Production of Atosiban's Key Intermediate Pentapeptide: Synthetic Approaches to the Development of a Peptide Synthesis with Less Racemization and Simplifier Purification Process.

The key intermediate NH-Ile-Thr(Bzl)-Asn-Cys(Bzl)-Pro-COOH of Atosiban was prepared from -Boc--Bzl-cysteine by the stepwise lengthening of the chain according to the repetitive ,-bis(trimethylsilyl)acetamide/-hydroxysuccinimide ester (BSA/NHS) strategy. This synthetic route required no chromatography purification and can be readily performed, yielding a highly pure pentapeptide compound.