Z-Ala–Ile-OH, a dipeptide building block suitable for the formation of ortho­rhom­bic microtubes

Self-assembling dipeptides have emerged in the last two decades as promising building blocks for the development of novel biomaterials. Among the various classes of dipeptides, aromatic dipeptides and especially di­phenyl­alanine (Phe–Phe), which forms hexa­gonal nanotubes, have been the most extensively studied. However, aliphatic peptides or mixed aromatic–aliphatic dipeptides seem just as promising, exhibiting various structures ranging from amyloid fibrils to microtubes. Herein we report the single-crystal structure of an aliphatic dipeptide, alanine–isoleucine (Ala–Ile), C(17)H(24)N(2)O(5), protected with a benzyl­oxycarbonyl (Z) group at the N-terminus. The protected dipeptide crystallizes in the ortho­rhom­bic space group P2(1)2(1)2(1) and forms hollow microtubes with ortho­rhom­bic symmetry upon evaporation on glass surfaces, as shown by field emission scanning electron microscopy (FESEM). These findings provide an increased understanding of the correlation between the single-crystal structure of the peptide building block and its self-assembly mechanism, and expand the library of available building blocks for microtechnological applications.