Eleven modified RGD (Arg-Gly-Asp) peptides were synthesized by using unnatural building blocks as the surrogates for Arg residues. Three kinds of backbone structures were concerned in present products: (1) thiazolino or oxazolino residues were used instead of Arg in 1～8; (2) Arg was substituted by a locally cyclized structure between α-amino and ω-amino groups of Lys with different bridge structures in 9 and 10; (3) globally cyclized RGD analogue with ether bond bridge was used in 11. Products 1～8 were prepared by a classical solution procedure, while 9～11 were constructed on a solid support. All products were characterized by an MS analysis. It is valuable that the protocols related in present paper would afford some feasible ways to synthesize novel cyclo peptide derivatives.

Key words: hetero-cyclo peptide, atypical cyclopeptide, RGD analogue, solid-phase synthesis