Patent ID: 7138489

Claim:
A method for producing a protected peptide fragment, wherein at least one amino acid or non-amino acid is modified as represented by the formula -A(R)—, wherein A represents an amino acid or a non-amino acid, and R represents a substituent bound to a side chain of A which is introduced for modification, which comprises: (a) preparing, on a weak acid-cleavable resin, a peptide main chain sequence of a peptide fragment which has a desired sequence comprising amino acids or amino acids and non-amino acids, wherein one or more reactive functional groups in a side chain of an amino acid or a non-amino acid which may cause an undesirable side reaction during preparation of a peptide fragment are protected with a protecting group, the one or more reactive functional groups being selected from the group consisting of a hydroxyl group, an amino group, a guanidino group, an imidazolyl group, an indolyl group, a mercapto group and a carboxyl group, in a side chain of an amino acid or a non-amino acid, (b) deprotecting the protecting group of at least one reactive functional group in the side chain of an amino acid or a non-amino acid A which is to be modified with a substituent R without cleaving the peptide fragment from the weak acid-cleavable resin, (c) modifying the deprotected side chain with a substituent R, and (d) cleaving the peptide fragment from the weak acid-cleavable resin under weakly acidic conditions.