The objective of the present invention is to provide a method for efficiently producing a long-chain peptide which method is suitable even for an industrial large scale production. The method for producing a long-chain peptide according to the present invention is characterized in comprising a step to deprotect an N-terminal site protected with BOC of a raw material peptide fragment with using a sulfonic acid compound, a step to selectively deprotect a C-terminal site protected with ONBn of a raw material peptide, and a step to condensate the obtained peptide fragment having the deprotected N-terminal site and the obtained peptide fragment having the deprotected C-terminal site in a liquid phase condition.

Provided are a method for producing a peptide compound including a step of using an aromatic heterocyclic compound represented by Formula (1) represented by Formula (1); a protective group-forming reagent including the compound; and the compound. In Formula (1), a ring A represents an aromatic heterocyclic ring, Y.sup.A's each independently represent —OH, —NHR, —SH, or —X.sup.0, where X.sup.0 represents Cl, Br, or I, R.sup.A and R.sup.C each independently represent an aliphatic hydrocarbon group or an organic group having an aliphatic hydrocarbon group, R.sup.Bs' each independently represent a monovalent aliphatic hydrocarbon group, a (1+c)-valent aromatic group, or a (1+c)-valent heteroaromatic group, where, in a case where both a and c is 0, R.sup.B is a monovalent aliphatic hydrocarbon group, and the number of carbon atoms in at least one aliphatic hydrocarbon group of R.sup.A, R.sup.B, or R.sup.C is 12 or more.

##STR00001##

Provided are a method for producing a peptide compound including a step of using an aromatic heterocyclic compound represented by Formula (1) represented by Formula (1); a protective group-forming reagent including the compound; and the compound. In Formula (1), a ring A represents an aromatic heterocyclic ring, Y.sup.A's each independently represent —OH, —NHR, —SH, or —X.sup.0, where X.sup.0 represents Cl, Br, or I, R.sup.A and R.sup.C each independently represent an aliphatic hydrocarbon group or an organic group having an aliphatic hydrocarbon group, R.sup.Bs' each independently represent a monovalent aliphatic hydrocarbon group, a (1+c)-valent aromatic group, or a (1+c)-valent heteroaromatic group, where, in a case where both a and c is 0, R.sup.B is a monovalent aliphatic hydrocarbon group, and the number of carbon atoms in at least one aliphatic hydrocarbon group of R.sup.A, R.sup.B, or R.sup.C is 12 or more.

##STR00001##

Provided are a method for producing a peptide compound including a step of using a condensed polycyclic aromatic hydrocarbon compound represented by Formula (1); a protective group-forming reagent including the compound; and the compound. In Formula (1), a ring A represents a condensed polycyclic aromatic hydrocarbon ring, Y.sup.A's each independently represent —CH.sub.2OH, —CH.sub.2NHR, —CH.sub.2SH, or —CH.sub.2X.sup.0, where R represents a hydrogen atom, an alkyl group, or an aralkyl group, and X.sup.0 represents Cl, Br, or I, k represents an integer of 1 to 5, n represents 1 or 2, and R.sup.A's each independently represent an aliphatic hydrocarbon group or an organic group having an aliphatic hydrocarbon group.

##STR00001##

Methods for making an arylomycin ring of formula t ##STR00001##
or salts or solvates thereof, wherein R, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.5, R.sup.10 and Pg.sup.1 are as defined herein.

The embodiments disclosed herein provide a peptoid, which is a compound of Formula I or a stereoisomer, a mixture of stereoisomers, or a pharmaceutically acceptable salt thereof. N—R.sub.4, N—R.sub.3, N—R.sub.2, and N—R.sub.1 in Formula I are ##STR00001##
respectively. The peptoid has a strong binding ability with EGFR protein. It can be used not only for targeted treatment of diseases associated with EGFR protein, but also for imaging detection or prognosis monitoring of diseases associated with EGFR protein. ##STR00002##

The embodiments disclosed herein provide a peptoid, which is a compound of Formula I or a stereoisomer, a mixture of stereoisomers, or a pharmaceutically acceptable salt thereof. N—R.sub.4, N—R.sub.3, N—R.sub.2, and N—R.sub.1 in Formula I are ##STR00001##
respectively. The peptoid has a strong binding ability with EGFR protein. It can be used not only for targeted treatment of diseases associated with EGFR protein, but also for imaging detection or prognosis monitoring of diseases associated with EGFR protein. ##STR00002##

The invention provides a method for the cleavage of Fmoc group characterized by using a solution comprising 3-(diethylamino)propylamine. In particular, it provides a method for the preparation of peptides in solid phase wherein Fmoc protected amino acids are used and the Fmoc group is cleaved by a solution comprising 3-(diethylamino)propylamine.

Provided are a method for producing a peptide compound including a step of using a hydrazine derivative represented by Formula (1); a reagent for forming a protective group including the compound; and a hydrazine derivative. In Formula (1), a ring A represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, R represents a hydrogen atom, an amino protective group, an amino acid residue, or a peptide residue, k represents an integer of 1 to 5, n represents 1 or 2, and R.sup.A's each independently represent an aliphatic hydrocarbon group or an organic group having an aliphatic hydrocarbon group.

##STR00001##

A method for producing a cyclic peptide, including the following step (1) and step (2):

(1) a step of cyclizing a linear peptide; and

(2) a step of obtaining a cyclic peptide by adding a poor solvent to a mixture of the cyclic peptide and multimeric impurity, which mixture is obtained in the above-mentioned step, and filtering off the multimeric impurity as an insoluble material can efficiently remove multimeric impurity by-produced during a cyclization reaction, improve the purity of the obtained cyclic peptide, and reduce a burden on the purification step.