Structure-Controlled Synthesis of Polyesteramides Utilizing Sugar Diols and Amino Acids

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1. Synthesis and biodegradability of polyesteramides consisting of amino acid, sugar diol, and aliphatic dicarboxylic acid unitsSome diamidodicarboxylic acids were prepared by condensations of combinations of L-phenylalanine and L-alanine with adipic acid and sebacic acid. Polyesteramides were synthesized by polycondensation of the diamidodicarboxylic acids with 1,4:3,6-dianhydro-D-glucitol (DAG) or 1,4:3,6-dianhydro-D-mannitol(DAM) in the presence of dicyclohexylcarbodiimide (DCC). NMR and IR analysis indicated that these polyesteramides were composed of well-defined structure. Enzymatic degradation and soil burial degradation tests suggested a correlation between the molecular structure and biodegradability of the polyesteramides. Those containing DAG or DAM units showed a somewhat lower degradability than that of polyesteramides containing aliphatic diol units.2. Synthesis and biodegradability of polyesteramides with hydroxyl groups as side chains.2,3-O-isopropyliden-L-threitol was prepared from L-tartaric acid via two-step reactions. The diamidodicarboxylic acid described above were polycondensed with the protected L-threitol in the presence of DCC to yield the corresponding polyesteramides. The isopropylidene protecting groups were removed by the treatment with trifluoroacetic acid to give polyesteramides having free hydroxyl groups as side chains. The introduction of hydroxyl groups significantly accelerated the biodegradation of the polyesteramides.Our research opened a promising way to synthesize structurally well-defined biodegradable polyesteramides utilizing renewable natural resources such as amino acids and sugar diols.