Pyrrolo[3,2-h]quinazolines as Photochemotherapeutic Agents

Recent developments using malononitrile in ultrasound-assisted multicomponent synthesis of heterocycles

Ultrasonic irradiation serves as a vigorous and environmentally sustainable approach for augmenting multicomponent reactions (MCRs), offering benefits such as thermal enhancement, agitation, and activation, among others. Malononitrile emerges as a versatile reagent in this context, participating in a myriad of MCRs to produce structurally diverse heterocyclic frameworks. This review encapsulates the critical role of malononitrile in the sonochemical multicomponent synthesis of these heterocyclic structures. The paper further delves into the biochemical and pharmacological implications of these heterocycles, elucidating their reaction mechanisms as well as delineating the method's scope and limitations. We furnish an overview of the merits and challenges inherent to this synthetic approach and offer insights for potential avenues in future research.

Recent Advances in the Transition-Metal-Free Synthesis of Quinazolines

Quinazolines are a privileged class of nitrogen-containing heterocycles, widely present in a variety of natural products and synthetic chemicals with a broad spectrum of biological and medicinal activities. Owing to their pharmaceutical applications and promising biological value, a variety of synthetic methodologies have been reported for these scaffolds. From the perspective of green and sustainable chemistry, transition-metal-free synthesis provides an alternative method for accessing several biologically active heterocycles. In this review, we summarize the recent progress achieved in the transition-metal-free synthesis of quinazolines and we cover the literature from 2015 to 2022. This aspect is present alongside the advantages, limitations, mechanistic rationalization, and future perspectives associated with the synthetic methodologies.

TMSOTf-catalyzed synthesis of substituted quinazolines using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

An efficient synthetic route for the synthesis of substituted quinazolines under neat, metal-free and microwave irradiation conditions has been developed by using TMSOTf as an acid catalyst and HMDS as a nitrogen source.

Hydrotalcite Clay+[TBA][OH] Ionic Liquid Combination for Selective Dihydroquinazolines

Background:

We are submitting an easy, effective and environmentally benign protocol for the synthesis of 18 different 1,2-dihydroquinazoline derivatives.

Methods:

We implemented [TMA][OH] ionic liquid mediated hydrotalcite clay catalytic system as a green catalyst to perform this reaction.

Results:

Three-component reaction pathway was utilized to synthesize 1,2-dihydroquinazoline derivatives using aromatic aldehydes, 2-amino benzophenones, and ammonium acetate with green and recyclable ionic liquid mediated hydrotalcite clay catalytic system.

Conclusion:

The notable highlights of this method comprise short reaction time, operational simplicity, high yields, and high selectivity. Additionally, the catalyst can be recovered and recycled for up to eight cycles without any loss in catalytic activity.

New insights into the mechanism of action of pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-one derivatives endowed with anticancer potential

Due to the scarce biological profile, the pyrazolo[1,2-a]benzo[1,2,3,4]tetrazine-3-one scaffold (PBT) has been recently explored as promising core for potential anticancer candidates. Several suitably decorated derivatives (PBTs) exhibited antiproliferative activity in the low-micromolar range associated with apoptosis induction and cell cycle arrest on S phase. Herein, we selected the most active derivatives and submitted them to further biological explorations to deepen the mechanism of action. At first, a DNA targeting is approached by means of flow Linear Dichroism experiments so as to evaluate how small planar molecules might interact with DNA, including the interference with the catalytic cycle of topoisomerase II and the influence on the cleavable complex stabilization (poisoning effect). In support of the experimental data, in silico studies have been achieved to better understand the chemical space of the interactions. Interestingly some meaningful structural features, useful for further developments, were found. The 8,9-di-Cl substituted derivative revealed as the most effective in the intercalative process, as well as on the inhibition of catalytic activity of topoisomerase II. Predicted ADME studies confirm that PBTs are promising as potential drug candidates.

