Fmoc-Amox, A Suitable Reagent for the Introduction of Fmoc

Synthesis of most peptides is achieved using solid-phase peptide synthesis employing the Fmoc/tert-butyl strategy. However, the introduction of Fmoc in N-unprotected amino acids seems to be challenging due to the formation of dipeptides and sometimes tripeptides as impurities and β-alanyl impurities when Fmoc-OSu is used as well. Herein, we report an efficient and successful method using Fmoc-Amox, which is an oxime based derivative, toward the synthesis of Fmoc-glycine with no traces of side reactions. Fmoc-Amox is inexpensive, and Amox can be easily removed after the reaction, thus affording pure Fmoc-Gly-OH devoid of any detrimental impurities or contamination, mainly dipeptide or Amox itself, as shown by high-performance liquid chromatography and NMR, respectively.