Quinazoline Ring System Research Articles

Synthesis of the new ring system 6,8-dihydro- 5H-pyrrolo[3,4- h]quinazoline

A convenient synthesis of the pyrrolo[3,4- h]quinazoline ring system is reported. Our synthetic approach consisted of the annelation of a pyrimidine ring to an isoindole moiety using tetrahydroisoindole-4-ones as building blocks. The antiproliferative activity of the new compounds was investigated and one of them showed antitumor activity against all the 59 tested cell lines at micromolar concentrations (1.46–18.4 μM).

Microwave-Promoted Syntheses of Quinazolines and Dihydroquinazolines from 2-Aminoarylalkanone O-Phenyl Oximes

A wide range of biologically active compounds contain the quinazoline ring system. A new free-radical-based method of making functionalized quinazolines is described, which relies on microwave-promoted reactions of O-phenyl oximes with aldehydes. A small set of 2-aminoaryl alkanone O-phenyl oximes was prepared and shown to produce dihydroquinazolines when mixed with an aldehyde in toluene and subjected to microwave heating. When ZnCl(2) was included in the reaction mixture, fully aromatic quinazolines were produced in high yields by a rapid and convenient process. The method worked well with alkyl, aryl, and heterocyclic aldehydes and for a variety of substituents in the benzenic part of the molecule. Similar reactions employing ketones instead of aldehydes were less efficient. Although some dihydroquinazolines did form, they were accompanied by several byproducts. Surprisingly, in each case, one of the byproducts was a quinoline derivative, and a plausible mechanism to account for this rearrangement is proposed.

3,3′-Bis(4-chlorophenyl)-2,2′-(m-phenylenedioxy)diquinazolin-4(3H)-one

In the title compound, C34H20Cl2N4O4, the two quinazoline heterocyclic systems and the adjacent chloro­benzene rings are not coplanar, but oriented at dihedral angles of 66.66 (13) and 52.48 (12)°, respectively. The quinazoline ring systems are nearly planar, with dihedral angles between the planes of the two rings of 5.43 (16) and 3.40 (14)°, and are oriented at dihedral angles of 79.73 (13) and 83.52 (13)° with respect to the adjacent benzene ring between them. Inter­molecular C—H⋯O hydrogen bonds contribute to the stability of the structure. In addition, weak π–π stacking inter­actions [centroid-to-centroid distances = 3.872 (1) and 3.876 (1) Å] are observed in the crystal structure.

3-(2-Aminoethyl)-2-(4-chloroanilino)quinazolin-4(3H)-one methanol 0.75-solvate

In the asymmetric unit of the title compound, C16H15ClN4O·0.75CH3OH, there are two independent quinazolin-4(3H)-one mol­ecules and one and a half methanol mol­ecules. One of the methanol mol­ecules is disordered over two positions with equal occupancies. The dihedral angles between the quinazoline ring system and the chloro­benzene ring in the two quinazolin-4(3H)-one mol­ecules are essentially the same, at 39.83 (1) and 39.84 (1)°. Intra­molecular N—H⋯N and O—H⋯O, and inter­molecular N—H⋯O and N—H⋯N hydrogen bonds are observed. In addition, π–π stacking inter­actions, with centroid-to-centroid distances of 3.654 (1), 3.766 (1) and 3.767 (1) Å, and weak C—H⋯π inter­actions, are observed.

Erlotinib hydrochloride: an anticancer agent

In the cation of the title compound, C22H24N3O4 +·Cl−, an active ingredient of the anti­cancer drug also known as Tarceva, the quinazoline ring system is planar within 0.044 (3) Å. The dihedral angle formed by the mean planes of the two six-membered quinazoline rings is 3.2 (1)°. Both N-bound H atoms participate in N—H⋯Cl bonds, which link the ions into infinite chains running along the b axis. C—H⋯O inter­actions involving neighboring cations provide additional stabilization of these aggregates.

N-(4-Chlorophenyl)-6,7-bis(2-methoxyethoxy)quinazolin-4-amine monohydrate

In the title compound, C20H22ClN3O4·H2O, the quinazoline and benzene ring systems are oriented at a dihedral angle of 4.99 (3)°. Intra­molecular C—H⋯N hydrogen bonding results in the formation of a nearly planar six-membered ring, which is nearly coplanar with the adjacent quinazoline ring system and the benzene ring, making dihedral angles of 2.39 (3) and 3.32 (3)°, respectively. In the crystal structure, inter­molecular N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules.

