Spectroscopic and Electrochemical Studies of Ferrocenyl Triazole Amino Acid and Peptide Bioconjugates Synthesized by Click Chemistry

Abstract

Ferrocenyl triazole amino acid (L-leucine methyl ester (2, 5), L-phenylalanine methyl ester (3, 7), L-alanine methyl ester (4), L-valine tert-butyl ester (6), L-proline methyl ester (8)) and peptide derivatives ([Leu 5 ]-enkephalin (9, 10)) were prepared by Cu(I)-catalyzed [3+2] cycloaddition of azidoferrocene and 1,1′-diazidoferrocene with the corresponding alkyne-modified amino acids and peptide. A purity of >95% for the peptide conjugates was confirmed by HPLC. All new compounds were comprehensively characterized by elemental analysis, mass spectrometry (FAB and ESI-MS, including high-resolution MS), IR, and multinuclear 1D and 2D NMR spectroscopy. Solution structures were studied by circular dichroism (CD) and NMR spectroscopy, showing that compounds 5, 6, and 7 form intramolecular hydrogen bonds (IHBs) in noncoordinating solvents. Electrochemical studies show reversible processes of the redox couple Fc 0 /Fc + (Fc ) ferrocenyl) for compounds 2-9, whereas compound 10 exhibits an irreversible oxidation. A good correlation between the diffusion coefficients as determined by electrochemical methods and the molecular weight was established.

A Novel Organometallic ReI Complex with Favourable Properties for Bioimaging and Applicability in Solid‐Phase Peptide Synthesis

“…[1] A useful strategy to enhance the bioavailability and target specificity of potentially active compounds is to link them to biological vectors such as peptides, carbohydrates or hormones. [2] In the past we have reported on the successful synthesis of peptide bioconjugates for such purposes, in which we have used a range of different transition metal complexes based on iron, [3][4][5] copper, [6] zinc, [6] cobalt, [4,[7][8][9] ruthenium, [10,11] rhenium, [12] platinum [12] and molybdenum. [13] One major advantage of peptide-based conjugates is their variability.…”

“…In this work we present a new class of Re I -tricarbonyl complexes with a substituted bis(phenanthridinylmethyl)amine (bpm) ligand. The complex Re(CO) 3 (R-bpm) could be conveniently prepared by microwave synthesis from [Re(CO) 3 (H 2 O) 3 ]Br and a suitably substituted bis(phenanthridinylmethyl)amine (R-bpm). Complex 5, with R = CH 2 -CO 2 -CH 3 , was characterized by a single-crystal X-ray structure.…”

“…For the synthesis of the metal complexes 5 and 6 (Scheme 2) we used the rhenium precursor [Re(CO) 3 (H 2 O) 3 ]Br, which was prepared from the rhenium(I)pentacarbonyl bromide by heating at reflux in water. [38] The bisphenanthridinylmethyl (bpm) rhenium(I) tricarbonyl complexes 5 and 6 were synthesised by two different methods (Scheme 2).…”

“…[38] The bisphenanthridinylmethyl (bpm) rhenium(I) tricarbonyl complexes 5 and 6 were synthesised by two different methods (Scheme 2). In the first method, the bpm ligand was heated at reflux together with [Re(CO) 3 3 ]Br in a microwave reactor in methanol for 10 min at 110 8C. In both cases the reaction mixture was filtered and concentrated to half volume.…”

Synthesis, characterisation and bioimaging of a fluorescent rhenium-containing PNA bioconjugate

“…9 In this work, we capitalize on our recent discoveries to efficiently attach organometallic complexes to peptides and PNA oligomers using the copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction, often referred to as "Click Chemistry". 29,40,[44][45][46][47][48] In order to label the PNA oligomer with Table S1 and Figures S11-12 in the SI for IR spectra and analytical HPL chromatograms). Thermal stability studies.…”