Electronic Structure–Property Relationships in Ketohexoses: Implications for Crystal Engineering and Functional Rare Sugar Materials

Rare sugars have garnered significant attention owing to their beneficial biological activities and their potential applications in sustainable materials, agriculture, and medicine. However, despite extensive crystallographic and hydrogen-bonding studies, the electronic factors governing their molecular stability and crystal packing are still not fully understood. In this study, the DV-Xα molecular orbital method was employed to systematically analyze intramolecular charge distribution in ketohexoses, comparing D-chiral and D,L-racemic forms. The results reveal a clear distinction between two types of electronic behavior: (i) electronically stable sites (C2 and C5), where charge variation remains minimal (typically < 1 %), and (ii) adaptive sites (C3, C4, and C6), where charge distribution exhibits significant responsiveness to molecular environment. This finding provides a new electronic-structure-based framework that explains how localized charge stability and flexibility cooperatively govern crystal packing and intermolecular interactions, particularly hydrogen bonding. Even subtle variations in charge (< 1 %) were found to be chemically meaningful, as they systematically influence interaction patterns across different ketohexoses. These insights go beyond conventional structural analyses by establishing a direct link between intramolecular electronic structure and macroscopic material behavior. The present approach offers a foundation for rational design and functionalization of rare sugars in applications such as crystal engineering, pharmaceuticals, and sustainable agrochemical materials.