Fmoc-His-Aib-OH as a Semaglutide Precursor: Efficient One-Pot Synthesis and Computational Insights

Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist used in the treatment of type 2 diabetes and for weight management. A crucial structural element of Semaglutide is the His–Aib dipeptide unit, which prevents racemization and protects the peptide from enzymatic degradation by dipeptidyl peptidase-4. The incorporation of Aib, an unnatural amino acid, introduces steric hindrance that enhances peptide stability and resistance to enzymatic cleavage, thereby prolonging its circulation time and increasing its half-life. In this study, we report the development of an efficient, robust, and commercially viable one-pot synthesis for Fmoc-His-Aib-OH, enabled by design of experiments (DoE) methodology. Factorial designs were employed to systematically evaluate the influence of key parameters on reaction conversion and yield. The optimized process achieved a throughput of 89%, surpassing the literature-reported 70%, while delivering exceptional chemical purity (>99.5%) and chiral purity (>99.9% ee). Related substances were consistently controlled below 0.10%, meeting regulatory requirements. Importantly, the process demonstrated a favorable process mass intensity (PMI) of 80.3 kg/kg, underscoring its efficiency and environmental sustainability. Beyond these immediate outcomes, the integration of one-pot synthesis with design of experiments driven optimization establishes a generalizable paradigm for peptide and fine chemical manufacturing. This approach enhances scalability, reproducibility and sustainability, offering a pathway toward greener, commercially viable processes aligned with industrial and environmental imperatives.