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A series of 1,2,4-triazolo[1,5-a]pyrimidine derivatives was designed, synthesized, and screened for their phosphodiesterase (PDE 4B) inhibitory activity and bronchodilation ability. Compound 7e showed 41.80% PDE 4B inhibition at 10 µM. Eight compounds were screened for their bronchodilator activity, where compounds 7f and 7e elicited promising bronchodilator activity with EC 50 values of 18.6 and 57.1 µM, respectively, compared to theophylline (EC 50  = 425 µM). Molecular docking at the PDE 4B active site revealed a binding mode and docking scores comparable to those of a reference ligand, consistent with their PDE 4B inhibition activity., (© 2019 Deutsche Pharmazeutische Gesellschaft.)

Selective inhibition of phosphodiesterase (PDE) 4B favorably suppresses the synthesis of inflammatory cytokines and subsequently arrest the development of atopic dermatitis via modulating the intracellular cAMP levels. Considering the side effects of corticosteroids, selective PDE4 inhibition could constitute an effective alternative therapy for the treatment of atopic dermatitis (AD). In this study, a series of novel catechol based compounds bearing pyrimidine as the core have been synthesized and screened for the PDE4 inhibitory properties. The PDE4 selectivity of the active compounds over other PDEs has been investigated. Compound 23 bearing pyrimidine core functionalized with catechol, pyridine and trifluoromethyl groups can effectively inhibit the PDE4B with IC 50 value in nanomolar range (IC 50  = 15 ± 0.4 nM). Compound 23 exhibited seven fold higher selectivity towards PDE4B over PDE4D. Molecular Docking study confirmed its stronger affinity towards catalytic domain of PDE4B. In-vivo analysis confirmed that compound 23 effectively alleviated the symptoms of atopic dermatitis in DNCB-treated Balb/c mice by suppressing the synthesis of inflammatory mediators such as TNF-α, and Ig-E. Taken together, this study suggested that compound 23 could be an effective PDE4 inhibitor for the potential treatment of AD., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

A new series of pyrazolo[1,5-a]pyrimidines exemplified by compound 1, has been identified with moderate activity (IC50=165nM), following GSK256066 rescaffolding. Compound 1 optimization at positions 2, 3, 6 and 7 gave compound 10 with high in vitro activity (IC50=0.7nM). Modeling studies based on the PDB structure 3GWT with compound 5 showed the expected overlay with the carboxamide, the aryl moiety and the sulfone. Cyclisation of the primary amide to the 5 position of the pyrazolo[1,5-a]pyrimidines scaffold afforded compounds 15 and 16 with 200-fold enhancement in activity and cellular potency., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

5-Carbamoyl-2-phenylpyrimidine derivative 2 has been identified as a phosphodiesterase 4 (PDE4) inhibitor with moderate PDE4B inhibitory activity (IC50=200 nM). Modification of the carboxylic acid moiety of 2 gave N-neopentylacetamide derivative 10f, which had high in vitro PDE4B inhibitory activity (IC50=8.3 nM) and in vivo efficacy against lipopolysaccharide (LPS)-induced pulmonary neutrophilia in mice (ID50=16 mg/kg, ip). Furthermore, based on the X-ray crystallography of 10f bound to the human PDE4B catalytic domain, we designed 7,8-dihydro-6H-pyrido[4,3-d]pyrimidin-5-one derivative 39 which has a fused bicyclic lactam scaffold. Compound 39 exhibited excellent inhibitory activity against LPS-induced tumor necrosis factor alpha (TNF-α) production in mouse splenocytes (IC50=0.21 nM) and in vivo anti-inflammatory activity against LPS-induced pulmonary neutrophilia in mice (41% inhibition at a dose of 1.0 mg/kg, i.t.)., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Novel thieno[2,3-d]pyrimidines containing a cyclohexane ring fused with a six- or five-membered heterocyclic moiety along with a benzylic nitrile were designed as potential inhibitors of PDE4. Expeditious synthesis of these compounds was carried out via a multi-step sequence consisting of a few key steps such as Gewald reaction, Dieckmann type cyclisation and Krapcho decarboxylation. This newly developed strategy involved construction of the thienopyrimidine ring followed by the cyclohexanone moiety and subsequently the fused heterocyclic ring. A number of thieno[2,3-d]pyrimidine based derivatives were synthesized using this method some of which showed promising PDE4B inhibitory properties. One of them was tested for PDE4D inhibition in vitro and dose dependent inhibition of TNF-α. A few selected molecules were docked into the PE4B protein the results of which showed good overall correlations to their observed PDE4B inhibitory properties in vitro. The crystal structure analysis of representative compounds along with hydrogen bonding patterns and molecular arrangement present within the molecule is described.

A conceptually new three-component reaction was developed to construct a six-membered fused N-heterocyclic ring affording (pyrazolo)pyrimidines/pyridines as potential inhibitors of PDE4. The reaction is catalyzed by triflic acid in acetic acid in the presence of aerial oxygen., (This journal is © The Royal Society of Chemistry 2012)

A series of pyrido[3',2':4,5]furo[3,2-d]pyrimidines (PFP) were synthesized and tested for phosphodiesterase type 4 (PDE4) inhibitory activity, with the potential to treat asthma and chronic obstructive pulmonary disease (COPD). Structure-activity relationships within this series, leading to an increase of potency on the enzyme, is presented. Both gem-dimethylcyclohexyl moieties fused to the pyridine ring and the substitution at the 5 position of the PFP scaffold, proved to be key elements in order to get a high affinity in the enzyme., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)