The title compound is prepared by solid-phase peptide synthesis starting from N-Fmoc-L-phenylalanine attached to Wang resin (I). Deprotection of (I) with piperidine in NMP removes the N-Fmoc group, yielding the phenylalanine resin (II). Coupling of (II) with N-trityl glycine (III) in the presence of PyBOP and HOBt, followed by acidic cleavage of the N-trityl group furnishes the dipeptide derivative (IV). To this is assembled N-Fmoc-S-trityl-D-penicillamine (V), followed by deprotection with piperidine in NMP, to produce resin (VI). Subsequent coupling of (VI) with N-Cbz-O-benzyl-L-tyrosine (VII) leads to the protected tetrapeptide (VIII). Removal of the S-trityl protecting group of (VIII) employing trifluoroacetic acid provides thiol (IX).

Treatment of N-trityl-D-serine benzyl ester (X) with I2/PPh3 gives rise to the iodoalanine derivative (XI). Thiol (IX) is then alkylated by iodide (XI) in the presence of Cs2CO3 to furnish thioether (XII). Simultaneous cleavage from the resin and removal of the N-trityl group in (XII) employing trifluoroacetic acid leads to the linear pentapeptide derivative (XIII). This is then cyclized to (XIV) in the presence of DPPA and NaHCO3 in dilute DMF solution. The Cbz and benzyl protecting groups of (XIV) are finally removed by HBr in AcOH to provide the title compound.