Polymerization of N‐carboxy–amino acid anhydrides in the solid state. II. Relation between polymerizability and molecular arrangement in L‐leucine NCA and L‐alanine NCA crystals
Polymerization of N‐carboxy–amino acid anhydrides in the solid state. II. Relation between polymerizability and molecular arrangement in L‐leucine NCA and L‐alanine NCA crystals
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N-羧基氨基酸酐的固态聚合II。L-亮氨酸NCA和L-丙氨酸NCA晶体中的聚合性和分子排列之间的关系。
DOI：
10.1002/pol.1982.180201008
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
T. Kawai
中科院分区：
文献类型：
--
作者：
H. Kanazawa;Y. Ohashi;Y. Sasada;T. Kawai
在固态和溶液中检查了 L-亮氨酸和 L-丙氨酸的 N-羧基氨基酸酐 (NCA) 的聚合性。 L-亮氨酸 NCA 在固态（浸入己烷中）的反应性比溶液（在乙腈中）高得多，但 L-丙氨酸 NCA 的情况正好相反。然而，两种 NCA 在每个聚合体系中给出相似的表观活化能值。与溶液中获得的相比，在固态L-亮氨酸NCA聚合中获得了较高分子量的多肽，而由L-丙氨酸NCA获得的聚合物的分子量在溶液中比在固态中更高。红外光谱表明，α螺旋主要是在固态的L-亮氨酸NCA和L-丙氨酸NCA聚合时形成的；在后期聚合中形成少量β结构。 X射线衍射和电子显微镜显示，L-亮氨酸NCA在晶体中主要沿c轴聚合，而L-丙氨酸NCA晶体中聚合物链以随机方向生长。这种差异可以通过晶体中的分子排列来解释。固态下的高反应活性有两个要求：单体的五元环必须形成层状结构，聚合物必须占据与反应单体几乎相同的空间。
The polymerizability of N-carboxy–amino acid anhydrides (NCAs) of L-leucine and L-alanine was examined in the solid state and in solution. L-leucine NCA shows much higher reactivity in the solid state (when immersed in hexane) than in solution (in acetonitrile), but the opposite is true for L-alanine NCA. However, the two NCAs give similar values of apparent activation energy in each polymerization system. Rather high-molecular-weight polypeptides were obtained in the polymerization of L-leucine NCA in the solid state compared with those obtained in solution, while the molecular weight of polymers obtained from L-alanine NCA was higher in solution than in the solid state. IR spectra showed that α helices form mainly in the polymerization of both L-leucine NCA and L-alanine NCA in the solid state; a small amount of the β structure forms in the latter polymerization. X-ray diffraction and electron microscopy revealed that L-leucine NCA polymerizes predominantly along the c axis in the crystal, while the polymer chains grow in random directions in the crystal of L-alanine NCA. The difference can be explained by the molecular arrangement in the crystal. There are two requirements for high reactivity in the solid state: the five-membered rings of the monomer must form a layer structure and the polymer must occupy nearly the same space as the reacting monomer.