Absolute Configuration Determination from Low ee Compounds by the Crystalline Sponge Method. Unusual Conglomerate Formation in a Pre‐Determined Crystalline Lattice. Issue 21 (15th April 2021)

• Record Type: Journal Article
• Authors: Dubey, Ritesh; Yan, KaKing; Kikuchi, Takashi; Sairenji, Shiho; Rossen, Anouk; Goh, Shermin S.; Feringa, Ben L.; Fujita, Makoto
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 21(2021)
• Page Start: 11809
• Page End: 11813
• Publication Date: 2021-04-15
• Subjects: absolute configuration determination -- crystalline sponge method -- host-guest systems -- X-ray crystallography; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202102559
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: When chiral compounds with low enantiomeric excess ( ee, R:S= m : n ) were absorbed into the void of the crystalline sponge (CS), enantiomerically pure [(R) m (S) n ] chiral composites were formed, changing the centrosymmetric space group into non‐centrosymmetric one. The absolute configuration of the analyte compounds was elucidated with a reasonable Flack (Parsons) parameter value. This phenomenon is characteristic to the "post‐crystallization" in the pre‐determined CS crystalline lattice, seldom found in common crystallization where the crystalline lattice is defined by an analyte itself. The results highlight the potential of the CS method for absolute configuration determination of low ee samples, an often encountered situation in asymmetric synthesis studies. Abstract : No need for ee enrichment: When a low ee chiral compound (even 17 % ee !) is absorbed into the pre‐determined crystalline lattice of the crystalline sponge, the analyte forms an enantiomerically pure [ Rm Sn ] aggregate, validating the Bijvoet method for the absolute structure analysis with a reasonable Flack (Parsons) parameter value.