Reagents and solvents were purchased
from commercial sources and used directedly. Flash chromatography
was performed using 300-mesh silica gel. Reactions were monitored
by thin-layer chromatography using silica gel plates with fluorescence
F254 and UV light visualization. Low-resolution electrospray
ionization mass spectrometry (ESI-MS) was performed on an Agilent
1200 high-performance liquid chromatography (HPLC)-mass selective
detector mass spectrometer and high-resolution ESI-MS on an Applied
Biosystems Q-STAR Elite ESI-LC-MS/MS mass spectrometer. 1H NMR spectra were performed on a Bruker AV-400 spectrometer at 400
MHz or a Bruker AV-500 spectrometer at 500 MHz. 13C NMR
spectra were performed on a Bruker AV-500 spectrometer at 125 MHz.
Coupling constants (J) were expressed in hertz (Hz).
Chemical shifts (δ) of NMR were reported in parts per million
units relative to an internal standard (tetramethylsilane). Purity
of the compounds was determined by reverse-phase high-performance
liquid chromatography (HPLC) analysis to be >95%. HPLC instrument:
Dionex Summit HPLC (column: Diamonsil C18, 5.0 μm, 4.6 ×
250 mm2 (Dikma Technologies); detector: PDA-100 photodiode
array; injector: ASI-100 autoinjector; pump: p-680A). A flow rate
of 1.0 mL/min was used with mobile phase of MeOH in H2O
with a 0.1% modifier (ammonia, v/v).
from commercial sources and used directedly. Flash chromatography
was performed using 300-mesh silica gel. Reactions were monitored
by thin-layer chromatography using silica gel plates with fluorescence
F254 and UV light visualization. Low-resolution electrospray
ionization mass spectrometry (ESI-MS) was performed on an Agilent
1200 high-performance liquid chromatography (HPLC)-mass selective
detector mass spectrometer and high-resolution ESI-MS on an Applied
Biosystems Q-STAR Elite ESI-LC-MS/MS mass spectrometer. 1H NMR spectra were performed on a Bruker AV-400 spectrometer at 400
MHz or a Bruker AV-500 spectrometer at 500 MHz. 13C NMR
spectra were performed on a Bruker AV-500 spectrometer at 125 MHz.
Coupling constants (J) were expressed in hertz (Hz).
Chemical shifts (δ) of NMR were reported in parts per million
units relative to an internal standard (tetramethylsilane). Purity
of the compounds was determined by reverse-phase high-performance
liquid chromatography (HPLC) analysis to be >95%. HPLC instrument:
Dionex Summit HPLC (column: Diamonsil C18, 5.0 μm, 4.6 ×
250 mm2 (Dikma Technologies); detector: PDA-100 photodiode
array; injector: ASI-100 autoinjector; pump: p-680A). A flow rate
of 1.0 mL/min was used with mobile phase of MeOH in H2O
with a 0.1% modifier (ammonia, v/v).