[Show abstract][Hide abstract] ABSTRACT: Adenosine regulates tissue function by activating four G-protein-coupled adenosine receptors (ARs). Selective agonists and antagonists for [Formula: see text] ARs have been investigated for the treatment of a variety of immune disorders, cancer, brain, and heart ischemic conditions. We herein present a QSAR study based on a Topological sub-structural molecular design (TOPS-MODE) approach, intended to predict the [Formula: see text] ARs of a diverse dataset of 124 (94 training set/ 30 prediction set) adenosine derivatives. The final model showed good fit and predictive capability, displaying 85.1 % of the experimental variance. The TOPS-MODE approach afforded a better understanding and interpretation of the developed model based on the useful information extracted from the analysis of the contribution of different molecular fragments to the affinity.
[Show abstract][Hide abstract] ABSTRACT: In the title compound, C21H24N2O2Si, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether group are placed toward opposite sides and the tert-butyl and pyridazinone moieties are anti-oriented across the Si—O bond [torsion angle = −168.44 (19)°]. In the crystal, molecules are assembled into inversion dimers through co-operative N—H⋯O hydrogen bonds between the NH groups and O atoms of the pyridazinone rings of neighbouring molecules. The dimers are linked by π–π interactions involving adjacent pyridazinone rings [centroid–centroid distance = 3.8095 (19) Å], generating ladder-like chains along the b-axis direction. The chains are further linked into a two-dimensional network parallel to the ab plane through weak C—H⋯π interactions.
[Show abstract][Hide abstract] ABSTRACT: Key indicators: single-crystal X-ray study; T = 293 K; mean (C–C) = 0.004 A ˚; R factor = 0.046; wR factor = 0.148; data-to-parameter ratio = 20.8. In the title compound, C 21 H 24 N 2 O 2 Si, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether group are placed toward opposite sides and the tert-butyl and pyridazinone moieties are anti-oriented across the Si—O bond [torsion angle = À168.44 (19) ]. In the crystal, molecules are assembled into inversion dimers through cooperative N— HÁ Á ÁO hydrogen bonds between the NH groups and O atoms of the pyridazinone rings of neighbouring molecules. The dimers are linked by – interactions involving adjacent pyridazinone rings [centroid–centroid distance = 3.8095 (19) A ˚ ], generating ladder-like chains along the b-axis direction. The chains are further linked into a two-dimensional network parallel to the ab plane through weak C— HÁ Á Á interactions.
[Show abstract][Hide abstract] ABSTRACT: The title N-benzyl-phthalimide derivative, C16H13NO3, consists of two planar moieties, viz. the phthalimide system (r.m.s. deviation = 0.007 Å) and the phenyl ring, which make a dihedral angle of 84.7 (6)°. The meth-oxy group is almost coplanar with the phathalimide ring, as shown by the C-C-O-C torsion angle of -171.5 (2)°. In the crystal, the mol-ecules are self-assembled via non-classical C-H⋯O hydrogen bonds, forming a tape motif along .
[Show abstract][Hide abstract] ABSTRACT: A total synthesis of a Greek tobacco lactonic natural product and three of its analogues has been achieved using a commercially available starting material and our furan approach to oxacyclic systems, the proven scope of which is thus broadened.
[Show abstract][Hide abstract] ABSTRACT: Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed.
Magnetic Resonance in Chemistry 07/2011; 49(7):437-42. DOI:10.1002/mrc.2755 · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: New 6-substituted and 2,6-disubstituted pyridazinone derivatives were obtained starting from easily accessible alkyl furans by using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of this synthetic strategy. The new pyridazinone derivatives have been studied as vasorelaxant and antiplatelet agents. Analysis of biological data revealed the silyl ethers (4a-i) and N,O-dibenzyl derivatives (6g-i) as the most active compounds.
[Show abstract][Hide abstract] ABSTRACT: Several new purine nucleosides derivatives of allofuranose were prepared according to Vorbrüggen method, starting from 1,2,5,6-di-O-isopropylidene-α-D-allofuranose and using 1,2,3,5,6-pentaacetoxy-β-D-allofuranose as key intermediate. The synthesized allofuranosyl nucleosides, as well as some acetyl derivatives, were evaluated for their cytotoxicity in vitro in three human cancer cell lines (MCF-7, Hela-229 and HL-60). Among the studied compounds the 9-(2,3,5,6-tetra-O-acetyl-β-D-allofuranosyl)-2,6-dichloropurine (9) was the most potent one on the three cell lines evaluated, being its activity against HL-60 cells similar to cisplatin.
European Journal of Medicinal Chemistry 09/2010; 45(12):6114-9. DOI:10.1016/j.ejmech.2010.09.046 · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: (1)H and (13)C NMR chemical shifts of cis and trans isonucleoside analogues of purine in which the furanose moiety is substituted by a tetrahydropyran ring were completely assigned using one- and two-dimensional NMR experiments that include NOE, DEPT, COSY and HSQC. The significant (1)H and (13)C NMR signals differentiating between the cis and trans stereoisomers were compared.
Magnetic Resonance in Chemistry 06/2010; 48(6):483-5. DOI:10.1002/mrc.2589 · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New tetrahydropyran isonucleoside derivatives of purine, with cis or trans configuration, were stereoselectively synthesized in moderate yield by a convergent strategy based on Mitsunobu coupling. The key starting material was a bicyclic lactone.
[Show abstract][Hide abstract] ABSTRACT: We describe an efficient new approach for the synthesis of highly substituted chiral tetrahydrothiophenes, based on the oxidation of a chiral furan substrate with singlet oxygen, followed by intramolecular hetero Michael addition.
