Starting from 0.5 mmol of 4-(2′,4′-dimethoxyphenyl-Fmoc-aminomethyl)phenoxyacetamido-norleucyl-4-methylbenzhydrylamine-polystyrene resin (Rink MBHA) the phosphonomethylpeptide was assembled on the resin in analogous manner as described in the example 1, adding the protected amino acids in the following order: Fmoc—Val—OH, Fmoc—Asn(Trt)—OH, Fmoc—Val—OH, Fmoc—Phe(p—CH2PO3Et2)—OH. The N-terminal acetylation was obtained by treatment of the peptidyl resin with 5 eq of acetic anhydride and 5 eq of DIEA in NMP for 30 min at 25° C. The cleavage from the resin and the removal of the protecting groups, except the phosphonate ethyl groups, were carried out as described in example 1. The 270 mg of crude peptide were suspended in refluxing DCM with 1 mL of trimethylbromosilane for 2 h. After evaporation of the solvent the completely deprotected peptide was purified by RP—HPLC as described in Example 1 (but with acetonitrile gradient 5-43.5 %) giving the title compound with chromatographic purity (HPLC) of 98.0%. Amino acid ratios: Val 2 (2); Asx 1.3 (1). Peptide content: 100%. FAB mass spectroscopy: m/z 613 [MH]+. (MW 612.6).
