Abstract: Methods of producing a peptide containing an N-substituted amino acid or N-substituted amino acid analog of the present invention include the steps of: preparing an Fmoc-protected amino acid, an Fmoc-protected amino acid analog, or an Fmoc-protected peptide; deprotecting a protecting group which have an Fmoc skeleton of the Fmoc-protected amino acid and such by using a base; and forming an amide bond by adding a new Fmoc-protected amino acid and such; and when the peptide is produced by a solid-phase method, the obtained peptide is cleaved off from the solid phase under conditions of weaker acidity than TFA. Furthermore, at least one side chain of the obtained peptide has a protecting group that is not deprotected under basic conditions and is deprotected under conditions of weaker acidity than TFA.

Abstract: Methods of producing a peptide containing an N-substituted amino acid or N-substituted amino acid analog of the present invention include the steps of: preparing an Fmoc-protected amino acid, an Fmoc-protected amino acid analog, or an Fmoc-protected peptide; deprotecting a protecting group which have an Fmoc skeleton of the Fmoc-protected amino acid and such by using a base; and forming an amide bond by adding a new Fmoc-protected amino acid and such; and when the peptide is produced by a solid-phase method, the obtained peptide is cleaved off from the solid phase under conditions of weaker acidity than TFA. Furthermore, at least one side chain of the obtained peptide has a protecting group that is not deprotected under basic conditions and is deprotected under conditions of weaker acidity than TFA.

Abstract: Methods of producing a peptide containing an N-substituted amino acid or N-substituted amino acid analog of the present invention include the steps of: preparing an Fmoc-protected amino acid, an Fmoc-protected amino acid analog, or an Fmoc-protected peptide; deprotecting a protecting group which have an Fmoc skeleton of the Fmoc-protected amino acid and such by using a base; and forming an amide bond by adding a new Fmoc-protected amino acid and such; and when the peptide is produced by a solid-phase method, the obtained peptide is cleaved off from the solid phase under conditions of weaker acidity than TFA. Furthermore, at least one side chain of the obtained peptide has a protecting group that is not deprotected under basic conditions and is deprotected under conditions of weaker acidity than TFA.

Abstract: It has been found that the membrane permeability of peptide compounds can be improved by making at least one of amino acids constituting the peptide compound be an amino acid having a side chain capable of forming an intramolecular hydrogen bond.

Abstract: Methods of producing a peptide containing an N-substituted amino acid or N-substituted amino acid analog of the present invention include the steps of: preparing an Fmoc-protected amino acid, an Fmoc-protected amino acid analog, or an Fmoc-protected peptide; deprotecting a protecting group which have an Fmoc skeleton of the Fmoc-protected amino acid and such by using a base; and forming an amide bond by adding a new Fmoc-protected amino acid and such; and when the peptide is produced by a solid-phase method, the obtained peptide is cleaved off from the solid phase under conditions of weaker acidity than TFA. Furthermore, at least one side chain of the obtained peptide has a protecting group that is not deprotected under basic conditions and is deprotected under conditions of weaker acidity than TFA.

Abstract: Methods of producing a peptide containing an N-substituted amino acid or N-substituted amino acid analog of the present invention include the steps of: preparing an Fmoc-protected amino acid, an Fmoc-protected amino acid analog, or an Fmoc-protected peptide; deprotecting a protecting group which have an Fmoc skeleton of the Fmoc-protected amino acid and such by using a base; and forming an amide bond by adding a new Fmoc-protected amino acid and such; and when the peptide is produced by a solid-phase method, the obtained peptide is cleaved off from the solid phase under conditions of weaker acidity than TFA. Furthermore, at least one side chain of the obtained peptide has a protecting group that is not deprotected under basic conditions and is deprotected under conditions of weaker acidity than TFA.

Abstract: The present inventors have found that when screening for cyclic peptide compounds that can specifically bind to a target molecule, the use of a library including cyclic peptide compounds having a long side chain in the cyclic portion can improve the hit rate for cyclic peptide compounds that can specifically bind to the target molecule. Meanwhile, the present inventors have found that tryptophan and tyrosine residues, which have conventionally been used in oral low molecular-weight pharmaceuticals and are amino acid residues having an indole skeleton or a hydroxyphenyl group, are not suitable for peptides intended to attain high membrane permeability.