FeCl₃‐Mediated Boc Deprotection: Mild Facile Boc‐Chemistry in Solution and on Resin

Abstract

A mild, practical, and straight forward method for Boc deprotection and its use in peptide synthesis both in solution and on solid support is presented. Boc protecting group is removed from the N‐terminal amino acid of the amino acid and the peptide using environment‐friendly cost‐effective Lewis acid, FeCl3. The deprotected amino group undergoes C−N bond formation with the next Boc‐protected amino acid in the presence of a suitable coupling reagent and base. A library of di‐ to tetrapeptides is synthesized with moderate to good yield from standard and nonstandard Boc‐protected amino acids in solution. Most importantly, this protocol can be used for the solid‐phase peptide synthesis (SPPS) using Boc‐protected amino acids on the acid‐sensitive Rink amide resin, which is usually used for Fmoc chemistry. This protocol thus allows practicing Boc chemistry in a greener manner, and on‐demand switching from Fmoc to Boc chemistry and vice‐versa while synthesizing one oligopeptide on the same resin. The inherent orthogonality of Fmoc and Boc chemistry allows facile synthesis of branched and cyclized peptides on the resin as well.

Crystal structure and supramolecular arrangement of heterochiral tripeptides

“…We first synthesized all protected tripeptides by conventional peptide synthesis method in solution (Scheme 1) using o-NosylOXY as a coupling reagent. [47][48][49] The purity of peptides was examined by reverse-phase analytical HPLC and characterized by 1D NMR spectroscopy and mass spectrometry.…”

Nanostructures from protected L/L and D/L amino acid containing dipeptides

“…The coupling reagent, Ethyl 2‐Cyano‐2‐(2‐nitrobenzenesulfonyloxyimino)acetate ( o ‐NosylOXY) was synthesized by our reported protocol. [ 45–47 ]…”

Development of a nitrogen-bound hydrophobic auxiliary: application to solid/hydrophobic-tag relay synthesis of calpinactam

“…To verify the STRS strategy (Scheme 6B), solid-supported pentapeptide 41 was prepared by following the previous SPPS via the 10-step sequence from commercially available Fmoc-Dallo-Ile-OH (40). Treatment of 41 with TCbz-OAr F (10e) in the presence of Et 3 N successfully installed the hydrophobic auxiliary on the solid-supported peptide, affording 42.…”