Previously, 2, 4, 6-trimethylpyridine (collidine), due to steric shielding around the N-atom, was found to be an efficient base for effecting peptide segment coupling via azabenzotriazole-based onium-style coupling reagents. A number of even more highly hindered bases, including 2, 3, 5, 6-tetramethylpyridine, 2, 6-di-tert-butyl-4-(dimethylamino) pyridine, triisopropylamine, and N-tert-butylmorpholine, have been compared with ...
