Thieno[2,3-d]pyrimidine as a promising scaffold in medicinal chemistry: Recent advances

A decade's overview of 2-aminothiophenes and their fused analogs as promising anticancer agents

Over the past decades, cancer has been a challenging domain for medicinal chemists as it is an international health concern. In association, small molecules such as 2-aminothiophenes and their derivatives showed significant antitumor activity through variable modes of action. Therefore, this article aims to review the advances regarding these core scaffolds over the past 10 years, where 2-aminothiophenes and their fused analogs are classified and discussed according to their biological activity and mode of action, in the interest of boosting new design pathways for medicinal chemists to develop targeted antitumor candidates.

Design and one-pot synthesis of new substituted pyrrolo[1,2-a]thieno[3,2-e]pyrimidine as potential antitumor agents: in vitro and in vivo studies

A new efficient and versatile one-pot three-component synthesis of substituted pyrrolo[1,2-a]thieno[3,2-e]pyrimidine derivatives has been developed. It is based on a multistep cascade reaction from 2-aminothiophenes and 2-hydroxy-4-oxobut-2-enoic acids, and derivatives of cyanoacetic acid catalyzed by diisopropylethylamine. As a result, novel pyrrolo[1,2-a]thieno[3,2-e]pyrimidine derivatives (21 compounds) were synthesized in a mild reaction conditions with a high yield. The structures of the developed compounds were confirmed by NMR and elemental analysis. The influence of electron-withdrawing or electron-donor substituents on the antitumor activity of the developed compounds has been identified. In vitro screening analysis of 21 compounds revealed six lead candidates (12aa, 12dc, 12hc, 12ic, 12lb, and 12mb) that demonstrated the most significant antitumor activity against B16-F10, 4T1 and CT26 cells. Necrosis/apoptosis assay showed that apoptosis was the predominant mechanism of cell death. Molecular docking analysis revealed several potential targets for tested compounds, i.e. phosphatidylinositol 5-phosphate 4-kinase (PI5P4K2C), proto-oncogene serine/threonine-protein kinase (Pim-1), nicotinamide phosphoribosyltransferase (NAMPT) and dihydrofolate reductase (DHFR). The lead compound (12aa) can effectively induce cell apoptosis, possesses a high yield (98 %) and requires low-cost starting chemicals for its synthesis. In vivo experiments with melanoma-bearing mice confirmed that 12aa compound resulted in the significant tumor inhibition on 15 d after the therapy. In particular, tumor volume was ∼0.19 cm3 for 50 mg/kg versus ∼2.39 cm3 in case of untreated mice and tumor weight was ∼71.6 mg for 50 mg/kg versus ∼452.4 mg when considered untreated mice. Thus, our results demonstrated the high potential of the 12aa compound in the treatment of melanoma and can be recommended for further preclinical studies.

Medicinal attributes of thienopyrimidine scaffolds incorporating the aryl urea motif as potential anticancer candidates via VEGFR inhibition

Worldwide, cancer is a major public health concern. It is a well-acknowledged life-threatening disease. Despite numerous advances in the understanding of the genetic basis of cancer growth and progression, therapeutic challenges remain high. Human tumors exhibited mutation or overexpression of several tyrosine kinases (TK). The vascular endothelial growth factor receptor (VEGFR) is a TK family member and is well known for tumor growth and progression. Therefore, VEGF/VEGFR pathway inhibition is an appealing approach for cancer drug discovery. This review will discuss the structure-based optimization of thienopyrimidines incorporating the aryl urea moiety to develop scaffolds of potent anticancer activity via VEGFR inhibition published between 2013 and 2023. Increasing knowledge of probable scaffolds that can act as VEGFR inhibitors might spur the hunt for novel anticancer medications that are safer, more effective, or both.

Identification of thienopyrimidine derivatives tethered with sulfonamide and other moieties as carbonic anhydrase inhibitors: Design, synthesis and anti-proliferative activity

Eighteen novel compounds harboring the privileged thienopyrimidine scaffold (5a-q, and 6a),were designed based on molecular hybridization strategy. These compounds were synthesized and tested for their inhibitory activity against four different carbonic anhydrase isoforms: CA I, II, IX, and XII. Microwave and conventional techniques were applied for their synthesis. Compounds 5b, 5g, 5l, and 5p showed the highest inhibition activity against the four CA isoforms. Compound 5p exhibited promising inhibitory activity against CA II, CA IX and CA XII with KI values of8.6, 13.8, and 19 nM, respectively, relative to AAZ, where KIs = 12, 25, and 5.7 nM, respectively. Also, compound 5 l showed significant activity against the tumor-associated isoform CA IX with KI = 16.1 nM. All the newly synthesized compounds were also screened for their anticancer activity against NCI 60 cancer cell lines at a 10 µM concentration. Compound 5n showed 80.38, 83.95, and 87.39 % growth inhibition against the leukemic cell lines CCRF-CEM, HL-60 (TB), and RPMI-8226, respectively. Also, 5 h showed 87.57 % growth inhibition against breast cancer cell line MDA-MB-468; and 66.58 and 60.95 % inhibitionagainst renal cancer cell lines UO-31, and ACHN, respectively. A molecular docking studywas carried out to predict binding modes of our synthesized compounds in the binding pockets of the four carbonic anhydrase isoforms, and results revealed that compounds 5b, 5g, 5l, and 5p succeeded in mimicking the binding mode of AAZ through metal coordination with Zn+2 ion and binding to the amino acids Thr199, His94, and His96 that are critical for activity.

