Australian Journal of Chemistry最新文献

Metal piano-stool complexes based on pyridinecarbothioamide (PCA) have shown promising antiproliferative and in vivo anticancer activity, in particular [Ru(cym)(p-F-PCA)Cl]PF₆ (cym is η⁶-p-cymene; plecstatin-1). The impact of modifications of the PCA and π-bound ligands on biological properties has been extensively investigated. Herein, we explored the influence of exchanging the chlorido ligand with the N-heterocycles 1-methylimidazole, 1-methylbenzimidazole and pyridine. In solution, an equilibrium between the protonated and deprotonated forms of the thioamide bond was observed, which was found dictated by the solvent system with both species detected in polar solvents. [Ru(cym)(PCA)Cl]⁺ complexes exhibit unique behaviour in an aqueous environment where they rapidly form dimeric species after substitution of the chlorido ligand for the sulfur donor of the PCA ligand of a second complex molecule. This was also observed for the synthesised complexes with the N-heterocyclic ligands being cleaved from the Ru centre allowing for dimerisation, which may be reversed by acidification of the solution resulting in the formation of equivalent mononuclear compounds. This behaviour explains the similar biological properties of the complexes with respect to that of plecstatin-1.

The development of new high-tech applications based on organic radical polymers has driven significant and renewed focus on these open shell macromolecules. The versatility in synthetic methods makes them highly accessible materials for a variety of researchers from different backgrounds. Although numerous overviews of the synthesis, structure and properties are available, the determination of radical concentration has been largely overlooked. This primer outlines the methods available and the non-trivial nature of the characterisation process. Although quantitative electron paramagnetic resonance and magnetometry are the gold standard for direct measurement of paramagnetism, there also exists a wide range of highly accessible complimentary methods for indirect measure such as ultraviolet–visible spectroscopy, elemental analysis and infrared spectroscopy.

Peptide therapeutics play an increasingly important role in modern drug discovery. Improving the pharmacokinetic profile of bioactive peptides has been effectively achieved with chemical modifications, especially macrocyclisation reactions. Consequently, there is a great demand for highly constrained compounds such as bicyclic peptides. In our previous research, we introduced peptide–bismuth bicycles and peptide–arsenic bicycles as new classes of constrained peptides. In this work, we extend our peptide bicyclisation strategy towards antimony. Similar to arsenic and bismuth, antimony(III) selectively binds to three cysteine residues in peptides, enabling the in situ formation of stable bicycles. The bicyclisation reaction occurs instantaneously under biocompatible conditions at physiological pH. Antimony–peptide bicycles remain largely intact in the presence of the common metal chelator ethylenediaminetetraacetic acid (EDTA) and the main endogenous thiol competitor glutathione (GSH). Furthermore, when challenged with bismuth(III) from water-soluble gastrodenol (bismuth tripotassium dicitrate), antimony–peptide bicycles convert into the corresponding bismuth–peptide bicycle, highlighting the superior thiophilicity of bismuth over other pnictogens. Our study further expands the toolbox of peptide multicyclisation with main group elements previously underexplored in chemical biology.

This review outlines the synthesis of alkyl citrate natural products using cyclobutene diester precursors. The approach is efficient and stereoselective and provides the correct oxidation state of the citrate core of these compounds. The synthesis of a number of alkyl citrates along with some higher oxidised members of this family is detailed.

A novel synthetic route has been designed to introduce fluorine functionality into a series of compounds containing thiazolidin-4-one rings. These compounds were synthesised from various aniline derivatives using a two-step approach: an addition reaction of ethyl isothiocyanate with different aromatic fluorinated anilines, followed by cyclisation to yield the final products. A total of 15 novel fluorinated thiazolidinone compounds were synthesised and characterised using ¹H NMR, ¹⁹F NMR, Fourier transform–infrared, elemental analysis and liquid chromatography–mass spectrometry. Stereochemistry around the imine bond in the synthesised derivatives was determined using nuclear Overhauser effect spectroscopy. The in vitro anticancer potential of the compounds was tested against two human cancer cell lines, liver (HepG2) and colon (HCT116). The study revealed that the derivatives having fluorine functionality at both the m-positions in the aromatic ring showed promising anticancer potential, as compared to those at o- and p-positions.

The unique structural and physicochemical properties of adamantane and its derivatives have attracted considerable attention in the field of medicinal chemistry. Substituting phenyl rings for adamantane or its derivatives has provided a promising strategy to introduce lipophilicity and escape the ‘flat land’ of modern drug discovery. Additionally, the unique three-dimensional structure of adamantane facilitates the precise positioning of substituents allowing for a more effective exploration of drug targets. Evidently, we have seen an increased use of adamantane in pharmaceutically relevant molecules. The following Account highlights our group’s research in five drug discovery programs over the past 15 years showcasing the use of adamantane and its analogues in these studies.

