Endo-BCN-PEG-PFP ester is a type of chemical compound that belongs to the family of reactive esters. This ester has several functional groups that make it useful for a variety of applications in pharmaceutical research and development. The functional groups of this compound include an endo-BCN group, a polyethylene glycol (PEG) chain, and a pentafluorophenyl (PFP) group. The endo-BCN group is particularly important as it enables bioorthogonal click chemistry, which is a powerful tool in drug development. The PEG chain, on the other hand, is known for its ability to increase solubility, improve bioavailability, and reduce toxicity of drugs. The PFP group is also useful as it can be easily modified to introduce other functional groups.