Synthesis of Analogues of Thyrotropin-Releasing Hormone

The synthesis of ten new thyrotropin-releasing hormone analogues ( 15–24 ) which contain uncoded amino acids (L- and D-homoleucine, L- and D-homophenylalanine, L-homoproline and 6-ketopipecolic acid) is described here. The peptide bond formation was achieved in solution phase using pentafluorophenyl ester activation of the N-protected amino acids. The analogues were tested for their ability to release thyrotropin and for CNS activities and proved to be fully inactive.