Cyclic peptide synthesis with thioacids.

ABSTRACT

C-Terminal amino acid 9-fluorenylmethylthioesters may be carried through Boc chemistry solution phase peptide synthesis sequences. After insertion of the final residue in the form of an Fmoc carbamate, treatment with piperidine releases a seco-peptide as a C-terminal thioacid that on treatment with Sanger's reagent undergoes cyclization to a cyclic peptide. Cyclic penta- and hexapeptides have been synthesized in this manner, as has a cyclic glycopeptide. Functional group compatibility with alcohols and carboxylic acids is demonstrated.