*3.4. ECD Calculation*

The relative configuration of **1** was established initially according to its ROESY NMR spectra. Monte Carlo conformational searches were carried out by means of the Spartan's 14 software using the Merck molecular force field (MMFF). The conformers with Boltzmann population of over 1% were chosen for ECD calculations, and then the conformers were initially optimized at the B3LYP/6-31G(d,p) level in gas. The theoretical calculation of ECD was conducted in MeOH using Time-dependent Density functional theory (TD-DFT) at the B3LYP/6-31+G(d,p) level for all conformers. Rotatory strengths for a total of 100 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. And UV-shift values of all configurations were −10 nm. The spectra of enantiomers were produced directly by mirror inversions.
