Ligand-terminated thiol

A common choice of crosslinker for this type of reaction is sulfo-SMCC, which has been used extensively for antibody conjugation (Chapter 20, Section 1.1). A better option for dendrimer conjugation is to use a similar crosslinker design, but one that contains a hydrophilic PEG spacer arm to promote dendrimer hydrophilicity after modification. Derivatization of an amine-dendrimer with a NHS-PEG-maleimide can create an intermediate that is coated with water-soluble PEG spacers. This modification helps to mask any potential for nonspecific interactions that the PAMAM surface may have, while providing terminal thiol-reactive maleimides for coupling ligands (Figure 7.10). 

Through systematic modification of the imidazole-appended 2-phenyl-aminobenzoate peptidomimetic scaffold (e.g., FTI-2148) a group at Abbott Pharmaceuticals have identified an expanded series of inhibitors that lack either the C-terminal Met carboxylate (as in compounds 14-23 of Ref. [55]) or the imidazole group (as in ABT-839) [56,70,71]. This latter compound became a clinical candidate and demonstrates that coordination to the zinc ion is not a prerequisite for potent inhibitors of FT. In place of metal-ligand (imidazole, thiol, etc.) coordination, ABT-839 exploits hydrophobic contact from the cyclohexylethyl and -butyl groups to the protein-binding pocket. For the structures of other CaaX peptidomimetics, please refer to Table 6.1. 

Another interesting application of specific interactions in SAMs is the use of ligand-derivatized thiols to build up complex biosupramolecular architectures via molecular recognition-driven processes. Typical examples include the use of biotin- and mannose-terminated SAMs to biorecognize and assemble streptavidin and concanavalin A protein layers, respectively, on metal surfaces with diverse purposes (Figure 12). " ... 

The authors proposed the complex [PdCl(SPh)(PhSH)]n 15 as an active catalyst, with thiol acting as a ligand of Pd(II) (Eq. 7.11). On the other hand, the reaction using RhCl(PPh3)3 as a catalyst precursor furnished the anti-Markovnikov ds-adducts 16 when a terminal acetylene was employed as a substrate (Eq. 7.12). 

Figure 2.2 A number of small thiol-containing molecules have proven useful for modification of gold or metallic surfaces. The dithiol derivatives provide better dative bond stability and can t be displaced easily by competing thiols or oxidation. Most thiol-containing compounds used for surface modification also contain terminal functional groups or reactive groups for coupling affinity ligands.

Abstract This review describes recent results in the field of poly(aryleneethynylene)s (PAEs) that contain metal ions in the polymer backbone, or in the polymer side chain. This work is focused primarily on polymers possessing ligands of metal complexes as part of the aryle-neethynylene chain. PAEs with porphyrinylene in the backbone have also been addressed. Synthetic routes toward the polymers, as well as their photochemical, photophysical, and electrochemical properties, are presented. Monodisperse oligo(phenyleneethynylene)s with terminal metal complexes or with a ferrocene and thiol at each end are mentioned. 

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