INTRODUCTION:

Pyrido[2,3-b]pyrazine (5-azaquinoxaline) derivatives are very important nitrogen-containing heterocycles, that are extensively used for their pharmacological and therapeutic properties [1].Pteridine and quinoxaline are structural analogues of them. Studies have shown that such compounds are widely involved in several fields, as they exhibitantimalarial, anti-cancer [2], antibacterial and anti-allergic activities [3,4]. They also exhibit antimitotic behavior. Pyrido[2,3-b]pyrazine derivatives are well-known for their strong inhibitory activities of phosphodiesterase IV (PDE IV) , the production of tumor necrosis factor (TNF),Platelet derived growth receptor, gonadotropin releasing harmone, IgE production [5]. Pyridopyrazine derivatives are broadly used as corrosion inhibitors for metals in acid environments, since they own the nitrogen and oxygen atoms which can easily be protonated to exhibit good inhibitory action on the corrosion of metals [6,7].

Mutations affecting EGFR (epidermal growth factor receptor) activity could result in cancers such as squamous-cell carcinoma of the lung, anal cancers, glioblastoma and epithelian tumors of the head and neck . The identification of EGFR as an oncogene (a gene that has the potential to cause cancer) has led to the development of anticancer therapeutics against EGFR, called "EGFR” inhibitors. Among them, using small molecule inhibitors to inhibit the EGFR tyrosine kinase is the most appropriate method, which acts on the cytoplasmic side of the receptor. Without kinase activity, EGFR is unable to activate itself, which is a prerequisite for binding of downstream adaptor proteins [8,9].

The EGFR inhibitor erlotinib is a good example of small molecule inhibitor, which possesses high anti-tumor effect. In search of small molecule inhibitors, pyrido [2, 3-b] pyrazine compounds were proved to be effective inhibitors of resistant cells. A series of novel pyrido [2, 3-b] pyrazines were synthesized as potential antitumor agents for erlotinib-resistant tumors. Studies revealed that, there is a promising effect of the substituent at position 7 and position 2 of the pyrido pyrazine core. Pyrido [2,3,-b]pyrazine core has hydrogen-bond acceptor site and hydrophobic center roles.

EXPERIMENTAL:

All the chemicals and solvents used were purchased either from Fluka or Merck. Reagents used were of analytical grade. Thin-layer chromatography (TLC) was performed on E.Merck AL silica gel 60 F254 plates and visualized under UV light. IR spectra were recorded as KBr pellet with a perkin-elmer spectrum gx FTIR instrument and only intense peaks are reported.¹H NMR spectra were recorded in DMSO- d₆ with a Varian Mercury plus 400 MHz instrument. TMS is used as an internal standard. All the chemical shifts were reported in δ (ppm). The ¹H NMR chemical shifts and coupling constants were determined assuming first-order behavior. Multiplicity is indicated by one or more of the following: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), br (broad); the list of coupling constants (J) corresponds to the order of multiplicity assignment. Mass spectra were recorded with a PE Sciex model API 3000 instrument. All the reactions were carried out under argon atmosphere.

RESULTS AND DISCUSSION:

Different pyrazine derivatives are synthesized from 5-bromo-2,3-diamino pyridine. First step involves the cyclisation with ethyl pyruvate using toluene as a solvent under heating condition to get cyclized compound (1) which further reacts with ethylchloroacetate to give compound (2). It isfollowed by the condensation with hydrazine hydrate to give aceto hydrazide (3) and finally leads to title compounds with different substituted aldehydes (4a-e). All the molecules synthesized in the above scheme shown are characterized by spectrum of ¹H NMR and Mass.

Synthesis of ethyl 2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetate (2) : To a paste of 7-bromo-2-methylpyrido[2,3-b]pyrazine-3-ol (500 mg, 0.002 mol) and DMF (2-3drops) was added ethylchloroacetate (0.22 mL, 0.002 mol) followed by the addition of dry K₂CO₃ (138 mg, 0.001 mol). The reaction mixture was stirred at irradiated under microwave for 2-3 min. After completion of the reaction checked by TLC, the mixture was allowed to cool to room temperature and product was recrystallized from methanol to give desired product (2) as solid (500 mg, 84 %).

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 1.18-1.23 (m, 6H), 4.12-4.20 (m, 2H), 5.08 (s, 2H), 8.52 (s, 1H), 8.69 (s, 1H). MS (ESI) 326 m/z (M+H)⁺.