Pyrrolo[3',2':6,7]cyclohepta[1,2-b]pyridines with potent photo-antiproliferative activity

Pyrrolo[3',2':6,7]cyclohepta[1,2-b]pyridines were synthesized as a new class of tricyclic system in which the pyridine ring is annelated to a cycloheptapyrrole scaffold, with the aim of obtaining new photosensitizing agents with improved antiproliferative activity and lower undesired toxic effects. A versatile synthetic pathway was approached, which allowed the isolation of derivatives of the title ring system with a good substitution pattern on the pyrrole moiety. Photobiological studies revealed that the majority of the new compounds showed a potent cytotoxic effect upon photoactivation with light of the proper wavelength, especially when decorated with a 2-ethoxycabonyl group and a N-benzyl substituted moiety, with EC₅₀ values reaching the submicromolar level. The mechanism of action was evaluated.

Ultrasound Mediated One-Pot, Three Component Synthesis, Docking and ADME Prediction of Novel 5-Amino-2-(4-chlorophenyl)-7-Substituted Phenyl-8,8a-dihydro-7H-(1,3,4)thiadiazolo(3,2-α)pyrimidine-6-carbonitrile Derivatives as Anticancer Agents

Herein, we report an environmentally friendly, rapid, and convenient one-pot ultrasound-promoted synthesis of 5-amino-2-(4-chlorophenyl)-7-substituted phenyl-8,8a-dihydro-7H-(1,3,4)thiadiazolo(3,2-α)pyrimidine-6-carbonitrile derivatives. The in-vitro anticancer activities of these compounds were evaluated against four human tumor cell lines. Among all the synthesized derivatives, compound 4i, which has substituent 3-hydroxy-4-methoxyphenyl is found to have the highest GI₅₀ value of 32.7 μM, 55.3 μM, 34.3 μM, 28.9 μM for MCF-7, K562, HeLa and PC-3 cancer cell lines respectively. A docking study of the newly synthesized compounds were performed, and the results showed good binding mode in the active site of thymidylate synthase enzyme. ADME properties of synthesized compounds were also studied and showed good drug like properties.

Preclinical Activity of New [1,2]Oxazolo[5,4-e]isoindole Derivatives in Diffuse Malignant Peritoneal Mesothelioma

A series of 22 derivatives of the [1,2]oxazolo[5,4-e]isoindole system were synthesized through an efficient and versatile procedure that involves the annelation of the [1,2]oxazole moiety to the isoindole ring, producing derivatives with a wide substitution pattern. The structure-activity relationship indicates that the N-4-methoxybenzyl group appears crucial for potent activity. In addition, the presence of a 6-phenyl moiety is important and the best activity is reached with a 3,4,5-trimethoxy substituent. The most active compound, bearing both the structural features, was able to inhibit tumor cell proliferation at nanomolar concentrations when tested against the full NCI human tumor cell line panel. Interestingly, this compound was effective in reducing in vitro and in vivo cell growth, impairing cell cycle progression and inducing apoptosis, as a consequence of the inhibition of tubulin polymerization, in experimental models of diffuse malignant peritoneal mesothelioma (DMPM), a rapidly lethal disease, poorly responsive to conventional therapeutic strategies.

Synthesis and antiproliferative mechanism of action of pyrrolo[3',2':6,7] cyclohepta[1,2-d]pyrimidin-2-amines as singlet oxygen photosensitizers

A new series of pyrrolo[3',2':6,7]cyclohepta[1,2-d]pyrimidin-2-amines, was conveniently prepared using a versatile and high yielding multistep sequence. A good number of derivatives was obtained and the cellular photocytotoxicity was evaluated in vitro against three different human tumor cell lines with EC50 (0.08-4.96 μM) values reaching the nanomolar level. Selected compounds were investigated by laser flash photolysis. The most photocytotoxic derivative, exhibiting a fairly long-lived triplet state (τ ∼ 7 μs) and absorbance in the UV-Vis, was tested in the photo-oxidations of 9,10-anthracenedipropionic acid (ADPA) by singlet oxygen. The photosentizing properties are responsible for the compounds' ability to photoinduce massive cell death with involvement of mitochondria.

