Lipophilic ligands

Simple metal compounds are poorly soluble in non-coordinating ILs, but the solubility of metal ions in an IL can be increased by addition of lipophilic ligands. LLowever, enhancement of lipophilicity also increases the tendency for the metal complex to leach into less polar organic phases. 

Lipophilic ligands, e.g. 45-49 having chiral L-2-pyrrolidine-methanol moieties, have been prepared and examined for their catalytic activities in reactions with optically active esters (50-52). 

Schmale H., Holtgreve-Grez H. and Christiansen H. (1990). Possible role for salivary gland protein in taste reception indicated by homology to lipophillic-ligand carrier proteins. Nature 343, 366-369. 

This chapter will summarize recent developments regarding the role of physicochemical properties in safety liability and the emerging use of physicochemical property-based lead optimization using lipophilic ligand efficiency (LLE or LipE). 

With solubility as one of the principal problems to obtain structural information, the introduction of lipophilic ligands has been particularly successful, as shown impressively with the silyl substituted [CH(SiMe3)2] and [C(SiMe3)3] ligands.20 Steric bulk has also been applied successfully to reduce the tendency toward aggregation. This has been vividly demonstrated by recent chemistry utilizing terphenyl ligands.21... 

Fig. 2. Schematic representation of selective ion transport through a lipophilic membrane by complex formation between cation 1+ and a lipophilic ligand S (Fig. 2a) or S (Fig. 2b)...

Simon et al. [47] developed a photometric flow-through sensor for the determination of zinc using a transparent PVC membrane accommodating a lipophilized ligand, viz. l-octadecyloxy-4-(2-pyridylazo)resorcinol, a water-insoluble derivative of PAR. The mechanism by which the analyte is retained in the membrane and eluted from it is similar to a liquid-liquid extraction... 

Blumberg, P.J., Jaken, S., Konig, B., Sharkey, N., Leach, K., Jeng, A., AND Yeh, E. (1984). Mechanism of action of the phorbol ester tumor promoters Specific receptors for lipophilic ligands, Biochem. Pharmacol., 33,933. 

These comparatively lipophilic ligands have been conceived as ion carriers for systems such as ion-selective electrodes, 29 therefore they do not have high stability constant values, but require fast complexation kinetics in order to achieve rapid equilibration. Nevertheless, it has been possible to recover crystalline species which often have present additional water molecules to help stabilize the crystal lattice. Coordinative participation of the carbonyl oxygen... 

Patel S. C., Asotra K., Patel Y. C., McConathy W. J., Patel R. C., and Suresh S. (1995). Astrocytes synthesize and secrete the lipophilic ligand carrier apolipoprotein D. NeuioReport 6 653-657. 

Perireceptor events and role of lipophilic ligand-carrier proteins... 

Enzyme receptors are transmembrane receptors with intrinsic enzymatic activity. Examples are the receptor tyrosine kinases (RTKs), which autophosphorylate their own tyrosine residues, such as the growth factor receptors and the insulin receptor. And, finally, there are the intracellular DNA sinding receptors. They bind lipophilic ligands that pass through the membrane. They address genes directly. Examples are the steroid hormone receptors (see Chapter 11). (This figure was donated by Professor Martin Lohse, University of Wurzburg.)... 

Nuclear receptors. Intracellular DNA-binding proteins which bind lipophilic ligands which pass the membrane without assistance. Examples are the steroid hormone receptors and the receptors for non-steroidal ligands, such as retinoids and the hormone thyroxin. 

Scrimin P, Tonellato U, and Zanta N. Cu(II) mediated selective transport of a-amino acids across a bulk liquid membrane using a chiral lipophilic ligand as a carrier. Tetrahedron Lett, 1988 29(39) 4967M-970. 

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