Cyclizations of Alkenyl(Alkynyl)-Functionalized Quinazolinones and their Heteroanalogues: A Powerful Strategy for the Construction of Polyheterocyclic Structures

Quinazolin-4-one, its heteroanalogues, and derivatives represent an outstandingly important class of compounds in modern organic, medicinal, and pharmaceutical chemistry, as these molecular structures are noted for their wide synthetic and pharmacological potential. In the last years, ever-increasing research attention has been paid to quinazolinone derivatives bearing alkenyl and alkynyl substituents on the pyrimidinone nucleus. The original structural combination of synthetically powerful endocyclic amidine (or amidine-related) and exocyclic unsaturated moieties provides a driving force for cyclizations, which offer an efficient toolkit to construct a variety of fused pyrimidine systems with saturated N- and N,S-heterocycles. In this connection, the present review article is mainly aimed at systematic coverage of the progress in using alkenyl(alkynyl)quinazolinones and their heteroanalogues as convenient bifunctional substrates for regioselective annulation of small- and medium-sized heterocyclic nuclei. Much attention is paid to elucidating the structural and electronic effects of reagents on the regio- and stereoselectivity of the cyclizations as well as to clarifying the relevant reaction mechanisms.

Discovery of new VEGFR-2 inhibitors and apoptosis inducer-based thieno[2,3-d]pyrimidine

Background: VEGFR-2 is a key regulator of cancer cell proliferation, migration and angiogenesis. Aim: Development of thieno[2,3-d]pyrimidine derivatives as potential anti-cancer agents targeting VEGFR-2. Methods: Seven in vitro and nine in silico studies were conducted. Results: Compound 10d demonstrated strong anticancer potential, boosting apoptosis based on VEGFR-2 inhibition. It arrested the S phase of the cell cycle and upregulated the apoptotic factors. Docking and molecular dynamics simulation studies confirm the stability of the VEGFR-2-10d complex and suggest that these compounds have good binding affinities to VEGFR-2. In addition, the drug-likeness was confirmed. Conclusion: Thieno[2,3-d]pyrimidines, particularly compound 10d, has good anticancer effects and may contribute to the development of new anticancer therapies.

2-Alkyl-Substituted-4-Amino-Thieno[2,3-d]Pyrimidines: Anti-Proliferative Properties to In Vitro Breast Cancer Models

Thienopyrimidines are structural analogs of quinazolines, and the creation of new 2-alkyl derivatives of ethyl 4-aminothienopyrimidine-6-carboxylates for the study of their anti-proliferative properties is of great pharmacological interest. Some 2-alkyl-4-amino-thieno[2,3-d]pyrimidines 2-5 were synthesized, and their cyto- and phototoxicity against BALB 3T3 cells were established by an in vitro 3T3 NRU test. The obtained results indicate that the tested compounds are not cytotoxic or phototoxic, and that they are appropriate to be studied for their anti-proliferative and anti-tumor properties. The anti-proliferative potential of the compounds was investigated on MCF-7 and MDA-MB-231 cancer cells, as well as a MCF-10A cell line (normal human mammary epithelial cells). The most toxic to MCF-7 was thienopyrimidine 3 with IC50 13.42 μg/mL (IC50 0.045 μM), followed by compound 4 (IC50 28.89 μg/mL or IC50 0.11 μM). The thienopyrimidine 4 revealed higher selectivity to MCF-7 and lower activity (IC50 367 μg/mL i.e., 1.4 μM) than compound 3 with MCF-10A cells. With respect to MDA-MB-231 cells, ester 2 manifested the highest effect with IC50 52.56 μg/mL (IC50 0.16 μM), and 2-ethyl derivative 4 revealed IC50 62.86 μg/mL (IC50 0.24 μM). It was estimated that the effect of the substances on the cell cycle progression was due to cell cycle arrest in the G2 stage for MDA-MB-231, while arrest in G1 was detected for the estrogen (ER)-positive MCF-7 cell line. The tested compound's effects on the change of the zeta potential in the tumorigenic cells utilized in this study were determined. The calculation which we performed of the physicochemical properties and pharmacokinetic parameters influencing the biological activity suggested high intestinal absorption, as well as drug-likeness.

Inhibition of FLT3-ITD Kinase in Acute Myeloid Leukemia by New Imidazo[1,2-b]pyridazine Derivatives Identified by Scaffold Hopping

FLT3 kinase is a potential drug target in acute myeloid leukemia (AML). Patients with FLT3 mutations typically have higher relapse rates and worse outcomes than patients without FLT3 mutations. In this study, we investigated the suitability of various heterocycles as central cores of FLT3 inhibitors, including thieno[3,2-d]pyrimidine, pyrazolo[1,5-a]pyrimidine, imidazo[4,5-b]pyridine, pyrido[4,3-d]pyrimidine, and imidazo[1,2-b]pyridazine. Our assays revealed a series of imidazo[1,2-b]pyridazines with high potency against FLT3. Compound 34f showed nanomolar inhibitory activity against recombinant FLT3-ITD and FLT3-D835Y (IC50 values 4 and 1 nM, respectively) as well as in the FLT3-ITD-positive AML cell lines MV4-11, MOLM-13, and MOLM-13 expressing the FLT3-ITD-D835Y mutant (GI50 values of 7, 9, and 4 nM, respectively). In contrast, FLT3-independent cell lines were much less sensitive. In vitro experiments confirmed suppression of FLT3 downstream signaling pathways. Finally, the treatment of MV4-11 xenograft-bearing mice with 34f at doses of 5 and 10 mg/kg markedly blocked tumor growth without any adverse effects.

