The investigation of the relative and absolute configuration of gymnomitr-3(15)-en-4β,9β-diol (1), a metabolite isolated from the culture medium of Calcarisporium arbuscula, is described. Since the pseudosymmetry of 1 hindered its configurational elucidation based on conventional spectral analysis, we resorted to DFT (Density Functional Theory)-based ¹³C NMR chemical shift calculations, which allowed identifying the rel-(2S,4R,6S,7R,9R,11S)-form as the candidate isomer giving 99.6% DP4 probability among the eight possible diastereomers. However, the root mean square value of its diastereomer at C-9 was also within the allowable level (1.9 ppm), considering the accuracy of this calculation method (around 2.0 ppm). The latter diastereomer could be ruled out by comparing the calculated ³J_H-9/C-7 and ³J_H-9/C-11 values with the intensities of the corresponding HMBC (Heteronuclear Multiple Bond Coherence) signals. The absolute configuration was established by reproducing the ECD (Electronic Circular Dichroism) spectrum of the dibenzoyl derivative 2. The biosynthesis of 1 is also discussed.

描述了对裸子实蝇（Calcarisporium arbuscula）培养基中分离出的代谢产物gymnomitr-3（15）-en-4β，9β-diol（1）的相对和绝对构型的研究。由于1的假对称性妨碍了基于常规光谱分析的构型阐明，因此我们诉诸于基于DFT（密度泛函理论）的¹³ C NMR化学位移计算，该计算可确定rel-（2 S，4 R，6 S，7 R，9 R，11 S）异构体作为候选异构体，在8种可能的非对映异构体中产生49.6％的DP4概率。但是，考虑到该计算方法的准确性（约2.0 ppm），其在C-9处的非对映异构体的均方根值也在允许水平内（1.9 ppm）。通过将计算的³ J _{H-9 / C-7}和³ J _{H-9 / C-11}值与相应HMBC（异核多键相干）信号的强度进行比较，可以排除后一种非对映异构体。通过重现二苯甲酰基衍生物2的ECD（电子圆二色性）光谱来建立绝对构型。还讨论了1的生物合成。