# Study of optical rotation based on the molecular structure in fused oligomers of macrocycles

## TL;DR

This paper explores how the optical rotation of fused macrocycle oligomers depends on their molecular structure and arrangement.

## Contribution

The study introduces a novel approach to analyze optical rotation based on structural arrangements in fused macrocyclic oligomers.

## Key findings

- Molar optical rotation per element is modulated by the rotational angle between elements.
- Optical rotation varies with different arrangements, even when measured values are similar.
- Diastereomeric excess was estimated based on the cooperative twisting of macrocycles.

## Abstract

We designed a unique oligomer form in which several helically twisted macrocycles (M- or P-helicity) are arranged through fusion. We investigated the optical rotation of a series of fused oligomers of macrocycles with a difference in the number and arrangement of elements associated with point-chiral auxiliary. Some oligomers cooperatively attained a situation where an identical sense of twisting was preferred throughout the entire molecule. On the basis of these results, we estimated diastereomeric excess induced in each oligomer. We revealed that the molar optical rotation per element was modulated with a rotational angle between elements: an increase via 0° rotational arrangement, a decrease via 180° rotational arrangement, or a decrease via cyclic arrangement. Alternatively, for other oligomers in which several diastereomeric conformers coexist, we uniquely attempted to consider the optical rotation based on the molecular structure through the assessment of a change ratio of the absorption dissymmetry factor before and after complexation with an achiral guest. We found that molar optical rotation could be different based on the arrangement, although actual measured values were similar.

The fusion of macrocyclic elements, which adopt twisted forms with M- or P-helicity, provides a variety of chiral architectures. The correlation between optical rotation and the molecular structure is discussed.