m-PEG2-amido-Ph-NH2

m-PEG2-amido-Ph-NH2, is designed to provide a flexible polyethylene glycol-based spacer coupled to an aniline functionality for efficient conjugation between targeting and E3-ligase-recruiting modules. Its ether-rich, hydrophilic character can improve solubility and mitigate steric constraints, supporting reliable construction of bifunctional degraders. The linker’s amide-bearing aromatic core enables robust, widely used coupling strategies, and the subsequent sections describe its structure and practical reactivity for PROTAC assembly in detail below.

Structure: The linker contains an aniline (primary amine) attached to a substituted phenyl ring bearing an amide-linked PEG segment. It features ether linkages within the PEG chain, aromatic C–C bonds, and an amide linkage capable of hydrogen bonding, contributing to enhanced hydrophilicity and conformational flexibility.

Reactivity: The primary amine enables nucleophilic acyl substitution or amide-bond formation with activated carboxylic acid derivatives commonly used in PROTAC synthesis, such as activated esters or acid chlorides. For efficient coupling, researchers typically employ base and polar aprotic solvents under mild, anhydrous conditions to suppress side reactions. The amine can also participate in carbamate or urea-forming routes when complementary activated electrophiles are used, following standard PROTAC linker-conjugation mechanisms.