Copper(II) Lysinate and Pseudoproline Assistance in the Convergent Synthesis of the GLP-1 Receptor Agonists Liraglutide and Semaglutide

Total wash elimination for solid phase peptide synthesis

We present a process for solid phase peptide synthesis (SPPS) that completely eliminates all solvent intensive washing steps during each amino acid addition cycle. A key breakthrough is the removal of a volatile Fmoc deprotection base through bulk evaporation at elevated temperature while preventing condensation on the vessel surfaces with a directed headspace gas flushing. This process was demonstrated at both research and production scales without any impact on product quality and when applied to a variety of challenging sequences (up to 89 amino acids in length). The overall result is an extremely fast, high purity, scalable process with a massive waste reduction (up to 95%) while only requiring 10-15% of the standard amount of base used. This transformation of SPPS represents a step-change in peptide manufacturing process efficiency, and should encourage expanded access to peptide-based therapeutics.

Carbodiimide-Mediated Beckmann Rearrangement of Oxyma-B as a Side Reaction in Peptide Synthesis

The suppression of side reactions is one of the most important objectives in peptide synthesis, where highly reactive compounds are involved. Recently, the violuric acid derivative Oxyma-B was introduced into peptide synthesis protocols as a promising additive to efficiently control the optical purity of the amino acids prone to racemization. However, we discovered a side reaction involving the Beckmann rearrangement of Oxyma-B during the coupling reaction, which compromises the yield and purity of the target peptides. Here, we present the investigation of the mechanism of this rearrangement and the optimization of the coupling reaction conditions to control it. These results can be taken into account for the design of novel efficient oxime-based coupling reagents.