Side products in the synthesis of secretin.

Analytical studies on side products in the synthesis of secretin led to the discovery of a further side reaction, involving conversion of the carboxamide function of glutamine to glutamic acid gamma-methyl ester. The chemical structure of the side products was determined by NMR spectroscopy upon their tryptic digestion and isolation of the modified secretin fragments. Possible pathways for the observed side reaction are discussed.