RESUMO
The structures of epoxyroussoenone (1) and epoxyroussoedione (3) isolated from a culture broth of Roussoella japanensis KT1651 were determined. Although NMR spectra provided insufficient structural information, computation of the theoretical chemical shifts with DFT EDF2/6-31G* enabled us to elucidate not only the planar structure, but also the relative configuration. Their ECD (electric circular dichroism) spectra suggested the absolute configurations, which were confirmed with time-dependent DFT calculations employing BHandHLYP/TZVP. The ECD calculations for other stereoisomers yielded obviously different spectral profiles, thus confirming the relative structures of 1 and 3.
Assuntos
Ascomicetos/química , Compostos de Epóxi/química , Compostos de Epóxi/isolamento & purificação , Compostos de Epóxi/farmacologia , Fungos/efeitos dos fármacos , Japão , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , EstereoisomerismoRESUMO
The structures of the tetracyclic fusicoccanes roussoellols A (1) and B (2) from Roussoella hysterioides KT1651 are described. NMR spectroscopic analyses involving NOESY experiments revealed that these molecules possessed unique bent structures that were supported by chemical derivatizations as well as chemical shift comparisons with theoretical shifts based on the density functional theory (DFT) at the EDF2/6-31G* level. Absolute configurations were established by the ECD couplet of positive chirality in both 1 and 2 at vacuum UV (VUV) region, which were further confirmed by successful reproduction of VUVCD spectra using theoretical calculations.
