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; or D Tic; T 2 is Pro; Pic; Oic; Tic; Ala; Abu; Leu; Ile; Val; Nva; N MeAla; N MeAbu; N MeLeu; N Melle; N MeVal; Tyr; Phe; Trp; Dab; Dap; Orn; or Lys; P 1 is Ala; Abu; Leu; Ile; Val; Nva; Nle; Cpa; Cpg; Phe; Tyr; or Trp; P 2 is Tyr; Phe; Trp; Dab; Dap; Orn; Lys; or Arg; P 3 is Val; t BuGly; Ala; Leu; Ile; Val; Nva; Tyr; Phe; or Trp; P 4 is Ala; Val; Abu; Leu; Ile; Nva; Dab; Dap; Orn; Lys; Arg; Asn; Gln; Thr; αllo Thr; Ser; or Hse; P 5 is Orn; Dap; Dab; Lys; Arg; Thr; αllo Thr; Ser; or Hse; P 6 is Gly; Dab; D Dab; Dap; D Dap; Orn; D Orn; Lys; D Lys; Arg; or D Arg; P 7 is Dab; Dap; Orn; Lys; or Arg; P 8 is Trp; Phe; Tyr; Phg; Leu; Ile; Val; Nva; Abu; or Ala; P 9 is Ala; Abu; Leu; Ile; Val; Nva; Tyr; Phe; Trp; Dab; Dap; Orn; Lys; Arg; Ser; Thr; αllo Thr; or Hse; P 10 is Val; t BuGly; Ala; Leu; Ile; Nva; Abu; Chg; Phg; Tyr; Phe; or Trp; P 11 is Ala; Val; Abu; Nva; Leu; Ile; Ser; Thr; αllo Thr; Hse; Asn; Gln; Asp; Glu; Dab; Dap; Orn; Lys; or Arg; P 12 is Val; Ala; Abu; Nva; Leu; Ile; Tyr; His; Phe; Trp; Dab; Dap; Orn; Lys; Arg; Ser; Thr; αllo Thr; or Hse; 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; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; Orn;or Lys; with the side chain of Asp; Glu; or hGlu; by a lactam linkage; or connection of the side chain of Dap; Dab; or Orn; with the side chain of Dap; Dab; or Orn; by an urea linkage; or a pharmaceutically acceptable salt thereof; with proviso that if no interstrand linkage is formed; and T 1 is D Pro; or D Tic; then T 2 is Ala; Abu; Leu; Ile; Val; Nva; N MeAla; N MeAbu; N MeLeu; N Melle; N MeVal; Tyr; Phe; Trp; Dab; Dap; Orn; or Lys. T 1 is D Pro; D Azt; or D Tic; T 2 is Pro; Pic; Oic; Tic; Ala; Abu; Leu; Ile; Val; Nva; N MeAla; N MeAbu; N MeLeu; N Melle; N MeVal; Tyr; Phe; Trp; Dab; Dap; Orn; or Lys; P 1 is Ala; Abu; Leu; Ile; Val; Nva; Nle; Cpa; Cpg; Phe; Tyr; or Trp; P 2 is Tyr; Phe; Trp; Dab; Dap; Orn; Lys; or Arg; P 3 is Val; t BuGly; Ala; Leu; Ile; Val; Nva; Tyr; Phe; or Trp; P 4 is Ala; Val; Abu; Leu; Ile; Nva; Dab; Dap; Orn; Lys; Arg; Asn; Gln; Thr; αllo Thr; Ser; or Hse; P 5 is Orn; Dap; Dab; Lys; Arg; Thr; αllo Thr; Ser; or Hse; P 6 is Gly; Dab; D Dab; Dap; D Dap; Orn; D Orn; Lys; D Lys; Arg; or D Arg; P 7 is Dab; Dap; Orn; Lys; or Arg; P 8 is Trp; Phe; Tyr; Phg; Leu; Ile; Val; Nva; Abu; or Ala; P 9 is Ala; Abu; Leu; Ile; Val; Nva; Tyr; Phe; Trp; Dab; Dap; Orn; Lys; Arg; Ser; Thr; αllo Thr; or Hse; P 10 is Val; t BuGly; Ala; Leu; Ile; Nva; Abu; Chg; Phg; Tyr; Phe; or Trp; P 11 is Ala; Val; Abu; Nva; Leu; Ile; Ser; Thr; αllo Thr; Hse; Asn; Gln; Asp; Glu; Dab; Dap; Orn; Lys; or Arg; P 12 is Val; Ala; Abu; Nva; Leu; Ile; Tyr; His; Phe; Trp; Dab; Dap; Orn; Lys; Arg; Ser; Thr; αllo Thr; or Hse; 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; or Hcy; with the side chain of Cys; or Hcy; by a disulfide linkage; or connection of the side chain of Dap; Dab; Orn;or Lys; with the side chain of Asp; Glu; or hGlu; by a lactam linkage; or connection of the side chain of Dap; Dab; or Orn; with the side chain of Dap; Dab; or Orn; by an urea linkage; 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; Orn;or Lys; with the side chain of Asp; Glu; or hGlu; by a lactam linkage; or connection of the side chain of Dap; Dab; or Orn; with the side chain of Dap; Dab; or Orn; by an urea linkage; T 1 is D Pro; or D Tic; then T 2 is Ala; Abu; Leu; Ile; Val; Nva; N MeAla; N MeAbu; N MeLeu; N Melle; N MeVal; Tyr; Phe; Trp; Dab; Dap; Orn; or Lys.