Schlüsselwort: reduktive Aminierung

In the course of this thesis, different new mono- and bifunctionalized dyes based on diaminoterephthalate scaffolds were prepared. Therefore, the reductive amination reaction was established as a new method to functionalize the scaffold at its amino moieties. The synthesis started from different succinates, which can be easily, prepared from succinic anhydride in two steps. Using a Claisen- followed by Dieckmann-condensation, the ring was closed to form the corresponding succinylsuccinates, which successively underwent an aminolysis reaction and oxidation to the diaminoterephthalates. In order to address the two amino moieties separately, only one amino group was Boc-protected to deliver the desired orthogonally protected diaminoterephthalate scaffolds for further functionalization. For the synthesis of monofunctionalized dyes, linkers with differently protected amino or carboxylate functions were installed at the scaffold by reductive amination using the corresponding aldehydes. After deprotection, effector groups could be attached by amide coupling delivering a variety of different monofunctionalized dyes. As effector groups, azides for click-chemistry, maleimide building blocks for conjugated addition to cysteine, biotin for selective binding to streptavidin or a fullerene (C60) as an electron-acceptor to form an optoelectronic dyad were used. In order to synthesize bifunctional dyes, different starting materials derived from diaminoterephthalate-scaffold were prepared. First, one linker was attached to the free amino function by reductive amination, followed by deprotection of the second amino group. Then, the second linker was attached by the same method, delivering different starting materials, which represent every possible combination of linkers with orthogonally protected amino or carboxylic acid functions with. Using these starting materials, three different bifunctionalized dyes were synthesized over four steps by a sequence including deprotections of the linkers and attachment of effector groups by amide coupling. The two dyes were crosslinkers for biological applications. Of which one was carrying a cyclooctin group, the other one an azide. Both groups can be used for click-chemistry and were combined with a maleimidegroup for binding to a cysteine residue. The third dye was equipped with an electron-accepting fullerene (C60) unit together with an electron-donating retinoic acid group and could therefore be used as an optoelectronic triade. Another part of the project was the synthesis of diaminoterephthalate-based dyes for electrochemical studies starting form scaffold. To attach the dye to gold surfaces, α-lipoic acid was bound to the scaffold either directly or with a linker unit. For reactions in solution, an acetyl group was used instead. Additionally, a group of dyes was prepared where the Boc-group was replaced with trifluoromethylated benzyl groups for detection by XPS.