Design And Synthesis Of Novel Quinazolinones And Their Antimicrobial Study

Quinazolinone is an important aromatic heterocyle composed by benzene ring fused pyridone skeleton, and it is extensively present in natural and synthetic drugs in which quinazolinone moiety plays important roles in exerting various biological activities. Thus it has been paid special attention in the development of new drugs. Many quinazolinone compounds such as methaqualone and piriqualone (anticonvulsant drugs), raltitrexed (anticancer drug) as well as Ketanserin (antihypertensive drug) etc. are widely used in clinic to treat various diseases. In recent years, quinazolinones have shown great development value in antibacterial and antifungal field. Meanwhile, a lot of azole compounds including various five-membered azoles such as imidazoles, triazoles and tetrazoles, and benzene fused azoles like benzimidazoles as well as benzotri azoles with nitrogen atom (s) and aromaticity are able to readily not only interact with biological active sites such as enzymes and receptors via coordination bonds, hydrogen bonds and so on, but also beneficially modulate the physicochemical and pharmacokinetic properties. The design, synthesis and antimicrobial activity of azole derivatives have become one of the highly active highlights and many considerable outstanding achievements have been obtained. In this thesis, based on the current situation in the researches of quinazolinone compounds, a series of novel quinazolinones were designed and synthesized. All the newly synthesized compounds were.evaluated for their antibacterial and antifungal activities. The preliminary structure-activity relationships, preparative methods and conditions were discussed. Further binding behaviors between the synthesized active compound and human serum albumin (HSA) were investigated by fluorescence and UV-vis absorption spectroscopy to evaluate their transportation and pharmacokinetic properties. The preliminary antimicrobial mechanism was also studied. The main work was summarized as follows:(1) Preparation of novel quinazolinone azoles:Commercially available fluoro or chloro substituted 2-aminobenzoic acid was reacted with formamidine acetate in the presence of 2-methoxyethanol via cyclization to produce 7-fluoroquinazolin-4(3H)-one or 7-chloroquinazolin-4(3H)-one Ⅱ-1a-b in high yield, and then compounds Ⅱ-1a-b were further treated with a series of alkyl dibromides to conveniently and efficiently afford bromides Ⅱ-2a-j. The target quinazolinone azoles Ⅱ-3a-j, Ⅱ-4a-j, Ⅱ-5a-d, Ⅱ6-a-d, Ⅱ-7a-b, Ⅱ-8a-b,Ⅱ-9a-b, Ⅱ-10a-d and Ⅱ-11a-b were obtained by the reaction of bromides Ⅱ-2a-j respectively with 2-methyl-5-nitroimidazole. 4-nitroimidazole, imidazole, triazole, 1,2,4-triazole-3-thiol,5-methyltetrazole, 1-methyltetrazole-5-thiol, benzimidazole and benzimidazole-2-thiol in acetonitrile at 50 ℃ in the presence of potassium carbonate as base.(2) Preparation of novel quinazolinone azole ethanols:Commercially available fluoro or chloro substituted 2-aminobenzoic acid was reacted with formamidine acetate in the presence of 2-methoxyethanol via cyclization to produce 7-fluoroquinazolin-4(3H)-one or 7-chloroquinazolin-4(3H)-one Ⅲ-1a-b in high yield, and then compounds Ⅲ-1a-b were further treated respectively with 2-(chloromethyl)oxirane to conveniently and efficiently afford epoxides Ⅲ-2a-b. The target quinazolinone azole ethanols Ⅲ-3a-b, Ⅲ-4a-h, Ⅲ-5a-b, Ⅲ-6a-b,Ⅲ-7a-d,Ⅲ-8a-b and Ⅲ-9a-d were obtained by the reaction of bromides Ⅲ-2a-b respectively with triazole. imidazole.4-nitroimidazole. 2-methyl-5-nitroimidazole,2-phenylimidazole,5-methyltetrazole. 1-methyltetrazole-5-thiol. benzimidazole,5.6-dimethvlbenzimidazole. benzimidazole-2-thiol. benzotriazole and 5-methylbenzotriazole in ethanol at 50℃ in the presence of potassium carbonate as base.