	393.662

 

Figure 1: Docking of the title ligand to the enzyme

 

Table 2: 2 D plot and decomposed Interaction Energies in kcal/mol

 

Table 2: Different types of bonds seen in the interaction between the Ligand and the enzyme

hydrogen bonds			hydrophobic			halogen-bond			other
N2 (13)	–	PRO35 (O)	C5 (5)	–	CYS37 (CB, SG)	Cl1 (7)	–	ASP53 (O)	C7 (8)	–	SER38 (CB, OG)
[2.74]			[3.28]			[3.82]			[2.94]
N2 (13)	–	SER38 (CB, OG)	C4 (4)	–	CYS37 (CB)				C3 (3)	–	SER38 (CB, OG)
[2.82]			[3.40]						[3.49]
H15 (29)	–	SER38 (OG)	C3 (3)	–	CYS37 (CB)				C10 (12)	–	SER38 (OG)
[3.58]			[3.73]						[3.25]
			C10 (12)	–	PRO40 (CG)				C2 (2)	–	SER38 (OG)
			[3.82]						[3.85]
			C10 (12)	–	TYR55 (CD1, CE1)
			[3.48]
			C9 (11)	–	TYR55 (CE1)
			[3.72]
			C4 (4)	–	PRO160 (CD)
			[3.89]
			C4 (4)	–	VAL165 (CG2)
			[3.84]

 

 

Figure 2: HB plot showing hydrogen bonding interaction

 

 

REFERENCES:

1.        Pozharskii, A. F.; Soldatenkov, A. T.; Katrizky, A. R. Heterocycles in Life and Society. Wiley: New York, 1997.

2.        Delaney, J.; Clarke, E.; Hughes, D.; Rice, M. Drug Discov. Today 11 (2006) 839.

3.        Jain, K. S.; Chitre, T. S.; Miniyar, P. B.; Kathiravan, M. K.; Bendre, V. S.; Veer, V. S.; Shahane, S. R.; Shishoo, C. J. Curr. Sci. 90 (2006) 793.

4.        Miwa, M.; Ura, M.; Nishida, M.; Sawada, N.; Ishikawa, T.; Mori, K.; Shimma, N.; Umeda, I.; Ishitsuka, H. Eur. J. Cancer, 34 (1998) 1274.

5.        Falcao, E. P. S.; Melo, S. J.; Srivastava, R. M.; Catanho, M. T. J.; Nascimento, S. C. Eur. J. Med. Chem. 41 (2006) 276.

6.        Jakubkiene, V.; Burbuliene, M. M.; Udrenaite, E.; Garaliene, V.; Vainilavicius, P. Pharmazie, 57 (2002) 610.

7.        Shao, L.; Zhou, X.; Jin, Z.; Fang, J. X. Heteroatom Chem. 9 (2008) 2.

8.        Benchabane, Y.; Di Giorgio, C.; Boyer, G.; Sabatier, A. S.; Allegro, D.; Peyrot, V.; De Meo, M. Eur. J. Med. Chem. 44 (2009) 2459.

9.        Pirisi, M. A.; Murineddu, J. M.; Mussinu, J. M.; Pinna, G. A. Il Farmaco 57 (2002) 331.

10.     Borrel, Ch.; Thoret, S.; Cachet, X.; Guenard, D.; Tilleguin, F.; Koch, M.; Michel, S. Bioorg. Med. Chem. 13 (2005) 3853.

11.     Sanmartin, C.; Echeveria, M.; Mendivil, B.; Corden, L.; Cubedo, E.; Garcia-Foncillas, J.; Font, M.; Palop, J. A. Bioorg. Med. Chem, 13 (2005) 2031.

12.     Kakadiya, R.; Dong, H.; Lee, P. C.; Kapuriya, N.; Zhang, X.; Chou, T. C.; Lee, T. C.; Kapuriya, K.; Shah, A.; Su, T. L. Bioorg. Med. Chem. 17 (2009) 17, 5614.

13.     Latthe, P. R.; Shinge, P. S.; Badami, B. V.; Patil, P. B.; Holihosur, S. N. J. Chem. Sci. 118 (2006) 249.

14.     Mor, M.; Lodola, A.; Rivara, S.; Vacondio, F.; Duranti, A.; Tontini, A.; Sanchini, S.; Piersanti, G.; Clapper, J. R.; King, A. R.; Tarzia, G.; Piomelli, D. J. Med. Chem. 51 (2008) 3487.

15.     Burns, C. J.; Harte, M. F.; Bu, X.; Fantino, E.; Joffe, M.; Sikanyika, H.; Su, S.; Tranberg, C. E.; Wilson, N.; Charman, S. A.; Shackleford, D. M.; Wilks, A. F. Bioorg. Med. Chem. Lett. 19 (2009) 4639.

16.     Tao, Z. F.; Chen, Z.; Bui, M. H.; Kovar, P.; Johnson, E.; Bouska, J.; Zhang, H.; Rosenberg, S.; Sowin, T.; Lin, N. H. Bioorg. Med. Chem. Lett. 23 (2007) 6593.

17.     Berman, H.M., Westbrook, J., Feng, Z., Gilliland, G., Bhat, T.N., Weissig, H., Shindyalov, I.N., Bourne, P.E., Nucleic Acids Res. 28 (2000) 235.

18.     Bikadi Z, Demko L, Hazai E. Arch Biochem Biophys. 461 (2) (2007) 225.

 

 

 

 

 

Received on 28.06.2017     Modified on 19.07.2017

Accepted on 20.08.2017     © AJRC All right reserved