Polymeric 2-mercaptopyridine and 2-mercapto-nitrobenzene derivatives. New reagents for peptide synthesis

Insoluble 2-mercaptopyridine and 2-mercapto-nitrobenzene derivatives were prepared by modification of commercially available polystyrene. Applicability of these polymers as reagents for the thiolytic removal of the 2-nitrophenylsulphenyl amino-protecting group and as supports for preparation of polymeric active esters was evaluated. Polymeric 2-mercaptopyridine (PMP) was found efficient for both purposes. It was used in the stepwise synthesis of Leu-enkephalin via the polymeric reagent approach, serving as an Nps-cleaver. Polymeric esters derived from PMP and Boc-amino acids proved to be excellent acylators. Their usefulness is exemplified in the preparation of two dipeptides, which were produced rapidly and in high yields and purity.