2. Materials and methods
2.1. General experimental procedures
Column chromatography was performed using commercial
silica gel (Merck, 0.040–0.063 mm) and analytical and
preparative thin-layer chromatography (TLC) was performed
with pre-coated silica gel plates Merck G60 F-254 or G50
UV-254. Infrared radiation spectra were recorded on a
Nicolet-510P spectrophotometer. 1H and 13C nuclear magnetic
resonance spectra were recorded on a Bruker Avance 500
(500 MHz for 1H and 125 MHz for 13C) spectrometer. Mass
spectrum and high resolution mass spectrum were recorded
in the electron ionization mode on a MAT 8200 and Micromass
LCT mass spectrometer. Microbiological methods and culture
conditions are as described previously[18,19].