Raju Cijil, Mridula Kozhukunnon, Srinivasan Nikitha, Kunnikuruvan Sooraj, Sureshan Kana M
School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram Thiruvananthapuram, Kerala, 695551, India.
Department of Chemistry, Indian Institute of Technology Madras, Chennai, 600036, India.
Angew Chem Int Ed Engl. 2023 Sep 11;62(37):e202306504. doi: 10.1002/anie.202306504. Epub 2023 Aug 3.
We report the topochemical syntheses of three polyarylopeptides, wherein triazolylphenyl group is integrated into the backbone of peptide chains. We synthesized three different monomers having azide and arylacetylene as end-groups from glycine, L-alanine and L-valine. We crystallized these monomers and the crystal structures of two of them were determined by single-crystal X-ray diffractometry. Due to the steric constraints, both of these monomers crystallized with two molecules, viz. conformers A and B, in the asymmetric unit. Consistently, in both cases, the A-conformers are antiparallelly π-stacked and B-conformers are parallelly slip-stacked, exploiting weak interactions. Though the arrangements of molecules in the pristine crystals were unsuitable for topochemical reaction, upon heating, they undergo large motion inside the crystal lattice to reach a transient reactive orientation and thereby the self-sorted conformer stacks react to give a blend of triazole-linked polyarylopeptides having two different linkages. Due to the large molecular motion inside crystals, the product phase loses its crystallinity.
我们报道了三种聚芳基肽的拓扑化学合成，其中三唑基苯基被整合到肽链主链中。我们从甘氨酸、L-丙氨酸和L-缬氨酸合成了三种不同的以叠氮化物和芳基乙炔为端基的单体。我们使这些单体结晶，并通过单晶X射线衍射测定了其中两种的晶体结构。由于空间位阻限制，这两种单体在不对称单元中均以两个分子（即构象异构体A和B）结晶。一致地，在这两种情况下，A-构象异构体通过利用弱相互作用以反平行方式进行π堆积，而B-构象异构体则以平行方式进行滑移堆积。尽管原始晶体中的分子排列不适合进行拓扑化学反应，但加热时，它们在晶格内发生大幅度运动，以达到瞬态反应取向，从而使自分类的构象异构体堆叠发生反应，生成具有两种不同连接方式的三唑连接的聚芳基肽混合物。由于晶体内分子的大幅度运动，产物相失去了结晶性。
