The conformation of the cyclic tetrapeptide L-Ser(O-t-Bu)-β-Ala-Gly-L-β-Asp(OMe) containing a 14-membered ring

Abstract

The title compound, CI7H28N407, is a synthetic crystalline cyclic tetrapeptide containing alternate 0c-amino peptide groups and fl-amino peptide groups similar to the naturally occurring depsipeptide serratamolide. The tetrapeptide represents a preliminary step in the proposed synthesis of a cylindrical polypeptide. The 14-membered 'ring' consists of four planar segments with each segment in the trans conformation. The corner atoms are C'(1), Ca(2), C~(3) and Ca(4). Two carbonyl oxygens are directed above the average plane of the ring and the other two below. If the side chains are disregarded, two of the peptide groups are related to the other two by an approximate center of symmetry. In the crystal the molecules are stacked over each other by translation in the a direction. Between each pair of molecules in the stack there are two NH. • • O bonds at 2-86 A. The remaining two NH moieties do not participate in hydrogen bonding. The space group is P21 with a=5.624 (4), b= 10.298 (7), c= 17.859 (13) A, and fl= 99"07 (5) °. The structure was solved by the symbolic addition procedure.

Self-Assembling Organic Nanotubes

“…[104] A crystallographic study of tetrapeptide cyclo[-(l-Ser(OtBu)-b-Ala-Gly-b-Asp(OMe))-] in 1974 only partially validated this proposal. [105] The peptide subunits adopted a ring-shaped conformation and stacked above one another in the crystal lattice; however, only two of the four amide groups participated in expected intersubunit hydrogen bonding.…”

Self‐Assembled Peptide Tubelets with 7 Å Pores

“…One of the most promising implementations of the stacked ring approach is the self‐assembling peptide nanotube (SPN) 4. The elementary components of SPNs are cyclic peptides, the chiralities of the amino acids of which allow the ring to adopt a quasiplanar conformation 4–7. In this conformation, peptide backbone NH and CO groups project perpendicularly from the plane of the ring on either side and are therefore able to form hydrogen bonds with those of neighboring rings, so constructing a nanotube.…”

“…In this conformation, peptide backbone NH and CO groups project perpendicularly from the plane of the ring on either side and are therefore able to form hydrogen bonds with those of neighboring rings, so constructing a nanotube. Specifically, self‐assembling nanotubes have been designed based on cyclic peptides of alternating D , L ‐α‐amino acids,4, 5 β‐amino acids,6 alternating α,β‐amino acids,7 δ‐amino acids,8 alternating α,ε‐amino acids,9 and oligoureas 10. These design choices are not purely artistic, because the functional characteristics of the nanotubes made by this strategy depend on the nature of both their interior and exterior surfaces.…”

Pyrrolinone-Based Peptidomimetics.“Let the Enzyme or Receptor be the Judge”

“…Based on the established ability of D-amino acids to stabilize β-turns,41 as well as the demonstrated turn conformations observed with peptides containing D- and L-amino acids,42 we reasoned that a sequence of alternating D,L-linked pyrrolinones might preferentially adopt a turn structure.…”