Synthesis of the protected repeat sequence of glutelin‐2 of maize, Boc‐Val‐His‐Leu‐Pro‐Pro‐Pro‐OH, via nucleophilic cleavage from an Nbb‐resin

The protected hexapeptide Boc‐Val‐His‐Leu‐Pro‐Pro‐Pro‐OH, the N ‐terminal protected repeat sequence of glutelin‐2 of maize, has been synthesized on a bromomethyl‐Nbb‐resin. After cleavage of the peptide‐resin bond by two 3‐min treatments with dioxane/methanol/4 n NaOH (30:9:1), gel filtration followed by anion‐exchange chromatography allowed the isolation of the target peptide (37% yield) and its methyl ester derivative (52% yield). Cleavage with dioxane/2‐dimethylaminoethanol/4 n NaOH (30:9:1) has been found to be a simple and effective alternative to the photolysis of the peptide‐Nbb‐resin bond. After two 15‐min treatments with this reagent the protected hexapeptide was isolated by chromatography without apparent epimerization.