Role of side-chain and chirality of the amino acids on the supramolecular assemblies of dipeptides

•The presence of an extra methylene (-CH2-) group in peptide Boc-l-Ile-l-Phe-OMe helps it to form a single helix-like architecture, whereas Boc-l-Ile-l-Phg-OMe forms a cylinder-like structure around the water molecules in the crystalline state.•A discontinued double helix-like structure was formed in the crystalline state of both Boc-l-Ile-d-Phe-OMe and Boc-l-Ile-d-Phg-OMe (Phg = phenylglycine).•Boc-l-Ile-l-Phe-OMe and Boc-l-Ile-l-Phg-OMe self-associate to form helical ribbon-like and nano tube-like structures, respectively, whereas both Boc-l-Ile-d-Phe-OMe and Boc-l-Ile-d-Phg-OMe build up nano rod-like structures in solution. The supramolecular self-association of alternating L/L and L/D amino acid-containing dipeptides, Boc-l-Ile-l-Phe-OMe (1), Boc-l-Ile-d-Phe-OMe (2), Boc-l-Ile-l-Phg-OMe (3, Phg = phenylglycine), and Boc-l-Ile-d-Phg-OMe (4) have been investigated. The presence of extra methylene (-CH2-) group on the side-chain of C-terminal Phe-of 1 causes a significant deviation of molecular arrangements from that of 3. While the molecules in 1 self-assemble to form a single helix-like architecture, the molecules in 3 self-associate around a water molecule to form a cylinder-like structure in the crystalline state. Alternatively, the observed supramolecular arrangements of 2 and 4 are similar, but deviate from that of 1 and 3, due to chirality difference. Peptides 2 and 4 exhibit a discontinued double helix-like structure in the crystalline state. While 1 and 3 self-associate to form helical ribbon-like and nano tube-like structures, respectively, both 2 and 4 form nano rod-like structures in solution. [Display omitted]