Grafting of single amino-acid units to polyhydroxy polymers

The reaction between N-carboxy anhydrides (NCAs) of amino acids and polymeric alkoxide derivatives of polyhydroxypolymers such as cellulose acetate in solution at (A/I) ratios of NCA to alkoxide≤1 was investigated. Amino-acid derivatives of the polyhydroxypolymers were thus obtained in which essentially single amino-acid units were attached to the polymeric backbone through either their carboxyl or amino group, as seen from end group titrations. NCAs of α-amino acids and N-substituted α- and β-amino acids were used. The reaction at A/I ratios between 1 and 4, led to the attachment of polypeptide side chains whose DP_n was given by A/I. The percentage terminal amino groups increased on increasing the A/I ratio above unity. The results obtained may help to elucidate the initiation mechanism of the polymerization of NCAs by alkoxides; this has been a subject of controversy.