Synthesis of Insulin-desB30 Analogs via an Enzymatically Removable N-Terminal Solubilizing Tag

Chemical synthesis enables rapid access to designed insulin analogs, but the efficiency is hindered by the insulin A-chain's poor solubility. We report a streamlined route using direct Fmoc-SPPS of a native A chain aided by a temporary polylysine solubility tag removable by Lys-C under mild aqueous conditions. The workflow improves isolation, folding, and chain combination and generalizes to difficult targets (A16Pro mutant insulin, methyl-ketone A6-A11 surrogate, four-disulfide insulin), delivering high-purity products.