Design, synthesis, and biological evaluation of thienopyrimidine derivatives as multifunctional agents against Alzheimer's disease

A series of 12 S-substituted tetrahydrobenzothienopyrimidines were designed and synthesized based on the donepezil scaffold. All the newly synthesized compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity and the most active compounds were tested for their butyrylcholinesterase (BuChE) inhibitory activity. Moreover, all the synthesized compounds were evaluated for their inhibitory effects against Aβ aggregation and antioxidant activity using the oxygen radical absorbance capacity method. Compounds 4b, 6b, and 8b displayed the most prominent AChE inhibitory action comparable to donepezil. Compound 6b showed the greatest AChE inhibitory action (IC50  = 0.07 ± 0.003 µM) and the most potent BuChE inhibitory action (IC50  = 0.059 ± 0.004 µM). Furthermore, the three compounds exhibited significant antioxidant activity. Compounds 6b and 8b exerted more inhibitory action on Aβ aggregation than donepezil. The cytotoxic activity of compounds 4b, 6b, and 8b against the WI-38 cell line in comparison with donepezil was examined using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. The results revealed that compounds 6b and 8b were less cytotixic than donepezil, while compound 4b showed nonsignificant cytotoxicity compared to donepezil. For more insights about the binding patterns of the most promising compounds (4b, 6b, and 8b) with the AChE at molecular levels; molecular docking and molecular dynamics simulations were performed. The density functional theory calculations and absorption, distribution, metabolism, excretion and toxicity properties were described as well. The results highlighted compound 6b, which incorporates a phenylpiperazine moiety coupled to a thienopyrimidone scaffold via two-atom spacer, to be a promising multifunctional therapeutic agent for the treatment of Alzheimer's disease. It is a potent dual AChE and BuChE inhibitor. Furthermore, it had stronger Aβ aggregation inhibitory action than donepezil. Additionally, compound 6b exerted significant antioxidant activity.

In Silico Screening and Anticancer-Apoptotic Evaluation of Newly Synthesized Thienopyrimidine/Sulfonamide Hybrids

This work describes the design and synthesis of new hybrids of thienopyrimidine and sulfonamides. The binding affinity of the prepared compounds to FGFR-1 enzyme and caspase-3 was investigated via molecular docking. The cytotoxic effect was estimated for the synthesized compounds against human breast cancer cell lines (MCF-7 and MDA-MB231) using Doxorubicin as a reference. All the tested compounds exhibited moderate to excellent anticancer efficacy against both tested cell lines, among which 3b and 4bi were the best. All the synthesized compounds exhibited distinguishing selectivity index values greater than Doxorubicin. The influence of the new hybrids under inquiry was further examined on both FGFR-1 and Caspase-3. The results revealed that compound 3b showed observed concordance between anti-proliferative activity and Caspase-3 activity. In respect to the compounds' effect on the apoptosis, compound 3b significantly increased the population of late apoptotic cells and necrotic cells. In silico pharmacokinetic investigation revealed that compound 3b showed the best intestinal absorption, BBB permeability, and, along with 4bi and 4bii, the best CNS penetrability.

Synthesis of 3-(Pyridin-2-yl)quinazolin-2,4(1H,3H)-diones via Annulation of Anthranilic Esters with N-pyridyl Ureas

A new route for the synthesis of quinazolin-2,4(1H,3H)-diones and thieno [2,3-d]pyrimidine-2,4(1H,3H)-diones substituted by pyridyl/quinolinyl moiety in position 3 has been developed. The proposed method concluded in an annulation of substituted anthranilic esters or 2-aminothiophene-3-carboxylates with 1,1-dimethyl-3-(pyridin-2-yl) ureas. The process consists of the formation of N-aryl-N'-pyridyl ureas followed by their cyclocondensation into the corresponding fused heterocycles. The reaction does not require the use of metal catalysts and proceeds with moderate to good yields (up to 89%). The scope of the method is more than 30 examples, including compounds with both electron-withdrawing and electron-donating groups, as well as diverse functionalities. At the same time, strong electron-acceptor substituents in the pyridine ring of the starting ureas reduce the product yield or even prevent the cyclocondensation step. The reaction can be easily scaled to gram quantities.

