inal chem ic is d t Abulkhair et al., Med Chem (Los Angeles) 2016, 6:9 e r M y Medicinal chemistry DOI: 10.4172/2161-0444.1000404 ISSN: 2161-0444 t Research Article Open Access Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted-3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents Hamada S Abulkhair1, Kamal M El-Gamal1,2, Khaled El-Adl3* and Mohamed F Fadl4 1Pharmaceutical Organic Chemistry Department, Faculty of Pharmacy, Al-Azhar University, Nasr City 11884, Cairo, Egypt 2Pharmaceutical Organic Chemistry Department, Faculty of Pharmacy and Pharmaceutical Industries, Delta University, Mansoura, Egypt 3Pharmaceutical Chemistry Department, Faculty of Pharmacy, Al-Azhar University, Nasr City 11884, Cairo, Egypt 4Pharmacology and Toxicology Department, Faculty of Pharmacy, Al-Azhar University, Nasr City 11884, Cairo, Egypt
Abstract
A new series of 2-substituted-3-allyl-4(3H)-quinazolinone derivatives (4a-e-8a-d) were synthesized and evaluated for their anticonvulsant activity against pentylenetetrazole (PTZ)-induced seizures and maximal electroshock test in mice and compared with the reference drugs methaqualone and sodium valproate. The neurotoxicity was assessed using rotarod test. The molecular modeling was performed for all synthesized compounds to predict their binding affinity towards GABA-A receptor as a proposed mode of their anticonvulsant activity. Thedata obtained from the molecular docking was strongly correlated with that obtained from the biological screening which
revealed that; compounds 4c, 4b and 4d showed the highest binding affinities towards GABA-A receptor and also showed the highest anticonvulsant activities in experimental mice with relatively low neurotoxicity and low toxicity in the median lethal dose test when compared with the reference drugs. The obtained results proved that the most active compounds could be useful as a model for future design, adaptation and investigation to construct more active analogs.
Keywords: Quinazolinone; Anticonvulsant; GABA-A receptor; protective index (PI) corresponding to (TD50/ED50) is too low [13]. Molecular docking In continuation to the efforts done toward the synthesis of Introduction potential molecules as anticonvulsant agents, our aim was to synthesize new 2-substituted-3-allyl-4(3H)-quinazolinone derivatives (4a-e-
Quinazolin-4(3H)-ones and their derivatives constitute an 8a-d) derivatives and evaluate their anticonvulsant potency. It was of important class of heterocyclic compounds and are shown to have special importance to incorporate some moieties that were reported potent CNS activities such as anticonvulsant [1-6] and CNS depressant to potentiate the anticonvulsant activity such as ketone, amide, [7]. 2-Methyl-3-O-tolyl 4(3H)-quinazolinone (methaqualone) is ester, hydrazide and/or arylidene [12,14]. Substituents were selected an important landmark in the field of synthetic anticonvulsant, following a second manual method of the Hansch approach to drug possessed quinazoline core which was responsible for its activity [8,9]. design suggested by Topliss [15]. Hansch approach is a procedure in Modification of the methyl group at position 2 by some other chemical which an initial small group of compounds are selected, tested and moieties yielded structural analogs with potent CNS activity [5]. The ordered according to potency. sedative-hypnotic (neurotoxicity) properties of 4(3H)-quinazolinone are well documented [10]. The title compounds were designed to contain unsubstituted, monosubstituted and disubstituted aromatic ring with different kinds Many quinazoline derivatives were reported as GABA-A receptor of halogens and other hydrophobic and hydrophilic groups of different stimulants [2,5]. The GABA-A receptor is an ionotropic receptor and electronic environment either electronic rich or electronic deficient a ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric groups to study SAR of these compounds and compare the differences acid (GABA), the major inhibitory neurotransmitter in the central in their anticonvulsant activity. nervous system. Upon activation, the GABA-A receptor selectively conducts Cl− through its pore, resulting in hyperpolarization of the Experimental Protocol neuron. This causes an inhibitory effect on neurotransmission by Chemistry diminishing the chance of a successful action potential [2]. The active site of the GABA-A receptor is the binding site for GABA and several Open capillary tubes were used to detect melting points. Pye Unicam drugs such as muscimol. The protein also contains a number of SP 3300 spectrophotometer was used to record the IR spectra (in KBr different allosteric binding sites which modulate the activity of the receptor indirectly. These allosteric sites are the targets of various other drugs, including benzodiazepines, barbiturates and ethanol [11,12]. *Corresponding author: Khaled El-Adl, Assistant Professor of Pharmaceutical Methaqualone is a positive allosteric GABA-A receptor modulator. It Chemistry, Faculty of Pharmacy, Al-Azhar University, Cairo, Egypt, Tel: binds to allosteric sites on the GABA-A receptor complex and affects +20224018031; E-mail: [email protected] it in a positive manner, causing increased efficiency of the main site − Received September 23, 2016; Accepted September 29, 2016; Published and therefore an indirect increase in Cl conductance [11,12]. Many September 30, 2016 quinazolinones structurally related to compound methaqualone were Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, synthesized and biologically tested for their anticonvulsant activity. Synthesis and Biological Evaluation of Some Novel 2-Substituted-3-allyl-4(3H)- None of those compounds are currently used [8]. A persistent problem quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: encountered with these compounds arises from the fact that, nearly 593-603. doi:10.4172/2161-0444.1000404 every derivative tested in combined neurotoxicity and anticonvulsant Copyright: © 2016 Abulkhair HS, et al. This is an open-access article distributed screenings exhibited neurotoxicity values (TD50’s) that are less than or under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the only slightly higher than the effective doses (ED50’s) consequently, the original author and source are credited.
