title: Relative population of S-form and F-form conformers of bryonolic acid and its derivatives in equilibrium in CdCl3 solutions.
abstract: Relative populations of S-form (D-E rings: boat-boat form) and F-form (D-E rings: chair-chair form) conformers, in equilibrium in CDCl3 solutions, of 20 derivatives (2-21) of bryonolic acid (D:C-friedoolean-8-en-3beta-ol-29-oic acid) (1) were calculated from NMR spectral data (J-values and chemical shifts), with the aid of molecular mechanic calculation using a MM2/CONFLEX program system. The principal deciding factor of the population ratio was found to be whether the functionality at C-29 is trigonal or tetrahedral; the S-form: F-form was 0:100-32:68 for the "trigonal" type and 48:52-100:0 for the "tetrahedral." The reliability of the results is discussed.
authors.affiliation: School of Pharmaceutical Sciences, Mukogawa Women's University, Koshien, Nishinomiya, Japan. hondac@mwu.mukogawa-u.ac.jp
authors.forename: Chie
authors.initials: C
authors.lastname: Honda
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Suwa
authors.forename: Shizuyo
authors.initials: S
authors.lastname: Takeyama
authors.forename: Wasuke
authors.initials: W
authors.lastname: Kamisako
mesh_terms: D002725:Chloroform / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry; D029776:Luffa / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012996:Solutions; D013237:Stereoisomerism; D014315:Triterpenes / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D012996:Solutions; D014315:Triterpenes; D002725:Chloroform; D003903:Deuterium; C074984:bryonolic acid