The present invention relates to a method for preparing a library of peptides or an isolated peptide comprising (a) releasing one or more linear dithiol peptides carrying a sulfhydryl group in the N-terminal region of the one or more peptides and being immobilized via a disulfide bridge in the C-terminal region of the one or more peptides on a solid phase from the solid phase by (i) an agent reducing the disulfide bridge, thereby releasing the one or more linear dithiol peptides from the solid phase, wherein the agent is volatile and is removable by evaporation, or (ii) a base that deprotonates the sulfhydryl group in the N-terminal region of the one or more linear dithiol peptides, thereby inducing an intramolecular disulfide exchange thereby releasing the one or more linear dithiol peptides from the solid phase in the form of one or more cyclic peptides.