Methyltetrazine-PEG5-nhs ester

Methyltetrazine-PEG5-nhs ester is a bifunctional PROTAC linker designed to integrate a methyltetrazine handle for bioorthogonal assembly with an NHS ester for efficient coupling to primary amines on targeting ligands. Its PEG-based spacer supports favorable solubility and conformational flexibility, which can improve conjugation outcomes and maintain productive ternary complex formation. The detailed structural and reactivity characteristics are provided below.

Structure: The molecule contains a methyltetrazine moiety linked to a polyethylene glycol chain terminated by an N-hydroxysuccinimide ester. It features an aromatic heterocycle, an ether-rich PEG segment, and an acyl–oxygen leaving group characteristic of NHS esters, contributing to aqueous compatibility and controlled reactivity toward amines.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution to form stable amide bonds under mildly basic aqueous buffer conditions. The methyltetrazine group participates in inverse-electron-demand Diels–Alder bioorthogonal chemistry with appropriate strained dienes, enabling stepwise PROTAC assembly. Typical coupling workflows use amine-containing ligands, buffered solvents, and temperature control to preserve linker integrity while maximizing coupling efficiency.