title: Longipinane derivatives from Stevia connata.
abstract: The hexane extracts of the roots of Stevia connata afforded three new longipinene derivatives, longipinane-7beta,8alpha, 9alpha-triol-1-one 7-angelate-8-methylbutyrate (1), longipin-2-ene-7beta,8alpha,9alpha-triol-1-one 8,9-diangelate (6), and longipin-2-ene-7beta,8alpha,9alpha-triol-1-one 8-angelate-9-methylbutyrate (8), together with the known longipinane-7beta,8alpha,9alpha-triol-1-one 8,9-diangelate (2), longipinane-7beta,8alpha,9alpha-triol-1-one 7,9-diangelate (3), longipinane-7beta,8alpha,9alpha-triol-1-one 7,8-diangelate (4), longipin-2-ene-7beta,8alpha,9alpha-triol-1-one 7,8-diangelate (5), longipin-2-ene-7beta,8alpha,9alpha-triol-1-one 7-angelate-8-methylbutyrate (12), and stigmasterol. The structures of the new compounds were determined by chemical transformations and spectral methods including 2D NMR measurements. Spontaneous intramolecular transesterifications starting from the 8-angelate-9-methylbutyrate 8 provided an equilibrated mixture of the 7-angelate-9-methylbutyrate 10, the 7-angelate-8-methylbutyrate 12 and the starting material when stored in MeOH-H(2)O solution, while the 8,9-diangelate 6 only provided a binary mixture of the 7, 9-diangelate 7 and the starting material under the same conditions. The structures of 6-8, 10, and 12 and those of the nonisolable reaction intermediates 9, 11, and 14 were further evaluated by AM1 semiempirical calculations.
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000 Mexico.
authors.forename: E
authors.initials: E
authors.lastname: Sánchez-Arreola
authors.forename: C M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.forename: L U
authors.initials: LU
authors.lastname: Román
authors.forename: J D
authors.initials: JD
authors.lastname: Hernández
authors.forename: P
authors.initials: P
authors.lastname: Joseph-Nathan
mesh_terms: D019659:Asteraceae / Q000737:chemistry*; D004951:Esterification; D008958:Models, Molecular; D015394:Molecular Structure; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification*; D013057:Spectrum Analysis
chemical_list: D012717:Sesquiterpenes