Remarkable Structure Effects on Chiroptical Properties of Polyisocyanides Carrying Proline Pendants
作者:Anqiu Xu、Guixia Hu、Yulong Hu、Xiuqiang Zhang、Kun Liu、Guichao Kuang、Afang Zhang
DOI:10.1002/asia.201300297
日期:2013.9
handedness of the helical conformation. To examine the effects of steric hindrance on the stabilities of the helical conformation for these aliphatic representatives, proline pendants with various substituents at both the carboxyl and amine terminals were designed. To further examine the steric effects of the proline pendants, aromatic counterparts were also prepared. In the latter case, the effects of hydrogen
具有简单化学结构和高螺旋构象稳定性的手性聚合物对于它们作为手性载体和不对称催化剂的应用很重要。我们在此报道了一系列带有不同手性脯氨酸侧基的脂族多异氰酸酯的合成,以及这些侧基的化学结构对聚合物的手性的影响的研究。脯氨酸侧链4位的手性中心构型从S更改为R检查其对螺旋构象的惯用性的影响。为了检查空间位阻对这些脂肪族代表的螺旋构象稳定性的影响,设计了在羧基和胺端均具有各种取代基的脯氨酸侧基。为了进一步检查脯氨酸侧基的空间效应,还制备了芳香族对应物。在后一种情况下,通过从酯键转变为酰胺键,研究了侧链单元之间的氢键对螺旋构象的增强和稳定性的影响。基于侧基的庞大,溶剂极性和溶液温度,比较了圆二色光谱法测定的脂肪族和芳香族多异氰酸酯的棉花效应和信号强度。