A compound of the general formula, cyclo[P 1 -P 2 -P 3 -P 4 -P 5 -P 6 -P 7 -P 8 -P 9 -P 10 -P 11 -P 12 -T 1 -T 2] wherein the single elements T or P are connected in either direction from the carbonyl (C=O) point of attachment to the nitrogen of the next element and wherein T 1 is D Pro; D Azt; D Ala; D Tyr; D Dab; D Thr; N MeAla; or N MeGly; T 2 is Pro; Ala; Leu; N MeAla; Tyr; Phe; Dab; Dap; Orn; Lys; or Arg; P 1 is Leu; Ile; Val; Cpa; Cpg; Phe; or Trp; P 2 is Tyr; Dab; Dap; Lys; Thr; Ser; Asp; or Glu; P 3 is Val; t BuGly; or Tyr; P 4 is Ala; Val; Dab; Arg; Asn; or Thr; P 5 is Orn; Dap; Dab; or Thr; P 6 is Gly; Dab; or D Dab; P 7 is Dab; P 8 is Trp; Phe; or Leu; P 9 is Ala; Tyr; Dab; Dap; Ser; or Thr; P 10 is Val; t BuGly; Chg; Phg; or Tyr; P 11 is Ala; Val; Ser; Thr; Asp; Dap; Dab; or Lys; P 12 is Val; Tyr; His; Dab; Ser; or Thr; P 2 and P 11 taken together and/or P 4 and P 9 taken together can form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; Hcy; or Pen; with the side chain of Cys; Hcy; or Pen; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; or connection of the side chain of Pra with the side chain of Abu(4N 3) by a 1,4-disubstituted 1,2,3-triazole-containing linkage; or a pharmaceutically acceptable salt thereof; with the proviso that if no interstrand linkage is formed; and P 2 isTyr; Dab; Dap; or Lys; or P 2 and P 11 taken together; or P 2 and P 11; and P 4 and P 9 taken together; form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; or P 2 is Tyr; Dab; Dap; or Lys; and P 4 and P 9 taken together form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; and T 1 is D Pro; or D Azt; then T 2 is Arg; and with the further proviso that if no interstrand linkage is formed; and T 1 is D Pro; and P 2 is Thr; Ser; Asp; or Glu; then T 2 isAla; Leu; N MeAla; Tyr; Phe; Dab; Dap; Orn; Lys; or Arg. T 1 is D Pro; D Azt; D Ala; D Tyr; D Dab; D Thr; N MeAla; or N MeGly; T 2 is Pro; Ala; Leu; N MeAla; Tyr; Phe; Dab; Dap; Orn; Lys; or Arg; P 1 is Leu; Ile; Val; Cpa; Cpg; Phe; or Trp; P 2 is Tyr; Dab; Dap; Lys; Thr; Ser; Asp; or Glu; P 3 is Val; t BuGly; or Tyr; P 4 is Ala; Val; Dab; Arg; Asn; or Thr; P 5 is Orn; Dap; Dab; or Thr; P 6 is Gly; Dab; or D Dab; P 7 is Dab; P 8 is Trp; Phe; or Leu; P 9 is Ala; Tyr; Dab; Dap; Ser; or Thr; P 10 is Val; t BuGly; Chg; Phg; or Tyr; P 11 is Ala; Val; Ser; Thr; Asp; Dap; Dab; or Lys; P 12 is Val; Tyr; His; Dab; Ser; or Thr; P 2 and P 11 taken together and/or P 4 and P 9 taken together can form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; Hcy; or Pen; with the side chain of Cys; Hcy; or Pen; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; or connection of the side chain of Pra with the side chain of Abu(4N 3) by a 1,4-disubstituted 1,2,3-triazole-containing linkage; P 2 and P 11 taken together; or P 2 and P 11; and P 4 and P 9 taken together; form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; P 2 is Tyr; Dab; Dap; or Lys; and P 4 and P 9 taken together form interstrand linking bis(amino acid)-structures based on the linkage of two L- or D- amino acid residues following connection of the side chain of Cys; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; or Lys; with the side chain of Asp; or Glu; by a lactam linkage; or connection of the side chain of Dap; with the side chain of Dap; by an urea linkage; T 1 is D Pro; or D Azt; T 1 is D Pro; P 2 is Thr; Ser; Asp; or Glu; T 2 isAla; Leu; N MeAla; Tyr; Phe; Dab; Dap; Orn; Lys; or Arg.