A unique "chiral amplification" exerted in a molecule with a multi-fold dynamic chiral space

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05031
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 33010:Structural organic chemistry and physical organic chemistry-related
• Research Institution: Hokkaido University
• Principal Investigator: KATOONO Ryo 北海道大学, 理学研究院, 助教 (60432142)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: テレフタルアミド / マクロサイクル / 三重結合 / ねじれ優先性 / 協同性 / 面不斉 / モル旋光度 / キラリティ伝達

Outline of Final Research Achievements

A unique "chiral amplification" was demonstrated with two original systems, (I) and (II). In either system, macrocycles are component elements that adopt dynamic chiral forms with P- or M-helicity by twisting clockwise or counterclockwise. Such a dynamic chiral element is repeatedly arranged to form a single molecule by (I) stacking or (II) fusion.
(I) Achiral planes are stacked and bridged at each corner to create a three-fold interlayer. The four-layer cyclophane can adopt two diastereomeric forms (PPP and MMM) by three-fold twisting clockwise or counterclockwise and prefers a particular sense of twisting.
(II) Several helically-twisted macrocycles are arranged through fusion. A series of fused oligomers of macrocycles with a difference in the number (n=2-6) and arrangement (rotational, cyclic, and acyclic) of elements were presented to consider (i) cooperativity in helical-sense preferences and (ii) optical rotation based on molecular structure.

Free Research Field

キラル化学

Academic Significance and Societal Importance of the Research Achievements

キラル増幅という用語は、既に多義的に用いられてきた。自身では極めて小さな光学活性しか示さない小分子が、錯体を形成することでより大きな光学活性を示すようになる現象や、鎖状分子あるいは超分子的集合体の伸長に際し、二次的に誘起された別のキラル構造が元の単位構造の光学活性より大きな光学活性を示すようになる現象等をさす。本研究では、光学活性の大小ではなく、分子内に複数の動的キラル構造を配した場合、単独で存在する場合と比べて、集積体中でそのねじれ優先性が増大する新たな現象として定義した。この増幅機構に基づけば、既存の限定的なキラルモチーフに依存せず、多様なキラル高次多量体を設計することが可能になるだろう。