Eutypellenoids A–C, New Pimarane Diterpenes from the Arctic Fungus Eutypella sp. D-1

Three new pimarane diterpenes, eutypellenoids A–C (1–3), together with a known compound, eutypenoid C (4), were isolated from the culture extract of Eutypella sp. D-1 derived from the Arctic region. Compounds 1–3 possessed an uncommon tetrahydrofuran-fused pimarane diterpene skeleton. The structures of all compounds were determined by detailed spectroscopic analysis, electronic circular dichroism (ECD) analysis, as well as a comparison with the literature data. Antibacterial, antifungal, and cytotoxic activities of these compounds were evaluated. Compound 2 displayed antibacterial activity against Staphylococcus aureus and Escherichia coli with MIC values of 8 and 8 μg/mL, respectively. Additionally, compound 2 showed antifungal activity against Candida parapsilosis, Candida albicans, Candida glabrata, and Candida tropicalis with MIC values of 8, 8, 16, and 32 μg/mL, respectively. Furthermore, compound 2 exhibited moderate cytotoxic activity against HCT-116 cell line with IC50 value of 3.7 μM.


Methods
Monte Carlo conformational searches were carried out by means of the Spartan's 10 software using Merck Molecular Force Field (MMFF). The conformers with Boltzmann-population of over 5% were chosen for ECD calculations, and then the conformers were initially optimized at B3LYP/6-31+g (d, p) level in MeOH using the CPCM polarizable conductor calculation model. The theoretical calculation of ECD was conducted in MeOH using Time-dependent Density functional theory (TD-DFT) at the B3LYP/6-311+g (d, p) level for all conformers of compounds 1 Rotatory strengths for a total of 50 excited states were calculated. ECD spectra were generated using the program SpecDis 1.6 (University of Würzburg, Würzburg, Germany) and GraphPad Prism 5 (University of California San Diego, USA) from dipole-length rotational strengths by applying Gaussian band shapes with sigma = 0.3 eV. ECD calculation details

Methods
Monte Carlo conformational searches were carried out by means of the Spartan's 10 software using Merck Molecular Force Field (MMFF). The conformers with Boltzmann-population of over 5% were chosen for ECD calculations, and then the conformers were initially optimized at B3LYP/6-31+g (d, p) level in MeOH using the CPCM polarizable conductor calculation model. The theoretical calculation of ECD was conducted in MeOH using Time-dependent Density functional theory (TD-DFT) at the B3LYP/6-311+g (d, p) level for all conformers of compound 2. Rotatory strengths for a total of 50 excited states were calculated. ECD spectra were generated using the program SpecDis 1.6 (University of Würzburg, Würzburg, Germany) and GraphPad Prism 5 (University of California San Diego, USA) from dipole-length rotational strengths by applying Gaussian band shapes with sigma = 0.3 eV.

Results
Table S1.2.1.Gibbs free energies a and equilibrium populations b of low-energy conformers of 2.

Conformers
In ECD calculation details

Methods
Monte Carlo conformational searches were carried out by means of the Spartan's 10 software using Merck Molecular Force Field (MMFF). The conformers with Boltzmann-population of over 5% were chosen for ECD calculations, and then the conformers were initially optimized at B3LYP/6-31+g (d, p) level in MeOH using the CPCM polarizable conductor calculation model. The theoretical calculation of ECD was conducted in MeOH using Time-dependent Density functional theory (TD-DFT) at the B3LYP/6-311+g (d, p) level for all conformers of compounds 3. Rotatory strengths for a total of 50 excited states were calculated. ECD spectra were generated using the program SpecDis 1.6 (University of Würzburg, Würzburg, Germany) and GraphPad Prism 5 (University of California San Diego, USA) from dipole-length rotational strengths by applying Gaussian band shapes with sigma = 0.3 eV.

Results
Table S1.2.1.Gibbs free energies a and equilibrium populations b of low-energy conformers of 3.

Conformers
In