S-acetyl-PEG6-Tos

This PEG-based linker, S-acetyl-PEG6-Tos, is designed to support efficient PROTAC assembly by providing a hydrophilic, flexible tether that can improve effective positioning between the target-binding ligand and the E3-recruiting moiety. Its functional handle enables robust conjugation strategies commonly used in targeted protein degradation workflows. The structure and reactivity considerations for constructing PROTACs with this linker are described in detail below.

Structure: S-acetyl-PEG6-Tos comprises an S-acetyl thioester that serves as a protected thiol, linked through a polyethylene glycol chain to a terminal alkyl tosylate. It contains ether linkages within the PEG segment, an S-acetyl thioester, and a tosylate leaving group, yielding a polar, water-compatible scaffold with conformational flexibility.

Reactivity: The linker is suited for PROTAC synthesis via SN2 substitution at the alkyl tosylate and controlled deacetylation of the S-acetyl group to reveal a free thiol. Typical approaches include nucleophilic substitution at the tosylate under conditions that preserve the PEG chain integrity, followed by thiol deprotection when needed. Mild bases or appropriate nucleophiles in polar organic solvents are commonly used to promote controlled bond formation; subsequent deprotection or exchange can be employed to unmask reactive sulfur functionality when required for final assembly.