開催日: 2017/09/20 - 2017/09/22
Neomacrophorin X (1) was isolated from Trichoderma sp. 1212-03. The HMBC spectral analysis indicated a unique [4.4.3]propellane framework, which was verified by the 1H and 13C chemical shift calculations based on DFT and subsequent comparison with experimental data obtained in CDCl3. The DFT-based ECD calculations were effective not only in determining the absolute configuration, but also confirming the relative structure. The predominant conformation of 1 was found to be solvent-dependent, with different conformations presenting different NMR and ECD profiles. Introduction of J-based analysis with a J-resolved HMBC aided in this investigation. This conformational alternation was reproduced by considering the solvation with the SM5.4 model in the calculation, although it was not sufficiently quantitative. Although the calculations without solvent effects suggested a conformer which satisfies the spectral profiles in CDCl3, post calculations with SM5.4 solvation protocol stabilized the second major conformer which reproduces the NMR and ECD profiles in CD3OD (CH3OH). Neomacrophorin X (1) is assumed to be biosynthesized by a coupling between the reduced form of anthraquinone and a neomacrophorin derivative. This hypothesis was supported experimentally by the isolation of pachybasin and chrysophanol, as well as acyclic premacrophorin (2) from the same fungus.