Med Chem (Los Angeles), an open access journal Volume 6(9): 593-603 (2016) - 593 ISSN: 2161-0444 Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted- 3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: 593-603. doi:10.4172/2161-0444.1000404
discs). Either Gemini 300MHz or (Varian USA) were used to record the Preparation of 3-Allyl-2-((2-substituted-2-oxoethyl) thio) 1HNMR spectra using TMS as an internal standard. Shimadzu GCMS- quinazolin-4(3H)-one (4a-e) QP 1000 EX mass spectrometer was used to record mass spectra. General procedure: A mixture of equimolar amounts of 3-allyl- Elemental analysis was determined at the Regional Center for Mycology 1,2-dihydro-2-thioxo-4(3H)-quinazolinone (3) (2.18 gm, 0.01 mol), and Biotechnology, Al-Azhar University, Egypt. Starting materials were α-chloroacetone and/or the appropriate α-bromoacetophenone (0.01 purchased from Aldrich Chemical Company and used without further mol) in DMF (10 ml) containing K2CO3 (2 gm) was heated on a water- purification. 3-Allyl-2,3-dihydro-2-thioxoquinazolin-4(1H)-one (3) bath with continuous stirring for 6 hrs. The reaction mixture was was prepared according to reported procedure. Alkyl chloroacetates, cooled and poured into crushed ice in water (20 ml). The solid was chloroacetone, α-bromoacetophenones, hydrazinehydrate and collected, washed with excess water and crystallized from acetic acid to aldehydes were purchased from Aldrich Chemical Company and used produce the corresponding ketone derivatives 4a-e. without further purification. Anticonvulsant evaluation was carried 4 : 3-Allyl-2-((2-methyl-2-oxoethyl) thio) quinazolin-4(3H)-one: out at the Department of Toxicology and Pharmacology, Faculty of a Yield (2.05 g, 75%), m.p. 65-67°C. C14H14N2O2S (274), Analysis % Calcd. Pharmacy, Al-Azhar University. Scheme 1 was adopted for synthesis (Found.), C: 61.29 (61.35), H: 5.14 (5.11), N: 10.21 (10.42). IR (KBr, of the new 2-substituted-3-allyl-4(3H)-quinazolinone derivatives. cm-1): 3085 (C-H aromatic), 2923 (C-H aliphatic), 1723 (C=O ketone), Progress of the reactions was monitored by TLC sheets and was 1677 (C=O quinazoline). MS (m/z, abund. %): 274 (M+,11.99%), 259 visualized using UV lamp and n-hexane: ethyl acetate 9: 1 as mobile 1 (17.59%), 231 (56.73%), 185 (96.37%), 162 (100%). HNMR (CDCl3, phase. ppm): 2.42 (s, 3H, -COCH3), 4.04 (s, 2H, SCH2), 4.78 (d, 2H, NCH2-
CH=), 5.30 (m, 2H, CH=CH2), 5.96 (m, H, CH2CH=CH2), 7.39 (dd, H,
COOH + N C S
NH2
O O O
N ClCH COOR N 1 2 BrCH2COR N
N S K2CO3 N S K2CO3 N S H OR R1 6a-e 3 O 4a-e = , , n-C , -C and n- O R CH3 C2H 3H7 iso 3H7 C4H9 5 R1 = CH , 4-ClC H , 4-BrC H , 3 6 4 6 4 H 4-CH C H and 4-NO C H N 3 6 4 2 6 4 R2 Cl O NH2NH2
O
N O N N S NH 2 S O 7 NH N 5 HN R2 O a-d
R2 = H, Br, F and OCH CHO 3 R3
R3 O O N S N N H N 8a-d
3 = and R 4-Cl, 4-F, 2,6-Cl2 4-NO2
Scheme 1: Synthetic protocol of compounds 3-8.
