Solid-phase synthesis of crystalline glucagon

Mammalian glucagon was synthesized by a stepwise solid-phase method. The support was an alkoxybenzyl alcohol resin, and the biphenylylisopropyloxycarbonyl group was used for temporary alpha-amino protection. After purification by gel filtration and ion-exchange chromatography, the 29-residue hormone was readily crystallized from water at alkaline pH. The product was homogeneous and indistinguishable from natural bovine glucagon by gel electrophoresis, ion-exchange chromatography, reverse-phase high-pressure liquid chromatography, fluorescence spectroscopy, and amino acid analysis. The synthetic hormone was fully active in the rabbit hyperglycemia assay.