Method for producing peptide compound

A method for producing a peptide which comprises the following Steps (1) to (3):

• (1) a step of mixing an N-terminal protected amino acid or an N-terminal protected peptide represented by the formula (I) P-A1-OH
• wherein P is an N-terminal protective group, and A1 represents a group derived from an amino acid, a group derived from an N—C1-6 alkylamino acid, where the C1-6 alkyl may have a substituent(s), or a group derived from a peptide,
• with an activating agent represented by the formula (II)
• wherein X represents a halogen atom, and R1 represents a secondary C5-40 alkyl group which may have a substituent(s);
• (2) a step of mixing an amino acid or a peptide represented by the formula (IV):
• H-A2-OH
• wherein A2 represents a group derived from an N—C1-6 alkylamino acid, where the C1-6 alkyl may have a substituent(s), or a group derived from a 4- to 6-membered cyclic secondary amino acid, where the 4- to 6-membered ring may be fused with a cyclic compound selected from the group consisting of a C6-14 aryl ring, a C6-14 haloaryl ring and a C3-8 cycloalkyl ring, or a group derived from a peptide in which the N-terminal residue is an N—C1-6 alkylamino acid, where the C1-6 alkyl may have a substituent(s), or a 4- to 6-membered cyclic secondary amino acid, where the 4- to 6-membered ring may be fused with a cyclic compound selected from the group consisting of a C6-14 aryl ring, a C6-14 haloaryl ring and a C3-8 cycloalkyl ring,
• with a silylating agent;
• and
• (3) a step of mixing a product obtained in Step (1) and a product obtained in Step (2).