Aldehydes heterobifunctionals

Figure 17.5 Structures of aldehyde-containing and hydrazine-containing heterobifunctional crosslinkers that can be used in chemoselective hydrazone conjugation procedures.

The ethylene diamine-dextran derivative may be used for the coupling of carboxylate-contain-ing molecules by the carbodiimide reaction, for the coupling of amine-reactive probes, or to modify further using heterobifunctional crosslinkers. The hydrazide-dextran derivative may be used to crosslink aldehyde-containing molecules, such as oxidized carbohydrates or glycoproteins. 

The complex resulting from triple C-H/N-H activation can be heterobifunc-tionalized by successive addition of CO2 (carboxylation of the hexamethylbenzene ligand) and water (acidic hydrolysis of the imine to the aldehyde on the Cp substituent). This heterobifunctional complex is very useful for the branching to nano-scopic substrates and yet keep the solubility in aqueous media by means of the carboxylate group. Use of this functionalized electron-reservoir system in redox catalysis is promising. Thus, from the starting 18-electron complex, the overall heterobifunctionalization can be carried out in one pot as shown in Scheme 16 [177, 178]. 

Fig. 2.6 Schematic representation of the S subsites of the p2 active site of the yeast 20S proteasome as structural model for the design of maleoyl-y -alanyl-dipeptide aldehydes as a new type selective heterobifunctional inhibitors.

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