Journal of Polymer Science Part A: Polymer Chemistry, Vol.33, No.5, 815-828, 1995
Esterification Reactions on Syndiotactic Poly(2-Methallyl Alcohol) .5. Homopolymers of 2-Methallyl-(L)-Dipeptidates and Dipeptides Cleaved from Them
Syndiotactic poly(2-methallyl alcohol) (sPMA) is esterified with N-alpha-protected (L)-alpha-amino acids by the DCC/HOBT method. The resulting polymer is deprotected by HBr/glacial acetic acid. A second N-alpha-protected (L)-alpha-amino acid is condensed to the free alpha-NH2 of the amino acid already bound to the sPMA by a water-soluble carbodiimide in mixed aqueous/organic solution. The formed N-alpha-protected dipeptide polymers were hydrazinolized to yield the N-alpha-protected dipeptide hydrazides. Alternatively, the dipeptidate polymers were N-alpha-deprotected and then hydrolyzed by aqueous KOH at pH = 11.0 to yield the deprotected dipeptides. All polymers and the dipeptides were characterized by H-1- and C-13-NMR and the water-soluble N-alpha-deprotected polymers in addition by potentiometry. The synthetic procedures open a path to defined tactic polymers with chiral oligopeptide side chains and, after their cleavage, also to oligopeptides. During synthesis, the oligopeptide is bound to a dissolved polymer chain of relatively extended macroconformation which facilitates both the accessibility and reactivity of the reaction centers as well as the precipitation and filtration after each synthesis step.