METHOD FOR THE SOLID-PHASE SYNTHESIS OF CYCLIC PENTAPEPTIDES

A method for the synthesis of a cyclic ornithine-proline-D-cyclohexylalanine-tryptophan- arginine pentapeptide of Formula A; wherein R1 and R2 are, independently, -H, or -C(O)R3 where R3 is -Ch2Ph, - CH2CH2Ph, -CH=CHPh, -C(NHAC)CH2Ph; the method comprising the steps of; forming a linear proline-D-cyclohexylalanine-tryptophan-arginine-ornithine pentapeptide of Formula B, attached to a polymeric resin; wherein R1 is as for Formula A, RES indicates the polymeric resin, and P1 and P2 are protecting groups; cyclising the linear pentapeptide of Formula B to form a cyclic pentapeptide of Formula C, attached to the polymeric resin; cleaving the cyclic peptide of Formula C from the resin providing a cleaved cyclic pentapeptide having a free amine group of an ornithine residue; optionally substituting the free amine group of the ornithine residue of the cleaved cyclic peptide; removing the protecting groups P1 and P2, to provide the cyclic peptide of Formula A.