DESIGN, SYNTHESIS AND COX1/2 INHIBITORY ACTIVITY OF NEW QUINAZOLINE-5-ONE DERIVATIVES

5923 | P a g e A p r i l 2 0 1 7 w w w . c i r w o r l d . c o m DESIGN, SYNTHESIS AND COX1/2 INHIBITORY ACTIVITY OF NEW QUINAZOLINE-5-ONE DERIVATIVES Mohammed A. Hara, Mostafa H. Abdelrahman, Ahmed S. Aboraia*, Mohamed M. Amin, Osama I. El-Sabbaghab a Department of Organic Chemistry, Faculty of pharmacy, Al-azhar University, Assuit Branch, 71524, Assuit, Egypt. mohammedhara79@yahoo.com, mhamed102004@yahoo.com b Department of Medicinal Chemistry, Faculty of Pharmacy, Assuit University, 71524, Assuit, Egypt. Ahmed.mohamed15@pharm.au.edu.eg c Department of Organic Chemistry, Faculty of Pharmacy, Suez Canal University, 41522, Ismailia, Egypt. msaid123eg@yahoo.com, mohamed_said1@pharm.suez.edu.eg d Departmentof Medicinal Chemistry, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt. osamaelsabbagh@yahoo.com e Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Taif University, 888 Al-Haweiah, Taif 21974, Saudi Arabia. o.elsabbagh@tu.edu.sa * Author to whom correspondence should be addressed ABSTRACT


INTRODUCTION:
Pain and inflammation are very commonly associated with numerous pathological conditions commonly prescribed with nonsteroidal anti-inflammatory drugs (NSAIDs). Most of the NSAIDs available in the market are known to inhibit isoforms of the enzyme cyclooxygenase (COX), a constitutive form COX-1 which is responsible for main side effects of antiinflammatory such as edema, abdominal colic and peptic ulcer, and an inducible (pathological) form COX-2 which responsible for therapeutic effects. There is continuous development of new drugs that have potent anti-inflammatory activity, with minimum side effects and high safety margin (1, 2). The design of effective agents that have fast action and provide relief from pain and inflammation is a major challenge for medicinal chemists such as our novel quinazolinone as non-acidic NSAIDs.
Cyclic -diketones are an important class of organic compounds, one of which is 5,5-dimethyl 1,3-cyclohexandione (Dimedone) which is used as a precursor for the preparation of different intermediates such as enaminones and different heterocyclic rings such as quinazoline, quinoline, acridine and hydrazone derivatives that have interesting biological activities. The choice of quinazolinone heterocycle as a central core was fundamental due to its presence in the potent anti-inflammatory natural alkaloids rutaecarpine1 and tryptanthrin2 (3).

Rutaecarpine (1) Tryptanthrin (2)
The presence of quinazoline moiety in the aforementioned natural alkaloids, which can undergo substitution at the heteroatom or the aromatic ring, is a necessary requirement for the anti-inflammatory activities (4,5). Moreover, the diaryl heterocycles template is considered as a typical model of selective inhibitor of COX-2 isozyme (6). Quinazoline derivatives with either halogen-or electron-rich substituent at 6th or 7th position are known to promote activity against bacteria and inflammation (7). Proquazone 1 (Fig. 1) is chemically known as 1-isopropyl-7-methyl-4-phenylquinazolin-2(1H)-one, which is chemically quinazoline derivative, has been known to have an excellent non-steroidal anti-inflammatory effect resulting from its anti-COX-2effect, therefore it was often used in the treatment of rheumatoid arthritis, osteoarthritis and other chronic inflammatory diseases (8).
I S S N 2 3 2 1 -807X V o l u m e 1 3 N u m b e r 1 J o u r n a l o f A d v a n c e s i n c h e m i s t r y 5924 | P a g e A p r i l 2 0 1 7 w w w . c i r w o r l d . c o m In the current study, as a complement to our previous work (9), we aimed to design and synthesize a novel series of 1-(4-Acetylphenyl)-7,7-dimethyl-3-(substitutedphenyl)-1,2,3,4,7,8-octahydroquinazolin-5(6H)-ones (6-15) which devoid acidic properties with the accompanied common NSAIDs side effects and at the same time provide the required molecular bulkiness that prevent the compounds to enter the narrow COX-1 binding site. Furthermore, the design takes into account that the synthesized compounds will have molecular weights which will not affect their oral absorption. Molecular hybridization strategy (10) was used to design the target compounds 6-15 as active anti-inflammatoryagents with reduced adverse effects (Fig. 2).

