A Mechanistic Study of α-(Amino acid)-N-carboxyanhydride Polymerization: Comparing Initiation and Termination Events in High-Vacuum and Traditional Polymerization Techniques
A Mechanistic Study of α-(Amino acid)-N-carboxyanhydride Polymerization: Comparing Initiation and Termination Events in High-Vacuum and Traditional Polymerization Techniques
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DOI：
10.1021/ma901340y
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发表时间：
2009-10-27
期刊：
影响因子：
5.5
通讯作者：
Messman, Jamie M.
中科院分区：
文献类型：
--
作者：
Pickel, Deanna L.;Politakos, Nikolaos;Messman, Jamie M.
高真空聚合的α-（氨基酸）-N-羧基氰（NCAs）提供聚合物与控制的分子量和窄的多分散性，然而，它的端基组成的所得多肽的全面研究尚未进行。这揭示了重要的信息，因为端基指示聚合机理（即，起始事件）和终止途径。为此，以1，6-己二胺为引发剂合成了聚（O-苄基-L-酪氨酸），并通过MALDI-TOF MS、NALDI-TOF MS和C-13 NMR光谱对其进行了表征，以确定端基结构。在DMF/THF中通过高真空和手套箱技术制备聚合物。通过高真空技术制备聚（O-苄基-L-酪氨酸），得到了一种聚合物，该聚合物完全由正常胺机理引发，并观察到与DMF反应的终止。相反，在手套箱中制备的聚合物由正常的胺和活化单体机制引发，并且几种终止产物是明显的。据我们所知，这是第一个严格的和比较分析的端基结构，它表明了高真空技术的优势，聚合的NCA的制备定义明确的多肽与端基保真度。
High-vacuum polymerization of alpha-(amino acid)-N-carboxyanhydrides (NCAs) affords polymers with controlled molecular weights and narrow polydispersities; however, it comprehensive study of the end-group composition of the resulting polypeptides has not yet been performed. This reveals crucial information, as the end-groups are indicative of both the polymerization mechanism (i.e., initiation event) and the termination pathways. To this end, poly(O-benzyl-L-tyrosine) initiated by 1,6-diaminohexane was synthesized and Subsequently characterized by MALDI-TOF MS, NALDI-TOF MS, and C-13 NMR spectroscopy to ascertain the end-group structure. Polymers were prepared by both high-vacuum and glovebox techniques in DMF/THF. Preparation of poly(O-benzyl-L-tyrosine) by high-vacuum techniques yielded a polymer initiated exclusively by the normal amine mechanism, and termination by reaction with DMF was observed. In contrast, polymers prepared in the glovebox were initiated by the normal amine and activated monomer mechanisms, and several termination products arc evident. To our knowledge, this is the First rigorous and comparative analysis of the end-group structure, and it demonstrates the advantage of high-vacuum techniques for polymerization of NCAs for the preparation of well-defined polypeptides with end-group fidelity.