A synthesis of 4-(arylmethyl)proline by using Suzuki cross-couplings was developed. The route permits access to a variety of 4-substituted proline derivatives bearing various aryl moieties that expand the toolbox of proline analogues for studies in chemistry and ­biology.

Proline and proline derivatives are useful tools to control the structural properties of peptides and proteins, and thereby modulate numerous processes. Here, we show that proline derivatives can have unique structural properties in the solid state by presenting the crystal structure of zwitterionic (2S,4S)/(2S,4R)‐4‐[(naphthalen‐2‐yl)methyl]proline (H‐Nap‐OH). This amphiphilic proline derivative forms a columnar structure around large hydrophilic and small hydrophobic channels with diameters of 9 Å and 4 Å, respectively. We show that this architecture, which is unprecedented for amino acids, results from the combination of a hydrogen bond network between the ammonium and carboxylate moieties and π–π as well as CH–π interactions between the aromatic moieties.

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