The intermediate peptide (II) has been synthesized by the known solid phase technique with the corresponding protected amino acids coupled sequentially to the resin to obtain the protected resin (I), which is cleaved and deprotected simultaneously with trifluoroacetic acid, phenol, methanedithiol and thioanisole yielding the free peptide (II). Finally, this peptide is treated with NaNO2 in aqueous HCl.