Antagonists of the human adenosine A2A receptor. Part 1: Discovery and synthesis of thieno[3,2-d]pyrimidine-4-methanone derivatives

The (−)-(11R,2′S)-enantiomer of the antimalarial drug mefloquine has been found to be a reasonably potent and moderately selective adenosine A_2A receptor antagonist. Further investigation of this compound has led to the discovery of a series of keto-aryl thieno[3,2-d]pyrimidine derivatives, which are potent and selective antagonists of the adenosine A_2A receptor. These derivatives show selectivity against the A₁ receptor. Furthermore, some of these compounds have been shown to have in vivo activity in a commonly used model, suggesting the potential for the treatment of Parkinson’s disease.     

Antagonists of the human adenosine A2A receptor. Part 2: Design and synthesis of 4-arylthieno[3,2-d]pyrimidine derivatives

We describe herein the discovery and development of a series of 4-arylthieno[3,2-d]pyrimidines which are potent adenosine A_2A receptor antagonists. These novel compounds show high degrees of selectivity against the human A₁, A_2B and A₃ receptor sub-types. Moreover, a number of these compounds show promising activity in vivo, suggesting potential utility in the treatment of Parkinson’s disease.     

Chlorotrimethylsilane-promoted one-pot synthesis of steroidal[17,16-d]pyrimidines

A novel and practical procedure was developed for the preparation of steroidal[17,16-d]pyrimidines by chlorotrimethylsilane (TMSCl)-promoted one-pot multicomponent Biginelli-like condensations of steroid-17-ones, urea and aromatic aldehydes. First, treatment of the steroid-17-ones with urea and aromatic aldehydes in dimethylformamide (DMF)/acetonitrile (ACN) gives the corresponding Biginelli products, following the aromatising reaction of the Biginelli products at the same time under air to yield the desired steroidal[17,16-d]pyrimidines (78-88%). Since steroidal[17,16-d]pyrimidines with hydroxyl group can be subsequently converted into steroidal[17,16-d]pyrimidine derivatives, this general method provides a highly efficient route to these biologically important compounds.     

Structural investigation on thiazolo[5,4-d]pyrimidines to obtain dual-acting blockers of CD73 and adenosine A2A receptor as potential antitumor agents

Adenosine pathway, including its generating enzyme (CD73) and its receptors represents a key target for cancer immunotherapy. Here we aimed to search for novel compounds able to co-target the CD73 and the A_2A adenosine receptor (A_2A AR) as dual-blockers of adenosine generation and activity. The design project was to combine in the same molecule the thiazolo[5,4-d]pyrimidine core, an essential pharmacophoric feature to block the A_2A AR, with a benzenesulfonamide group which is a characteristic group of CD73 inhibitors. Most of the reported compounds resulted in inverse agonists of the human (h) A_2A AR endowed with high affinity, selectivity and potency. However they were weak inhibitors of CD73 enzyme. Nevertheless, this study can be considered as a starting point to develop more active compounds.     

Solid-phase Parallel Synthesis of 4-β-D-Ribofuranosylpyrazolo[4,3-d]pyrimidine Nucleosides

The synthesis of pyrazolo[4,3-d]pyrimidine nucleoside library using solid-phase parallel synthesis methodology is described. Glycosylation of the trimethylsilyl (TMS) derivative of 1- and 2-(methyl)-1H and 2H-pyrazolo[4,3-d]pyrimidine-5,7-(4H,6H)-dione (5) with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of TMS triflate provided two novel protected nucleosides 6 and 7. The structures of 6 and 7 were assigned by 1H and 2D NMR experiments. Nucleosides 6 and 7 were then transformed to the key intermediates 12 and 15 respectively. Reaction of 12 and 15 with MMTCl resin in the presence of 2,6-lutidine afforded the necessary scaffolds B and C. Different amines (96) were introduced selectively by nucleophilic substitution on scaffolds B and C using solid-phase parallel semi-automated synthesizer. Cleavage of the products from the solid support with 30% HFIP in a parallel fashion yielded nucleoside libraries simultaneously, and they were analyzed and characterized by high-throughput LC-MS.     

