Design and Synthesis of Polyacetylenes as a Probe for Chirality of Sugars and Carboxylic Acids

螺旋聚合物在合成、结构和功能等方面引起了人们的广泛兴趣。在本论文中，我们报道了基于无手性聚(4-二羟基硼苯基)乙炔(Poly-1)和聚(4-二丙氨基甲基苯基)乙炔(Poly-2)分别与光学活性分子，例如手性胺、糖和手性酸，通过络合形成螺旋的诱导圆二色谱(ICD)。用[Rh(NBD)Cl]2与Poly-1和Poly-2进行立体定向聚合制备了Poly-1和Poly-2。它们与手性分子络合后在紫外可见光区表现出ICD，这可能是由于聚合物的单手螺旋构象所致。例如，Poly-1显示了含有各种手性分子的ICD，如二元醇、氨基醇、羟基羧酸、二元酸、二胺…水溶液中有更多的ES、碳水化合物和类固醇，这取决于分子的构型和立体化学。Poly-2与旋光性羧酸和α-羟基酸的络合也显示出类似的ICD。我们还发现了旋光性聚苯乙炔(Poly-3)与手性酸络合手性氨基醇残基的新的螺旋-螺旋转变。Poly-3是一种光学活性聚合物，在紫外可见光区显示ICD。然而，由于(R)-扁桃酸和(R)-1-苯丙酸等手性酸与聚-3的结合，导致聚-3在溶液中的ICD发生了很大的变化，而聚-3的圆二色谱几乎没有变化，即使在过量的(S)-扁桃酸和(S)-1-苯丙酸的存在下也是如此。因此，Poly-3的ICD变化可以作为手性识别酸类的探针。虽然在多肽、多核苷酸和聚甲基丙烯酸酯中已经观察到了这种构象转变，但它们的螺旋意义受到外部无手性因素的影响，包括pH、温度、光和盐浓度。这可能是第一个由外部手性因素通过非对映异构体酸碱相互作用诱导的螺旋-螺旋转变的例子。Poly-3被用作不对称烷基化的光学活性催化剂。由苯甲醛和二乙基锌在Poly-3催化量下反应得到的1-苯乙醇对映体过量为30-49%。较少

Helical polymers have aroused wide interest from synthetic, structural, and functional viewpoints. In the present dy, we report the induced circular dichroism (ICD) based on the helix formation of achiral poly ((4-dihydroxyborophenyl) acetylene) (poly-1) and poly ((4-disopropylaminomethylphenyl) acetylene) (poly-2) by the complexation with optically active molecules, for instance, chiral amines, sugars, and chiral acids, respectively. The split-type and magnitude of the Cotton effects can be used as a novel probe for determining the chirality of amines, sugars, or acids.Poly-1 and poly-2 were prepared through the stereospecific polymerization with [Rh (nbd) Cl] 2. They exhibited an ICD in the UV-visible region upon complexation with chiral molecules, probably due to the predominantly one-handed helical conformation of the polymers. For instance, poly-1 showed an ICD with various kinds of chiral molecules such as diols, amino alcohols, hydroxycarboxylic acids, dicarboxylic acids, diamin … More es, carbohydrates, and steroids in aqueous solution depending on the configuration and stereochemistry of the molecules. Poly-2 also showed similar ICDs upon complexation with optically active carboxylic and alpha-hydroxy acids.We also found a novel helix-helix transition of optically active polyphenylacetylene (poly-3) bearing chiral aminoalcohol residues induced by the complexation with chiral acids. Poly-3 is an optically active polymer and shows an ICD in the UV-visible region. However, the binding of chiral acids, for instance, (R) -mandelic acid and (R) -1-phenylpropionic acid to poly-3, results in a dramatic change in the ICD of poly-3 in solution owing to a x-helix transition, while the CD spectrum of poly-3 hardly changed even in the presence of excess (S) -mandelic acid and (S) -1-phenylpropionic acid. Therefore, the changes in the ICD of poly-3 can be used as a probe for chiral recognition of the acids. Although such a conformational transition has been observed in polypeptides, polynucleotides, and polymethacrylates, their helix-sense is governed by external achiral factors including pH,temperature, light, and salt concentration. This may the first example of a helix-helix transition induced by external chiral factor through diastereomeric acid-base interactions.Poly-3 was used as an optically active catalyst for asymmetric alkylation. Enantiomeric excess of 1-phenylethanol obtained by the reaction of benzaldehyde with diethylzinc in the presence of catalytic amount of poly-3 was 30 - 49 %. Less