Design and synthesis of peptides passing through the blood-brain barrier

The blood-brain barrier (BBB) is a highly selective membranous barrier regulating the transport of substances in blood into the brain parenchyma. At present, delivery of biologically active peptides or peptide drugs into the brain is quite an important subject from the standpoint of chemotherapy for brain diseases. H-MeTyr-Arg-MeArg-D-Leu-NH(CH2)(8)NH2 termed 001-C8 was first synthesized to elucidate the structural specificity of peptides for passing through the BBB. The N-a-methylamino acid and D-amino acid residues were appropriately situated in this peptide to protect against the digestion by peptidase. Furthermore, a number of basic peptides were prepared as 001-C8 analogs for studying the relationship between structure and BBB permeability of peptides.