title: The epimerization of sesamin and asarinin.
abstract: Sesamin (1) and asarinin (2) are two C-7' epimeric lignans. Molecular modeling by semiempirical methods indicated that 1 is more stable than 2 by about 2.5 kcal/mol. However, epimerization under acidic conditions led to a 44.8/55.2 equilibrium ratio of 1 and 2. Single-crystal X-ray diffraction analyses indicated that 1 was monoclinic with a = 10.0435(19) A, b = 6.9151(8) A, c = 11.8460(13) A, and 2 was triclinic with a = 5.595(5) A, b = 9.5910(18) A, c = 15.620(4) A. The unexpected equilibrium ratio of 1 and 2 indicated that structural changes are dependent on the conditions of the extraction processes.
authors.affiliation: Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan, Republic of China.
authors.forename: Chia-Ying
authors.initials: CY
authors.lastname: Li
authors.forename: Tahsin J
authors.initials: TJ
authors.lastname: Chow
authors.forename: Tian-Shung
authors.initials: TS
authors.lastname: Wu
mesh_terms: D018360:Crystallography, X-Ray; D004149:Dioxoles / Q000737:chemistry*; D004365:Drugs, Chinese Herbal / Q000737:chemistry*; D017705:Lignans / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D004149:Dioxoles; D004365:Drugs, Chinese Herbal; D017705:Lignans; C054125:sesamin