Cyclic peptide derivatives

A compound of the formula I

• cyclo-(Arg-X-Asp-R1) I
• in which
• X is Gly, Ala or NH—NH—CO, where the amino acids mentioned can also be derivatized, and the amino acid residues are linked to one another in a peptide-like manner via the α-carboxyl groups,
• R1 is a radical of the formula II
• R2,R3,R4 in each case independently of one another are H, A, Ar, R5-Ar, Het or R5-Het, wherein if R4 is A, a methylene group present therein can be replaced by N, O or S,
• A is alkyl having 1-6 C atoms,
• Ar is phenyl which is unsubstituted or mono-, di- or trisubstituted by R7, R8 or R9, or is unsubstituted naphthyl,
• R5 is alkylene having 1-6 C atoms,
• R6,R6′ in each case, independently of one another, are H, A, benzyl or phenyl, R7,R8,R9 in each case, independently of one another, are R6, OR6, Hal, NO2, NR6R6′, NHCOR6, CN, NHSO2R6, COOR6 or COR6,
• Hal is F, Cl, Br or I, and
• Het is a mono- or binuclear heterocycle having 1 to 4 N, O, and/or S atoms, which can be unsubstituted or mono-, di- or trisubstituted by Hal, NR6R6′, A, CN or N02,
• wherein optically active amino acids and amino acid derivatives can be present in either their D- or L-forms, or a salt thereof.