Tert-Butyl 3-(2-(2-hydroxyethoxy)ethoxy)propanoate

This substance is typically encountered as a colorless to pale yellow viscous liquid at ambient temperature with a faint ester-like odor. Its molecular formula is C11H22O5, corresponding to a molecular weight of 234.29. The boiling point is approximately 140–145 °C at reduced pressure (0.5 mmHg), with a calculated density near 1.04 g/cm³ at 20 °C. It is freely miscible with common organic solvents including dichloromethane, tetrahydrofuran, methanol, and ethyl acetate, while showing moderate solubility in water due to the hydrophilic polyether chain and terminal hydroxyl group. The molecule contains a tert-butyl ester protecting group at one terminus and a primary alcohol at the other, with a flexible diethylene glycol spacer connecting them. The tert-butyl ester is stable under basic conditions but readily cleaved under acidic conditions to reveal the carboxylic acid. Storage in tightly sealed containers under inert atmosphere at reduced temperature (2–8 °C) is recommended to prevent hydrolysis and moisture absorption. Contact with strong acids, strong bases, and oxidizing agents should be avoided.

Tert-Butyl 3-(2-(2-hydroxyethoxy)ethoxy)propanoate consists of a propanoate backbone extended by a diethylene glycol spacer and terminated with a primary alcohol, with the carboxylic acid protected as its tert-butyl ester. This molecular architecture combines three distinct functional elements: a latent carboxylic acid (the Boc-protected ester), a flexible hydrophilic polyether tether, and a nucleophilic primary alcohol. The diethylene glycol segment imparts water solubility and conformational flexibility, enabling the molecule to serve as a solubilizing spacer in various applications. The primary alcohol provides a handle for further functionalization through esterification, etherification, or oxidation to the corresponding aldehyde or carboxylic acid. The tert-butyl ester serves as a protecting group that can be selectively removed under mild acidic conditions without affecting the alcohol or ether linkages. This combination of orthogonal reactive centers and a hydrophilic spacer makes the compound a valuable building block for constructing complex molecules in pharmaceutical research, bioconjugation, and materials science.

PEGylation and Bioconjugation
This heterobifunctional PEG derivative is extensively employed for introducing hydrophilic spacers into peptides, proteins, and small molecules. The primary alcohol can be activated as a leaving group or oxidized to an aldehyde for conjugation, while the tert-butyl ester can be deprotected to reveal a carboxylic acid for amide coupling with amines. The flexible diethylene glycol chain enhances aqueous solubility and reduces nonspecific binding of the resulting conjugates, making it valuable for developing antibody-drug conjugates and long-circulating therapeutics.

Pharmaceutical Intermediate
In medicinal chemistry, this compound serves as a building block for synthesizing prodrugs and targeted drug delivery systems. The hydrophilic spacer can improve the pharmacokinetic properties of hydrophobic drug candidates by increasing solubility and reducing clearance rates. After incorporation into a drug molecule, the tert-butyl ester can be hydrolyzed in vivo to release the active carboxylic acid-containing pharmacophore, enabling controlled release strategies.

Surface Functionalization and Hydrogel Synthesis
The molecule is employed to modify surfaces with hydrophilic coatings and to prepare crosslinked hydrogels for biomedical applications. The primary alcohol can be conjugated to activated surfaces or polymer backbones, while the protected carboxylic acid remains available for subsequent crosslinking or attachment of bioactive molecules. These materials are investigated for drug delivery, tissue engineering, and biosensor development where controlled hydrophilicity and biocompatibility are required.

Organic Synthesis Building Block
As a versatile synthetic intermediate, tert-butyl 3-(2-(2-hydroxyethoxy)ethoxy)propanoate participates in diverse transformations including esterification of the primary alcohol with activated carboxylic acids, oxidation to the corresponding aldehyde or acid, and conversion to the corresponding halide or tosylate for nucleophilic substitution reactions. The orthogonal protecting group strategy enables sequential functionalization of both termini, allowing construction of complex PEGylated architectures for drug discovery, materials chemistry, and chemical biology applications.