In this paper, the bimetallic metal–organic frameworks (MOFs) of FeNi-BDC and FeNi-BDC-NH₂ (BDC, 1,4-benzenedicarboxylate) with similar Fe/Ni molar ratio, crystal structure, porosity and thermal stability were synthesized by a solvothermal method. The results of adsorption experiments at ambient conditions showed that the adsorptive uptake of NO, CO₂, O₂ and N₂ on FeNi-BDC were all very small under different adsorption partial pressures, with FeNi-BDC displaying a weak adsorption property because of its lack of unsaturated adsorption sites. On the contrary, at 100 kPa, the adsorption of NO by FeNi-BDC-NH₂ was considerably higher than that by FeNi-BDC, indicating that the incorporation of NH₂ on the ligand could effectively enhance the adsorption of NO. The adsorption capacity of FeNi-BDC-NH₂ for NO reached 142.17 cm³ g⁻¹, which was considerably higher than its capacity for CO₂, O₂ and N₂ under the same conditions. Ideal Adsorption Solution Theory simulations calculated the adsorption selectivity for NO/CO₂ and NO/O₂ under a mixed atmosphere to reach 1325 and 13,346 respectively, demonstrating high adsorption selectivity. Through in situ infrared experiments and calculations of the enthalpy of adsorption, it was demonstrated that FeNi-BDC-NH₂ adsorbed NO because NO can combine with NH₂ in the material to form a NONOate structure. A preliminarily exploration of the mechanism of NO adsorption and the influence of NH₂ functional groups on the adsorption and separation of NO revealed that the selectivity of adsorption was closely related to the variability of the enthalpy of adsorption. This also provided a new strategy for the adsorption and separation of NO in the flue gas environment.

A synthetic route to the preparation of cobalt(III) complexes coordinated by bidentate phenylthioether ligands is described. Complexes of the type ((2-(X-phenylthio)ethylamine)-N,S)bis(ethylenediamine)cobalt(III) perchlorate, [(en)₂Co(S(X-phenyl)CH₂CH₂NH₂)](ClO₄)₃, where X = 4-methoxy (2a), 4-methyl (2b), 3-methyl (2c), nothing (2d), 3-methoxy (2e), 4-bromo (2f) and 3-bromo (2g) were prepared. The synthetic route involves reaction of trans-dichloridobis(ethylenediamine)cobalt(III) chloride with NH₂CH₂CH₂SC₆H₄X to produce cis-[(en)₂CoCl(NH₂CH₂CH₂SC₆H₄X)]Cl₂ (1a–g). Formation of the Co–S bond, completing the ring closure, is then accomplished by removing the coordinated chlorido by addition of AgClO₄ in sulfolane. Complexes were characterized by ¹H and ¹³C NMR spectroscopy, UV-Vis spectroscopy and elemental analysis. In addition, the solid-state structure (X-ray) of the monohydrate of 2d confirms the coordination mode of the ligand. Preliminary kinetic investigations in basic solution show that the Co–S bond is broken resulting in the formation of [(en)₂Co(OH)(NH₂CH₂CH₂SC₆H₄X)]²⁺. At 15.0°C, a Hammett Plot is linear (r² = 0.981) with ρ = 2.24 ± 0.13.

In addition to three known compounds (1–3), two new rearranged spongian diterpenes (4 and 5) with perhydroazulene and dioxabicyclooctane ring systems were isolated from the mantle and viscera of the Australian nudibranch Goniobranchus coi. The relative configuration of the major spiroepoxide 4 was explored by comparison with those of m-chloroperbenzoic acid oxidation products derived from dendrillolide A (1). Aldehydes 6 and 7 were identified as the ring-opened artefacts of the spiroepoxides 5 and 4 respectively, and yielded ketone 3 on storage. The relative configurations of lactols 8 and 9, isolated as an inseparable mixture of diastereomers, were deduced by molecular modelling and computational studies. Acetylation of the lactol mixture provided dendrillolide A (1), further confirming the structural assignments of 8 and 9. Dissection of animal tissue established that the norditerpenoid metabolites were present in both mantle and viscera tissues.

Four 1-D chain coordination polymers containing bent 1,1′-binaphthyl ligands were synthesised with Ni^II, Cu^II and Ag^I. The use of (R)-4,4′-(2,2′-diethoxy-[1,1′-binaphthalene]-6,6′)dipyridine as a ligand yielded isostructural 1-D looping chains with Ni^II and Cu^II, whereas the use of Ag^I yielded both linear and helical 1-D chains. Changing the dipyridyl coordination groups to dicarboxylates in (S)-6,6′-dicarboxyl-2,2′-diethoxy-1,1′-binaphthalene yielded a 1-D looping chain with a Cu^II paddlewheel motif. The Ag^I 1-D chain features two crystallographically distinct 1-D chain morphologies with a triple helix and linear strips. The packing arrangement of the 1-D chains differs because of the intermolecular interactions present, with the steric bulk of the ethoxy substituent on the 1,1′-binaphthyl enabling the formation of large void spaces.