(3) Preparation of novel non-azole quinazolinones:Commercially available chloro substituted 2-aminobenzoic acid was reacted with formamidine acetate in the presence of 2-methoxyethanol via cyclization to produce 7-chloroquinazolin-4(3H)-one Ⅳ-1 in high yield. The new structural quinazolinones Ⅳ-2a-i, Ⅳ-3a-i, Ⅳ-4 and Ⅳ-5 were synthesized by the reaction of compound Ⅳ-1 respectively with 1-bromoalkane, halogen benzene,3-bromoprop-1-yne and N-acetylsulianilyl chloride. Compound Ⅳ-5 was then cyclized in ethanol under reflux to produce the desired sulfanilamide compound IV-6.(4) The preparative condition (solvent and catalyst) of quinazolinone azole ethanols III-3a-b was explored. The study found the yield of compounds Ⅲ-3a-b was the highest when ethanol as solvent and potassium carbonate as catalyst. The reason was that the use of sodium hydroxide and triethylamine etc. base would result in the increase of by-products and decrease of reaction velocity.(5) All the newly synthesized compounds were characterized by’H NMR,13C NMR, IR, MS and HRMS spectra.(6) The prepared intermediates and target compounds were evaluated for their in vitro antimicrobial activities. The biological assays indicated that some synthesized compounds could significantly inhibit the growth of tested microorganisms and some of them displayed equipotent or superior efficacies to the current clinical drugs. Notably, 2-methyl-5-nitroimidazole derivative II-3a displayed comparable or even better antimicrobial activities (MIC= 8-16 μg/mL) in contrast with the reference drugs norfloxacin (MIC= 1-16μg/mL) and chloromycin (MIC= 8-32μg/mL) except for P. aeruginosa. Moreover, triazolyl ethanol III-3a could effectively inhibit the growth of MRSA at the concentrations of 8 μg/mL, which was more active than the reference drug chloromycin (MIC= 16 μg/mL).(7) The preliminary structure-activity relationships showed that alkyl chain lengths had great effects on biological activities. The fluoro or chloro substituent of quinazolinone at C-7 position did not exert significantly different influence on antimicrobial potency. The introduction of thioether fragment was not conductive to the biological activities. Azolyl moiety exerted an important effect on the antimicrobial activity.(8) The specific interaction of highly active compound Ⅱ-3a with calf thymus DNA displayed that compound Ⅱ-3a could intercalate into DNA to form Ⅱ-3a-DNA complex which might further block DNA replication to exert its powerful antibacterial and antifungal activities. Binding investigations with HSA revealed that HSA could generate fluorescent quenching by Ⅱ-3a as a result of the formation of ground-state Ⅱ-3a-HSA complex, and the calculated parameters suggested that the binding process should be spontaneous. Hydrogen bonds and van der Waals forces played an important role in the association of compound Ⅱ-3a-HSA.(9) The genomic DNA was isolated from the most sensitive MRSA bacteria to compound Ⅲ-3a and its preliminarily interactive investigation with the highly active compound Ⅲ-3a revealed that compound Ⅲ-3a could form Ⅲ-3a-MRSA DNA complex by an intercalative mode and further block DNA replication. Molecular docking displayed that compound Ⅲ-3a also intercalated into MRSA DNA by formation of four hydrogen bonds with DNA and amino acid residues. Furthermore, the DNA cleavage properties of Ⅲ-3a-Cu2+ and Ⅲ-3a-Zn2+ complexes were confirmed by agarose gel electrophoresis experiments. These results suggested that both DNA intercalative binding and cleavage should exert powerful antibacterial activities, and the proposed antibacterial mechanism might be synergetic effects by both of target material and its complex formed with free metal ion.Ninety nine compounds were successfully synthesized in this thesis. Eighty eight compounds were new, including twelve intermediates, nine alkyl compounds, nine halogen benzyl compounds, one alkynyl compound, two sulfanilamide compounds, thirty two imidazoles, six triazoles, two triazole-3-thiols, four tetrazoles, four tetrazole-5-thiols, eight benzimidazoles, four benzimidazole-2-thiol and four benzotriazoles.