title: Stereochemical studies of odorous 2-substituted-3(2H)-furanones by vibrational circular dichroism.
abstract: Chiral naturally occurring aroma compounds often exhibit enantiomeric excesses due to their stereoselective biogenesis. In general, significant organoleptic differences are perceived between these enantiomers. Chiral 2-substituted-3(2H)-furanones, featuring a unique keto-enol tautomer, the cause of their racemization, have been known to play an important role in flavor because of their extremely low threshold values and their burnt sugar odor characteristics. Since the discovery of these important aroma chemicals, they have been used in large quantities as raw materials in the flavor and fragrance industry. However, absolute configurations of these furanone derivatives have remained ambiguous for the past 40 years. Here optical resolutions of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2,5-dimethyl-4-methoxy-3(2H)-furanone, and 4-acetoxy-2,5-dimethyl-3(2H)-furanone were accomplished using chiral CO(2) supercritical fluid chromatography (SFC). Their absolute configurations were unraveled for the first time using the vibrational circular dichroism (VCD) technique as well as by chemical relay reactions. Odor evaluation of each enantiomer revealed relationships between their configurations and odor activities.
authors.affiliation: Corporate Research and Development Division, Takasago International Corporation, 4-11, 1-Chome, Nishi-yawata, Hiratsuka city, Kanagawa 254-0073, Japan. makoto_emura@takasago.com
authors.forename: Makoto
authors.initials: M
authors.lastname: Emura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yaguchi
authors.forename: Atsufumi
authors.initials: A
authors.lastname: Nakahashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sugimoto
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Miura
authors.forename: Kenji
authors.initials: K
authors.lastname: Monde
mesh_terms: D002942:Circular Dichroism; D005663:Furans / Q000737:chemistry*; D006801:Humans; D009812:Odorants / Q000032:analysis*; D012903:Smell; D013237:Stereoisomerism
chemical_list: D005663:Furans