Novel AMPA and kainate receptor antagonists containing the pyrazolo[1,5- c]quinazoline ring system: Synthesis and structure–activity relationships

This paper reports the synthesis and AMPA, Gly/NMDA, and KA receptor binding affinities of a new set of 1,9-disubstituted-8-chloro-pyrazolo[1,5- c]quinazoline-2-carboxylates 2– 34. Binding data show that, in general, compounds 2– 34 bind to the AMPA receptor with good affinity and selectivity. In particular, the obtained results indicate that the contemporary presence of a 1,2-dicarboxylic acid moiety and suitable benzo-substituents on the PQZ system is important to gain selective AMPA receptor antagonists. Moreover, this study shows that the presence of a 2-carboxybenzoylamino substituent at position-9 (compounds 33– 34) is important for obtaining selective KA receptor antagonists. Some selected compounds were also tested for their functional antagonistic activity at both AMPA and NMDA receptor-ion channels.

Progress Toward the Synthesis of Hinckdentine A

AbstractFor Abstract see ChemInform Abstract in Full Text.

Photodecomposition of an acaricide, fenazaquin, in aqueous alcoholic solution.

Fenazaquin (I) is a new acaricide of the quinazoline class. The photodecomposition of I was studied in aqueous methanolic and 2-propanolic solution under UV light (30 h) and sunlight (70 h) separately. The photolytic half-lives in aqueous methanolic solution were found to be 17.1 h (UV) and 38.1 h (sunlight), whereas these were 12.9 h (UV) and 29.2 h (sunlight) for aqueous 2-propanolic solution; all followed a first-order reaction kinetics. Six photoproducts were obtained: beta-phenyl (p-tert-butyl) ethyl alcohol (II), 4-hydroxyquinazoline (III), p-tert-butyl vinyl benzene (IV), 2,4-dihydroxyquinazoline (V), phenyl (p-tert-butyl) acetic acid (VI), and 2-methyl-2-[4'-(2' '-hydroxyethyl)phenyl]propanoic acid (VII). Compounds VI and VII could be isolated only from aqueous 2-propanolic solution under sunlight irradiation. The major degradation products are formed as a result of cleavage of the ether bridge linking the quinazoline and phenyl ring systems of the molecule, oxidation of the tert-butyl substituent, and oxidation of the heterocyclic portion of the quinazoline ring. A probable mechanism of formation of the photoproducts is also suggested.

Synthesis of 8-desbromohinckdentine A1.

Hinckdentine A is an alkaloid isolated from the bryozoan Hincksinoflustra denticulate. This natural product contains a novel and unique 11b,12,13,14,15,16-hexahydroazepino[4',5':2,3]indolo[1,2-c]quinazoline ring system that has not previously been synthesized. We have synthesized 8-desbromohinckdentine A from a 2-aryl indole by first preparing the quaternary center of the natural product and then building the seven-membered lactam and dihydropyrimidine rings onto this intermediate to form the framework of hinckdentine A.

Analysis of quinazoline and pyrido[2,3-d]pyrimidine N9-C10 reversed-bridge antifolates in complex with NADP+ and Pneumocystis carinii dihydrofolate reductase.

Structural studies of two ternary complexes of Pneumocystis carinii dihydrofolate reductase (pcDHFR) with the cofactor NADP(+) and potent antifolates, the N9-C10 reversed-bridge inhibitor 2,4-diamino-6-[N-(2',5'-dimethoxybenzyl)-N-methylamino]quinazoline (1) and its 3',5'-dimethoxypyrido[2,3-d]pyrimidine analog (2), were carried out. Data for the monoclinic crystals were refined to 1.90 A resolution for the complex with (1) (R = 0.178) and to 2.1 A resolution for the complex with (2) (R = 0.193). The effect of the N9-C10 reversed-bridge geometry is to distort the bridge from coplanarity with the pyrido[2,3-d]pyrimidine or quinazoline ring system and to twist the C10 methylene conformation toward a gauche conformation. This change also influences the conformation of the methoxybenzyl ring, moving it away from a trans position. This change places the 5'-methoxy group deeper within the hydrophobic pocket made by Ile65, Pro66 and Phe69 of the pcDHFR active site. These results also revealed the first observation of an unusual conformation for the reversed-bridge geometry (C5-C6-N9-C10 torsion angle) in antifolate (2). The electron density is consistent with the presence of two models (conformers 2-1 and 2-2) that result from inversion of the geometry at N9. The four examples of N9-C10 reversed-bridge antifolates cluster in two conformations, with the structure of quinazoline (1) similar to that previously reported for its 2',5'-dimethoxypyrido[2,3-d]pyrimidine analog (3). The two conformers of (2) differ from these and each other by a twisted-bridge geometry that results in the dimethoxybenzyl ring occupying the same conformational space. Conformer 2-2 also has the N9-C10 reversed bridge perpendicular to the pyrido[2,3-d]pyrimidine plane, in contrast to the gauche-trans conformation normally observed. As a result of these changes, the N9 methyl probes conformational space in the active site not normally occupied by antifolate structures. The N9 methyl of conformer 2-2 makes close contacts to the conserved Leu25 as well as the hydroxyl O atoms of the nicotinamide ribose and Ser64, whereas the other three reversed-bridge conformers make weak hydrophobic contacts with Ile123, Thr61 and Ile65. These antifolates are ten times more selective for pcDHFR than the C9-N10 bridge parent trimetrexate. However, pyrido[2,3-d]pyrimidines (2) and (3) are three times more selective for pcDHFR than quinazoline (1) is for rat liver DHFR. These data suggest that the loss of hydrogen-bonding interactions with N8 is more important to potency than the interactions of the methoxybenzyl substituents.

