Bioactive peptides: Conformational studies of [TYR 4 ] cyclolinopeptide A

The solid state conformational analysis of [Tyr 4 ] cyclolinopeptide A has been carried out by x‐ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane‐water mixture [a = 9.849 (5) Å, b = 20.752 (4) Å, c = 16.728 (5) Å, β = 98.83 (3)°, space group P2 1 , Z = 2], shows the presence of five intramolecular N‐H OC hydrogen bonds, with formation of one C 17 ring structure, one α‐turn (C 13 ), one inverse γ‐turn (C 7 ), and two β‐turns (C 10 , one of type III and one of type 1). The Pro 1 ‐Pro 2 peptide unit is cis (ω = 5°) all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 Å. © 1995 John Wiley & Sons, Inc.