title: Absolute Configuration of Menthene Derivatives by Vibrational Circular Dichroism.
abstract: The aerial parts of Ageratina glabrata afforded (-)-(3S,4R,5R,6S)-3,5,6-trihydroxy-1-menthene 3-O-β-d-glucopyranoside (1) and (-)-(3S,4S,6R)-3,6-dihydroxy-1-menthene 3-O-β-d-glucopyranoside (3). Acid hydrolysis of 1 yielded (+)-(1R,4S,5R,6R)-1,5,6-trihydroxy-2-menthene (5) and (+)-(1S,4S,5R,6R)-1,5,6-trihydroxy-2-menthene (6), while hydrolysis of 3 yielded (+)-(3S,4S,6R)-3,6-dihydroxy-1-menthene (10), (+)-(1R,4S,6R)-1,6-dihydroxy-2-menthene (11), and (+)-(1S,4S,6R)-1,6-dihydroxy-2-menthene (12). The structures of the new compounds 1, 2, 5-9, and 11 were defined by 1D and 2D NMR experiments, while the absolute configurations of the series of compounds were determined by comparison of the experimental vibrational circular dichroism (VCD) spectra of the 1,6-acetonide 5-acetate derived from 6 and of the 1,6-acetonide derived from 12 with their DFT-calculated spectra. In addition, Flack and Hooft X-ray parameters of 10 permitted the same conclusion. The results further led to the absolute configuration reassignment of 10 isolated from Brickellia rosmarinifolia, Mikania saltensis, Ligularia muliensis, L. sagitta, and Lindera strychnifolia, as well as of 11 from Cacalia tangutica, as ent-11.
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria , Morelia, Michoacán 58030, Mexico.
authors.forename: Julio C
authors.initials: JC
authors.lastname: Pardo-Novoa
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria , Morelia, Michoacán 58030, Mexico.
authors.forename: Héctor M
authors.initials: HM
authors.lastname: Arreaga-González
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria , Morelia, Michoacán 58030, Mexico.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Gómez-Hurtado
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria , Morelia, Michoacán 58030, Mexico.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Rodríguez-García
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Apartado 14-740, Mexico City 07000, Mexico.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Apartado 14-740, Mexico City 07000, Mexico.
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria , Morelia, Michoacán 58030, Mexico.
authors.forename: Rosa E
authors.initials: RE
authors.lastname: Del Río
mesh_terms: D036603:Ageratina / Q000737:chemistry*; D019659:Asteraceae; D002942:Circular Dichroism / Q000379:methods*; D008800:Mexico; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D013237:Stereoisomerism; D013729:Terpenes / Q000737:chemistry*
chemical_list: D013729:Terpenes; C048063:1-menthene