Four photoreactants N-(amidosilane terminated polyproline peptide chain) phthalimide (4a～4d) were synthesized by using proline as the starting material, and were irradiated in methanol. The results confirmed that photoinduced excited states of 4a～4d were observed to promote formation of zwitterion biradical (8) by single electron transfer in the molecule. In this process, intrachain SET (ISET) happened among electron donors and an equation of resonant appeared. Intermolecular biradicals (9) were formed in high selectivity by shuck off the leaving group of 1,ω-zwitterionic biradicals (8). The biradicals 9 copulated to give the title compound cyclopeptides 5 in high yield and high regioselectivity. Structures of all compounds were characterized by FAB-MS, NMR techniques.

Key words: photoinduced, single electro transfer, cyclic peptide, regioselectivity