Model 341 lc polarimeter

Optical rotation: Perkin-Elmer Model 341 LC polarimeter (Perkin-Elmer, Waltham, MA, USA). UV spectra: in MeOH using a Perkin-Elmer Lambda 25 UV/VIS spectrophotometer (Perkin-Elmer, Waltham, MA, USA). IR spectra: Shimadzu Infrared-400 spectrophotometer (Shimadzu, Kyoto, Japan). ESIMS spectra: Agilent 6320 Ion trap mass spectrometer (Agilent Technologies, Santa Clara, CA, USA) equipped with an electrospray ionization interface. NMR spectra: Bruker DRX 700 spectrometer (Bruker, Rheinstetten, Germany). Column chromatographic separations: silica gel 60 (0.04–0.063 mm, Merck, Darmstadt, Germany). TLC analyses: pre-coated silica gel F254 aluminum sheets (Merck, Darmstadt, Germany).

The active fractions obtained from column chromatography were analysed for Nuclear magnetic resonance spectroscopy (NMR) analysis. Optical rotations were measured on a Perkin- Elmer Model 341 LC polarimeter. ¹H NMR and ¹³C NMR experiments were performed on Bruker Unity 400 and 600 MHz spectrometers. NMR spectra were referenced to the CD3OD solvent signals at δ 3.30 (1H) and 49.00 (13C), respectively. The spectra were obtained using the standard Bruker software. The samples were dissolved in different solvents (i.e. DMSO-d6, CDCl3, and CD3OD), the choice of which was dependent on the solubility of the samples. The observed chemical shift (δ) values were given in ppm and the coupling constants (J) in Hz.