Med Chem (Los Angeles), an open access journal Volume 6(9): 593-603 (2016) - 594 ISSN: 2161-0444 Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted- 3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: 593-603. doi:10.4172/2161-0444.1000404
H-6 quinaz.), 7.47 (d, J = 12.36 Hz, H, H-8 quinaz.), 7.66 (dd, H, H-7 aromatic), 2933 (C-H aliphatic), 1688 (2 C=O). MS (m/z, abund. %): quinaz.), 8.21 (d, J = 11.91 Hz, H, H-5 quinaz.). 432 (M++2, 4.80 %), 430 (M+, 4.60%), 432 (4.60%), 259 (100%). 1HNMR (CDCl , ppm): 4.02 (s, 2H, SCH ), 4.82 (d, 2H, NCH -CH=), 5.35 (m, 4 : 3-Allyl-2-((2-(4-chlorophenyl)-2-oxoethyl) thio) quinazolin- 3 2 2 b 2H, CH=CH , 5.95 (m, H, CH CH=CH ), 6.94-8.30 (m, 8H, aromatic 4(3H)-one: Yield (1.85 g, 50%), m.p. 175-177°C. C H ClN O S 2) 2 2 19 15 2 2 protons), 9.81 (s, 1H, NH). (370.5), Analysis % Calcd. (Found.), C: 61.54 (61.50), H: 4.08 (4.10), N: -1 7.55 (7.56). IR (KBr, cm ): 3081 (C-H aromatic), 2921 (C-H aliphatic), 5c:2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N- 1682 (2 C=O). MS (m/z, abund. %): 371 (M++1, 1.91%), 370 (M+, (4-fluorophenyl)acetamide: Yield (2.58 g, 70%), m.p. 163-165°C. 1 4.34%), 372 (1.50%), 259 (12.25%), 231 (53.11%), 139 (100%). HNMR C19H16FN3O2S (369), Analysis % Calcd. (Found.), C: 61.78 (61.75), H: -1 (CDCl3, ppm): 4.60 (s, 2H, SCH2), 4.80 (d, 2H, NCH2-CH=), 5.30 (m, 4.37 (4.39), N: 11.38 (11.35). IR (KBr, cm ): 3330 (NH), 3068 (C-H
2H, CH=CH2), 5.96 (m, H, CH2CH=CH2), 7.10-8.20 (m, 8H, aromatic aromatic), 2918 (C-H aliphatic), 1671 (2 C=O). MS (m/z, abund. %): protons). 370 (M++1, 6.00%), 259 (100%), 217 (10.00%), 185 (15.70%). 1HNMR (CDCl , ppm): 4.03 (s, 2H, SCH ), 4.83 (d, 2H, NCH -CH=), 5.36 (m, 4 : 3-Allyl-2-((2-(4-bromophenyl)-2-oxoethyl)thio)quinazolin- 3 2 2 c 2H, CH=CH , 5.93 (m, H, CH CH=CH ), 6.94-8.30 (m, 8H, aromatic 4(3H)-one: Yield (1.86 g, 45%), m.p. 142-144°C. C H BrN O S 2) 2 2 19 15 2 2 protons), 9.82 (s, 1H, NH). (415), Analysis % Calcd. (Found.), C: 54.95(54.89), H: 3.64(3.62), N: -1 6.75(6.79). IR (KBr, cm ): 3064 (C-H aromatic), 2916 (C-H aliphatic), 5d: 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N-(4- 1680 (2 C=O). MS (m/z, abund. %): 416 (M++1, 1.59%), 415 (M+, methoxyphenyl)acetamide: Yield (2.28 g, 60%), m.p. 152-154°C. 1 2.37%), 231 (27.59%), 217 (41.26%), 185 (100%), 162 (8.12%). HNMR C20H19N3O3S (381), Analysis % Calcd. (Found.), C: 62.98 (62.90), H: -1 (CDCl3, ppm): 4.64 (s, 2H, SCH2), 4.84 (d, 2H, NCH2-CH=), 5.33 (m, 5.02 (5.15), N: 11.02 (11.04). IR (KBr, cm ): 3272 (NH), 3072 (C-H
2H, CH=CH2), 5.98 (m, H, CH2CH=CH2), 7.09-8.19 (m, 8H, aromatic aromatic), 2940 (C-H aliphatic), 1692 (2 C=O). MS (m/z, abund. %): 1 protons). 381 (3.60%), 185 (18.20%), 259 (100%). HNMR (CDCl3, ppm): 3.79 (s, 3H, OCH ), 4.03 (s, 2H, SCH ), 4.80 (d, 2H, NCH -CH=), 5.31 (m, 4 : 3-Allyl-2-((2-(4-methylphenyl)-2-oxoethyl)thio)quinazolin- 3 2 2 d 2H, CH=CH , 5.96 (m, H, CH CH=CH ), 6.92-8.31 (m, 8H, aromatic 4(3H)-one: Yield (1.75 g, 50%), m.p. 180-182°C. C H N O S (350), 2) 2 2 20 18 2 2 protons), 9.82 (s, 1H, NH). Analysis % Calcd. (Found.), C: 68.55 (68.53), H: 5.18 (5.15), N: 7.99 (7.93). IR (KBr, cm-1): 3060 (C-H aromatic), 2923 (C-H aliphatic), Preparation of Alkyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl) 1 1682 (2 C=O). HNMR (CDCl3, ppm): 2.47 (s, 3H, CH3), 4.72 (s, 2H, thio)acetate (6a-e) SCH ), 4.86 (d, 2H, NCH -CH=), 5.32 (m, 2H, CH=CH , 5.98 (m, H, 2 2 2) General procedure: A mixture of 3 (2.18 gm, 0.01 mol) and the CH CH=CH ), 7.20-8.21 (m, 8H, aromatic protons). 2 2 appropriate alkyl α-chloroacetate (0.01 mol) in DMF (20 ml) in the
4e: 3-Allyl-2-((2-(4-nitrophenyl)-2-oxoethyl)thio)quinazolin- presence of anhydrous K2CO3 (2 gm) was heated on water-bath with