Synthesis and Anti-HCV Activity of 4-Methoxy-7H-Pyrrolo[2,3-d] Pyrimidine Carbocyclic Nucleosides

The present study includes the exploration of new possible nucleoside mimetics based on 4-methoxy-7H-pyrrolo[2,3-d]pyrimidine carbocyclic nucleosides (4a–g), which were synthesized by 10–15 synthetic steps and characterized adequately. We report the anti-HCV activities and cytotoxicities of 4a–g. Compound 4a was analyzed by single crystal X-ray diffraction which showed some puckering in the cyclopentene ring with a 2′-endo conformation and anti-base disposition (χ = ?125.7°).     

Furo[2,3-d]pyrimidines as Mackinazolinone/Isaindigotone Analogs: Synthesis,Modification, Antitumor Activity,and Molecular Docking Study

The chemical transformation of the tricyclic furo[2,3-d]pyrimidines was performed under isosteric and scaffold-hopping strategies focusing on the synthesis of its arylidene and imine-containing derivatives. Naturally-occurring alkaloids mackinazolinone and isaindigotone were as templates of target heterocycles. Synthesized compounds evaluated for their antitumor activity on human cancer cervical HeLa, breast MCF-7, and colon HT-29 cell lines. Four compounds: 8c , 8e , 10b , and 10c demonstrated potency against HeLa and HT-29 cell lines, and IC₅₀ values were between 7.37–13.72 μM, respectively. The molecular docking results showed that compounds 8c and 10b had good binding and high matching with the target EGFR protein.     

Pyrazolo[3,4-d]pyrimidines as inhibitor of anti-coagulation and inflammation activities of phospholipase A 2 : insight from molecular docking studies

Phospholipase A₂ (PLA2), isolated from Daboia russelli pulchella (Russell’s viper), is enzymatically active as well as induces several pharmacological disorders including neurotoxicity, myotoxicity, cardiotoxicity, anti-coagulant, hemolytic, and platelet effects. Indomethacin reduces the effects of anti-coagulant and pro-inflammatory actions of PLA2. Pyrazolo[3,4-d]pyrimidines constitute a class of naturally occurring fused uracils that posses diverse biological activities. The in-silico docking studies of nine pyrazolo[3,4-d]pyrimidine molecules have been carried out with the X-ray crystal structure of Russell’s viper PLA2 (PDB ID: 3H1X) to predict the binding affinity, molecular recognition, and to explicate the binding modes, using AUTODOCK and GLIDE (Standard precision and Extra precision) modules, respectively. Docking results through each method make obvious that pyrazolo[3,4-d]pyrimidine molecules with trimethylene linker can bind with both anti-coagulation and enzymatic regions of PLA₂.     

Guanosine analog in the pyrido[2,3-d]pyrimidine ring system As a potential Toll-like receptor agonist

The synthesis of a guanosine analog in the pyrido[2,3-d]pyrimidine ring system has been accomplished by glycosylation of the preformed aromatic heterocyclic base, which was prepared in 2 steps by condensation of methyl acrylate with guanidine carbonate and methyl cyanoacetate in the presence of sodium methoxide, followed by dehydrogenation. The analog was evaluated in vitro for its ability to modulate the innate immune response by acting as an agonist or as an antagonist of Toll-like receptor (TLR) signaling by measuring cytokine induction or inhibition of induction, respectively, in mouse bone marrow-derived macrophages. Despite its structural similarity to 7-thia-8-oxoguanosine, a known TLR7 agonist, the analog was found to antagonize TLR7-induced cytokine induction in this cell-based assay.     

Synthesis and BZR affinity of pyrazolo[1,5-a]pyrimidine derivatives. Part 1: study of the structural features for BZR recognition

Examination of the pharmacophoric points of the pyrazolo[1,5-a]pyrimidine derivatives, ligands for BZR, previously published led us to the design of a novel class of 3,6-diaryl-4,7-dihydro-pyrazolo[1,5-a]pyrimidin-7-ones and to determine the groups involved in the BZR recognition.     

1,2,4-triazolo[4,3-a]pyrimidines: a new kind of ligands. Structure of the silver(I) dimer with the 7-oxo derivative

This paper describes the silver dinuclear complex [Ag₂L₂(NO₃)₂] · 2H₂O, where L represents the bridging ligand 7,8-dihydro-7-oxo-1,2,4-triazolo[4,3-a]pyrimidine, this being the first example of a coordination compound of a 1,2,4-triazolo[4,3-a]pyrimidine derivative. As a difference with the most studied 1,2,4-triazolo[1,5-a]pyrimidine derivatives, the coordination takes place through the contiguous nitrogen atoms of the triazole ring, closing a six member Ag₂N₄ core with a higher intermetallic distance, 3.4791(3) Å. Linear coordination of silver is not possible in this geometry, so flat trigonal coordination involving also the nitrate counteranion is found instead.     

