Syntheses and evaluation of pyrido[2,3-dlpyrimidine-2,4-diones as PDE 4 inhibitors

2-Aminopyridine - an unsung hero in drug discovery

2-Aminopyridine is a simple, low molecular weight and perfectly functionalised moiety known for the synthesis of diverse biological molecules. Many pharmaceutical companies across the globe aim to synthesise low-molecular weight molecules for use as pharmacophores against various biological targets. 2-Aminopyridine can serve as a perfect locomotive in the synthesis and pulling of such molecules towards respective pharmacological goals. The major advantage of this moiety is its simple design, which can be used to produce single products with minimum side reactions. Moreover, the exact weight of synthesised compounds is low, which enables facile identification of toxicity-causing metabolites in drug discovery programmes. This manuscript is a quick review of such pharmacophores derived from 2-aminopyridine.

Synthesis of arylidene hydrazinylpyrido[2,3-d]pyrimidin-4-ones as potent anti-microbial agents

Combination of arylidene hydrazinyl moiety with pyrido[2,3-d]pyrimidin-4-one skeleton in compounds 7‒26 results in the output of unprecedented anti-microbial agents. Arylidene hydrazinyl based on Pyrido[2,3-d]pyrimidin-4-one analoges 7‒26 prepared by the treatment of [2,3-d]pyrimidin-4-ones 6a,b with various aromatic aldehydes. The antimicrobial action for recently synthesized compounds was considered towards gram positive bacterial species (Staphylococcus aurous ATCC- 47077; Bacillus cereus ATCC-12228), gram negative bacterial species (Escherichia coli ATCC-25922; Salmonella typhi ATCC-15566) and Candida albicans ATCC-10231 as fungal strains. The antimicrobial action expanded by expanding the electron donating group in position 2 and 5 for Pyrido[2,3-d]pyrimidin-4-one core. Derivatives 13, 14, 15, 16 and 12; individually appeared hopeful anti-microbial action towards all strains utilized with inhibition zone higher than that of standard reference drug with lowest MIC.

Enantioselective N-Heterocyclic Carbene-Catalyzed Synthesis of Spirocyclic Oxindole-benzofuroazepinones

Herein, we report an enantioselective synthesis of azepinones via the N-heterocyclic carbene (NHC) catalyzed [3+4] annulation reaction of isatin-derived enals and aurone-derived azadienes. The corresponding spirocyclic oxindole-benzofuroazepinones were obtained in good yields, with excellent diastereo- and enantioselectivities. The resulted azepinones were evaluated for their in vitro cytotoxic activities against six human tumor cell lines, with two compounds showing significant inhibitory activity comparable with that of cisplatin.

Utility of 2-thioxo-pyrido[2,3-d]pyrimidinone in synthesis of pyridopyrimido[2,1-b][1,3,5]-thiadiazinones and pyridopyrimido[2,1-b][1,3]thiazinones as antimicrobial agents

Background

Pyridopyrimidines are of current interest because of their extensive variety of biological and pharmacological activities.

Results

A series of pyrido[2′,3′:4,5]pyrimido[2,1-b][1,3,5]thiadiazinones was obtained by aminomethylation of pyridopyrimidinethione with formaldehyde solution (37%) and different primary aromatic amines. Another series of pyrido[2′,3:4,5]pyrimido[2,1-b][1,3]thiazinones was prepared by Michael addition reaction of pyridopyrimidinethione to the activated double bond of a number of arylidene malononitrile and 2-(benzo[d][1,3]dioxol-5-ylmethylene)malononitrile. The mechanisms of formation of the synthesized compounds were discussed and the assigned structure was established via microanalysis and spectral data (IR, ¹H NMR, and Ms.). A comparative study of the biological activity of the synthesized compounds with chloramphenicol and trimethoprim/sulphamethoxazole is shown in Table 1. Generally, all synthesized compounds showed adequate inhibitory effects on the growth of Gram-positive and Gram-negative bacteria.