Synthesis of thieno[3,2-e]pyrrolo[1,2-a]pyrimidine derivatives and their precursors containing 2-aminothiophenes fragments as anticancer agents for therapy of pulmonary metastatic melanoma

The design and synthesis of new promising compounds based on thienopyrimidine scaffold containing 2-aminothiophene fragments with good safety and favorable drug-like properties are highly relevant for chemotherapy. In this study, a series of 14 variants of thieno[3,2-e]pyrrolo[1,2-a]pyrimidine derivatives (11aa-oa) and their precursors (31 compounds) containing 2-aminothiophenes fragments (9aa-mb, 10aa-oa) were synthesized and screened for their cytotoxicity against B16-F10 melanoma cells. The selectivity of the developed compounds was assessed by determining the cytotoxicity using normal mouse embryonic fibroblasts (MEF NF2 cells). The lead compounds 9cb, 10ic and 11jc with the most significant antitumor activity and minimum cytotoxicity on normal non-cancerous cells were chosen for further in vivo experiments. Additional in vitro experiments with compounds 9cb, 10ic and 11jc showed that apoptosis was the predominant mechanism of death in B16-F10 melanoma cells. With support from in vivo studies, compounds 9cb, 10ic and 11jc demonstrated the biosafety to healthy mice and significant inhibition of the metastatic nodules in pulmonary metastatic melanoma mouse model. Histological analysis detected no abnormal changes in the main organs (the liver, spleen, kidneys, and heart) after the therapy. Thus, the developed compounds 9cb, 10ic and 11jc demonstrate high efficiency in the treatment of pulmonary metastatic melanoma and can be recommended for further preclinical investigation of the melanoma treatment.

Recent updates on thienopyrimidine derivatives as anticancer agents

Thienopyrimidine derivatives hold a unique place between fused pyrimidine compounds. They are important and widely represented in medicinal chemistry as they are structural analogs of purines. Thienopyrimidine derivatives have various biological activities. The current review discusses different synthetic methods for the preparation of heterocyclic thienopyrimidine derivatives. It also highlights the most recent research on the anticancer effects of thienopyrimidines through the inhibition of various enzymes and pathways, which was published within the last 9 years.

Graphical Abstract

Thienopyrimidine-based agents bearing diphenylurea: Design, synthesis, and evaluation of antiproliferative and antiangiogenic activity

An important role has been considered for the vascular endothelial growth factor receptor 2 (VEGFR-2) in the angiogenesis process, so that its inhibition is an important scientific way for cancer treatment. In this work, new thienopyrimidine derivatives were synthesized and evaluated. Compared with sorafenib, the majority of the target compounds had antiproliferative activity against the PC3, HepG2, MCF7, SW480, and HUVEC cell lines, especially 9h with IC₅₀ values of 4.5-15.1 μM, confirming the noticeable cytotoxic effects on the listed cell lines (PC3, HepG2, SW480, and HUVEC). Analyses by flow cytometry on SW480 and HUVEC cells revealed that 9n, 9k, 9h, and 9q led to apoptotic cell death. The result of the chick chorioallantoic membrane assay showed that 9h effectively reduced the number of corresponding blood vessels. Finally, the inhibitory effect on VEGFR-2 phosphorylation was considered as the outcome of Western blot analysis of compound 9h.

Synthesis and Theoretical Studies of Biologically Active Thieno Nucleus Incorporated Tri and Tetracyclic Nitrogen Containing Heterocyclics Scaffolds via Suzuki Cross-Coupling Reaction

A new series of thieno nucleus embellished trinuclear (19, 20) and tetranuclear (21-24) nitrogen heteroaryl have been synthesized by the Suzuki cross-coupling reaction using bis(triphenylphosphine)palladium(II) dichloride. All the synthesized compounds were characterized by IR, ¹ H-NMR, ¹³ CNMR and Mass spectral properties. In vitro antibacterial studies of the synthesized compound were conducted using broth microdilution assay employing Gram-positive and Gram-negative strains and half-maximal inhibitory concentration (IC₅₀ ) was determined. The result showed that compound 20 possess best antibacterial activity against S. aureus and E. coli with IC₅₀ values of 60 μg mL^-1 and 90 μg mL^-1 . Further to determine the mode of antibacterial action, compounds 20 and 21 were examined for in vitro bacterial dehydrogenase inhibitory assay. To understand the binding affinity of the synthesized compounds, the docking study was performed in the bacterial dehydrogenase enzyme by AutoDock Vina software and structure was confirmed by Discovery Studio Visualizer. All the synthesized compounds were docked in a good manner within the active sites of the bacterial dehydrogenase enzyme and exhibited good binding energies.

Thieno[2,3-d]pyrimidine-Core Compounds Show Activity Against Clinically Relevant Gram-Positive Bacteria

Thieno[2,3- d ]pyrimidines represent a novel antibacterial prodrug scaffold, previously identified through a screening campaign against Mycobacterium tuberculosis in which the formation of highly antimycobacterial metabolites catalyzed by the nitroreductase Mrx2 is suggested to be the relevant killing mechanism. As analogical activation pathways may also be employed in other prokaryotes, in this work we explored general antibacterial effects of this compound class. Through exploration of the chemical space by different synthetic strategies, 51 novel derivatives were generated, biologically evaluated and thus enabled initial conclusions about structure-activity-relationships. Remarkably, anti-Gram-positive activity can be well modulated, particularly towards Staphylococci (MRSA) and even slightly against some Gram-negative strains. The two most promising hit compounds showed good pharmacokinetic properties in vitro as well as acceptable toxicity in HeLa cells qualifying them as starting points for lead generation campaigns.

1,3-Bis(5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4-yl)imidazolidine-4,5-dione

A thieno[2,3-d]pyrimidine derivative 3 bearing a 4,5-imidazolidinedione moiety, 1,3-bis(5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4-yl)imidazolidine-4,5-dione, was efficiently synthesized in 66% yield by the reaction of N,N′-bis(5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4-yl)methanediamine 2 with oxalyl chloride in the presence of pyridine in refluxing dichloroethane for 10 h. The structure of the new synthesized compounds was fully characterized by 1H, 13C NMR, IR spectroscopy, mass-spectrometry and elemental analysis.