2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (3): To the paste of ethyl 2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetate (500mg, 0.001 mol) in methanol (10 mL) was added hydrazine hydrate (80%, 20 mL) and irradiated under microwave for 3min. Progress of the reaction was monitored by TLC. The mixture was cooled to room temperature and poured in to crushed ice with stirring. Then the resulting solid was collected by filtration and dried compound (3) as a solid (100 mg, 21 %).

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.42 (s, 3H), 4.42 (brs, 2H), 4.78 (s, 2H), 8.52 (s, 1H), 8.69 (s, 1H), 8.80 (brs, 1H). MS (ESI) 312 m/z (M+H)⁺.

N'-benzylidene-2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (4a) : A mixture of 2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (100 mg, 0.0003 mol) and benzaldehyde (33 mg, 0.0003 mol) were made as paste in DMF . Then the reaction mixture was heated under microwave. The completion of the reaction was checked by TLC, the mixture was poured in to crushed ice and the resulting solid was collected by filtration and dried to give title compound (4a) as a brown solid (50 mg, 40%).

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.89 (s, 3H), 4.78 (s, 2H), 7.52 (s, 4H), 7.88 (s, 2H), 7.95 (s, 1H), 8.72 (s, 1H). MS (ESI) 400 m/z (M+H)⁺.

N'-(4-methoxybenzylidene)-2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3yl)oxy)acetohydrazide (4b)

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.90 (s, 3H), 3.81 (s, 3H), 4.76 (s, 2H), 7.50 (s, 4H), 7.87 (s, 1H), 7.96 (s, 1H), 8.71 (s, 1H). MS (ESI) 431 m/z (M+H)⁺.

N'-(4-chlorobenzylidene)-2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (4c)

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.90 (s, 3H), 4.74 (s, 2H), 7.54 (s, 4H), 7.86 (s, 1H), 7.96 (s, 1H), 8.74 (s, 1H). MS (ESI) 435 m/z (M+H)⁺.

N'-(3-chlorobenzylidene)-2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (4d)

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.91 (s, 3H), 4.76 (s, 2H), 7.53 (s, 4H), 7.85 (s, 1H), 7.95 (s, 1H), 8.76 (s, 1H). MS (ESI) 435 m/z (M+H)⁺.

N'-(4-hydoxybenzylidene)-2-((7-bromo-2-methylpyrido[2,3-b]pyrazin-3-yl)oxy)acetohydrazide (4e)

¹H NMR (400 MHZ, DMSO-D₆): (ppm) 2.92 (s, 3H), 4.76 (s, 2H), 7.52 (s, 4H), 7.85 (s, 1H), 7.94 (s, 1H), 8.76 (s, 1H), 11.23 (brs, 1H). MS (ESI) 417 m/z (M+H)⁺.

REFERENCES:

1. Haley T. J., A. M. Flesher and R. Vcomelt, Proc. Soc. Biol. Med., 1957, 96, 579-584.

2. Mathew B and S. Srivastava, Bioorganic and Medicinal Chemistry, 2011, 19, 7120-7128.

3. Wiseloge F and W. L. F. Armarego, Academic Press, 1963, 1, 304.

4. David J. Blythin, North Caldwell, Ho-Jane Shue, Pine Brook,. U.S Patent, 1988, 4760073.

5. Shimazaki, Norihiko, Nagakuni, Tsuchiura-shi, Ibaraki, Sawada, Akihiko, Watanabe and Shinya, 1997, PCT/JP 96/03666, patent WO97/24355.

6. Ebenso EE, N. O. Eddy and A. O. Odiongenyi, Portugaliae Electrochimica Acta, 2009, 27(1), 13.

7. CherifAlaoui I, KandriRodi, El Hadrami, Haoudi E. M. A., Skalli M., Garrigues B. and Essassi M. E., J. Mar. Chim. Heterocyclic, 2007, 6 (1), 32-37.

8. Kékesi L, A. Sipos, G. Németh, A. Dancsó, E. Illyés, S. Boros, N. Breza, Z. Nemes, B. Hegymegi-Barakonyi and J. Pató, Acta Pharm Hung. 2014, 84(3), 91-104.

9. Kékesi L, A. Sipos, G. Németh, J. Pató, N. Breza, F. Baska, L. Őrfi and G. Kéri, . Bioorg Med Chem Lett, 2013, 23(22), 6152-6155.

Received on 01.12.2017 Modified on 24.12.2017

Asian J. Research Chem. 2018; 11(2):279-281.

DOI:10.5958/0974-4150.2018.00052.4