Pyrazolo[3,4-h]quinolines promising photosensitizing agents in the treatment of cancer

A new series of pyrazolo[3,4-h]quinolines, heteroanalogues of angelicin was conveniently prepared with a broad substitution pattern. A large number of derivatives was obtained and the cellular photocytotoxicity was evaluated in vitro against 5 different human tumor cell lines with GI50 values reaching the nanomolar level (14.52-0.04 μM). Selected compounds were able to photoinduce a massive cell death with the involvement of mitochondria. Their photodamage cellular targets were proteins and lipids and they did not cause any kind of DNA photodamage. This latter event is of considerable importance in the modulation of long term side effects, generally associated with the use of classical furocoumarins.

3-[4-(1H-indol-3-yl)-1,3-thiazol-2-yl]-1H-pyrrolo[2,3-b]pyridines, nortopsentin analogues with antiproliferative activity

A new series of nortopsentin analogues, in which the imidazole ring of the natural product was replaced by thiazole and the indole unit bound to position 2 of the thiazole ring was substituted by a 7-azaindole moiety, was efficiently synthesized. Two of the new nortopsentin analogues showed good antiproliferative effect against the totality of the NCI full panel of human tumor cell lines (~60) having GI₅₀ values ranging from low micromolar to nanomolar level. The mechanism of the antiproliferative effect of these derivatives, investigated on human hepatoma HepG2 cells, was pro-apoptotic, being associated with externalization of plasma membrane phosphatidylserine and mitochondrial dysfunction. Moreover, the compounds induced a concentration-dependent accumulation of cells in the subG0/G1phase, while confined viable cells in G2/M phase.

Water-soluble isoindolo[2,1-a]quinoxalin-6-imines: in vitro antiproliferative activity and molecular mechanism(s) of action

Water-soluble isoindoloquinoxalin (IIQ) imines and the corresponding acetates were conveniently prepared from the key intermediates 2-(2'-aminophenyl)-2H-isoindole-1-carbonitriles obtained by a Strecker reaction between substituted 1,2-dicarbaldehydes and 1,2-phenylenediamines. Both series were screened by the National Cancer Institute (Bethesda, MD) and showed potent antiproliferative activity against a panel of 60 human tumor cell lines. Several of the novel compounds showed GI50 values at a nanomolar level on the majority of the tested cell lines. Among IIQ derivatives, methoxy substituents at positions 3 and 8 or/and 9 were especially effective in impairing cell cycle progression and inducing apoptosis in cancer cells. These effects were associated to IIQ-mediated impairment of tubulin polymerization at pharmacologically significant concentrations of tested compounds. In addition, impaired DNA topoisomerase I functions and perturbation in telomere architecture were observed in cells exposed to micromolar concentrations of IIQ derivatives. The above results suggest that IIQ derivatives exhibit multi-target cytotoxic activities.

Synthesis and antiproliferative activity of thiazolyl-bis-pyrrolo[2,3-b]pyridines and indolyl-thiazolyl-pyrrolo[2,3-c]pyridines, nortopsentin analogues

Two new series of nortopsentin analogues, in which the imidazole ring of the natural product was replaced by thiazole and indole units were both substituted by 7-azaindole moieties or one indole unit was replaced by a 6-azaindole portion, were efficiently synthesized. Compounds belonging to both series inhibited the growth of HCT-116 colorectal cancer cells at low micromolar concentrations, whereas they did not affect the viability of normal-like intestinal cells. A compound of the former series induced apoptosis, evident as externalization of plasma membrane phosphatidylserine (PS), and changes of mitochondrial trans-membrane potential, while blocking the cell cycle in G2/M phase. In contrast, a derivative of the latter series elicited distinct responses in accordance with the dose. Thus, low concentrations (GI₃₀) induced morphological changes characteristic of autophagic death with massive formation of cytoplasmic acid vacuoles without apparent loss of nuclear material, and with arrest of cell cycle at the G1 phase, whereas higher concentrations (GI₇₀) induced apoptosis with arrest of cell cycle at the G1 phase.