4(3H)-one: Yield (2.09 g, 55%), m.p. 145-147°C. C19H15N3O4S (381), continuous stirring for 6 h and the solid so obtained was filtered, Analysis % Calcd. (Found.), C: 59.83 (59.87), H: 3.96 (3.80), N: 11.02 dried and crystallized from ethanol to afford the corresponding ester -1 (11.09). IR (KBr, cm ): 3078 (C-H aromatic), 2937 (C-H aliphatic), derivatives 6a-e. 1676 (2 C=O). MS (m/z, abund. %): 381 (M+, 10.50%), 259 (10.40%), 6 : Methyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) 231 (48.40%), 185 (100%), 162 (8.12%).1HNMR (CDCl , ppm): 4.74 (s, a 3 acetate: Yield (1.30 g, 45%), m.p. 65-67°C. C H N O S (290), Analysis 2H, SCH ), 4.82 (d, 2H, NCH -CH=), 5.31 (m, 2H, CH=CH , 5.94 (m, 14 14 2 3 2 2 2) % Calcd. (Found.): C: 57.92 (57.99), H: 4.86 (4.80), N: 9.65 (9.80). IR H, CH CH=CH ), 7.42-8.24 (m, 8H, aromatic protons). 2 2 (KBr, cm-1): 3068 (C-H aromatic), 2926 (C-H aliphatic), 1745 (C=O Preparation of 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2- ester), 1687 (C=O quinazoline). MS (m/z, abund. %): 290 (M+, 1.94%), 217 (9.38%), 59 (100%). 1HNMR (CDCl , ppm): 3.79 (s, 3H, OCH ), yl)thio)-N-(4-substitutedphenyl)acetamide (5a-d) 3 3 4.04 (s, 2H, SCH2), 4.78 (d, J = 9.6 Hz, 2H, NCH2-CH=), 5.31 (m, J = General procedure: A mixture of equimolar amounts of 3-allyl- 9.6 Hz, 2H, CH=CH2), 5.95 (m, H, CH2CH=CH2), 7.39 (dd, H, H-6 1,2-dihydro-2-thioxo-4(3H)-quinazolinone (3) (2.18 gm, 0.01 mol) quinaz.), 7.51 (d, H, H-8 quinaz.), 7.69 (dd, H, H-7 quinaz.), 8.20 (d, J and the appropriate α-chloroacetanilide derivatives (0.01 mol) in DMF = 9.6 Hz, H, H-5 quinaz.). (10 ml) containing K2CO3 (2 gm) was heated on a water-bath for 6 hrs with continuous stirring. The reaction mixture was then cooled poured 6b: Ethyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) into cold water. The obtained solid was collected, dried and crystallized acetate: Yield (3.38 g, 70%), m.p. 70-72°C as. C15H16N2O3S (304), Analysis % Calcd. (Found.): C: 59.19 (59.22), H: 5.30 (5.30), N: 9.20 from ethanol to get the corresponding amide derivatives 5a-d. (9.21). IR (KBr, cm-1): 3067 (C-H aromatic), 2935 (C-H aliphatic), 1747 + 5a:2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N- (C=O ester), 1683 (C=O quinazoline). MS (m/z, abund. %): 304 (M , 1 phenylacetamide: Yield (2.03 g, 58%), m.p. 170-172°C. C19H17N3O2S 12.98%), 217 (60.23%), 185 (100%). HNMR (CDCl3, ppm): 1.28 (t, 3H, (351), Analysis % Calcd. (Found.), C: 64.94 (64.83), H: 4.88 (4.80), N: CH ), 4.00 (s, 2H, SCH ), 4.28 (q, 2H, OCH -CH , 4.78 (d, 2H, NCH - -1 3 2 2 3) 2 11.96 (12.02). IR (KBr, cm ): 3328 (NH), 3071 (C-H aromatic), 2934 CH=), 5.30 (m, 2H, CH=CH , 5.93 (m, H, CH CH=CH ), 7.36 (dd, H, + 2) 2 2 (C-H aliphatic), 1670 (2 C=O). MS (m/z, abund. %): 352 (M +1, 8.30%), H-6 quinaz.), 7.48 (d, J = 11.88 Hz, H, H-8 quinaz.), 7.66 (dd, H, H-7 1 217 (15.10%), 185 (19.70%), 259 (100%). HNMR (CDHCl3, ppm): 4.02 quinaz.), 8.20 (d, J = 11.97 Hz, H, H-5 quinaz.). (s, 2H, SCH2), 4.83 (d, 2H, NCH2-CH=), 5.34 (m, 2H, CH=CH2), 5.98 6 : Propyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) (m, H, CH2CH=CH2), 7.05-8.31 (m, 9H, aromatic protons), 9.79 (s, 1H, c NH). acetate: Yield (1.90 g, 60%), m.p. 68-70°C. C16H18N2O3S (318), Analysis % Calcd. (Found.), C: 60.36 (60.32), H: 5.70 (5.75), N: 8.80 (8.76). IR -1 5b:2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N- (KBr, cm ): 3062 (C-H aromatic), 2945 (C-H aliphatic), 1741 (C=O (4-bromophenyl)acetamide: Yield (3.01 g, 70%), m.p. 137-139°C. ester), 1682 (C=O quinazoline). MS (m/z, abund. %): 318 (M+, 9.09%), 1 C19H16BrN3O2S (430), Analysis % Calcd. (Found.), C: 53.03 (52.92), 217 (58.70%), 185 (100%). HNMR (CDCl3, ppm): 0.8 (t, J = 9.6 Hz, 3H, H: 3.75 (3.76), N: 9.76 (9.72). IR (KBr, cm-1): 3244 (NH), 3081 (C-H CH2-CH3), 1.70 (m, J = 9.6 Hz, 2H, CH2-CH3), 4.04 (s, 2H, SCH2), 4.14
Med Chem (Los Angeles), an open access journal Volume 6(9): 593-603 (2016) - 595 ISSN: 2161-0444 Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted- 3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: 593-603. doi:10.4172/2161-0444.1000404