II. Synthesis and biological evaluation of some bioisosteres and congeners of the antitumor agent, 2-(4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy)propionic acid (XK469).

XK469 (1) is among the most highly and broadly active antitumor agents to have been evaluated in our laboratories. Subsequent developmental studies led to the entry of (R)-(+) 1 (NSC 698215) into phase 1 clinical trials (NIH UO1-CA62487). The antitumor mechanism of action of 1 remains to be elucidated, which has prompted a sustained effort to elaborate a pharmacophoric pattern of 1. The present study focused on a strategy of synthesis and biological evaluation of topologically based, bioisosteric replacements of the quinoxaline moiety in the lead compound (1) by quinazoline (4a-d), 1,2,4-benzotriazine (12a-18b), and quinoline (21a-g) ring systems. The synthetic approach to each of the bioisosteres of 1 utilized the methodology developed in previous work (see Hazeldine, S. T.; Polin, L.; Kushner, J.; Paluch, J.; White, K.; Edelstein, M.; Palomino, E.; Corbett, T. H.; Horwitz, J. P. Design, Synthesis, and Biological Evaluation of Analogues of the Antitumor Agent 2-(4-[(7-Chloro-2-quinoxalinyl)oxy]phenoxy)propionic acid (XK469). J. Med. Chem. 2001, 44, 1758-1776.), which is extended to the procurement of the benzoxazole (23a,b), benzthiazole (23c,d), pyridine (25a,b), and pyrazine (27) congeners of 1. Only quinoline analogues, bearing a 7-halo (21a,b,d,e) or a 7-methoxy substituent (21g), showed antitumor activities (Br > Cl > CH(3)O > F approximately I), at levels comparable to or greater than the range of activities manifested by 1 and corresponding analogues. At high individual dosages, the (S)-(-) enantiomers of 1 and 21b,d all produce a reversible slowing of nerve-conduction velocity in the mice, the onset of which is characterized by a distinctive dysfunction of the hind legs, causing uncoordinated movements. The condition resolves within 5-10 min. However, at higher dosages, which approach a lethal level, the behavior extended to the front legs, lasting from 20 min to 1 h. By contrast, the (R)-(+) forms of these same agents did not induce the phenomenon of slowing of nerve-conduction velocity.

X-Ray crystal structures of Candida albicans dihydrofolate reductase: high resolution ternary complexes in which the dihydronicotinamide moiety of NADPH is displaced by an inhibitor.

X-ray crystallographic analysis of 5-(4'-substituted phenyl)sulfanyl-2,4-diaminoquinazoline inhibitors in ternary complex with Candida albicans dihydrofolate reductase (DHFR) and NADPH revealed two distinct modes of binding. The two compounds with small 4'-substituents (H and CH3) were found to bind with the phenyl group oriented in the plane of the quinazoline ring system and positioned adjacent to the C-helix. In contrast, the more selective inhibitors with larger 4'-substituents (tert-butyl and N-morpholino) were bound to the enzyme with the phenyl group perpendicular to the quinazoline ring and positioned in the region of the active site that typically binds the dihydronicotinamide moiety of NADPH. The cofactor appeared bound to DHFR but with the disordered dihydronicotinamide swung away from the protein surface and into solution. This unusual inhibitor binding mode may play an important role in the high DHFR selectivity of these compounds and also may provide new ideas for inhibitor design.

