title: Photoinduced isomerization of 23-oxosapogenins: conformational analysis and spectroscopic characterization of 22-isosapogenins.
abstract: The first synthesis of 22-isospirostane derivatives is described. They were obtained by photochemical isomerization of 23-oxosapogenins. The structure of 23-oxo-22-isotigogenin acetate (12) was proved by a single crystal X-ray diffraction, while structures of 23-oxo-22-isodiosgenin acetate (13) and 23-oxo-22-isosarsasapogenin acetate (14) were elucidated by spectroscopic methods. 22-Isodiosgenin acetate (17) was obtained by NaBH(4) reduction of the 23-oxo derivative 13 followed by the two-step Barton-McCombie deoxygenation procedure. Conformational analysis of 22-iso compounds was carried out with CD and NMR, as well as DFT calculations.
authors.affiliation: Institute of Chemistry, University of Białystok, Piłsudskiego 11/4, 15-443 Białystok, Poland.
authors.forename: Izabella
authors.initials: I
authors.lastname: Jastrzębska
authors.forename: Marcin
authors.initials: M
authors.lastname: Górecki
authors.forename: Jadwiga
authors.initials: J
authors.lastname: Frelek
authors.forename: Rosa
authors.initials: R
authors.lastname: Santillan
authors.forename: Leszek
authors.initials: L
authors.lastname: Siergiejczyk
authors.forename: Jacek W
authors.initials: JW
authors.lastname: Morzycki
mesh_terms: D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D055668:Photochemical Processes; D012502:Sapogenins / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D012502:Sapogenins