Reagent for protection of carboxyl termini of peptides as 4-picolyl esters, providing a polar 'handle' which aids in separation and purification of the peptide. The group can be introduced in the presence of a base, e.g. tetramethylguanidine, is stable to acid-catalyzed removal of Cbz protecting group and can be removed by base, Na in liquid ammonia or catalytic hydrogenolysis: J. Chem. Soc. (C), 1911 (1969); 46, 50 (1971). For use in conjunction with Amberlyst?15 resin in peptide synthesis, see: J. Chem. Soc., Chem. Commun., 1057 (1971). As its free base, has been used for the protection of OH groups as 4-picolyl derivatives, relatively stable to acid (HF, TFA) but selectively cleaved by electrolytic reduction: J. Chem. Soc., Chem. Commun., 1123 (1972); Acta Chem. Scand. B, B37, 475 (1983); J. Chem. Res. (Synop.), 22 (1977).