Anticytokinin activity of 4-substituted triazolo[4,5-d]pyrimidines and 4-substituted pyrazolo[3,4-d]pyrimidines

The synthesis and physiological activity of some novel 4-substituted triazolo[4,5-d]pyrimidines and 4-substituted pyrazolo[3,4-d]pyrimidines are described. Most of the compounds possessed high anticytokinin activity towards purine (benzyladenine) and phenylurea (4-PU-30) type cytokinins. 1-Benzyl-4-ethoxycarbonylpiperazinyl-1H-1,2,3-triazolo[4,5-d]pyrimidine almost completely removed cytokinin stimulated effects—betacyanin synthesis in Amaranthus caudatus cotyledons; growth of radish cotyledons and retention of chlorophyll in leaf explants. Some chemical structurephysiological activity relationships have been established.     

Pyrazolo[3,4-d]pyrimidines as adenosine antagonists

A large number of nitrogen heterocycles structurally related to caffeine and theophylline have been tested for activity as adenosine antagonists. Preliminary screening, utilizing displacement of [3H]N6-phenylisopropyladenosine (PIA) binding to rat brain membranes, identified several pyrazolo[3,4-d]pyrimidines with potential antagonist activity. These were then tested for their ability to antagonize adenosine-stimulated adenylate cyclase of guinea-pig slices and to block adenosine receptors which mediate presynaptic inhibition of transmitter release from cholinergic nerves in guinea-pig ileum. Of several compounds found to have antagonist activity, one of these, 4,6-bis-alpha- carbamoylethylthio -1-phenylpyrazolo[3,4-d]pyrimidine ( DJB -KK) was approximately an order of magnitude more potent than theophylline in both tests. GTP greatly reduces the potency of purine agonists, but not antagonists, as inhibitors of [3H] PIA binding; the potency of the pyrazolo[3,4-d]pyrimidine compounds was not altered by GTP. The compounds have no significant activity against [3H]adenosine uptake or on the binding of ligands to muscarinic cholinergic, beta-adrenergic, GABA or L-glutamate receptors.     

Synthesis and evaluation of optically pure dioxolanes as inhibitors of hepatitis C virus RNA replication

A series of optically pure 1,3-dioxolane nucleoside mimics was synthesized by a synthetic route that allowed incorporation of a 5R-methyl substituent from commercially available starting materials. The pyrrolo[2,3-d]pyrimidine heterocycle was chosen as a substitute for the purine derivative. Coupling of the pyrrolo[2,3-d]pyrimidine and the dioxolane was performed under solid–liquid phase transfer conditions. The ability to inhibit HCV RNA replication was assessed in a cell based subgenomic replicon assay. None of the described compounds displayed significant anti-HCV activity.     

Synthesis and Biological Activity Studies of Novel Pyrido[2,3-d]pyrimidines and Pyrido[2,3-d]triazines

Russian Journal of Bioorganic Chemistry - Novel derivatives of pyrido[2,3-d]pyrimidin-2,4(1H,3H)-dithione, 2,3-dimethylpyrido[2,3-d]pyrimidin-4-one, 4-chloro-2-methypyrido[2,3-d]pyrimidine and...     

Targeting p21-activated kinase 4 (PAK4) with pyrazolo[3,4-d]pyrimidine derivative SPA7012 attenuates hepatic ischaemia-reperfusion injury in mice

