Aminoacids in the Synthesis of Heterocyclic Systems: The Synthesis of Triazinoquinazolinones, Triazepinoquinazolinones and Triazocinoquinazolinones of Potential Biological Interest

A number of novel triazinoquinazolinones (5b,c and 8), triazepinoquinazolinones(5a, 6b, 7 and 9) and triazocinoquinazolinones (6a and 10) were obtained via nucleophilic interaction of 3-aminoquinazolinone derivatives 3 with different reagents.


Introduction
Varied biological activities have been attributed to quinazoline compounds, including analgesic, antiinflammatory, antipyretic [1][2][3], antimicrobial [4], anticonvulsant [5], fungicidal [6], antidepressant and other central nervous system affecting activities [7]. The use of aminoacids as starting materials for the design and synthesis of new quinazoline compounds with the aim of preparing potent biologically active compounds is a subject of recent interest [8][9][10][11]. Now we report a facile synthesis of several heterocyclic compounds containing six, seven and eight membered rings fused to a quinazoline moiety starting from amino acids.

Synthesis and characterization
The starting materials 1a-f were prepared via reaction of the appropriate sulfonyl chloride derivatives with amino acids in the presence of 10 % sodium hydroxide solution, followed by acidification [12]. The amides 2a-f have been prepared by condensation of the corresponding 1a-f with methyl anthranilate in presence of PCl 3 . 3-Aminoquinazolinones 3a-f were obtained by refluxing compounds 2a-f with hydrazine hydrate in n-butanol (Scheme 1). Compounds 2a-f and 3af have been fully characterized by their analytical and spectral data. For example, the IR spectrum of compound 3e showed the presence of NH, NH 2 , CH-aliphatic, C=O and S=O functional groups. Also, the 1 H-NMR spectrum of compound 3e exhibited signals in the range of 0.85-0.92; 1.88; 2.15-2.24; 2.50-2.51; 5.51; 6.82-8.02; 10.6 ppm due to 2CH 3 (d); CH 3 (s); CH (m); CH (d); NH 2 (s); Ar-H's (m) and SO 2 NH (s) respectively. The mass spectrum of compound 3c showed a molecular ion peak at m/z 434 (1.01%) which underwent fragmentation to give the well established fragment at m/z 91 (100%; base peak; see Scheme 2). 3-Aminoquinazolinone derivatives 3d,e were used as a precursors for further cyclizations with the purpose of synthesizing several heterocyclic compounds fused to the quinazoline moiety. Thus, condensation of 3e with p-chlorobenzaldehyde in acetic acid furnished the corresponding Schiff's base 4. The structure of compound 4 was deduced from elemental analyses and spectral data. The IR spectrum showed the absence of the NH 2 group present in the parent compound and the presence of a C=N group. On the other hand, refluxing compounds 3d,e with p-fluoro, p-chloro and p-methoxybenzaldehydes in DMF yielded the novel heterocyclic compounds 5a-c. Formation of 5 from the reaction of 3 and an aldehyde is assumed to proceed in three steps. First, condensation of 3 and aldehyde to yield Schiff's bases 4; second, nucleophilic addition of NHSO 2 to the activated C=N bond to form intermediate (A) followed by the third step, elimination of sulphinic acid to furnish 5, Scheme 3.  [7,1-b]quinazolinone (6b) were obtained by refluxing compounds 3d and 3e, respectively, with 2,3-dichloro-1,4-naphthoquinone in DMF. This reaction takes place via loss of two HCl molecules followed by elimination of toluenesulphinic acid.
As an extension of this work, when compound 3d was allowed to react with Cl(CH 2 ) n COOEt system (n=0,1) in DMF and under reflux conditions, the triazepinoquinazolinone 9 and triazocinoquinazolinone 10 were isolated, respectively. The postulated mechanism for this reaction involves the initial attack by the chloroester followed then by a sequential elimination of ethanol and then toluenesulphinic acid, which is a good leaving group, to give the intermediate (C) which is finally alkylated, Scheme 5. Biological Activity

Antifungal activities
The selected compounds were also tested for their antifungal activity using Aspergillus ochraceus Wilhelm (AUCC-230) and Penicillium chrysogenum Thom (AUCC-530) ( Table 2). Some of the synthesized compounds were found to possess antifungal activities towards all the microorganisms used with minimal inhibitory concentration (MIC). The amide 2d possesses a high antifungal activity towards Aspergillus ochraceus Wilhelm (AUCC-230). Also compound 3d which contain the N-amino moiety was found to possess the highest antifungal activity towards Penicillium chrysogenum Thom (AUCC-530). On the other hand the triazepinoquinazolinone 9 was found to possess antifungal activity against Penicillium chrysogenum Thom (AUCC-530).
Key to the results: Inhibition zones were measured in mm. The concentration used was 4x10 -5 M. Control discs were done using dimethylformamide (DMF) and no inhibition zones were observed. Results are reported as (R) resistant, (+) moderately sensitive giving a 5 mm inhibition zone; (++) sensitive giving a 14 mm inhibition zone; (+++) very sensitive giving a 20 mm inhibition zone.

General
Melting points were taken on a STUART apparatus and are uncorrected. The IR spectra (KBr disks) were measured with a Jasco FT/IR 5300 spectrometer. The 1 H-NMR spectra were obtained on a Varian Gemini 200 instrument at 200 MHz using DMSO-d 6 as a solvent and TMS as internal standard. Mass spectra were performed by Shimadzu-GC MS QP 1000 EX using the direct inlet system. Thin layer chromatography (TLC) was carried out on silica gel (MN-Kieselgel G., 0.2 mm thickness) with ethylacetate:n-hexane (E/H) as the solvent and the plates were scanned under 254 nm ultraviolet light. Microanalyses were performed by the Microanalytical Unit at Cairo University. All the compounds gave satisfactory elemental analyses. Antimicrobial and antifungal activity tests were carried out by the Microbiology Lab., Faculty of Science, Al-Azhar University, Cairo, Egypt.

General procedure for synthesis of tosyl aminoacids 1a-f.-
The tosyl amino acid derivatives were prepared according to McChesney et al [12] whereby the aminoacid (0.026 mol) was dissolved in 1N sodium hydroxide (25 mL) and over a period of thirteen minutes a solution of p-toluenesulphonyl chloride (0.027 mol) in ether (30 mL) was added in portions. The mixture was stirred at room temperature for 3hrs. The excess p-toluenesulphonyl chloride was filtered off and the solution treated with 2N HCl until acidic to Congo Red (pH 5). After cooling acidification caused the product to precipitate. The crude product was filtered, washed with water and dried. The crude materials were recrystallized to give 1a-f.

General procedure for synthesis of the amides 2a-f.-
To a mixture of tosyl aminoacid (0.01 mol) and methyl anthranilate (0.01 mol) in xylene (20 mL), phosphorous trichloride (2-3 mL) was added. The mixture was heated under reflux for 3-4 hrs. After cooling and addition of pet.ether (bp 40-60°C; 10 mL) the precipitate was filtered and washed with two 5 mL portions of pet.ether, dried and recrystallized from the appropriate solvent to give 2a-f.

3-
General procedure for the synthesis of 5a-c.-Compounds 3d,e (0.01 mol) and the corresponding aldehyde derivative (0.01 mol) in DMF (20 mL) containing 2 drops of triethylamine was refluxed for 6-8 hrs., after cooling and acidification with dil. HCl, a precipitate was formed, which was collected by filtration, washed with water and recrystallized to give 5a-c.