Carboxylic-containing ligands

Loll, P.J. et ah. Simultaneous recognition of a carboxylate-containing ligand and an intramolecular surrogate ligand in the crystal structure of an asymmetric vancomycin dimer, J. Am. Chem. Soc., 119, 1516, 1997. 

Much effort has been devoted to development of BFCAs for this versatile radiometal. The most common Tc(V) complexes are usually obtained by conjugating the biomolecules with BFCAs containing nitrogen and sulfur atoms [NjcS(4-jc) coordination set], but stable complexes can also be obtained with phosphino-, carboxylate-containing ligands, and so on. The coordination approach may vary as well [tetradentate complexes, mixed (3-1-1) approach, Tc(1)(CO)3 approach, direct labeling, etc.], depending on the biomolecule to be labeled (27,28). 

Figure 2.3 SAM surface modification has been done using monothiol and dithiol compounds containing PEG linkers. Useful coatings typically contain mainly PEG-hydroxyl or PEG-monomethyl ether linkers that provide a biocompatible lawn, which prevents nonspecific binding of proteins to the metallic surface. About 10 percent of the surface modifications are done using a longer carboxylate-containing thiol-PEG linker that provides sites for attachment of affinity ligands.

Figure 13.5 Modification of an APTS surface with glutaric anhydride creates terminal carboxylates for coupling of amine-containing ligands.

Figure 13.7 Carboxylethylsilanetriol can be used to modify an inorganic substrate to containing carboxylate groups for coupling amine-containing ligands.

Dissolve the amine-containing ligand to be coupled in 5 ml coupling buffer at a concentration sufficient to provide a 1- to 10-fold molar excess of ligand over the maximal calculated carboxylate group concentration for the amount and type of beads used. For particle manufacturers reporting a carboxylate concentration in meq/g, this is equivalent to pmol/mg. 

Carboxylated silica particles may be coupled with amine-containing ligands, such as proteins, using a carbodiimide reaction with EDC. A similar protocol to that previously described for coupling to carboxylate polymer particles may be used. The following protocol is based on the method of Zhao et al. (2004), which was used for immobilizing monoclonal antibodies to E. coli 0157. 

The PCBM methyl ester can be used for coupling amine-containing ligands after removal of the methyl group and activation of the carboxylate using a number of different reaction strategies. Hummelen et al. (1995) successfully coupled cholestanol and histamine to the fuller-ene-PCBM derivative (after acid chloride formation) for use in fabrication of photodetectors and biological studies, respectively. For specific applications of PCBM-fullerenes, see Shaheen et al. (2001), Brabec et al. (2001), Yu et al. (1995), Mecher et al. (2002), Meijer et al. (2003), van Duren et al. (2004), and Anthopoulos et al. (2004). 

Figure 15.15 An aldehyde derivative of pyrene can be used to couple a hydrophilic amino-PEG-carboxylate spacer by reductive amination. The resultant derivative then can be used to coat a carbon nanotube through pyrene ring adsorption and result in a water-soluble derivative containing terminal carboxylates for coupling amine-containing ligands.

NMR studies of the mixed carboxylates containing acetates and trichloroacetates have indicated that ligand scrambling reactions occur in solution although all of the species were isolated, and isomerization possibilities occur, no discrete isomers were identified.329 Gas... 

Copper-catalyzed allylic oxidation allows the functionalization of unactivated alkenes into chiral allylic carboxylates.1347 The use of oxazoline-containing ligands give good enantioselectivities, but the reaction is extremely slow.1348-1351 Chiral bipyridine complexes, in turn, are much more active and give products in good yields and enantioselectivities up to 70% when applied in benzoyloxylation of cycloalkenes with rm-butyl perbenzoate.1352,1353... 

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