Cell-penetrating peptoids: Introduction of novel cationic side chains

•Peptoids with novel cationic side chains are presented.•The peptoids were labeled with rhodamine B for fluorescence microscopy.•The cell-penetrating properties of these peptoids are evaluated.•Peptoids with polyamine side chains accumulate in cytosol.

During the last decade peptoid-based molecular transporters have been broadly applied. They are highly valued for their easy synthesis and their superior stability against enzymatic degradation. The special structure of peptoids generally allows introducing a variety of different side chains. Yet, the cationic side chains of cell-penetrating peptoids displayed solely lysine- or arginine-like structures. Thus this report is intended to extend the spectrum of cationic peptoid side chains. Herein, we present novel functional groups, like polyamines, aza-crown ethers, or triphenylphosphonium ions that are introduced into peptoids for the first time. In addition, the obtained peptoids were tested for their cell-penetrating properties.

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