Binding Mode of the 4-Anilinoquinazoline Class of Protein Kinase Inhibitor: X-ray Crystallographic Studies of 4-Anilinoquinazolines Bound to Cyclin-Dependent Kinase 2 and p38 Kinase

4-Anilinoquinazolines represent an important class of protein kinase inhibitor. Modes of binding for two members of this inhibitor class were determined by X-ray crystallographic analysis of one inhibitor (4-[3-hydroxyanilino]-6,7-dimethoxyquinazoline) in complex with cyclin-dependent kinase 2 (CDK2) and the other (4-[3-methylsulfanylanilino]-6,7-dimethoxyquinazoline) in complex with p38 kinase. In both inhibitor/kinase structures, the 4-anilinoquinazoline was bound in the ATP site with the quinazoline ring system oriented along the peptide strand that links the two domains of the protein and with the anilino substituent projecting into a hydrophobic pocket within the protein interior. In each case, the nitrogen at position-1 of the quinazoline accepted a hydrogen bond from a backbone NH (CDK2, Leu-83; p38, Met-109) of the domain connector strand, and aromatic hydrogen atoms at C2 and C8 interacted with backbone carbonyl oxygen atoms of the peptide strand. The anilino group of the CDK2-bound compound was essentially coplanar with the quinazoline ring system and occupied a pocket between Lys-33 and Phe-80. For the p38-bound inhibitor, the anilino group was angled out of plane and was positioned between Lys-53 and Thr-106 in a manner similar to that observed for the aryl substituent of the pyridinylimidazole class of inhibitor.

ChemInform Abstract: Synthesis of [1,2‐b] and [2,1‐b]Quinazoline Ring Systems via Suitably Substituted α‐Cyanoamines.

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Synthesis of [1,2-b] and [2,1-b]Quinazoline Ring Systems via Suitably Substituted α-Cyanoamines

Synthesis of [1,2-<i>b</i>] and [2,1-<i>b</i>]Quinazoline Ring Systems via Suitably Substituted α-Cyanoamines

Substituted xanthines, pteridinediones, and related compounds as potential antiinflammatory agents. Synthesis and biological evaluation of inhibitors of tumor necrosis factor alpha.

A series of analogues of pentoxifylline metabolites were prepared in the purine, pteridine, [1,2,5]-thiadiazolo[3,4-d]pyrimidine, and quinazoline ring systems and evaluated for their ability to inhibit the production of tumor necrosis factor-alpha (TNF alpha) in human peripheral blood monocytes stimulated with bacterial lipopolysaccharide (LPS). The more active compounds were also tested for inhibition of cyclic AMP phosphodiesterase type IV (PDE IV) from human neutrophils in order to help determine their mechanism of action. Selected compounds which showed good activity in the in vitro TNF alpha assay were evaluated in an in vivo LPS-induced leukopenia model in mice. The most potent compounds in the TNF alpha assay, 6, 31, and 58, inhibited TNF alpha production at an IC50 of approximately 5 microM for each. Compound 58 was a very poor inhibitor of PDE IV but was the most active at preventing the leukopenia induced by TNF alpha in mice, providing more than 60% protection at 50 mg/kg. Thus, compounds such as 58, which are good inhibitors of TNF alpha production but are devoid of PDE IV inhibitory properties, may have potential as new antiinflammatory agents.

Concise Syntheses of the Novel 1H-Pyrrolo[3,2-g]quinazoline Ring System and its [2,3-f] Angular Isomer

Concise Syntheses of the Novel 1<i>H</i>-Pyrrolo[3,2-<i>g</i>]quinazoline Ring System and its [2,3-<i>f</i>] Angular Isomer

Mesoionic 1,2,4‐triazolo[4,3‐c]quinazolines

AbstractBecause of the close structural similarity between triazoloquinazolines and certain 5‐membered ring mesoionic heterocycles, all of which possess antiinflammatory activity, we prepared several examples of the novel mesoionic 1,2,4‐triazolo[4,3‐c]quinazoline ring system for their therapeutic potential. These compounds can be prepared by the cyclization of the appropriately substituted 4‐hydrazinoquinazolines with phosgene. When the mesoionic product was unsubstituted at the 5‐position (i.e., quinazoline 2‐position), it could only be isolated as its hydrochloride salt and not as its unstable free base. None of the mesoionic products were sufficiently stable in solution to allow for evaluation of their antiinflammatory activity.

Base Catalyzed Rearrangement of Isoxazolinyl Heterocycles: Synthesis of Annelated Pyrimidines

The rearrangement of a number of ethyl 2-(heterocyclic)-5-oxo-2,5-dihydroisoxazole-4-carb-oxylates by mild base is described, leading to new syntheses of the pyrimido [2,1-a] isoquinoline, pyrimido [1,2-a]quinoline, pyrimido [2,1-b] benzothiazole , pyrirnido [1,2-a] pyrimidine, pyrimido [1,2-b]pyridazine and pyrimido [1,2-c] quinazoline ring systems. A mechanism is suggested, and X-ray crystallographic evidence presented for the structure of one of the products, ethyl 2-hydroxy-4-oxo-4H-pyrimido[2,1-a]isoquinoline-3-carboxylate.