(t, J = 9.6 Hz, 2H, OCH2-CH2), 4.80 (d, 2H, NCH2-CH=), 5.30 (m, 2H, NCH2-CH=), 5.23 (m, 2H, CH=CH2), 5.96 (m, H, CH2CH=CH2), 7.30-
CH=CH2), 5.94 (m, H, CH2CH=CH2), 7.41 (dd, H, H-6 quinaz.), 7.46 8.33 (m, 8H, aromatic protons), 8.42 (s, H, N=CH), 11.93 (s, 1H, NH). (d, J = 11.91 Hz, H, H-8 quinaz.), 7.68 (dd, H, H-7 quinaz.), 8.22 (d, J = 8 : 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N'-(4- 11.91 Hz, H, H-5 quinaz.). b fluorobenzylidene)acetohydrazide: Yield (1.38 g, 35%), m.p. 170-
6d: Isopropyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) 172°C. C20H17FN4O2S (396), Analysis % Calcd. (Found.), C: 60.59 -1 acetate: Yield (2.06 g, 65%), m.p. 65-67°C. C16H18N2O3S (318), Analysis (60.62), H: 4.32 (4.35), N: 14.13 (14.08). IR (KBr, cm ): 3231 (NH), % Calcd. (Found.), C: 60.36 (60.25), H: 5.70 (5.87), N: 8.80 (8.70). IR 3063 (C-H aromatic), 2927 (C-H aliphatic), 1683 (C=O quinazoline), (KBr, cm-1): 3061 (C-H aromatic), 2984 (C-H aliphatic), 1735 (C=O 1656 (C=O hydrazide). MS (m/z, abund. %): 396 (M+, 1.20%), 259 + 1 ester), 1684 (C=O quinazoline). MS (m/z, abund. %): 318 (M , 10.27%), (100%), 203 (47.49%), 185 (23.42%). HNMR (CDCl3, ppm): 4.08 (s, 1 217 (72.70%), 185 (100%). HNMR (CDCl3, ppm): 1.25, 1.28 (2s, 6H, 2H, SCH2), 4.70 (d, 2H, NCH2-CH=), 5.19 (m, 2H, CH=CH2), 5.99
CH(CH3)2), 3.99 (s, 2H, SCH2), 4.80 (d, 2H, NCH2-CH=), 5.08 (m, 2H, (m, H, CH2CH=CH2), 7.28-8.31 (m, 8H, aromatic protons), 8.50 (s, H,
OCH), 5.31 (m, 2H, CH=CH2), 5.97 (m, H, CH2CH=CH2), 7.37 (dd, H, N=CH), 11.88 (s, 1H, NH). H-6 quinaz.), 7.46 (d, J = 11.55 Hz, H, H-8 quinaz.), 7.67 (dd, H, H-7 8 : 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N'-(2,6- quinaz.), 8.22 (d, J = 12.06 Hz, H, H-5 quinaz.). c dichlorobenzylidene)acetohydrazide: Yield (2.89 g, 65%), m.p. 220-
6e: Butyl 2-((3-allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio) 222°C. C20H16Cl2N4O2S (446), Analysis % Calcd. (Found.), C: 53.70 o -1 acetate: Yield (2.32g, 70%), m.p. 65-67 C. C17H20N2O3S (332), Analysis (53.66), H: 3.61 (3.55), N: 12.52 (12.43). IR (KBr, cm ): 3209 (NH), % Calcd. (Found.), C: 61.42 (61.35), H: 6.06 (6.10), N: 8.43 (8.42). IR 3071 (C-H aromatic), 2926 (C-H aliphatic), 1672 (2C=O). MS (m/z, (KBr, cm-1): 3073 (C-H aromatic), 2957 (C-H aliphatic), 1740 (C=O abund. %): 449 (M++3, 0.37%), 448 (M++2, 0.42%), 446 (M+, 0.47%), + 1 ester), 1675 (C=O quinazoline). MS (m/z, abund. %): 332 (M , 7.00 %), 259 (100%), 203 (62.16%), 185 (30.92%). HNMR (CDCl3, ppm): 4.10 1 217 (66.62 %), 185 (100 %). HNMR (CDCl3, ppm): 0.88 (t, J = 10.98 (s, 2H, SCH2), 4.74 (d, 2H, NCH2-CH=), 5.21 (m, 2H, CH=CH2), 5.91
Hz, 3H, CH2-CH3), 1.37 (m, J = 10.98 Hz, 2H, CH2-CH3), 1.67 (m, 2H, (m, H, CH2CH=CH2), 7.37-8.08 (m, 7H, aromatic protons), 8.33 (s, H,
CH2-CH2-CH3), 4.03 (s, 2H, SCH2), 4.18 (t, 2H, OCH2-CH2), 4.80 (d, N=CH), 11.90 (s, 1H, NH). 2H, NCH -CH=), 5.31 (m, 2H, CH=CH , 5.97 (m, H, CH CH=CH ), 2 2) 2 2 8 : 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N'-(4- 7.38 (dd, H, H-6 quinaz.), 7.46 (d, J = 11.97 Hz, H, H-8 quinaz.), 7.68 d nitrobenzylidene)acetohydrazide: Yield (2.96 g, 70%), m.p. 173- (dd, H, H-7 quinaz.), 8.22 (d, J = 11.97 Hz, H, H-5 quinaz.). 175°C. C20H17N5O4S (423), Analysis % Calcd. (Found.), C: 56.73 (56.70), Preparation of 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2- H: 4.05 (4.18), N: 16.54 (16.62). IR (KBr, cm-1): 3179 (NH), 3078 (C-H yl)thio)acetohydrazide (7) aromatic), 2933 (C-H aliphatic), 1675 (2C=O). MS (m/z, abund. %): + 1 423 (M , 1.20%), 259 (64.28%), 203 (100%). HNMR (CDCl3, ppm): A mixture of hydrazine hydrate (0.64 g, 0.2 mol) and 3-allyl-2- 4.04 (s, 2H, SCH2), 4.80 (d, 2H, NCH2-CH=), 5.30 (m, 2H, CH=CH2), ethoxy-carbonylmethylthio-4(3H)-quinazolinone (4b) (3.04 gm, 0.1 5.97 (m, H, CH2CH=CH2), 7.38-8.22 (m, 8H, aromatic protons), 8.42 