Microwave-assisted synthesis of pyrazolo[3,4-d]pyrimidines from 2-amino-4,6-dichloropyrimidine-5-carbaldehyde under solvent-free conditions

Synthesis of pyrimido[4,5-b]quinolindiones and formylation: ultrasonically assisted reactions

Ultrasound-assisted synthesis of pyrimido‌quinolindione derivatives via a multicomponent reaction and subsequent formylation with Vilsmeier-Haack reagent were performed. Compounds were prepared by a one-pot method from aminopyrimidinones, dimedone and aromatic aldehydes through a Mannich-type reaction sequence, and then functionalized under ultrasound irradiation and Vilsmeier-Haack conditions to give β-chlorovinylaldehyde products. Ultrasonically assisted reactions, experimental simplicity, good yields without using metallic catalysts and the control of hazardous material release are features of this simple procedure.

SNAr Reactions on 2-Amino-4,6-dichloropyrimidine-5-carbaldehyde

We report the experimental results of unexpected aromatic nucleophilic substitution reaction products on 2-amino-4,6-dichloropyrimidine-5-carbaldehyde. The isolated compounds are products of amination, solvolysis, and condensation processes under mild and environmentally friendly conditions, due to the influence of structural factors of the starting pyrimidine and a high concentration of alkoxide ions. This method allows the building of pyrimidine-based compound precursors of N-heterocyclic systems.

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.

Parallel Synthesis of 1H-Pyrazolo[3,4-d]pyrimidines via Condensation of N-Pyrazolylamides and Nitriles

A novel parallel medicinal chemistry (PMC)-enabled synthesis of 1H-pyrazolo[3,4-d]pyrimidines employing condensation of easily accessible N-pyrazolylamides and nitriles has been developed. The presented studies describe singleton and library enablements that allowed rapid generation of molecular diversity to examine C4 and C6 vectors. This chemistry enabled access to challenging alkyl substituents, expanding the overall chemical space beyond that available via typical C(sp²)-C(sp²) coupling and S_NAr transformations. Furthermore, monomer group interconversions allowing the use of larger and more diverse amides and carboxylic acids as precursors to nitriles are discussed.

Microwave-Assisted Synthesis of Novel Pyrazolo[3,4-g][1,8]naphthyridin-5-amine with Potential Antifungal and Antitumor Activity

The microwave assisted reaction between heterocyclic o-aminonitriles 1 and cyclic ketones 2 catalyzed by zinc chloride led to new series of pyrazolo[3,4-b][1,8]naphthyridin-5-amines 3 in good yields. This procedure provides several advantages such as being environmentally friendly, high yields, simple work-up procedure, broad scope of applicability and the protocol provides an alternative for the synthesis of pyrazolonaphthyridines. The whole series showed antifungal activities against Candida albicans and Cryptococcus neoformans standardized strains, being compounds with a 4-p-tolyl substituent of the naphthyridin scheleton (3a, 3d and 3g), the most active ones mainly against C. albicans, which appear to be related to their comparative hydrophobicity. Among them, 3d, containing a cyclohexyl fused ring, showed the best activity. The anti-Candida activity was corroborated by testing the three most active compounds against clinical isolates of albicans and non-albicans Candida strains. These compounds were also screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Compounds 3a and 3e showed remarkable antitumor activity against cancer cell lines, with the most important GI₅₀ values ranging from 0.62 to 2.18 μM.

(E)-3-tert-Butyl-4-(4-chlorobenzyl)-N-(4-chlorobenzylidene)-1-phenyl-1H-pyrazol-5-amine: sheets built from π-stacked hydrogen-bonded dimers

The title compound, C27H25Cl2N3, is an unexpected but high-yield product from the microwave-mediated reaction between 3-tert-butyl-N-4-chlorobenzyl-1-phenyl-1H-pyrazol-5-amine and 4-chlorobenzaldehyde. Inversion-related pairs of molecules are linked by C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, and dimers of this type are linked into sheets by two independent π–π stacking interactions.

Microwave-assisted, divergent solution-phase synthesis of 1,3,6-trisubstituted pyrazolo[3,4-d]pyrimidines

A concise and highly divergent synthetic route has been developed to rapidly access 1,3,6-trisubstituted pyrazolopyrimidines. The synthesis features a microwave assisted one-pot N1-alkylation/Suzuki-Miyaura reaction as the key step. The sequence of the synthetic scheme can be varied to selectively modify the N1, C3, or C6 position at a late synthetic stage, thereby providing a highly efficient approach to explore the structure-activity relationships of pyrazolopyrimidine derivatives. The scope of these reactions has also been explored.

Functionalization of fatty acid mimetics for solid-phase coupling and subsequent target identification

Fatty acid mimetics such as pirinixic acid (PA) derivatives and 2-(phenylthio)alkanoic acid derivatives are drug-like small molecules with an interesting pharmacological profile. Previously, we have characterized PA derivatives (e.g., 1) as dual agonists of peroxisome proliferator-activated receptors (PPARs) α and γ and as inhibitors of microsomal prostaglandin E(2)-synthase-1 (mPGES-1) and 5-lipoxygenase (5-LO). 2-(Phenylthio)alkanoic acids (e.g., 2) were shown to act as highly active and selective PPARα agonists. Encouraged by these results, we would like to identify other target proteins and, thereby, further explore the pharmacological profile of these molecules. An elegant method to screen for potential interaction partners is the so-called "protein-fishing" approach. Requirement is coupling of a functionalized small molecule to a solid phase which is used for biological experiments. Ideally, the pharmacophore of the small molecule remains intact as far as possible. Here, we describe the successful design and synthesis of functionalized fatty acid mimetics, thus providing an eligible starting point for solid-phase coupling and subsequent "protein-fishing" experiments.

A facile one-pot synthesis of 1-arylpyrazolo[3,4-d]pyrimidin-4-ones

One pot synthesis of 1-arylpyrazolo[3,4-d]pyrimidin-4-ones by the reaction of 5-amino-N-substituted-1H-pyrazole-4-carbonitrile with different lower aliphatic acids in the presence of POCl(3) has been developed. The structures of all the title compounds have been confirmed by IR, (1)H-NMR, (13)CNMR, and elemental analyses. Moreover, the structures of one of these compounds, 2c, was confirmed by single-crystal X-ray diffraction.