Imidazole carbamate

Figure 3.13 CDI reacts with hydroxyl groups to form an active imidazole carbamate intermediate. In the pres ence of amine-containing compounds, a carbamate linkage is created with loss of imidazole.

The imidazole carbamate group is more stable to hydrolysis in aqueous buffer than the NHS-carbonate group, which is similar in reactivity to an NHS ester. However, this means that the imidazole carbamate also is slower to react and couple with amines. NHS-carbonate reactions usually go to completion within 1-2 hours at room temperature, whereas imidazole carbamates typically require higher pH conditions and overnight incubations to get maximal yield of ligand coupling. 

Wash the activated particles 3 times with anhydrous THF to remove excess CDI and reaction by-products. After the final wash, remove the solvent and perform a quick wash with ice-cold water to remove most traces of solvent in the particle pellet. Finally, resuspend the particles at 10 mg/ml in cold 0.1 M sodium phosphate, pH 8.2, or 0.1 M sodium carbonate, pH 9.5 (coupling buffer). The higher pH coupling buffer will result in greater reactivity of the imidazole carbamate and greater coupling yields for proteins. 

Figure 14.15 CDI can be used to activate hydroxyl-particles in organic solvent and then the intermediate reactive imidazole carbamate brought into aqueous solution for coupling amine-containing ligands.

Figure 15.13 Tween 20 can be activated with CDI using its hydroxyl groups to create an amine-reactive imidazole carbamate intermediate that then can be used to coat a carbon nanotube. The result is an activated nanotube that can be used to couple proteins and other amine-containing molecules.

Figure 25.8 N,N -carbonyldiimidazole (CDI) may be used to activate the terminal hydroxyl of mPEG to an imidazole carbamate. Reaction of this intermediate with an amine-containing compound results in the formation of a stable carbamate linkage.

To remove excess CDI and reaction by-products, Beauchamp et al. (1983) dialyzed against water at 4°C. However, the imidazole carbamate groups on mPEG formed during the activation process are subject to hydrolysis in aqueous environments. A better method may be to precipitate the activated mPEG with diethyl ether as in the protocol described previously for SC activation (Section 1.2, this chapter). 

SYNS METHYL-2-BENZIMIDAZOLE CARBAMATE and SODIUM NITRITE SODIUM NITRITE and CARBENDAZIM (1 5) SODIUM NITRITE and METHYL-2-BENZ-IMIDAZOLE CARBAMATE... 

N-Alkoxycarbonyl)- and (N-aryloxycarbonyl)imidazoles (carbamates) were unambiguously proven to be the products of the reaction of JV,JV -carbonyldiimidazole (CDI) with alcohols [448]. Reaction of CDI with 2,6-dimethylphenol or 1-indanol gave (on the basis of IR and NMR evidence) the corresponding carbamate in yields of 91% and 42%, respectively. 

Preparation of diol-Eupergit from epoxy-Eupergit Aldehyde-silica activation of diol-silica Tresyl-silica activation of diol-silica Imidazol carbamate-silica activation of diol-silica Epoxy-Separon KXK) activation of a synthetic gel with free hydroxyl groups... 

Imidazol carbamate-silica activation of diol-sUka -n... 

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