Environmentally friendly SPPS I. Application of NaOH in 2-MeTHF/methanol for Fmoc removal

Abstract

Focusing on the step-by-step transformation of the traditional solid-phase peptide synthesis (SPPS) into an environmentally friendly process, we herein report the elimination of environmentally hazardous components (piperidine, DMF and DCM) from this technique. We developed a synthetic protocol that employs sodium hydroxide in a 2-MeTHF/MeOH mixture for Fmoc group cleavage and uses 2-MeTHF alone as the coupling solvent. The protocol was developed with the most frequently used PS/DVB-based resin. This synthetic strategy was used to prepare Leu-enkephalin amide, and the results (crude purity 99%, yield 62%) were fully comparable to those achieved with the traditional protocol using piperidine, DMF and DCM.