The synthesis of biologically relevant conjugates of Re(CO)3 using pyridine-2-carboxyaldehyde

Abstract

The new pyridine-2-carboxaldehyde adduct, Re(CO)3(NC6H5C(O)H)Cl 1, and previously reported complex Re(CO)3(NC6H5C(O)H)Br 2 react with aniline derivatives sulfanilamide or 4-aminofluorescein in methanol giving Schiff base conjugates Re(CO)3(pyca-R)X (pyca = pyridinecarbaldehyde imine, X = Cl, Br), 3–6. Pre-isolation of compounds 1 and 2 provides a convenient method for preparing conjugate complexes in addition to the known methods of ligand synthesis and one-pot reactions. All new compounds were completely characterized, and compound 1 and the sulfanilamide derivatives 3 and 4 were structurally elucidated by X-ray crystallography.

The Synthesis of Dimeric ReI–Phenylenediimine Conjugates: Spectroscopic and Electrochemical Studies

“…As previously demonstrated in our work18–20 and in the work of Miguel et al,46–48 chelating aldehydes readily react with primary amines in the presence of [Re(CO) 5 X] to afford the corresponding Schiff base compounds (Scheme ). For example, mononuclear Re I complexes 1 and 2 were synthesized by using this method for use as controls in this study.…”

“…In addition to these traditional ligands, the chemistry of substituted 1,4‐diazabutadienes (DAB) has also gained significant attention 13–17. For several years, we have been investigating the syntheses of Re(CO) 3 compounds with DAB‐type ligands by means of metal‐mediated one‐pot reactions that involve Schiff base condensation 18–20. Relative to traditional aromatic diimine ligands like bipyridine or phenanthroline, DAB complexes have lower π*‐orbital energies.…”

“…We hypothesized that the degree of coupling between Re(CO) 3 centers might depend on the position of substitution on the phenylene ring. Having experience with the preparation and characterization of d 6 rhenium pyridine‐2‐carbaldimine compounds,18–20 we decided to explore this area further.…”

Facile solid phase peptide synthesis with a Re-lysine conjugate generated via a one-pot procedure

“…19 We and others have used this reaction to generate covalent diimine adducts, often with a substituted phenyl ring attached to the imine nitrogen. 14,20-21 However, this chemistry can also be used to produce compounds where the imine group is substituted with a biologically relevant moiety, such as a peptide or a fluorescein. 14,17,19 We surmised that we could extend this chemistry to the Nε of a protected lysine that could subsequently be employed as a reagent for solid phase peptide synthesis (SPPS).…”

“…14,20-21 However, this chemistry can also be used to produce compounds where the imine group is substituted with a biologically relevant moiety, such as a peptide or a fluorescein. 14,17,19 We surmised that we could extend this chemistry to the Nε of a protected lysine that could subsequently be employed as a reagent for solid phase peptide synthesis (SPPS). The resultant compound would be a side chain-modified amino acid that could be incorporated anywhere into a peptide growing off the solid support matrix.…”