Pd-catalyzed C-C and C-N cross-coupling reactions in 2-aminothieno[3,2-d]pyrimidin-4(3H)-one series for antiplasmodial pharmacomodulation

In 2015, we identified gamhepathiopine (M1), a 2-tert-butylaminothieno[3,2-d]pyrimidin-4(3H)-one antiplasmodial hit targeting all development stages of the human malarial parasite P. falciparum. However, this hit compound suffers from sensitivity to hepatic oxidative metabolism. Herein, we describe the synthesis of 33 new compounds in the 2-aminothieno[3,2-d]pyrimidin-4(3H)-one series modulated at position 6 of this scaffold. The modulations were performed using three palladium-catalyzed cross coupling reactions, namely Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig. For the latter, we developed the reaction conditions. Then, we evaluated the synthesized compounds for their antiplasmodial activity on the K₁ P. falciparum strain and their cytotoxicity on the human HepG2 cell line. Although we did not obtain a compound better than M1 in terms of the antiplasmodial activity, we identified compound 1g bearing a piperidine at position 6 of the thieno[3,2-d]pyrimidin-4(3H)-one ring with an improved cytotoxicity and metabolic stability. 1g is an interesting new starting point for further pharmacomodulation studies. This study also provides valuable antiplasmodial SAR data regarding the nature of the ring at position 6, the possible substituent on this ring, and the introduction of a spacer between this ring and the thienopyrimidinone moiety.

Design, synthesis and antibacterial activity of novel pleuromutilin derivatives with thieno[2,3-d]pyrimidine substitution

A series of novel pleuromutilin derivatives with substituted thienopyrimidines were designed, synthesized, and evaluated for antibacterial act ivity. In this study, the activities of these compounds were investigated using the inhibition circle test, the minimum inhibitory concentration (MIC) test, real-time growth curves, time-kill kinetic assays, cytotoxicity assays, and molecular docking. Most of the tested compounds exhibited moderate antibacterial activity against Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli. Compound A11 was the most active and displayed bacteriostatic activities against methicillin-resistant S. aureus, with MIC values as low as 0.00191 μg/mL, which is 162 and 32 times lower than that of the marketed antibiotics tiamulin and retapamulin, respectively. Furthermore, the mechanism of action of A11 was confirmed by molecular docking studies.

In Vitro Anticancer Activity Screening of Novel Fused Thiophene Derivatives as VEGFR-2/AKT Dual Inhibitors and Apoptosis Inducers

Protein kinases are seen as promising targets in controlling cell proliferation and survival in treating cancer where fused thiophene synthon was utilized in many kinase inhibitors approved by the FDA. Accordingly, this work focused on adopting fused thienopyrrole and pyrrolothienopyrimidine scaffolds in preparing new inhibitors, which were evaluated as antiproliferative agents in the HepG2 and PC-3 cell lines. The compounds 3b (IC₅₀ = 3.105 and 2.15 μM) and 4c (IC₅₀ = 3.023 and 3.12 μM) were the most promising candidates on both cells with good selective toxicity-sparing normal cells. A further mechanistic evaluation revealed promising kinase inhibitory activity, where 4c inhibited VEGFR-2 and AKT at IC₅₀ = 0.075 and 4.60 μM, respectively, while 3b showed IC₅₀ = 0.126 and 6.96 μM, respectively. Moreover, they resulted in S phase cell cycle arrest with subsequent caspase-3-induced apoptosis. Lastly, docking studies evaluated the binding patterns of these active derivatives and demonstrated a similar fitting pattern to the reference ligands inside the active sites of both VEGFR-2 and AKT (allosteric pocket) crystal structures. To conclude, these thiophene derivatives represent promising antiproliferative leads inhibiting both VEGFR-2 and AKT and inducing apoptosis in liver cell carcinoma.

In-Silico Screening of Novel Synthesized Thienopyrimidines Targeting Fms Related Receptor Tyrosine Kinase-3 and Their In-Vitro Biological Evaluation

The present investigation describes the design strategy and synthesis of novel thienopyrimidine compounds in addition to their anticancer activity targeting tyrosine kinase FLT3 enzyme. The synthesized compounds were subjected to a cytotoxic study where compounds 9a and 9b showed the most potent cytotoxicity against HT-29, HepG-2, and MCF-7 cell lines reflected by their IC₅₀ values for 9a (1.21 ± 0.34, 6.62 ± 0.7 and 7.2 ± 1.9 μM), for 9b (0.85 ± 0.16, 9.11 ± 0.3 and 16.26 ± 2.3 μM) and better than that of reference standard which recorded (1.4 ± 1.16, 13.915 ± 2.2, and 8.43 ± 0.5 μM), respectively. Compounds’ selectivity to malignant cells was determined using selectivity assay, interestingly, all the tested compounds demonstrated an excellent selectivity index (SI) range from 20.2 to 99.7. Target in-silico prediction revealed the FLT3 kinase enzyme was the kinase enzyme of highest probability. Molecular docking studies were performed on the prepared compounds which showed promising binding affinity for FLT3 kinase enzyme and the main interactions between the synthesized ligands and kinase active site were similar to those between the co-crystallized ligand and the receptor. Further biological exploration was performed using in-vitro FLT3 kinase enzyme inhibition assay. The results showed that the 2-morpholinoacetamido derivative 10a exhibited highest FLT3 inhibitory activity among the tested compounds followed by compound 9a then 12. Pharmacokinetic assessment disclosed that all the investigated compounds were considered as “drug-like” molecules with promising bioavailability.

