Esterification reactions on syndiotactic poly(2-methallyl alcohol). V. Homopolymers of 2-methallyl-(L)-dipeptidates and dipeptides cleaved from them

Syndiotactic poly(2-methallyl alcohol) (sPMA) is esterified with N^α-protected (L)-α-amino acids by the DCC/HOBT method. The resulting polymer is deprotected by HBr/glacial acetic acid. A second N^α-protected (L)-α-amino acid is condensed to the free α-NH₂ of the amino acid already bound to the sPMA by a water-soluble carbodiimide in mixed aqueous/organic solution. The formed N^α-protected dipeptide polymers were hydrazinolized to yield the N^α-protected dipeptide hydrazides. Alternatively, the dipeptidate polymers were N^α-deprotected and then hydrolyzed by aqueous KOH at pH = 11.0 to yield the deprotected dipeptides. All polymers and the dipeptides were characterized by ¹H- and ¹³C-NMR and the water-soluble N^α-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. © 1995 John Wiley & Sons, Inc.