A Vibrational Circular Dichroism Approach to the Determination of the Absolute Configurations of Flavorous 5-Substituted-2(5H)-furanones

• Published in: Journal of natural products (Washington, D.C.) Vol. 74; no. 4; pp. 707 - 711
• Main Authors: Nakahashi, Atsufumi, Yaguchi, Yoshihiro, Miura, Nobuaki, Emura, Makoto, Monde, Kenji
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society and American Society of Pharmacognosy 25.04.2011; Amer Chemical Soc; American Society of Pharmacognosy
• Subjects: Aroma and flavouring agent industries; Biological and medical sciences; Chemistry; Chemistry, Medicinal; Circular Dichroism - methods; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; Furans - chemistry; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Life Sciences & Biomedicine; Models, Molecular; Molecular Structure; Odorants - analysis; Organic chemistry; Pharmacology & Pharmacy; Plant Sciences; Preparations and properties; Science & Technology; Stereoisomerism; IMPACT; 3-HYDROXY-4,5-DIMETHYL-2(5H)-FURANONE; TRIGONELLA-FOENUM-GRAECUM; ENANTIOMERS; AROMA; SOTOLON; IDENTIFICATION; ODOR; KEY COMPOUND; CHIRAL MOLECULES; Separation; Preparative chromatography; Enantiomer; Circular dichroism spectrometry; Absolute configuration; Furan derivatives; Lactone; Aroma; Vibrational circular dichroism; Structural analysis; Supercritical fluid chromatography
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/np1007763

Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The absolute configuration of 1 was confirmed as (R)-(−)-1 and (S)-(+)-1 by adopting the vibrational circular dichroism (VCD) approach. The absolute configuration of 2, which has remained ambiguous since its discovery in 1957, was determined as (R)-(+)-2 and (S)-(−)-2 for the first time by the VCD technique. Surprisingly, the signs of the optical rotation of 2 are opposite of those of 1 regardless of their identical absolute configurations. This observation emphasizes the risk in absolute configurational assignments based on comparison of optical rotation signs of similar structures. Odor evaluation of the enantiomers of 2 revealed different odor intensities.