Some Cyclic Oligopeptide with S_2n Symmetry

Abstract

Some cyclic oligopeptides formed by an equal number of alternating D‐ and L‐amino‐acid residues have been synthesized by using the hydrochloride of the open‐chain peptide acid as precursor and the mixed‐anhydride condensation method. The cyclic oligopeptides (tetra‐, hexa‐, and octavaline, hexaleucine, and hexaphenylalanine) form very stable H‐bonded structures (IR‐amide band at 3270–3290 cm−1) which are insoluble in common organic solvents. In CF3COOH/CDCI3 (25°), they yield 1H‐NMR spectra snowing the expected equivalency of the various amino‐acid residues.

Self-Assembling Organic Nanotubes

“…[79±82] Initial attempts to experimentally demonstrate this type of tubular construct proved inconclusive. [83] In 1989 an X-ray crystallographic study by Lorenzi and co-workers on the hexapeptides cyclo-[-(l-Phe-d-Phe) 3 -] and cyclo[-(l-Val-d-Val) 3 -] revealed that the expected intersubunit associations were absent and each peptide was found instead to be tightly hydrogen bonded to several cocrystallized solvent molecules. [84] In 1993 our laboratory compellingly demonstrated the formation of hollow tubular structures by the stacking of cyclic d,l-peptide rings (Scheme 1).…”

Design, Synthesis, and Structural Analysis of d,l-Mixed Polypyrrolinones. 2. Macrocyclic Hexapyrrolinones

“…Additionally, the staggered nanotube structure of (+)- 3 forms an infinite array in the crystal lattice (four molecules/unit cell as illustrated in Figure 4b–d). Given the pyrrolinone scaffold comprises a designed peptidomimetic, our work has obvious parallels to the cyclic peptides pioneered by Karle,15 Lorenzi,16 and Ghadiri 17,9. Of particular interest, the 1987 report by G. P. Lorenzi et al discloses a series of D,L-alternating cyclic hexapeptides 16.…”

“…Given the pyrrolinone scaffold comprises a designed peptidomimetic, our work has obvious parallels to the cyclic peptides pioneered by Karle,15 Lorenzi,16 and Ghadiri 17,9. Of particular interest, the 1987 report by G. P. Lorenzi et al discloses a series of D,L-alternating cyclic hexapeptides 16. In contrast to the hexapeptides, which were reported to be completely insoluble in all common organic solvents, (+)- 2 and (+)- 3 are moderately soluble in most polar organic solvents (i.e., EtOAc, EtOH), and display excellent solubility in CHCl 3 .…”

Shape‐Persistent Macrocycles: From Molecules to Materials

“…For example, macrocycles with an orthogonal arrangement (orthogonal substituents, Figure 2, left) of polar functional groups are able to form tubular superstructures in the solid state. [5] If the polar functional groups point to the outside of the macrocycle (extraannular substituents, Figure 2, middle) this may lead to the formation of a 2D network in the solid state. [6] Shape-persistent macrocycles with polar groups pointing to the inside (intraannular substituents, Figure 2, right) play a special role in supramolecular chemistry.…”