tert-Butyl protected carboxylate PEG

Tert-butyl protected carboxylate PEGs have emerged as versatile tools in the fields of drug delivery and biomaterials. Its unique properties, such as hydroxyl protection and controlled deprotection, enable precise manipulation of PEG-based materials. Exposed carboxylic acid groups allow conjugation of drugs or biomolecules, facilitating targeted drug delivery and enhancing the functionality of biomaterials. As research and development continue, tert-butyl-protected carboxylate PEGs hold great promise for the advancement of drug delivery systems and biomaterials in various biomedical applications.

Structure of HO-PEG-COOtBu and NH2-PEG-COOtBu

Properties of Tert-butyl Protected Carboxylate PEG

Tert-butyl protected carboxylate PEG is a modified form of PEG in which the hydroxyl group is capped with a tert-butyl group (tBu). This modification has several advantages over unmodified PEG. First, the tBu group shields the hydroxyl groups, preventing unwanted interactions with other molecules, such as proteins or cell membranes. This protection increases the stability of PEG-based materials and reduces the chance of premature degradation. Second, tert-butyl protected carboxylate PEG can be easily deprotected to expose the carboxylic acid group. The tBu group can be selectively cleaved under mild conditions, such as treatment with trifluoroacetic acid (TFA) or hydrogen chloride (HCl). This controlled deprotection enables precise manipulation of PEG-based materials, allowing attachment of functional groups or conjugation of drugs.

Synthesis of Tert-butyl Protected Carboxylate PEG

The synthesis of tert-butyl-protected carboxylate PEGs generally involves two steps: protection of the hydroxyl group with a tBu group, followed by deprotection to expose the carboxylic acid group. A common approach to the protection step is the reaction of PEG with tert-butyl bromoacetate in the presence of a base such as sodium hydroxide. This reaction results in the formation of the tert-butyl protected carboxylate ester PEG. The deprotection step can be achieved by treating the protected PEG with a suitable acid (eg TFA or HCl). The acid selectively cleaves the tBu group, resulting in the exposure of the carboxylic acid group. The degree of deprotection can be controlled by adjusting the reaction conditions, thereby synthesizing PEGs with different degrees of deprotection.

Representative PEG-COOtBu Derivatives


HO-PEG-COOtBu stands for tert-butyl hydroxypolyethylene glycol carboxylate. It is a derivative of PEG and contains hydroxyl, carboxylic acid groups and tert-butyl ester groups. PEG derivatives such as HO-PEG-COOtBu are commonly used in a variety of applications such as drug delivery systems, biomaterials, and surface modifications due to their biocompatibility and ability to modify the properties of other molecules.


NH2-PEG-COOtBu is a compound consisting of a PEG chain connected to a tert-butyl ester group (COOtBu) through an amino group (NH2). In chemical synthesis, the tert-butyl ester group is a popular protective group used to shield carboxylic acids. NH2-PEG-COOtBu, as a derivative of PEG, can be used as a building block for the synthesis of various functional materials.

Applications of Tert-butyl Protected Carboxylate PEG

1. Drug Delivery System

Tert-butyl-protected carboxylate PEGs have broad applications in the development of drug delivery systems. The exposed carboxylic acid groups can be easily conjugated to various drugs or targeting ligands, enabling precise delivery of therapeutics to specific sites. PEG's hydrophilic properties improve hydrophobic medications' solubility and stability, and tBu protection shields them against premature release or contact with living things. In addition, drug release may be triggered via the regulated deprotection of tert-butyl-protected carboxylate PEG in response to certain stimuli like pH or enzymes. The invention of smart drug delivery systems that release medications only at the intended place, decreasing off-target effects, and enhancing therapeutic efficacy have taken use of this capability.

2. Biological Materials

In addition to drug delivery, tert-butyl-protected carboxylate PEGs have also been used in the development of biomaterials. To improve the material's biocompatibility and functioning, biomolecules like proteins or peptides can be conjugated to the exposed carboxylic acid groups. While handling or storing biological materials, tBu protection preserves their stability, and controlled deprotection permits the release of bound biomolecules as needed. Moreover, the construction of biomaterials with customized characteristics is made possible by the tert-butyl-protected carboxylate PEG's variable molecular weight and degree of deprotection. These substances can be applied to medical devices as coatings to encourage cell adhesion, proliferation, and differentiation or employed in tissue engineering and regenerative medicine.

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