General information The 1 H and 13 C NMR spectra were recorded on a Bruker AC-300 FT spectrometer (300 MHz and 75 MHz, respectively) using tetramethylsilane as internal reference, and the chemical shifts (δ) and coupling constants (J) were expressed in ppm and Hz, respectively. The 2D NOESY spectra were recorded on a Bruker AC-400 FT spectrometer (400 MHz). The high resolution mass spectra were recorded on a LC-TOF spectrometer (Micromass). High pressure liquid chromatography (HPLC) analyses

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... e performed on an instrument equipped with an isostatic pump and a Chiralpak OD column (250 x 4.6 mm), and the UV detection was monitored at 254 nm. The melting points were uncorrected. The chemicals were purchased from Acros, Alfa Aesar, AstaTech Pharmaceutical Co., Meryer, Sigma-Aldrich, TCI, and the Sinopharm Chemical Reagent Co., and used as received. All the solvents were untreated before use.