CHO-CH2-PEG2-CH2tBu-ester (CAS: 2230956-95-1) is a polyethylene glycol (PEG2) derivative containing an aldehyde group (CHO) and a tert-butyl ester (tBu-ester). Its structure consists of an aldehyde group, a methylene group (CH2), a dimeric polyethylene glycol chain (PEG2), and a tert-butyl ester moiety, combining hydrophilicity and reactivity. The production process typically involves esterification, using carboxylic acids or their salts as raw materials. The reaction is catalyzed by triphenylphosphine (PPh3) and diazodibenzene dicarboxylate (e.g., DIAD) in solvents such as tet