We developed a Two-fold Symmetric tridentate Linchpins (TSL) that allows aqueous, biocompatible one-pot synthesis of bicyclic architecture from synthetically and ribosomally-made phage-displayed peptides. The linchpin combines an aldehyde-reactive n-alkyl aminoxy and thiol-reactive bis benzyl chloride groups to enable the modification of peptides with H-SX_mCX_nC structural motifs (X = any natural amino acid). The bicyclization starts with oxidation of the N-terminal serine of an unprotected peptide in water followed by one pot oxime ligation of TSL to N-terminus, TCEP reduction and quantitative bicyclization via sequential alkylation of the cysteine thiols. The resulting bicyclic architectures are stable in buffered solution for over a month and resist degradation in serum and aggressive mixture of proteases (Pronase^TM) The bicyclization protocol is compatible with modification of phage-displayed libraries and it converts readily available genetically-encoded (GE) starting material, libraries of peptides, to GE libraries of new value-added bicyclic topologies.