Chemistry
In this work, as a complement to our previous work (9), the novel key intermediate enaminone 5 was prepared by condensation of equimolar amounts of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) 4 with 4-aminoacetophenone via heating the reactants under reflux in toluene using our reported method (9). Toluene provides the reaction with a relatively higher temperature necessary for the completion of the reaction.
The new compounds were confirmed using High Resolution Mass Spectrometry and elemental analyses and various spectroscopic methods. 1H-NMR spectrum proved the disappearance of both singlets at δ= 7.85 ppm (NH group) and at δ= 5.65 (vinylic proton) of starting enaminone 5 and appearance of two characteristic singlets at δ= 4.88 and 4.21 ppm indicating the formation of two methylene groups at 2-and 4-position of the quinazoline skeleton. 13 C-NMR spectra proved the proposed 5-oxo-octahydroquinazolin structures due to the appearance of characteristic peaks around δ = 69.68 and 50.35 ppm which were assignable to C2-and C4-of the quinazoline nucleus.

Docking studies:
Docking studies have been carried out to explore the ability of the most potent and most selective synthesized compound 6 to bind to the COX-1 and COX-2 receptors at the same active site as reported in the literature (11).
Redocking of the known cyclooxygenase-1 inhibitor Meloxicam in the COX-1 crystal structure (PDB: 4O1Z). As shown in (Fig. 3) And the known cyclooxygenase-2 inhibitor Celecoxib in the COX-2 crystal structure (PDB: 3LN1). As shown in (Fig. 4) Showed Root-mean-square deviation (RMSD) values of less than 2 (1.891) and (1.435), respectively; which indicates the confidence in the produced docking results.  The docking of compound 6 in COX-1 and COX-2 isozymes showed good fit in the active site of COX-2 ( Fig. 5b) receptor rather than the active site of COX-1 (Fig. 5a) mainly due to the bulk size of the tested compound which hindered it from good fitting in smaller COX-1 active site.

Chemistry:
Melting points were determined with a Gallenkamp (London, U.K.) melting point apparatus and are uncorrected. Infrared (IR) spectra were recorded in potassium bromide (KBr) discs using Bruker Vector, 22FT-IR Fourier Transform Infrared (FTIR) spectrometer (Germany), and expressed in wave number ν ;(cm -1 ). NMR Spectra (NMR) Spectra were taken using a Varian Unity INOVA 400 MHz for proton and 101 MHz for carbon; university of Aberdeen, UK. All numbers referring to NMR data obtained are in parts per million (ppm).
High Resolution Mass Spectra (HRESI-MS Spectra) were obtained using the Thermo Instruments MS system (LTQ XL/LTQ Orbitrap Discovery) coupled to a Thermo Instruments HPLC system (Accela PDA detector, Accela PDA autosampler and Pump) at university of Aberdeen, UK. Elemental analyses were determined using Vario EL III German CHN Elemental analyzer model, Regional Centre for Mycology and Biotechnology, Al-Azhar University, Cairo, Egypt. All the results of elemental analyses corresponded to the calculated values within experimental error.
Chemicals and solvents used in the preparation of the target compounds are of commercial grade and purchased from Sigma Aldrich, Alfa Aesar, Merck, Fluka. Chemicals and solvents were used without purification. Thin layer chromatography (TLC) was used for monitoring chemical reaction and was carried out using silica gel 60 F254 precoated sheet 2020 cm, layer thickening 0.2 mm (E, Merck, Germany), and were visualized using UVlamp at 254 nm.

Docking study:
The Protein structures were first repaired, Ramchandran plot was plotted to ascertain the health of protein and then appropriately protonated in the presence of ligands using the Protonate 3-D process in MOE (14).
The original 4O1Z PDB file contained crystallized Heme and N-Acetyl-D-Glucosamine beside the receptor chains and the bound Meloxicam. The receptor (first chain) and the bound Meloxicam were kept.
The original 3LN1 PDB file contained crystallized Heme, -Octylglucoside and N-Acetyl-D-Glucosamine beside the receptor chains and the bound Celecoxib. The receptor (first chain) and the bound Celecoxib were kept.

Ligand Preparation:
Compound 6 was built in ChemBioDraw Ultra 12.0 for further preparation in the MOE. In MOE, the ligand prepared for docking through the following steps: hydrogens were added, conformational search has been run for compound 6 and the best conformers subjected to energy minimization was performed using the MMFF94 force field (15).
Steepest descent algorithm was used for minimization, followed by conjugate gradient method, until it reached an RMS (root mean square) gradient of 0.00001 kcal/mol/  A. A database of the ligand was generated for further docking studies in the target receptors.

Docking Procedure:
The standard protocol of the procedure in MOE 2016.08 was applied in this work. The Alpha Triangle placement which derives poses by random superposition of ligand atom triplets alpha sphere dummies in the receptor site is to determine the poses. The London dG scoring function estimates the free energy of binding of the ligand from a given pose.
The output database dock file was created with different poses for the ligand and arranged according to the final sco re function (S), which is the score of the last stage that was not set to none. The database browser was used for the visual inspection of different poses for the ligand and the best poses were chosen.