mole) in ethanol (10 ml) was heated under reflux for about 6 hrs. The (s, H, N=CH), 11.88 (s, 1H, NH). mixture was then concentrated by evaporation of the solvent whereby the hydrazide derivative 7 crystallized out as fine pale yellow crystals. Docking studies In the present work, all the target compounds were subjected to Yield (1.88g, 65%), m.p. 145-147°C. C13H14N4O2S (290), Analysis % Calcd. (Found.), C: 53.78 (53.64), H: 4.86 (4.90), N: 19.30 (19.32). IR docking study to explore their binding mode to GABA-A receptor -1 as a proposed mode of their anticonvulsant activity. All modeling (KBr, cm : 3279 (NH2), 3230 (NH), 3037 (C-H aromatic), 2917 (C-H aliphatic), 1681 (C=O quinazoline), 1658 (C=O hydrazide). MS (m/z, experiments were performed using molsoft (ICM-Pro) program which abund. %): 290 (M+, 4.75%), 259 (100%), 217 (9.17%), 203 (61.47%), provides a unique set of tools for the modeling of protein/ligand 1 interactions. It predicts how small flexible molecules such as substrates 185 (10.59%). HNMR (CDCl3, ppm): 3.97 (s, 2H, SCH2), 4.37 (s, 2H, or drug candidates bind to a protein of known 3D structure represented NH2, D2O exchangeable), 4.73 (d, 2H, NCH2-CH=), 5.21 (m, 2H, by grid interaction potentials (http://www.molsoft.com/icm_pro. CH=CH2), 5.92 (m, H, CH2CH=CH2), 7.43-8.09 (m, 8H, aromatic html). Each experiment used the biological target GABA-A receptor protons), 9.36 (s, 1H, NH, D2O exchangeable). downloaded from the Brookhaven Protein Databank (http://www.rcsb. Preparation of 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2- org/pdb/explore/explore.do?structureId=4COF). In order to qualify yl)thio)-N'-(substitutedbenzylidene)aceto-hydrazide (8a-d). the docking results in terms of accuracy of the predicted binding 4.6.1 General procedure: The appropriate aromatic aldehyde (0.01 conformations in comparison with the experimental procedure, the mol) was dissolved in glacial acetic (15 ml) and added to the hydrazide reported GABA-A receptor stimulant drug (Methaqualone) was used derivative 6 (2.9 g, 0.01 mol) in acetic acid (15 ml). The reaction mixture as a reference ligand. The docking study has been conducted to predict was heated under reflux overnight. Solvent was then removed out under the binding mode and to rationalize the observed biological activity. reduced pressure, and the solid product was collected, crystallized Anticonvulsant evaluation from ethanol to obtain the corresponding benzylideneacetohydrazide The animal studies were undertaken with approval from the derivative 8a-d. Ethics Committee (approval # 23PD/3/12/8R) of Al-Azhar University, 8a: 2-((3-Allyl-4-oxo-3,4-dihydroquinazolin-2-yl)thio)-N'-(4- Nasr City, Cairo, Egypt. All the trials were carried out according to chlorobenzylidene)acetohydrazide: Yield (1.85 g, 45%), m.p. 175- the respective internationally guidelines. Swiss albino adult male 177°C. C20H17ClN4O2S (412.5), Analysis % Calcd. (Found.), C: 58.18 mice, weighing 20-25 g, were used as experimental animals. They -1 (58.14), H: 4.15 (4.13), N: 13.57 (13.41). IR (KBr, cm ): 3211 (NH), 3045 were obtained from an animal facility (Animal house, Department (C-H aromatic), 2940 (C-H aliphatic), 1684 (2C=O). MS (m/z, abund. of Pharmacology and Toxicology, Faculty of Pharmacy, Al-Azhar + + %): 413 (M +1, 2.18%), 412 (M , 6.44%), 259 (33.97%), 203 (100%), University). Mice were housed in stainless steel wire-floored cages 1 185 (75.33%). HNMR (CDCl3, ppm): 4.11 (s, 2H, SCH2), 4.75 (d, 2H,
Med Chem (Los Angeles), an open access journal Volume 6(9): 593-603 (2016) - 596 ISSN: 2161-0444 Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted- 3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: 593-603. doi:10.4172/2161-0444.1000404
