Urea receptor

One example of this approach is illustrated in Fig. 1, which represents the interaction at the sulphonyl urea receptor associated with the Katp potassium channel and which is involved in the control of insulin release in the pancreas. This pharmacophore map was obtained by an analysis... 

Sulfonylureas bind to a 140 kDa high-affinity sulfonyl-urea receptor that is associated with a B cell inward rectifier ATP-sensitive potassium channel. Binding of a sulfonylurea inhibits the efflux of potassium ions through the channel (Figure 41-2) and results in depolarization. Depolarization, in turn, opens a voltage-gated calcium channel and results in calcium influx and the release of preformed insulin. 

Ravikumar I, Lakshminarayanan PS, Arunachalam M et al (2009) Anion complexation of a pentafluorophenyl-substituted tripodal urea receptor in solution and the solid state selectivity toward phosphate. Dalton Trans 4160 -168... 

Kelly and Kim have carried out a detailed study of the relative binding affinities of carboxylate, nitro, phosphate, phosphonate, sulfonate and 5-lactones with a urea-derived host (Figure 105) [138]. The effects of solvents on the binding affinity were also studied. This bis(urea) receptor was found to bind isophthalate in DMSO-dg with a greater than 10 M- . 

Hamilton studied the properties of several bis-urea receptors for dicarboxy-lates (Fig. 3A). Cooperative interactions in these complexes can be compared with the simple urea—carboxylate complex shown in Fig. 3B. 

Figure 3 (A) Hamilton s bis-urea receptor for glutarate and (B) the corresponding reference system.

For a number of years, Thummel fabricated various nitrogen-based heterocyclic receptors using Fischer indolization. For example, urea receptors 178-180 are depicted in Scheme 49 (equations 1 and 2) [365]. Thummel, Wang, and their coworkers synthesized luminescent diphenylboron... 

Figure 31 Anion-assisted helical assembly of 56 and AgBp4 in (a) space filling and (b) ball and stick views. In (b) Ag" " and BF4 atoms are shown as balls and urea receptors are shown as sticks.

Due to the favorable conformation for multiple H-bonds, tren-based tripodal tris (urea) receptors, including 38a-j, have proven to be a promising scaffold for anion binding. Such receptors not only complementarily encapsulate oxoanions (sulfate, carbonate, and phosphate) but also display excellent binding ability to spherical halide ions. Several groups studied tripodal trisurea receptors with different substituents. 

Das and co-workers reported nitrophenyl-substituted tripodal tris(urea) receptor 38d showed preferential binding for sulfate/phosphate anions. Two receptors form a neutral molecular capsule, within which a unique sulfate-(H20)3-sulfate adduct was... 

Oligourea receptors bearing up to six covalently linked urea groups have been designed for anion coordination and supramolecular self-assembly. In 2010, Wu and co-workers synthesized a fully complementary tris(urea) receptor 39 by... 

BUN, blood urea nitrogen Cl, calcineurin inhibitor CSA, cyclosporine IL-2RA, interleukin 2 receptor antagonist LFTs, liver function tests MMF, mycophenolate mofetil OKT-3, muronomab-CD3 RATG, rabbit antithymocyte immunoglobulin ... 

ATC, lymphocyte immune globulin, antithymoglobulin equine AZA, azathioprine BUN, blood urea nitrogen CSA, cyclosporine Cl, gastrointestinal IL-2RA, interleukin 2 receptor antagonist MMF, mycophenalate mofetil OKT-3, muronomonab-CD3 PRED, prednisone SCr, serum creatinine SRL, sirolimus TAC, tacrolimus WBC, white blood cell. 

Shi SR, Chaiwun B, Young L, et al. Antigen retrieval technique utilizing citrate buffer or urea solution for immunohistochemical demonstration of androgen receptor in formalin-fixed paraffin sections. J. Histochem. Cytochem. 1993 41 1599-1604. 

UDP-a-glucuronic acid 90 unbound drug concentration 50 unbound drug 24,125 GABA uptake inhibitors 6 histamine -receptor antagonists uptake of drugs in the brain 6 urea 42 urine 62, 67... 

A series of imidazo[l,5-a]quinoxaline amides, carbamates, and ureas which have high affinity for the y-aminobutyric acid A/benzodiazepine receptor complex was developed. Compounds within this class have varying activities ranging from antagonists to full agonists. However, most analogs were found to be partial agonists as indicated by [ S]TBPS and Cl current ratios. Many of these... 

Kim, Chin, and co-workers have described a highly interesting oxyanion hole mimic that transforms L-amino acids to D-amino acids [97]. The mechanism involves stabilization of the enolate intermediate by an internal hydrogen bond array generated by urea group (Scheme 4.14). In the presence of an external base, such as triethylamine, the receptors readily promote the epimerization of a-amino acids, favoring the D-amino acids due to unfavorable steric interactions in the receptor-L-amino acid complex. These receptors can also be viewed as chiral mimics of pyridoxal phosphate [98]. 

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