Linker molecule and use thereof in methods for purifying peptides

A method for the purification of peptides, comprising the following steps:

• i. contacting a composition of a full-length peptide to be purified and at least one impurity with a capture compound of the formula X1-L-X2 (1), wherein
• X1 is selected from
• wherein each of R1 and R2 is independently from each other selected from H or B, wherein at least R1 or R2 is B, wherein
• R3 is selected from H or B,
• wherein B is an acid labile amine protecting group, wherein
• L is selected from functional linkers, that are cleavable nucleophilically from X2 under basic conditions, wherein L has the structure -T-U—, wherein
• T is a spacer between X1 and U, and T is of the form —CH2—C(═O)—NH—(CH2)2—, —CH2—C(═O)—O—(CH2)2—, —C(═O)—O—(CH2)2— and
• U is the cleavage activating part of the functional linker, wherein the activating part is formed to stabilize an anion formed during a basic cleavage from X2, wherein U is a moiety of formula (5) or (6)
• X2 is of the form —Y—Z, wherein
• Y is —O—C(═O)—, and
• Z is an electron-withdrawing leaving group, selected from the consisting of —F, —Cl, —Br, I, —N3, —SR12, —OCF3, —OCH2CF3, —OSO2CF3, —SO2C6H4CH3, —SO2CF3, —SO2CH3,
• wherein R12 is a C1-C6-alkyl, an aryl- or a benzyl residue;
• and subsequent reaction to form a compound of formula X1-L-Y-PEP (12), wherein PEP comprises a full-length peptide bound to Y via its N-terminus;
• ii. cleaving the acid labile protecting groups by addition of an acid,
• iii. contacting the composition of ii. with a surface-modified solid support, wherein a covalent hydrazone or oxime bond is formed between the capture compound and the solid support, and a compound of formula D-X1′-L-Y-PEP (13) wherein D is a surface-modified solid support, which is characterized in that the surface is modified by synthetic or natural polymers, wherein X1′ is of the form —NH—O—, —NH—NH— is formed, and
• iv. cleaving the full-length peptide from the solid support.