| Abstract: | Constituents of Osmanthus-Absolute, 3rd communication: Derivatives of Theaspiranes Four isomeric new 7-oxo-dihydrotheaspiranes were identified in Osmanthus absolute. Their configuration was proved by synthetic correlations with racemic as well as optically active theaspiranes A and B. These two compounds also occurring in the same natural substrate were first correlated with the (?)-theaspirone A of known absolute configuration and the (+)-theaspirone B, respectively, thus giving the background for all further stereochemical relationship work. In depth studies in the 1H- and 13C-NMR.-spectroscopy field including all possible and now synthetically available hydroxy derivatives of the new oxo compounds enabled us to unambiguously assign structures 1 to 4 to the natural products. Some further constituents bearing the same spirocyclic skeleton were also detected in Osmanthus absolute. |
