The azido acid approach to beta-peptides: parallel synthesis of a tri-beta-peptide library by fluorous tagging.

A small tri-beta-peptide library was prepared starting from three enantio- and diastereopure azido acids. Fluorous tagging followed by two cycles of azide reduction, fluorous solid phase extraction (f-SPE), peptide coupling with the original azido acids and f-SPE provided 27 protected azido peptides. Reduction and HPLC purification provided 25 of the 27 targeted tri-beta-peptides in acceptable yields and excellent purities.