Synthesis of the new ring system bispyrido[4',3':4,5]pyrrolo [1,2-a:1',2'-d]pyrazine and its deaza analogue

Derivatives of the new ring systems bispyrido[4',3':4,5]pyrrolo[1,2-a:1',2'-d]pyrazine-6,13-dione and its deaza analogue pyrido[4'',3'':4',5']pyrrolo-[1',2':4,5]pyrazino[1,2-a]indole-6,13-dione were conveniently synthesized through a four-step sequence. Symmetrical derivatives of the former ring system were obtained through self condensation. On the other hand, condensation of 6-azaindole carboxylic acid with indole 2-carboxylic acid afforded the deaza analogue ring system. Derivatives of the title ring system were tested by the National Cancer Institute (Bethesda, MD, USA) and four of them exhibited modest activity against MCF7 (a breast cancer cell line) and/or UO-31 (a renal cancer cell line).

Synthesis and biological evaluation of certain 3-substituted benzylideneamino-2-(4-nitrophenyl)quinazolin-4(3H)-one derivatives

Certain new 3H-quinazolin-4-one Schiff's bases were synthesized and screened for their activities against ulcerative colitis "UC". Their activity against phospholipase A2 and protease enzymes was also investigated. Some compounds possessed remarkable effect with different potentials against acetic acid-induced colitis model in rats. Compound 14 (50 mg/kg) was more effective than dexamesathone (0.01 mg/kg). It produced 79.78% protection of control colitis; however, compound 13 produced 75.80% protection and was considered as effective as dexamesathone with 75.30% protection. The observed results could be explained partially by their anti-inflammatory activities which appear as phospholipase A2 (hGIIA) and/or through protease inhibitor potentials. However, all the compounds under test showed preferential inhibition towards hG-IIA type of PLA2 rather than DrG-IB with varying degrees. Interestingly, compounds 14, 13, 12 and 11 displayed excellent inhibitory activity against phospholipase A2 accompanied by protease inhibitory profile.

One-pot tandem synthesis of 2-arylquinazolines by a multicomponent cyclization reaction

A series of 2-arylquinazolines have been synthesized in moderate to excellent yields by one-pot tandem reaction of (2-aminophenyl)methanols, aldehydes and ceric ammonium nitrate (CAN). The utility of this transformation was demonstrated by its compatibility with a wide range of functional groups. Thus, the method represents a simple and practical procedure to access 2-arylquinazolines.

Novel 1H-pyrrolo[2,3-b]pyridine derivative nortopsentin analogues: synthesis and antitumor activity in peritoneal mesothelioma experimental models

In this study, we describe the synthesis of new nortopsentin analogues, 1H-pyrrolo[2,3-b]pyridine derivatives and their biological effects in experimental models of diffuse malignant peritoneal mesothelioma (DMPM), a rare and rapidly fatal disease, poorly responsive to conventional therapies. The three most active compounds, 1f (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1H-pyrrolo[2,3-b]pyridine), 3f (3-[2-(1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b]pyridine), and 1l (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b] pyridine), which were shown to act as cyclin-dependent kinase 1 inhibitors, consistently reduced DMPM cell proliferation and induced a caspase-dependent apoptotic response, with a concomitant reduction of the expression of the active Thr(34)-phosphorylated form of the antiapoptotic protein survivin. Moreover, the combined treatment of DMPM cells with 3f derivative and paclitaxel produced a synergistic cytotoxic effect, which was paralleled by an enhanced apoptotic response. In the mouse model, i.p. administration of 1f, 3f, and 1l derivatives was effective, resulting in a significant tumor volume inhibition of DMPM xenografts (range, 58-75%) at well-tolerated doses, and two complete responses were observed in each treatment group.