p21-Activated kinase 4 (PAK4), one of the serine/threonine kinases activated by Rho-family GTPases, has been widely studied as an oncogenic protein that is overexpressed in many types of cancers. In our recent study, PAK4 upregulation was observed in mice exhibiting hepatic ischaemia-reperfusion (I/R) and in liver transplantation patients. Liver I/R injury was also attenuated in Pak4 KO mice. Herein, we report a novel series of pyrazolo[3,4-d]pyrimidine derivatives of type I ½ PAK4 inhibitors. The most potent compound SPA7012 was evaluated to determine the pharmacological potential of PAK4 inhibitor in I/R injury in mice. Mice with I/R injury showed typical patterns of liver damage, as demonstrated by increases in serum levels of aminotransferases and proinflammatory cytokines, hepatocellular necrosis and apoptosis, and inflammatory cell infiltration, relative to sham mice. Conversely, intraperitoneal administration of SPA7012 dramatically attenuated biochemical and histopathologic changes. Mechanistically, stabilisation of nuclear factor-erythroid 2-related factor 2 (Nrf2), a master regulator of anti-oxidative response, was observed following SPA7012 treatment. SPA7012 treatment in primary hepatocytes also attenuated hypoxia-reoxygenation-induced apoptotic cell death and inflammation. Together, these results provide experimental evidence supporting the use of PAK4 inhibitors for alleviation of I/R-induced liver damage.     

Identification and SAR of a new series of thieno[3,2-d]pyrimidines as Tpl2 kinase inhibitors

We report here the synthesis and SAR of a new series of thieno[3,2-d]pyrimidines as potent Tpl2 kinase inhibitors. The proposed binding mode suggests the potential flipped binding mode depending on the substitution. Biacore studies show evidence of binding of these molecules to the protein kinase. The kinome inhibition profile of these molecules suggests good selectivity.     

Synthesis and anticancer evaluation of certain indolo[2,3-b]quinoline derivatives

The present report describes the synthesis and anticancer evaluation of certain 11-substituted 6H-indolo[2,3-b]quinolines and their methylated derivatives. These 6H-indolo[2,3-b]quinoline derivatives 11–13 were prepared from the commercially available 1,4-dihydroxyquinoline through alkylation, chlorination, nucleophilic reaction, and ring cyclization. Depending on the ratio of 11, (MeO)₂SO₂, and K₂CO₃, alkylation occurred primarily on N-5 (1:0.8:0.8) or N-6 (1:1.5:1.5) leading to the isolation of 14a or 14b as a major product. Accordingly, major product 15a (2/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 15b (1:1:1), respectively, was obtained by alkylation of 12 while 16a (13/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 16b (1:1:1), respectively, was obtained by alkylation of 13. The in vitro anticancer assay indicated 5-methylated derivatives 14a, 15a, 16a are more cytotoxic than their respective 6-methylated counterparts 14b, 15b, 16b and 6H-indolo[2,3-b]quinoline precursors 11, 12, 13. Among them, 11-(4-methoxyanilino)-6-methyl-6H-indolo[2,3-b]quinoline (16a) was the most cytotoxic with a mean GI₅₀ value of 0.78 μM and also exhibited selective cytotoxicities for HL-60 (TB), K-562, MOLT-4, RPMI-8226, and SR with GI₅₀ values of 0.11, 0.42, 0.09, 0.14, and 0.19 μM, respectively.     

Synthesis of 4-amino-6-(hetero)arylalkylamino-1,2,4-triazolo[4,3-a]quinoxalin-1-one derivatives as potent A(2A) adenosine receptor antagonists

In previous papers (Colotta, V. et al. Arch. Pharm. Pharm. Med. Chem. 1999, 332, 39. Colotta, V. et al. J. Med. Chem. 2000, 43, 1158) we reported the synthesis and binding affinity at bovine (b) A₁ and A_2A and human (h) A₃ adenosine receptors (ARs) of the 4-amino-6-benzylamino-2-phenyl-1,2,4-triazolo[4,3-a]quinoxalin-1-one (compound A) which resulted in a potent and selective A_2A AR antagonist. Compound A provided the lead compound of a series of 6- or 8-(hetero)arylalkylamino-4-amino-2-phenyl-1,2,4-triazolo[4,3-a]quinoxalin-1-one derivatives (compounds 1–20) which are the object of this paper. Most of the newly synthesized compounds are inactive at hA₃ ARs while they possess both nanomolar bA_2A affinities and different degrees of bA_2A versus bA₁ selectivity. The binding data show that hydrophilic substituents on the benzyl moiety are the most profitable for bA_2A receptor affinity. Furthermore, their steric hindrance seems to play an important role for the bA_2A AR interaction, thus suggesting that the 6-aralkylamino moiety of these ligands interacts with a size-limited binding pocket of this AR subtype. Thus, the SAR studies provided us some new insights about the structural requirements of the bA_2A AR recognition site.