Two linkers have been constructed for the Fmoc solid-phase synthesis of peptides and peptide bioconjugates possessing C-terminal esters that will, due to the linkers' pendant disulfide-protected thiols, reveal masked reactivities of C-terminal thioesters under suitable conditions.  Both of these thioester equivalent linkers have been incorporated on solid supports (1 and 2).  One of the linkers has been analyzed, and in solution functions as would a C-terminal peptide thioester under the reaction conditions used for native chemical ligation (NCL).  Thus, when 3 was treated with cysteine (Cys) in the presence of sodium 2-mercaptoethanesulfonate (MES-Na) in aqueous buffer (pH ~7.4), H₂N-Phe-Cys-OH was generated in 80% yield.  As an alternative, modified trityl linker 2 would provide a convenient route toward peptide thioesters terminating in traditionally difficult residues such as histidine, cysteine, and proline because its loading does not involve acyl activation of epimerizable C-terminal residues and because its steric bulk prevents diketopiperazine formation.  Solid-phase resins based on these linkers will permit facile construction of peptide thioester or thioester equivalent bioconjugates that were previously considered difficult or impossible to synthesize.  These thioester equivalent linkers will also expose new avenues toward the solid-phase synthesis of cyclic, cysteine-containing peptidic materials.