Peptides inhibiting the blood coagulation, their process of preparation and their use

There are peptides of the formula I.<br />A1-A2-A3-A4-A5-A6-A7-A8-A9-A10-A11-A12-A13-A14-A15<br />whereinA1Is hydrogen, cysteine, acetylcysteine, one or two alkyl groups having 1-4 C atoms, an acyl group having 2-10 C atoms, an acyl group having 2-10 C atoms and another carboxyl group or a protective group customary in peptide chemistry,A2a bond, Asn, Asp, Gln or Glu,A3a bond, Gly or Ala,A4Glu or Asp,A5Phe, Tyr, Trp, Pgl (phenylglycine) or Nal (naphthylalanine),A6Glu or Asp,A7Glu, Asp, Pro or Ala,A8Ile, Leu, Val, Nle or Phe,A9Pro or Hyp,A10Glu or Asp,A11Glu or Asp,A12Phe (SO₃H) or Phe (PO₃H₂) (preferably in the p-position) or<br />Pgl (SO₃H) or Pgl (PO₃H₂) (preferably in the p-position),A13a bond, Leu, Ile, Val, or Ala,A14a bond, Gln, Asn, Glu, Asp or Cys andA15Cys, Cys-amide, an OH group of the alpha-carboxyl group, free or esterified with a lower alcohol having up to 4 carbon atoms, which may also be present as a carboxamide function, the hydrogens optionally substituted with alkyl groups having up to 4 carbon atoms could be,<br /> are described, and a method for their preparation. These peptides inhibit blood clotting and can be used as anticoagulants.