Thienopyrimidine: A Promising Scaffold to Access Anti-Infective Agents

Thienopyrimidines are widely represented in the literature, mainly due to their structural relationship with purine base such as adenine and guanine. This current review presents three isomers-thieno[2,3-d]pyrimidines, thieno[3,2-d]pyrimidines and thieno[3,4-d]pyrimidines-and their anti-infective properties. Broad-spectrum thienopyrimidines with biological properties such as antibacterial, antifungal, antiparasitic and antiviral inspired us to analyze and compile their structure-activity relationship (SAR) and classify their synthetic pathways. This review explains the main access route to synthesize thienopyrimidines from thiophene derivatives or from pyrimidine analogs. In addition, SAR study and promising anti-infective activity of these scaffolds are summarized in figures and explanatory diagrams. Ligand-receptor interactions were modeled when the biological target was identified and the crystal structure was solved.

2-Amino-4,5-dihydrothiophene-3-carbonitriles: A New Synthesis, Quantum Chemical Studies, and Mannich-Type Reactions Leading to New Hexahydrothieno[2,3-d]pyrimidines

trans-2-Amino-4-aryl-5-benzoyl-4,5-dihydrothiophene-3-carbonitriles were prepared either by the reaction of 3-aryl-2-cyanothioacrylamides with α-thiocyanatoacetophenone or by the Michael-type addition of cyanothioacetamide to α-bromochalcones followed by intramolecular cyclization. The mechanism of the first reaction was studied using high-level quantum chemical calculations. Density functional theory (DFT) studies were carried out to determine the mechanism of the first reaction. A new approach toward the construction of the thieno[2,3-d]pyrimidine core system was demonstrated by the reaction of the prepared dihydrothiophenes with HCHO and RNH2 under noncatalyzed Mannich conditions.

Expedition of sulfur-containing heterocyclic derivatives as cytotoxic agents in medicinal chemistry: A decade update

This review article proposes a comprehensive report of the design strategies engaged in the development of various sulfur-bearing cytotoxic agents. The outcomes of various studies depict that the sulfur heterocyclic framework is a fundamental structure in diverse synthetic analogs representing a myriad scope of therapeutic activities. A number of five-, six- and seven-membered sulfur-containing heterocyclic scaffolds, such as thiazoles, thiadiazoles, thiazolidinediones, thiophenes, thiopyrans, benzothiazoles, benzothiophenes, thienopyrimidines, simple and modified phenothiazines, and thiazepines have been discussed. The subsequent studies of the derivatives unveiled their cytotoxic effects through multiple mechanisms (viz. inhibition of tyrosine kinases, topoisomerase I and II, tubulin, COX, DNA synthesis, and PI3K/Akt and Raf/MEK/ERK signaling pathways), and several others. Thus, our concise illustration explains the design strategy and anticancer potential of these five- and six-membered sulfur-containing heterocyclic molecules along with a brief outline on seven-membered sulfur heterocycles. The thorough assessment of antiproliferative activities with the reference drug allows a proficient assessment of the structure-activity relationships (SARs) of the diversely synthesized molecules of the series.

Structure-Based Designing, Solvent Less Synthesis of 1,2,3,4-Tetrahydropyrimidine-5-carboxylate Derivatives: A Combined In Vitro and In Silico Screening Approach

Objective: In this study, small molecules possessing tetrahydropyrimidine derivatives have been synthesized having halogenated benzyl derivatives and carboxylate linkage. As previously reported, FDA approved halogenated pyrimidine derivatives prompted us to synthesize novel compounds in order to evaluate their biological potential. Methodology: Eight pyrimidine derivatives have been synthesized from ethyl acetoacetate, secondary amine, aromatic benzaldehyde by adding catalytic amount of CuCl₂·2H₂O via solvent less Grindstone multicomponent reagent method. Molecular structure reactivity and virtual screening were performed to check their biological efficacy as an anti-oxidant, anti-cancer and anti-diabetic agent. These studies were supported by in vitro analysis and QSAR studies. Results: After combined experimental and virtual screening 5c, 5g and 5e could serve as lead compounds, having low IC₅₀ and high binding affinity.

Novel thienopyrimidine-aminothiazole hybrids: Design, synthesis, antimicrobial screening, anticancer activity, effects on cell cycle profile, caspase-3 mediated apoptosis and VEGFR-2 inhibition

