Tos-PEG7-OH

Tos-PEG7-OH is a PEG-based linker designed for constructing PROTACs that require a flexible, hydrophilic spacer between the target-binding ligand and the E3 ligase-recruiting moiety. Its ether-rich PEG architecture can improve solubility and help tune the effective distance and conformational freedom during ternary complex formation. The tosyl end group provides a chemically addressable handle, enabling controlled conjugation chemistry. Detailed structural and reactivity considerations are provided below to support experimental PROTAC synthesis.

Structure: Tos-PEG7-OH comprises a tosyl-protected terminus linked to a poly(ethylene glycol) chain terminating in a hydroxyl group. The molecule contains aromatic sulfonate functionality, ether linkages, and a terminal alcohol, yielding high polarity, flexibility, and favorable water compatibility typical of PEG spacers.

Reactivity: The tosyl group acts as an activated leaving group for nucleophilic substitution, enabling attachment of PROTAC fragments bearing suitable nucleophiles under standard organic synthesis conditions. Typical approaches involve using bases to generate the nucleophile, followed by reaction in polar aprotic or mixed solvent systems to promote efficient displacement. The PEG chain generally confers conformational flexibility without strongly altering the fundamental substitution mechanism.