Synthesis of radiohalogen-labeled peptides with high affinity to HER2/neu receptor

Sasaki, Ichiro; Yamada, Keiichi*; Watanabe, Shigeki; Hanaoka, Hirofumi*; Sugo, Yumi; Oku, Hiroyuki*; Ishioka, Noriko

Radioisotope (RI)-labeled peptides which have the high affinity to receptors on surface of the tumor cell are promising for diagnostic radiography (PET and SPECT) and radiotherapy. MARSGL (H-Met-Ala-Arg-Ser-Gly-Leu-OH), a linear hexapeptide consisting of six amino acids, has the high affinity to HER2/neu receptor overexpressing in various cancer cells. Thus, radiolabeled MARSGL has potential for the above mentioned purposes. Radiohalogens have various useful radionuclides, which could be introduced to aromatic compounds via tin-halogen exchange reaction. In this study, stannylated peptide Boc-F(-SnBu)MAR(Pbf)S(Bu)GL-OH was synthesized to prepare radiohalogen (Br or I)-labeled FMARSGL derivatives. First, Boc-Phe(-SnBu)-OH was prepared from Boc-Phe(-I)-OMe via Pd(0)-catalyzed coupling reaction with (BuSn) and was successfully introduced into -terminal of H-MARSGL-Trt(2-Cl) resin synthesized from H-Leu-Trt(2-Cl) resin by Fmoc-SPPS. After cleavage reaction of Boc-F(-SnBu)MAR(Pbf)S(Bu)GL-Trt(2-Cl) resin with 25% 1,1,1,3,3,3-hexafluoro-2-propanol in CHCl, Boc-F(-SnBu)MAR(Pbf)S(Bu)GL-OH was obtained and identified by using ESI-MS and NMR. Synthesis of I-labeled FMARSGL is due to report in this presentation.