A series of novel hybrid compounds of hexahydrobenzo[4,5]thieno[2,3-d]pyrimidine with aminothiazole scaffolds were synthesized. The synthesized compounds were evaluated for their cytotoxic activity against the NCI-60 human tumor cell line panel. Compounds 7c, 7d and 7e exhibited significant antiproliferative activities at 10^-5 M dose. Compound 7c exhibited excellent cytotoxic activity against CNS cancer cell lines including SNB-75 and SF-295 as well as renal cancer cell line CAKI-1 when compared with sorafenib as standard anticancer drug. In addition, compound 7d showed almost comparable anticancer activity to sorafenib against SNB-75 cell line and displayed moderate activity against SF-295 and CAKI-1 cell lines in comparison to sorafenib. Compound 7c inhibited the vascular endothelial growth factor receptor 2 (VEGFR-2) with IC₅₀ of 62.48 ± 3.7 nM and decreased both total VEGFR-2 and phosphorylated VEGFR-2 in treated SNB-75 cells suggesting its ability to down regulate cell proliferation, growth, and survival.. The flow cytometric analysis showed that 7c displayed its cytotoxic activity through the reduction of the cellular proliferation and induction of cell cycle arrest at the G2/M phase. Compound 7c clearly boosted the level of the apoptotic caspase-3. All the synthesized compounds were also screened for their antibacterial and antifungal activity against four pathogenic strains of both Gram-positive and Gram-negative as well as Candida albicans. Only compound 7d exhibited antifungal activity against Candida albicans compared to nystatin as the standard antifungal compound.

2-Cyclopropyl-6-phenyl-2,3-dihydrothieno[3,2-d][1,3,2]diazaborinin-4(1H)-one

As part of our ongoing scaffold hopping work on antimalarial 2-aminothieno[3,2-d]pyrimidin-4-one scaffold, we explored the dihydrothieno[3,2-d][1,3,2]diazaborinin-4(1H)-one as a potential new antimalarial series. Using conditions found in the literature, we obtained 2-cyclopropyl-6-phenyl-2,3-dihydrothieno[3,2-d][1,3,2]diazaborinin-4(1H)-one with 93% yield through a simple treatment. It was then characterized by NMR (1H and 13C) and HRMS. Given the structure of this molecule, its aqueous stability was assessed to determine its suitability for biological tests. To our knowledge, this is the first dihydrothieno[3,2-d][1,3,2]diazaborinin-4(1H)-one described.

Design, Synthesis, Molecular Modeling and Antitumor Evaluation of Novel Indolyl-Pyrimidine Derivatives with EGFR Inhibitory Activity

Scaffolds hybridization is a well-known drug design strategy for antitumor agents. Herein, series of novel indolyl-pyrimidine hybrids were synthesized and evaluated in vitro and in vivo for their antitumor activity. The in vitro antiproliferative activity of all compounds was obtained against MCF-7, HepG2, and HCT-116 cancer cell lines, as well as against WI38 normal cells using the resazurin assay. Compounds 1-4 showed broad spectrum cytotoxic activity against all these cancer cell lines compared to normal cells. Compound 4g showed potent antiproliferative activity against these cell lines (IC₅₀ = 5.1, 5.02, and 6.6 μM, respectively) comparable to the standard treatment (5-FU and erlotinib). In addition, the most promising group of compounds was further evaluated for their in vivo antitumor efficacy against EAC tumor bearing mice. Notably, compound 4g showed the most potent in vivo antitumor activity. The most active compounds were evaluated for their EGFR inhibitory (range 53-79%) activity. Compound 4g was found to be the most active compound against EGFR (IC₅₀ = 0.25 µM) showing equipotency as the reference treatment (erlotinib). Molecular modeling study was performed on compound 4g revealed a proper binding of this compound inside the EGFR active site comparable to erlotinib. The data suggest that compound 4g could be used as a potential anticancer agent.

4,4'-trimethylenedipiperidine as a nitrogen heterocycle solvent and/or catalyst: Liquid phase tandem Knoevenagel-Michael condensation

Liquid phase tandem Knoevenagel-Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time, TMDP was employed as a safe and efficient solvent and/or catalyst in the liquid and aqueous ethanol medium, respectively, for the practical and eco-friendly Knoevenagel-Michael condensation. The reactions were carried out by using greener procedures, including a) the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol (1:1 v/v) at reflux temperature, and b) the use of TMDP as a dual solvent-catalyst at 65 °C in the absence of any solvent. High to excellent yields of the desired pyrano[2,3- d ]pyrimidinones were obtained under the two earlier mentioned conditions. The current methodologies have advantages, including (a) avoiding hazardous, toxic, volatile, and flammable materials and solvents, (b) avoiding tedious processes, harsh conditions, and multiple steps for the preparation of catalysts, (c) using a less toxic and noncorrosive catalyst, (d) minimizing hazardous waste generation and simple workup process, and (e) high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic, volatile, and flammable base reagents such as piperidine and triethylamine in liquid phase organic syntheses owing to its unique properties such as being less toxic, nonflammable, and nonvolatile, and having a low melting point, broad liquid range temperature, high thermal stability, and safe handling and storage.

Discovery and development of novel pyrimidine and pyrazolo/thieno-fused pyrimidine derivatives as potent and orally active inducible nitric oxide synthase dimerization inhibitor with efficacy for arthritis

In order to discover and develop drug-like anti-inflammatory agents against arthritis, based on "Hit" we found earlier and to overcome drawbacks of toxicity, twelve series of total 89 novel pyrimidine, pyrazolo[4,3-d]pyrimidine and thieno[3,2-d]pyrimidine derivatives were designed, synthesized and screened for their anti-inflammatory activity against NO and toxicity for normal liver cells (LO2). Relationships of balance toxicity and activity have been summarized through multi-steps, and title compounds 22o, 22l were found to show lower toxicity (against LO2: IC₅₀ = 2934, 2301 μM, respectively) and potent effect against NO release (IR = 98.3, 97.67%, at 10 μM, respectively). Furthermore, compound 22o showed potent iNOS inhibitory activity with value of IC₅₀ is 0.96 μM and could interfere stability and formation of the active dimeric iNOS. It's anti-inflammatory activity in vivo was assessed by AIA rat model. Furthermore, the results of metabolic stability, CYP, PK study in vivo, acute toxicity study and subacute toxicity assessment indicated this compound had good drug-like properties for treatment.

