Asymmetric cyclopropanation of olefins catalysed by Cu(I) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*)

The synthesis and characterisation of copper(I) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*) and their use as catalysts in asymmetric cyclopropanation reactions are reported. All ligands and metal complexes were fully characterised, including crystal structures of some species determined by X-ray diffraction on single crystals. This allowed characterising the very different conformations of the macrocycles which could be induced by different substituents or by metal complexation. The strategy adopted for the ligand synthesis is very flexible allowing several structural modifications. A small library of macrocyclic ligands possessing the same donor properties but with either C-1 or C-2 symmetry was synthesized. Cyclopropane products with both aromatic and aliphatic olefins were obtained in good yields and enantiomeric excesses up to 99%.

New copper(II) complexes with isoconazole: Synthesis, structures and biological properties

There is an increasing demand for novel metal-based complexes with biologically relevant molecules in technology and medicine. Three new Cu(II) coordination compounds with antifungal agent isoconazole (L), namely mononuclear complexes CuCl2(L)(2) (1), and Cu(O2CMe)(2)(L)(2)center dot 2H(2)O (2) and coordination polymer Cu(pht)(L)(2)(n) (3) (where H(2)pht - o-phthalic acid) were synthesized and characterized by IR spectroscopy, thermogravimetric analysis and X-ray crystallography. X-ray analysis showed that in all complexes, the isoconazole is coordinated to Cu(II) centres by a N atom of the imidazole fragment. In complex I, the square-planar environment of Cu(II) atoms is completed by two N atoms of isoconazole and two chloride ligands, whereas the Cu(II) atoms are coordinated by two N atoms from two isoconazole ligands and two O atoms from the different carboxylate residues: acetate in 2 and phthalate in 3. The formation of an infinite chain through the bridging phthalate ligand is observed in 3. The biosynthetic ability of micromycetes Aspergillus niger CNMN FD 10 in the presence of the prepared complexes 1-3 as well as the antifungal drug isoconazole were studied. Complexes 2 and 3 accelerate the biosynthesis of enzymes (beta-glucosidase, xylanase and endoglucanase) by this fungus. Moreover, a simplified and improved method for the preparation of isoconazole nitrate was developed.

Interactions between Siglec-7/9 receptors and ligands influence NK cell-dependent tumor immunosurveillance

Abstract Alteration of the surface glycosylation pattern on malignant cells potentially affects tumor immunity by directly influencing interactions with glycan-binding proteins (lectins) on the surface of immunomodulatory cells. The sialic acid-binding Ig-like lectins Siglec-7 and -9 are MHC class I-independent inhibitory receptors on human NK cells that recognize sialic acid-containing carbohydrates. Here, we found that the presence of Siglec-9 defined a subset of cytotoxic NK cells with a mature phenotype and enhanced chemotactic potential. Interestingly, this Siglec-9+ NK cell population was reduced in the peripheral blood of cancer patients. Broad analysis of primary tumor samples revealed that ligands of Siglec-7 and -9 were expressed on human cancer cells of different histological types. Expression of Siglec-7 and -9 ligands was associated with susceptibility of NK cell-sensitive tumor cells and, unexpectedly, of presumably NK cell-resistant tumor cells to NK cell-mediated cytotoxicity. Together, these observations have direct implications for NK cell-based therapies and highlight the requirement to consider both MHC class I haplotype and tumor-specific glycosylation.

NOTCH ligands JAG1 and JAG2 as critical pro-survival factors in childhood medulloblastoma.

Medulloblastoma (MB), the most common pediatric malignant brain cancer, typically arises as pathological result of deregulated developmental pathways, including the NOTCH signaling cascade. Unlike the evidence supporting a role for NOTCH receptors in MB development, the pathological functions of NOTCH ligands remain largely unexplored. By examining the expression in large cohorts of MB primary tumors, and in established in vitro MB models, this research study demonstrates that MB cells bear abnormal levels of distinct NOTCH ligands. We explored the potential association between NOTCH ligands and the clinical outcome of MB patients, and investigated the rational of inhibiting NOTCH signaling by targeting specific ligands to ultimately provide therapeutic benefits in MB. The research revealed a significant over-expression of ligand JAG1 in the vast majority of MBs, and proved that JAG1 mediates pro-proliferative signals via activation of NOTCH2 receptor and induction of HES1 expression, thus representing an attractive therapeutic target. Furthermore, we could identify a clinically relevant association between ligand JAG2 and the oncogene MYC, specific for MYC-driven Group 3 MB cases. We describe for the first time a mechanistic link between the oncogene MYC and NOTCH pathway in MB, by identifying JAG2 as MYC target, and by showing that MB cells acquire induced expression of JAG2 through MYC-induced transcriptional activation. Finally, the positive correlation of MYC and JAG2 also with aggressive anaplastic tumors and highly metastatic MB stages suggested that high JAG2 expression may be useful as additional marker to identify aggressive MBs.

Accelerated discovery of novel benzodiazepine ligands by experiment-guided virtual screening.

High throughput discovery of ligand scaffolds for target proteins can accelerate development of leads and drug candidates enormously. Here we describe an innovative workflow for the discovery of high affinity ligands for the benzodiazepine-binding site on the so far not crystallized mammalian GABAA receptors. The procedure includes chemical biology techniques that may be generally applied to other proteins. Prerequisites are a ligand that can be chemically modified with cysteine-reactive groups, knowledge of amino acid residues contributing to the drug-binding pocket, and crystal structures either of proteins homologous to the target protein or, better, of the target itself. Part of the protocol is virtual screening that without additional rounds of optimization in many cases results only in low affinity ligands, even when a target protein has been crystallized. Here we show how the integration of functional data into structure-based screening dramatically improves the performance of the virtual screening. Thus, lead compounds with 14 different scaffolds were identified on the basis of an updated structural model of the diazepam-bound state of the GABAA receptor. Some of these compounds show considerable preference for the α3β2γ2 GABAA receptor subtype.