4.1. General Experimental Procedures

Chiroptical measurements ([α]_D) were obtained on a JASCO P-1010 polarimeter (JASCO International Co. Ltd., Tokyo, Japan) in a 100 × 2 mm cell at 23 °C. Electronic Circular Dichroism (ECD) measurement were obtained on a JASCO J-810 spectropolarimeter (JASCO International Co. Ltd., Tokyo, Japan) in a 0.1 cm path-length cell. Nuclear magnetic resonance (NMR) spectra were acquired on a Bruker Avance 600 MHz spectrometer (Bruker Pty. Ltd., Alexandria, Australia) with a 5 mm PASEL ¹H/D-¹³C Z-Gradient probe at 25 °C in methanol-d₄ by referencing to residual ¹H or ¹³C signals (δ_H 3.30 and δ_C 49.15). High-resolution ESIMS spectra were obtained on a Bruker micrOTOF mass spectrometer (Bruker Daltonik Pty. Ltd., Preston, Australia) by direct injection in MeOH at 3 μL/min, using sodium formate clusters as an internal calibrant. Semi-preparative HPLC was performed using Agilent 1100 series HPLC instrument (Agilent Technologies Inc., Mulgrave, Australia) with corresponding detector, fraction collector and software inclusively. Analytical-grade solvents were used for extractions and partitions. Chromatography solvents were of HPLC grade and filtered/degassed through 0.45 μm polytetrafluoroethylene (PTFE) membrane prior to use. Deuterated solvents were purchased from Cambridge Isotopes (Cambridge Isotope Laboratories, Tewksbury, MA, USA). The human colorectal (SW620) and lung (NCI-H460) carcinoma cell lines were kindly provided by Susan E. Bates and Robert W. Robey of the National Cancer Institute, Bethesda, MD, USA.