without any stressful stimuli. Animals were kept under well-ventilated third positions of methaqualone have led to the generation of many conditions at room temperature (25-30°C). They were fed on an CNS active agents such as afloqualone, etaqualone, mebroqualone, adequate standard laboratory chow (El-Nasr Co., Abou-Zabal, Egypt) mecloqualone and diproqualone (Figure 1). Mecloqualone was found and allowed to acclimatize with free access to food and water for 24 h to possess a significant anticonvulsant action 1.5 times more potent period before testing except during the short time they were removed than phenytoin against MES-induced convulsions and ten times more from the cages for testing. Methaqualone and sodium valproate potent than troxidone against PTZ-induced seizures [13]. Second fact (Sigma-Aldrich Chemical Co, Milwaukee, WI, USA) were used as explained that: replacement of the phenyl group at second position reference drugs for comparison. The newly synthesized compounds of quinazolin-4(3H)-one by ethyl one and replacement of the methyl were screened to evaluate their anticonvulsant activity and their group at position 2 by substituted thiazolidine distal moiety linked at neurotoxicity. The anticonvulsant activities of the selected compounds 2-position through SCH2CONHN and/or SCH2CONH linkers yielded were evaluated by two models, pentylenetetrazole (PTZ), and maximal good anticonvulsant agents as in compounds (A and B) [16]. Figure electroshock (MES) models according to the reported procedures. 1 represents the structural similarities and pharmacophoric features PTZ (Sigma-Aldrich Chemical Co, Milwaukee, WI, USA) was used to of some reported anticonvulsants quinazolinones and our designed induce convulsions in the experimental animals. The test compounds compounds. Based on the previously mentioned facts, it appeared were dissolved in 10% DMSO and injected intraperitoneally (i.p.) at a to us that considerable promise for discovering new anticonvulsants dose of 0.5 mmol/kg 30 min before seizures induction. Methaqualone might be found through the synthesis of structural analogs of these (0.8 mmol/kg) and sodium valproate (1.8 mmol/kg) were used as compounds. reference drugs. PTZ (PTZ, Sigma) was dissolved in normal saline Figure 1 shows that structure of the title final compounds (4 - in 2% concentration and was given (i.p.) in a dose of 60 mg/kg body a-e 8 ) fulfilled all the pharmacophoric structural requirements. These weight (dose that could induce convulsions in at least 80% of the a-d requirements include: the presence of quinazolin-4(3H)-one moiety as animals without death during the following 24 h). All drugs were hydrophobic portion, N as electron donor system, the presence of the freshly prepared to the desired concentration just before use. carbonyl group as hydrogen bonding site, the allyl group at 3-position Groups of six mice were administered the graded doses of the test as hydrophobic domain and the presence of the distal moiety linked compounds. Control animals received an equal volume of saline (10 at 2-position through SCH2CO, SCH2COO, SCH2CONH and/or ml/kg). After 30 min, the animals were subcutaneously injected with SCH2CONHN linkers as another hydrophobic domain responsible for the convulsive dose of PTZ (60 mg/kg). The criterion of anticonvulsant controlling the pharmacokinetic properties of the antiepileptic activity. activity is complete protection against convulsions of any kind. Our target compounds are designed as hybrid molecules formed Observations were made at least 60 min after the administration of quinazolinone ring system to maintain basic features of the lead of PTZ. In the MES test, the electrical stimulus produced from structure methaqualone with replacement of the phenyl group at electroconvulsiometer was 50 mA, 60 Hz. Current was applied for position 3 of synthesized compounds by allyl one and replacement of 0.2 s via auricular electrodes. Protection against the spread of MES- the methyl group at position 2 by different moieties as hydrophobic induced seizures was identified by the abolition of the hind leg and portions. These moieties were joined at 2-position through different tonic maximal extension component of the seizure. linkers having different electronic environments to study the SAR
