Imidazolyl carbamate

CDI-activated hydroxyls also may undergo a side reaction to form active carbonates. This occurs when an imidazolyl carbamate reacts with another hydroxyl group before the second hydroxyl has had a chance to get activated with CDI. Particularly with adjacent hydroxyls on the same molecule, this can be a problem if a defined reactive species is desired. Any carbonates formed, however, are still reactive toward amines to create carbamate linkages. 

There are a few precautions that should be noted when doing a CDI activation and coupling experiment. First, CDI itself is extremely unstable to aqueous environments, much more so than the active imidazolyl carbamate that s formed after PEG activation. Therefore, the activation step must be done in a solvent that is free of water. If unacceptable amounts of water are present, CDI will be immediately broken down to C02 and imidazole. The evolution of bubbles upon addition of CDI to a PEG solution is the telltale sign of high water content. Only freshly obtained solvents analyzed to be extremely low in moisture or those dried over a molecular sieve should be used. A water content of less than 0.1 percent in the solvent is usually all right for a CDI activation procedure. 

Imidazolyl carbamate -nh2 carbonyldiimidazole affinity resins (S) Reacti-gel (P)... 

Reacti-Gel Pierce Agarose Imidazolyl carbamate None — Primary amino groups... 

HMR-3647 (telithromycin TLM) (91i), one of the 11,12-cyclic carbamate ketolides bearing various heterocyclic butyl substituents at 11-Ai of carbamate (91), was synthesized from 10,ll-anhydro-12-O-imidazolyl carbonyl ketolide (90) by the reaction with the corresponding amine (Scheme 8) [125]. The synthesis of the heterocyclicbutylamines (Scheme 8, a-i) was achieved by alkylation of the respective heterocyclic amine with 4-bromobutylphthalimide in the presence of NaH or K2CO3 in DMF, followed by hydrazinolysis of phthalimide intermediates. The overall yields of these steps were 24-64%. 

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