1593-08-4Relevant articles and documents
Electron localisation in electrochemically reduced mono- and bi-nuclear rhenium(I) complexes with bridged polypyridyl ligands
Page, Simon E.,Flood, Amar,Gordon, Keith C.
, p. 1180 - 1187 (2002)
A number of mono- and bi-nuclear rhenium(I) complexes have been prepared and their physical properties, including the infrared spectra of the reduced complexes, have been studied. These compounds have the general formula [Re(CO)3Cl(L)] and [Cl(CO)3Re(μ-L)Re(CO)3Cl], where L can be 2,3-(2′,2″)-diquinolylquinoxaline, 6,7-dimethyl-2,3-(2′,2″)-diquinolylquinoxaline, 2,3-(2′,2″)-diquinolylbenzoquinoxaline, 6,7-dichloro-2,3-(2′,2″)-diquinolylquinoxaline, 2,3-(2′,2″)-diquinoxalylquinoxaline, 6,7-dimethyl-2,3-(2′,2″)-diquinoxalylquinoxaline, 2,3-(2′,2″)-diquinoxalylbenzoquinoxaline and 6,7-dichloro-2,3-(2′,2″)-diquinoxalylquinoxaline. The electrochemical studies show that the first reduction potential of the free ligands correlates with the reductions of the corresponding mono- and bi-nuclear complexes. The properties of the complexes have been modelled using semi-empirical methods. These show linear correlations between: (a) the energy of the MLCT transitions versus the difference in energy between the LUMO and the HOMO and (b) the change in carbonyl force constant with reduction vs. the wavefunction amplitude of the π* LUMO at the site of coordination. The experimental data and calculations point to significant alterations in the π* LUMO with substitution at the ligand and with the chelation of a second Re(I) center.
Towards echinomycin mimetics by grafting quinoxaline residues on glycophane scaffolds
Jarikote, Dilip V.,Li, Wei,Jiang, Tao,Eriksson, Leif A.,Murphy, Paul V.
, p. 826 - 835 (2011)
Echinomycin is a natural depsipeptide, which is a bisintercalator, inserting quinoxaline units preferentially adjacent to CG base pairs of DNA. Herein the design and synthesis of echinomycin mimetics based on grafting of two quinoxaline residues onto a macrocyclic scaffold (glycophane) is addressed. Binding of the compounds to calf-thymus DNA was studied using UV-vis and steady state fluorescence spectroscopy, as well as thermal denaturation. An interesting observation was enhancement of fluorescence emission for the peptidomimetics on binding to DNA, which contrasted with observations for echinomycin. Molecular dynamics simulations were exploited to explore in more detail if bis-intercalation to DNA was possible for one of the glycophanes. Bis-intercalating echinomycin complexes with DNA were found to be stable during 20 ns simulations at 298 K. However, the MD simulations of a glycophane complexed with a DNA octamer displayed very different behaviour to echinomycin and its quinoxaline units were found to rapidly migrate out from the intercalation site. Release of bis-intercalation strain occurred with only one of the quinoxaline chromophores remaining intercalated throughout the simulation. The distance between the quinoxaline residues in the glycophane at the end of the MD simulation was 7.3-7.5 , whereas in echinomycin, the distance between the residues was ～11 , suggesting that longer glycophane scaffolds would be required to generate bis-intercalating echinomycin mimetics.
Synthesis, crystal structures, and fluorescent properties of zinc(II) complexes with benzazino-2-carboxalidin-2-aminophenols
Nosova, Emiliya,Stupina, Tatyana,Chupakhin, Artem,Lipunova, Galina,Valova, Marina,Slepukhin, Pavel,Charushin, Valery
, p. 61 - 67 (2015)
Complexes ZnL2 with novel fluorinated benzazines as tridentate ligands (HL = 6,7-difluoroquinoxalinand 6,7-difluoroquinolincarboxalidin-2-aminophenol) have been prepared. The photophisical properties of the ligands and the complexes has been studied.
Copper-Catalyzed Aerobic Oxidation of Azinylmethanes for Access to Trifluoromethylazinylols
Zheng, Gang,Liu, Hao,Wang, Mang
, p. 519 - 523 (2016)
A copper-catalyzed oxygenation of methylazaarenes was found to occur in the absence of both ligand and additive, and has been successfully employed for the synthesis of trifluoromethylazinylketols. This synthetic strategy incorporates aerobic oxidation and a trifluoromethylation in one-pot and provides a novel method for the trifluoromethylation of aliphatic C-H bond.
Methanol as a formylating agent in nitrogen heterocycles
Xu, Zhengbao,Zhang, Lizhi
, p. 9476 - 9482 (2021/11/17)
A radical mediated C-H direct formylation of N-heteroarenes with methanol is reported. The reaction features a novel iron-catalyzed Minisci oxidative coupling process using commercially available methanol as a formylating reagent. It effectively solved the long-standing problems associated with using methanol as a formylating reagent in these types of reactions. Compared to the traditional Minisci C-H formylation methods, this protocol is highly atom-economical, simple to operate, and environmentally friendly and shows good functional group tolerance. This Minisci formylation strategy is a straightforward approach for the late-stage functionalization of N-heteroarenes. This journal is
Biocatalytic reduction of α,β-unsaturated carboxylic acids to allylic alcohols
Aleku, Godwin A.,Leys, David,Roberts, George W.
, p. 3927 - 3939 (2020/07/09)
We have developed robust in vivo and in vitro biocatalytic systems that enable reduction of α,β-unsaturated carboxylic acids to allylic alcohols and their saturated analogues. These compounds are prevalent scaffolds in many industrial chemicals and pharmaceuticals. A substrate profiling study of a carboxylic acid reductase (CAR) investigating unexplored substrate space, such as benzo-fused (hetero)aromatic carboxylic acids and α,β-unsaturated carboxylic acids, revealed broad substrate tolerance and provided information on the reactivity patterns of these substrates. E. coli cells expressing a heterologous CAR were employed as a multi-step hydrogenation catalyst to convert a variety of α,β-unsaturated carboxylic acids to the corresponding saturated primary alcohols, affording up to >99percent conversion. This was supported by the broad substrate scope of E. coli endogenous alcohol dehydrogenase (ADH), as well as the unexpected CC bond reducing activity of E. coli cells. In addition, a broad range of benzofused (hetero)aromatic carboxylic acids were converted to the corresponding primary alcohols by the recombinant E. coli cells. An alternative one-pot in vitro two-enzyme system, consisting of CAR and glucose dehydrogenase (GDH), demonstrates promiscuous carbonyl reductase activity of GDH towards a wide range of unsaturated aldehydes. Hence, coupling CAR with a GDH-driven NADP(H) recycling system provides access to a variety of (hetero)aromatic primary alcohols and allylic alcohols from the parent carboxylates, in up to >99percent conversion. To demonstrate the applicability of these systems in preparative synthesis, we performed 100 mg scale biotransformations for the preparation of indole-3-aldehyde and 3-(naphthalen-1-yl)propan-1-ol using the whole-cell system, and cinnamyl alcohol using the in vitro system, affording up to 85percent isolated yield.