Evaluation of 1,1-cyclopropylidene as a thioether isostere in the 4-thio-thienopyrimidine (TTP) series of antimalarials

The 4-(heteroarylthio)thieno[2,3-d]pyrimidine (TTP) series of antimalarials, represented by 1 and 17, potently inhibit proliferation of the 3D7 strain of P. falciparum (EC₅₀ 70-100 nM), but suffer from oxidative metabolism. The 1,1-cyclopropylidene isosteres 6 and 16 were designed to obviate this drawback. They were prepared by a short route that features a combined Peterson methylenation / cyclopropanation transformation of, e. g., ketone 7. Isosteres 6 and 16 possess significantly attenuated antimalarial potency relative to parents 1 and 17. This outcome can be rationalized based on the increased out-of-plane steric demands of the latter two. In support of this hypothesis, the relatively flat ketone 7 retains some of the potency of 1, even though it appears to be a comparatively inferior mimic with respect to electronics and bond lengths and angles. We also demonstrate crystallographically and computationally an apparent increase in the strength of the intramolecular sulfur hole interaction of 1 upon protonation.

Design, synthesis and evaluation of novel thienopyrimidine-based agents bearing diaryl urea functionality as potential inhibitors of angiogenesis

Inhibition of angiogenesis is a promising strategy for the treatment of cancer. Herein, we describe the design and synthesis of thieno[2,3-d]pyrimidine-1,3,4-thiadiazole-aryl urea derivatives 11a-m to evaluate their efficacy in the chick chorioallantoic membrane (CAM) assay. Among target agents, 11i had a considerable activity against prostate cancer cell line, PC3 (IC₅₀ = 3.6 μM). Moreover, induction of apoptosis, good inhibitory activity against the growth of capillary blood vessels, and inhibition of VEGFR-2 phosphorylation were noticeable parameters which convinced us that 11i could be considered as a promising candidate for the discovery of novel drugs to treat tumors, particularly prostate cancer.

4-(3-Phenyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl)thieno[3,2-d]pyrimidine

A new hybrid compound, 4-(3-phenyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl)thieno[3,2-d]pyrimidine 3, with promising biological activity was efficiently synthesized by the reaction of 3-phenyl-1-(thieno[3,2-d]pyrimidin-4-yl)-1H-pyrazol-5-amine with Vilsmeier–Haack reagent and subsequent treatment with ammonium carbonate. The structure of the synthesized compound was fully characterized by 1H-, 13C-NMR, IR spectroscopy, mass-spectrometry and elemental analysis.

Synthesis, Characterization, and Biological Evaluation of Novel 7-Oxo-7H-thiazolo[3,2-b]-1,2,4-triazine-2-carboxylic Acid Derivatives

A series of novel 7-oxo-7H-thiazolo[3,2-b]-1,2,4-triazine-2-carboxylic acid derivatives was synthesized in good yields by a multi-step procedure that included the generation of the S-alkylated derivatives from 6-substituted arylmethyl-3-mercapto-1,2,4-triazin-5-ones with ethyl 2-chloroacetoacetate, intramolecular cyclization with microwave irradiation, hydrolysis and amidation. All of the target compounds were fully characterized through ¹H-NMR, ¹³C-NMR and HRMS spectra. The intramolecular cyclization occurred regioselectively at the N2-position of 1,2,4-triazine ring, which was confirmed by compound 3e using single-crystal X-ray diffraction analysis. The antibacterial and antitubercular activities of the target compounds were evaluated. Compared with Ciprofloxacin and Rifampicin, compounds 5d, 5f and 5g containing the terminal amide fragment exhibited broad spectrum antibacterial activity, and carboxylic acid derivatives or its corresponding ethyl esters had less effect on antibacterial properties. The most potent compound 5f also displayed excellent in vitro antitubercular activity against Mycobacterium smegmatis (minimum inhibitory concentration (MIC) = 50 μg/mL) and better growth inhibition activity of leucyl-tRNA synthetase (78.24 ± 4.05% at 15 μg/mL).

Synthesis of Novel Analogs of Thieno[2,3-d] Pyrimidin-4(3H)-ones as Selective Inhibitors of Cancer Cell Growth

New 2,3-disubstituted thieno[2,3-d]pyrimidin-4(3H)-ones were synthesized via a one-pot reaction from 2H-thieno[2,3-d] [1,3]oxazine-2,4(1H)-diones, aromatic aldehydes, and benzylamine or 4-hydroxylbezylamine. The obtained compounds were tested in vitro for cancer cell growth inhibition. Compound 19 can inhibit all four types of tested cancer cells, i.e., MCF-7, A549, PC-9, and PC-3 cells. Most of the compounds inhibited the proliferation of A549 and MCF-7 cells. Compound 15 exhibited the strongest anti-proliferative effect against A549 cell lines with IC50 values of 0.94 μM, and with no toxicity to normal human liver cells. Its potency was further proved by cell clone formation assay, Hoechst 33258 staining, and evaluation on the effects of apoptosis-related proteins.