Effective Methods for the Biotinylation of Azamacrocycles

Extending the Scope of the C-Functionalization of Cyclam via Copper(I)-Catalyzed Alkyne-Azide Cycloaddition to Bifunctional Chelators of Interest

Cyclam, known for its potent chelation properties, is explored for diverse applications through selective N-functionalization, offering versatile ligands for catalysis, medical research, and materials science. The challenges arising from N-alkylation, which could decrease the coordination properties, are addressed by introducing a robust C-functionalization method. The facile two-step synthesis proposed here involves the click chemistry-based C-functionalization of a hydroxyethyl cyclam derivative using Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC). Boc-protecting groups prevent undesired copper coordination, resulting in compounds with a wide range of functionalities. The optimized synthesis conditions enable C-functional cyclams to be obtained easily and advantageously, with high application potential in the previously cited fields. The methodology has been extended to trehalose-based Siamese twin amphiphiles, enabling efficient gene delivery applications.

CO2 Electroreduction in Water with a Heterogenized C-Substituted Nickel Cyclam Catalyst

Molecular catalysis for selective CO₂ electroreduction into CO can be achieved with a variety of metal complexes. Their immobilization on cathodes is required for their practical implementation in electrolytic cells and can benefit from the advantages of a solid material such as easy separation of products and catalysts, efficient electron transfer to the catalyst, and high stability. However, this approach remains insufficiently explored up to now. Here, using an appropriate and original modification of the cyclam ligand, we report a novel [Ni(cyclam)]²⁺ complex which can be immobilized on carbon nanotubes. This material, once deposited on a gas diffusion layer, provides a novel electrode which is remarkably selective for CO₂ electroreduction to CO, not only in organic solvents but also, more remarkably, in water, with faradic efficiencies for CO larger than 90% and current densities of 5-10 mA cm^-2 during controlled potential electrolysis in H-cells.

Mechanistic Insights into the Chaperoning of Human Lysosomal-Galactosidase Activity: Highly Functionalized Aminocyclopentanes and C-5a-Substituted Derivatives of 4-epi-Isofagomine

Glycosidase inhibitors have shown great potential as pharmacological chaperones for lysosomal storage diseases. In light of this, a series of new cyclopentanoid β-galactosidase inhibitors were prepared and their inhibitory and pharmacological chaperoning activities determined and compared with those of lipophilic analogs of the potent β-d-galactosidase inhibitor 4-epi-isofagomine. Structure-activity relationships were investigated by X-ray crystallography as well as by alterations in the cyclopentane moiety such as deoxygenation and replacement by fluorine of a “strategic” hydroxyl group. New compounds have revealed highly promising activities with a range of β-galactosidase-compromised human cell lines and may serve as leads towards new pharmacological chaperones for G_M1-gangliosidosis and Morquio B disease.

Design, Synthesis, and Optimization of Balanced Dual NK1/NK3 Receptor Antagonists

In connection with a program directed at potent and balanced dual NK1/NK3 receptor ligands, a focused exploration of an original class of peptidomimetic derivatives was performed. The rational design and molecular hybridization of a novel phenylalanine core series was achieved to maximize the in vitro affinity and antagonism at both human NK1 and NK3 receptors. This study led to the identification of a new potent dual NK1/NK3 antagonist with pK i values of 8.6 and 8.1, respectively.

Biological evaluation of avidin-based tumor pretargeting with DOTA-Triazole-Biotin constructed via versatile Cu(I) catalyzed click chemistry

BACKGROUND

The biotin-avidin interaction remains a gold standard for the two-step pretargeting approach to image tumor sites. We aim to develop two-step pretargeting systems utilizing (99m)Tc labeled biotin functionalized macrocyclic chelating agents synthesized using the highly efficient Cu(I) catalyzed azide-alkyne cycloaddition for potential radioimaging applications.

METHODS

A facile synthesis of DOTA-Triazole-Biotin, radiocomplexation with (99m)Tc and the pretargeting protocol is described. The synthesis features Cu(I) catalyzed click conjugation between biotinylated azide and propynyl functionalized DO3A. (99m)Tc radiolabeling was performed to detect the accumulation of avidin as the pretargeting agent. Cytotoxicity was determined using the trypan blue exclusion assay, macrocolony, and MTT assay. Cell uptake studies were performed using radiolabeled DOTA-Triazole-Biotin and compared with avidin treated cells for 2 h. Tumor imaging was performed in U-87MG cell line implanted tumor bearing nude mice and uptake of the radiotracer was estimated.

RESULTS

All compounds have been successfully characterized by NMR and MS spectroscopy. More than 96% radiolabeling efficiency was obtained and the radioconjugate exhibited sufficient stability under physiological conditions.

CONCLUSION

To summarize, a new candidate for avidin based two-step pretargeting of tumors has been synthesized and evaluated for potential imaging and diagnostic applications. The chelate possesses high stability under physiological conditions, exhibits effective interaction with its avidin target, and low nonspecific retention in vivo.

Synthesis of lipophilic 1-deoxygalactonojirimycin derivatives as D-galactosidase inhibitors

N-Alkylation at the ring nitrogen of the D-galactosidase inhibitor 1-deoxygalactonojirimycin with a functionalised C ₆alkyl chain followed by modification with different aromatic substituents provided lipophilic 1-deoxygalactonojirimycin derivatives which exhibit inhibitory properties against β-glycosidases from E. coli and Agrobacterium sp. as well as green coffee bean α-galactosidase. In preliminary studies, these compounds also showed potential as chemical chaperones for GM1-gangliosidosis related β-galactosidase mutants.

A synthetically simple, click-generated cyclam-based zinc(II) sensor

A cyclam-based macrocyclic sensor has been prepared using synthetically simple "click" chemistry to link a fluorophore to the macrocyclic receptor. This sensor shows high selectivity for Zn(II) over a range of other metals, providing a significant enhancement of fluorescence intensity over a wide pH range. As such, this is the first cyclam-based sensor demonstrated to be selective for Zn(II) and is the first example of a triazole being used as a coordinating ligand on an azamacrocycle. The sensor can access biologically available zinc in mammalian cells, sensing the Zn(II) flux that exists during apoptotic cell death.