Benzyl-PEG-CH2CO2tBu is a class of compounds that is widely used in pharmaceutical research and development. It belongs to the class of polyethylene glycol (PEG) derivatives that are designed to have a benzyl group attached to the PEG backbone, which is terminated with a t-butyl carboxylate group. These functional groups provide unique properties to the compound that make it suitable for use in pharmaceutical applications. For example, the benzyl group can be used for conjugation with other biomolecules, such as proteins or drugs, to improve their solubility and pharmacokinetics. The t-butyl carboxylate group can also act as a protecting group for carboxylic acids, which is commonly used in drug synthesis.