Conclusions

In this study, we use a simple (synthetic) strategy for the synthesis of pyrimidothiadiazines, based on their aminomethylation through the Mannich reaction; they have also been synthesized by the application of the Michael addition to activated nitriles. Mechanisms and structures of the newly synthesized compounds were examined: the antimicrobial activity of some selected compounds was evaluated, which demonstrated adequate inhibitory effects. Graphical abstract

S-Nanoparticle/SDS: an efficient and recyclable catalytic system for synthesis of substituted 4H-pyrido[1,2-a]pyrimidines in aqueous admicellar medium

A green protocol has been described for the synthesis of 4H-pyrido[1,2-a]pyrimidines under admicellar catalysis by S₈ NPs.

A facile approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives via a three-component domino reaction

A concise and efficient approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives has been accomplished for the first-time by a three-component reaction involving alkylsulfonyl acetonitrile, an aromatic aldehyde, and 6-aminouracil.

Combination of 2D/3D ligand-based similarity search in rapid virtual screening from multimillion compound repositories. Selection and biological evaluation of potential PDE4 and PDE5 inhibitors

Rapid in silico selection of target focused libraries from commercial repositories is an attractive and cost effective approach. If structures of active compounds are available rapid 2D similarity search can be performed on multimillion compound databases but the generated library requires further focusing by various 2D/3D chemoinformatics tools. We report here a combination of the 2D approach with a ligand-based 3D method (Screen3D) which applies flexible matching to align reference and target compounds in a dynamic manner and thus to assess their structural and conformational similarity. In the first case study we compared the 2D and 3D similarity scores on an existing dataset derived from the biological evaluation of a PDE5 focused library. Based on the obtained similarity metrices a fusion score was proposed. The fusion score was applied to refine the 2D similarity search in a second case study where we aimed at selecting and evaluating a PDE4B focused library. The application of this fused 2D/3D similarity measure led to an increase of the hit rate from 8.5% (1st round, 47% inhibition at 10 µM) to 28.5% (2nd round at 50% inhibition at 10 µM) and the best two hits had 53 nM inhibitory activities.

Synthesis and antibacterial activity of a new series of 2,3,5,7-substituted-pyrido[2,3-d]pyrimidin-4(3h)-one derivatives

A new series of 2,3,5,7-substituted-pyrido[2,3-d]pyrimidin-4(3H)-one derivatives were prepared from 2-amino-N,6-substituted phenyl-4-(trifluoromethyl or methyl)nicotinamides. The key intermediate 2-amino-N,6-substituted phenyl-4-(trifluoromethyl or methyl)nicotinamides were synthesized from 2-bromo-N,6-disubstituted phenyl-4-(trifluoromethyl or methyl)nicotinamides as well as from ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) coupling of 2-amino-4,6-substituted nicotinic acid and substituted arylamines. All the synthesized compounds were screened for antibacterial activity against Gram +ve and Gram -ve bacteria. Compound 7c showed better antibacterial activity against Gram +ve and Gram -ve bacteria.

An efficient route for the synthesis of a new class of pyrido[2,3-d]pyrimidine derivatives

A new reaction of 4-arylidene-3-methylisoxazol-5(4H)-one or 4-arylidene-2-phenyloxazol-5(4H)-one with 2,6-diaminopyrimidin-4(3H)-one is described and a number of new pyrido[2,3-d]pyrimidine-4,7-dione derivatives are synthesized. This protocol has the advantages of good yields, broad substrate scope and simple work-up.

The antidepressant and antiinflammatory effects of rolipram in the central nervous system

Rolipram is a selective inhibitor of phosphodiesterases (PDE) IV, especially of the subtype PDE IVB. These phosphodiesterases are responsible for hydrolysis of the cyclic nucleotides cAMP and cGMP, particularly in nerve and immune cells. Consequences of rolipram-induced elevation of intracellular cAMP are increased synthesis and release of norepinephrine, which enhance central noradrenergic transmission, and suppress expression of proinflammatory cytokines and other mediators of inflammation. In humans and animals rolipram produces thereby a variety of biological effects. These effects include attenuation of endogenous depression and inflammation in the central nervous system (CNS), both effects are of potential clinical relevance. There are some discrepancies between in vitro and in vivo effects of rolipram, as well as between results obtained in animal models and clinical studies. The clinical use of rolipram is limited because of its behavioral and other side effects. Newly developed selective PDE IV inhibitors with presumably higher potency and lower toxicity are currently under investigation.