The highest potent compounds 4c, 4b and 4d were further evaluated of these compounds and the effect of each substituent on their at different doses in PTZ model to determine their protective and anticonvulsant activity hoping to obtain more potent anticonvulsant therapeutic indexes. Neurotoxicity which was indicated by median agents. toxic dose producing minimal neurological toxicity in 50% of mice Molecular docking study (TD50) was calculated (in mg/kg) and used for comparison among compounds under test as shown in Table 3. Neurological toxicity (NT) The obtained results indicated that all studied ligands have similar was determined by rotarod test in mice using the method reported by position and orientation inside the putative binding site of GABA-A Dunham and Miya. In brief, a group of animals (mice) were trained receptor (PDB code 4COF), as a proposed mode of their anticonvulsant to balance on a rotating rod (3 cm diameter and 6 rpm speed) and activity, which revealed a large space bounded by a membrane-binding they were allowed three attempts to remain on the rotating rod for domain which serves as an entry channel for substrate to the active 20 s. The trained animals were treated with the tested compounds at site (Figure 2). In addition, the affinity of any small molecule can various dose levels by i.p. administration. The tested compounds were be considered as a unique tool in the field of drug design. There is a considered to be neurotoxic at a particular dose level if the trained relationship between the affinity of organic molecules and the free animal showed lack of Rolling Roller Performance. The trained energy of binding. This relationship can contribute in prediction and animals were tested in this manner at 30 min and 4 h after the drug interpretation of the activity of the organic compounds toward the administration and then the neurotoxic effect was recorded in terms of specific target protein [17,18] The obtained results of the free energy median toxic dose (TD50). The protective index was determined from of binding (∆G) explained that most of these compounds had good the equation (PI=TD50/ED50). The median lethal dose (LD50), the dose binding affinity toward the receptor and the computed values reflected that causes 50% mortality in mice was calculated (in mg/kg) and used the overall trend (Table 1). for comparison among compounds under test as shown in Table 3. Therapeutic index was determined from the equation (TI=LD /ED ). The proposed binding mode of methaqualone revealed an affinity 50 50 value of -50.69 kcal/mol and formed 2 H-bonds with Lysine215 (1.52 Results and Discussion Å) and Isoleucine218 (1.81 Å). These are key amino acids acting as a gate for ligand entrance to the GABA-A (Figure 3). The quinazolinone Rationale and structure-based design moiety occupied the hydrophobic pocket formed by Serine187, Two reported facts were analyzed before the chemical synthesis Lysine215, Asparagine217, Isoleucine218 and Glycine219. The phenyl of our target compounds. First fact was: modifications at second and ring at position-3 was oriented in the hydrophobic cleft formed by Arginine142, Leucine145, Aspartate146, Glutamate147, Lysine215,
Med Chem (Los Angeles), an open access journal Volume 6(9): 593-603 (2016) - 597 ISSN: 2161-0444 Citation: Abulkhair HS, El-Gamal KM, El-Adl K, Fadl MF (2016) Molecular Docking, Synthesis and Biological Evaluation of Some Novel 2-Substituted- 3-allyl-4(3H)-quinazolinone Derivatives as Anticonvulsant Agents. Med Chem (Los Angeles) 6: 593-603. doi:10.4172/2161-0444.1000404