Ligands anthraquinone

More recent results have been obtained using a modified version of the previously reported H cell (see Figure 3 below). Two potentiostats are used simultaneously, one to reduce the anthraquinone ligand near the donor organic interface and the other to oxidize the complexed, neutral species near the receiving interface. Such an experimental arrangement has been reported by Saji [20] and is clearly not without its problems. Nevertheless, we have recently shown further cation transport rate enhancements using this approach. Refinements in this approach are still required. 

In this sense, quinone oxygen-coordinated palladium complexes 2 and 3 with anthraquinone ligands bearing Al-heterocyclic coordination sites are synthesized and characterized (Fig. 3.2) [10]. 

The kinetics of removal of iron(III) from its complexes with the aminocarboxylate-anthraquinone analytical reagent calcein and with the antitumor anthracycline doxorubicin by l,2-dimethyl-3-hydroxy-4-pyridinone (LI, (251) with R = R = Me) have been monitored. Rate constants for metal removal are almost independent of the concentration of the replacing ligand, indicating dissociative mechanisms they are approximately 1 x 10 s for displacement from doxorubin and between 12 x 10 s and 2 x 10 s from calcein. 

This chapter is concerned with dyes and pigments which are complexes of azo, formazan, azomethine, nitroso, anthraquinone and phthalocyanine ligands. Many of these compounds find important applications in other fields, particularly colour photography and reprography, analysis, catalysis, biology, and some modem high technology industries such as electronics. These applications are described in other chapters of this volume. 

Anthracene can be selectively oxidized to anthraquinone by molecular oxygen in the presence of copper(II) bromide in an ethylene glycol solution. Ethylene glycol (EG) acts as a bidendate ligand for copper and prevents the formation of bromoanthracene as a by-product (equation 267).596... 

An important improvement with regard to both substrate tolerance and enantioselectivity of the AD was the introduction of the anthraquinone-bridged ligands (DHQ)2AQN and (DHQD)2AQN [2], These ligands are easily accessible fromphthalic anhydride and 1,4-difluoro benzene, and in many aspects their catalytic behavior reflects that of the standard bis-cinchona alkaloids described in Section 6D.1. 

The Streptomyces strain that produces celastramycin A (1212) has also yielded celastramycin B (2166) (1225). Another Streptomyces sp. has afforded bischloro-anthrabenzoxocinone ((-)-BABX) (2167), which has antibacterial activity and inhibits ligand-binding activity of liver X receptors (1937). An example of a rare chlorinated anthraquinone is anthrasesamone C (2168), which was characterized in the Japanese plant Sesamum indicum (1938). The angucycline-type marmycin B... 

Compound 18 showed a remarkable color change from orange to brown (Amax=670 nm) in DMSO upon adding F". Color changes are most probably due to a charge-transfer process and electron-rich formation of hydrogen bonds between thiourea-bound F and the electron-deficient anthraquinone moiety. The anion was believed to form a 2 1 anion-to-ligand ratio as shown in Fig. 4. 

Additional studies using the same complexes in both cisplatin sensitive and resistant forms of U2-OS cells also showed differences in the cellular processing of the drugs both the free ligands and platinum complexes were rapidly found to accumulate in the nucleus, after uptake into the Golgi, which was hypothesized to be involved in transport of the platinum complexes out of the cells (56). In this set of studies, fluorescence imaging helped to illustrate the differences in the intracellular interactions of dinuclear platinum-anthraquinone complexes in different cell lines and in the different resistance profiles of A2780 and U2-OS resistant sub lines. 

The Sharpless regioreversed asymmetric aminohydroxylation protocol was used as a key step in the total synthesis of ustiloxin D by M.M. Joullie and co-workers.The ( )-ethyl cinnamate derivative was subjected to in situ generated sodium salt of the N-Cbz chloroamine in the presence of catalytic amounts of the anthraquinone-based chiral ligand to afford the desired A/-Cbz protected (2S,3R)-(3-hydroxy amino ester in good yield and with good diastereoselectivity. 

The regioselective process is suitable for the synthesis of protected (3-amino-a-hydroxycarboxylic acid derivatives (racemic, no chiral ligand added) from the corresponding acrylic acid substrates. On the other hand, 1,4-bis(dihydroquininoxy)-anthraquinone mediates enantioselective formation of A-benzyloxycarbonylphenylserine. ... 

More recently discovered ligands21 include the diphenylpyrazinopyridazine (DPP) 98 and anthraquinone (AQN) 99 ligands as well as the diphenyl analogue of the phthalazine ligands (DP-PHAL) 97. 

A member of the new ligand class for the asymmetric dihydroxylation is the bis(dihydroquinidine) ether of l,4-dihydroxy-9,10-anthraquinone. Cinchona alkaloid ligands bound to soluble polymer supports" are effective catalysts for asymmetric dihydroxylation. 

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