Inspired by the uniqueness and ubiquity of thioesters in nature, much attention has been paid to thioester functionalized materials, yielding applications ranging from responsive polymers to bioconjugates and (bio)degradable polymers.
A strategy for the synthesis of sequence-defined oligomers using a selective side-group insertion approach making use of thiophenol-catalyzed amidation reactions is herein reported. In this context, a new thiolactone-based, multistep, iterative protocol is designed, utilizing thioacrylates in combination with solid-phase synthesis for step-by-step growth, resulting in sequence-defined oligomers. Sequence definition and structure variation are introduced by substituting the thioacrylate side groups with a wide variety of amines. The step-by-step growth of the oligomers is followed by liquid chromatography-mass spectrometry and high-resolution mass spectroscopy to determine both conversion and purity.
The synthesis of a new class of Cu‐mediated polymerization initiators with thioester functionality is demonstrated and their polymerization kinetics via single‐electron transfer living radical polymerization is reported. From periodic sampling, it is found that thioester‐ or ester‐based initiators can be employed interchangeably, resulting in very similar polymerization rates. Furthermore, a multifunctional thioester initiator is employed for the preparation of a well‐defined four‐arm star‐shaped polymer. It is further shown that the full dissociation of the star polymer into linear arms via native chemical ligation can easily be followed via size exclusion chromatography, as a result of the change in hydrodynamic volume. Finally, the obtained linear polymers are characterized via matrix‐assisted laser desorption/ionization–time of flight mass spectrometry and found to be in good agreement with the expected molecular weight distribution that confirms the successful transformation.
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