[Show abstract][Hide abstract] ABSTRACT: The purpose of the study was to determine whether novel, selective antagonists of human A3 adenosine receptors (ARs) derived from the A3-selective agonist Cl-IB-MECA lower intraocular pressure (IOP) and act across species. IOP was measured invasively with a micropipette by the Servo-Null Micropipette System (SNMS) and by non-invasive pneumotonometry during topical drug application. Antagonist efficacy was also assayed by measuring inhibition of adenosine-triggered shrinkage of native bovine nonpigmented ciliary epithelial (NPE) cells. Five agonist-based A3AR antagonists lowered mouse IOP measured with SNMS tonometry by 3-5 mm Hg within minutes of topical application. Of the five agonist derivatives, LJ 1251 was the only antagonist to lower IOP measured by pneumotonometry. No effect was detected pneumotonometrically over 30 min following application of the other four compounds, consonant with slower, smaller responses previously measured non-invasively following topical application of A3AR agonists and the dihydropyridine A3AR antagonist MRS 1191. Latanoprost similarly lowered SNMS-measured IOP, but not IOP measured non-invasively over 30 min. Like MRS 1191, agonist-based A3AR antagonists applied to native bovine NPE cells inhibited adenosine-triggered shrinkage. In summary, the results indicate that antagonists of human A3ARs derived from the potent, selective A3 agonist Cl-IB-MECA display efficacy in mouse and bovine cells, as well. When intraocular delivery was enhanced by measuring mouse IOP invasively, five derivatives of the A3AR agonist Cl-IB-MECA lowered IOP but only one rapidly reduced IOP measured non-invasively after topical application. We conclude that derivatives of the highly-selective A3AR agonist Cl-IB-MECA can reduce IOP upon reaching their intraocular target, and that nucleoside-based derivatives are promising A3 antagonists for study in multiple animal models.
Experimental Eye Research 10/2009; 90(1):146-54. DOI:10.1016/j.exer.2009.10.001 · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent work has identified nucleotide agonists selective for P2Y1, P2Y2 and P2Y6 receptors and nucleotide antagonists selective for P2Y1, P2Y12 and P2X1 receptors. Selective non-nucleotide antagonists have been reported for P2Y1, P2Y2, P2Y6, P2Y12, P2Y13, P2X2/3/P2X3 and P2X7 receptors. For example, the dinucleotide INS 37217 (Up4dC) potently activates the P2Y2 receptor, and the non-nucleotide antagonist A-317491 is selective for P2X2/3/P2X3 receptors. Nucleotide analogues in which the ribose moiety is substituted by a variety of novel ring systems, including conformationally locked moieties, have been synthesized as ligands for P2Y receptors. The focus on conformational factors of the ribose-like moiety allows the inclusion of general modifications that lead to enhanced potency and selectivity. At P2Y1,2,4,11 receptors, there is a preference for the North conformation as indicated with (N)-methanocarba analogues. The P2Y1 antagonist MRS2500 inhibited ADP-induced human platelet aggregation with an IC50 of 0.95 nM. MRS2365, an (N)-methanocarba analogue of 2-MeSADP, displayed potency (EC50) of 0.4 nM at the P2Y1 receptor, with >10 000-fold selectivity in comparison to P2Y12 and P2Y13 receptors. At P2Y6 receptors there is a dramatic preference for the South conformation. Three-dimensional structures of P2Y receptors have been deduced from structure activity relationships (SAR), mutagenesis and modelling studies. Detailed three-dimensional structures of P2X receptors have not yet been proposed.
Purinergic Signalling in Neuron-Glia Interactions: Novartis Foundation Symposium 276, 10/2008: pages 58 - 72; , ISBN: 9780470032244
[Show abstract][Hide abstract] ABSTRACT: Activation of the G(q)-coupled P2Y(6) receptor heterologously expressed in astrocytes significantly attenuates apoptosis induced by tumor necrosis factor alpha (TNFalpha). We have extended the analysis of P2Y(6) receptor-induced cytoprotection to mouse skeletal muscle cells endogenously expressing this receptor. The endogenous P2Y(6) receptor agonist UDP and synthetic agonist MRS2693 protected C2C12 skeletal muscle cells against apoptosis in a concentration-dependent manner (0.1-10 nM) as determined by propidium iodide staining, histochemical analysis using hematoxylin and Hoechst 33258, and DNA fragmentation. The insurmountable P2Y(6) receptor antagonist MRS2578 blocked the protection. TNFalpha-induced apoptosis in C2C12 cells correlated with activation of the transcription factor NF-kappaB. The NF-kappaB activation was attenuated by 10nM MRS2693, which activated the antiapoptic ERK1/2 pathway. In an in vivo mouse hindlimb model, MRS2693 protected against skeletal muscle ischemia/reperfusion injury. The P2Y(6) receptor is a novel cytoprotective receptor that deserves further exploration in ameliorating skeletal muscle injury.
Pharmacological Research 09/2008; 58(3-4):232-9. DOI:10.1016/j.phrs.2008.08.004 · 4.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The synthesis of phosphonate 1.2-disubstituted carbocyclic nucleosides with a cyclopentane ring is described following two different strategies: inclusion of the phosphonomethyl group before or after coupling of the carbocyclic moiety with the heterocyclic base. The diethyl [(trifluoromethanesulfonyl)oxy]methanephosphonate is the key phosphonylating agent for both the strategies.