piperidines and picolinic-acid

The synthesis and characterization of Hno1pa2py, a new tacn-based ligand, is reported. The complexation process with Cu(2+) was proved to be very fast even in acidic medium. Potentiometric titrations allowed us to establish that Hno1pa2py exhibits an overall low basicity as well as a high selectivity for Cu(2+) over Zn(2+) cations. The copper(II) complex was synthesized and characterized using UV-vis and EPR spectroscopies and density functional theory (DFT) calculations. The studies clearly showed that the [Cu(no1pa2py)](+) complex is present in solution as a mixture of two isomers in which the ligand is coordinated to the metal center using a N5O donor set with the metal center in a distorted octahedral geometry. The very high kinetic inertness of the [Cu(no1pa2py)](+) complex was demonstrated by using acid-assisted dissociation assays as well as cyclic voltammetry. Preliminary investigations of (64)Cu complexation were performed to validate the potential use of such chelating agent for further application in nuclear medicine. The X-ray crystal structures of copper(II) complexes of L1, the ester derivative of Hno1pa2py, have been determined.

Topics: Aza Compounds; Coordination Complexes; Copper; Crystallography, X-Ray; Electron Spin Resonance Spectroscopy; Ligands; Models, Molecular; Picolinic Acids; Piperidines; Spectrophotometry, Ultraviolet

The picolinoxy group was found to be an extremely powerful leaving group for allylic substitution with aryl nucleophiles derived from ArMgBr and CuBr*Me2S. The substitution proceeds with anti SN2' pathway and with high chirality transfer. The electron-withdrawing effect of the pyridyl group and chelation to MgBr2 are likely the origin of success. Results suggesting these effects were obtained.

Topics: Allyl Compounds; Anions; Indicators and Reagents; Molecular Structure; Picolinic Acids; Piperidines; Stereoisomerism

Human neuroblastoma (NB) tumors elaborate angiogenic peptides, and enhanced angiogenesis correlates with their aggressive behavior, metastatic spread and poor clinical outcome. Hence, inhibition of angiogenic factor production may represent a potential therapeutic target for NB treatment. There is currently little information regarding the stimuli that control NB production of angiogenic mediators. In this study, we analyzed the effects of hypoxia, a common feature of solid tumors and a major drive to tumor angiogenesis, and of PA, a tryptophan catabolite produced under inflammatory conditions and endowed with several biologic properties, on the production of the angiogenic activator VEGF by advanced-stage human NB cell lines. We demonstrate that both stimuli are potent inducers of VEGF expression and secretion. VEGF upregulation by PA involved iron chelation because iron sulfate prevented this effect whereas the iron-chelating agent DFX induced VEGF production. Conversely, the CDK inhibitor Flp completely blocked VEGF induction by hypoxia. This effect occurred as early as 3 hr after stimulation and did not require de novo protein synthesis. Moreover, Flp exerted similar inhibitory activity on VEGF induction by PA or DFX, suggesting that this compound targets an essential step in the signaling pathway that leads to VEGF expression. Our findings demonstrate that PA can modulate angiogenic factor production by tumor cells and establish the importance of Flp as an inhibitor of VEGF production by human NB.

Topics: Antineoplastic Agents; Cell Hypoxia; Deferoxamine; Endothelial Growth Factors; Ferrous Compounds; Flavonoids; Gene Expression; Humans; Iron Chelating Agents; Lymphokines; Neuroblastoma; Picolinic Acids; Piperidines; RNA, Messenger; Tumor Cells, Cultured; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors