Poly(2‐ethyl‐2‐oxazoline) Featuring a Central Amino Moiety

Abstract

The incorporation of an amino group into a bifunctional initiator for the cationic ring‐opening polymerization (CROP) is achieved in a two‐step reaction. Detailed kinetic studies using 2‐ethyl‐2‐oxazoline demonstrate the initiators’ eligibility for the CROP yielding well‐defined polymers featuring molar masses of about 2000 g mol–1. Deprotection of the phthalimide moiety subsequent to polymerization enables the introduction of a cyclooctyne group in central position of the polymer which is further exploited in a strain‐promoted alkyne‐azide click reaction (SpAAC) with a Fmoc‐protected azido lysine representing a commonly used binding motif for site specific polymer–protein/peptide conjugation. In‐depth characterization via electrospray ionization mass spectrometry (ESI) confirms the success of all post polymerization modification steps.

Molecular Insights into Site-Specific Interferon-α2a Bioconjugates Originated from PEG, LPG, and PEtOx

“…Alternatively, the living oxazolinium ω-chain-end was further functionalized with phthalimide and subsequently deprotected by hydrazinolysis yielding the ω-amino PEtOx . The insertion of the cyclooctyne moiety was performed as for the LPGs utilizing the BCN-NHS ester . The successful modifications were demonstrated by 1 H NMR spectroscopy.…”

“…35 The insertion of the cyclooctyne moiety was performed as for the LPGs utilizing the BCN-NHS ester. 85 The successful modifications were demonstrated by 1 H NMR spectroscopy. The molar masses as well as dispersity values were determined by SEC (Figures S9, S10 and Table 1).…”

Protected amine-functional initiators for the synthesis of α-amine homo- and heterotelechelic poly(2-ethyl-2-oxazoline)s

“…This indicates that phthalimide initiators remain unaffected throughout the course of the CROP rendering them desirable protected amine initiators with respect to stability. 72…”

“…This indicates that phthalimide initiators remain unaffected throughout the course of the CROP rendering them desirable protected amine initiators with respect to stability. 72 Overall, the phthalimide initiators have proven superior with respect to stability, but like the BOC-protected amine initiators, they suffer from a slow and incomplete initiation and low control over the molar mass and Đ under the conditions presented. Thus, further optimization of the polymerization conditions was necessary to furnish defined α-amino PEtOx.…”

“…The polymer was treated with hydrazine monohydrate to obtain the diaminefunctionalized PEtOx. 51,75 Characterization of the product by 1 H NMR spectroscopy revealed the success of the reaction (Fig. S27a †).…”