Selective synthesis of heterobifunctional poly(ethylene glycol) derivatives containing both mercapto and acetal terminals

A novel synthetic route to heterobifunctional poly(ethylene glycol) (PEG) d erivatives containing both mercapto and acetal terminal groups was establis hed in this study using anionic ring opening polymerization of ethylene oxi de (EO) using potassium 3,3-diethoxypropanolate (PDP) as the initiator, fol lowed by the successive conversion of the end-alkoxide group to a methanesu lfonic group, and then to an ethyldithiocarbonate moiety. Molecular functio nalities of the acetal and the mercapto terminal groups of the heterotelech elic PEG (acetal-PEG-SH) thus prepared were confirmed to 1.00 and 0.85, res pectively, indicating that the reaction proceeds almost quantitatively. The obtained acetal-PEG-SH products, including 2-pyridyldithio derivatives, ha ve a promising utility for bioconjugation in the fields of medicine and bio logy.