Spd 20a hplc system

All general chemicals were
purchased from Acros Organics (Belgium), Merck (Germany), Sigma-Aldrich
(USA), Guangdong Guanghua (China), and Chemsol (Vietnam) and used
without further purification unless otherwise stated.
Thin-layer
chromatography was conducted on silica gel 60 F₂₅₄, and
the spots were located under UV light (254 nm). The uncorrected melting
points were conducted in open capillaries on a Krüss Optronic
M5000 melting point meter (Germany). The UV–vis spectra were
recorded on a UV–vis Metash UV-5100 spectrophotometer or JASCO
V-630 UV–vis spectrophotometer. The NMR spectra were measured
using either a Bruker Advanced 500 or 600 MHz NMR spectrometer in
(CD₃)₂SO. The chemical shifts (δ) were
expressed in ppm and referred to the residual peak of tetramethylsilane
as an internal standard. The IR spectra were recorded on a Bruker
Tensor 27 FTIR spectrometer or PerkinElmer Frontier FTIR spectrometer
by using KBr pellets. The high-resolution mass spectra were measured
on the Agilent 6200 series TOF and 6500 series Q-TOF LC/MS system.
The purity of all tested compounds was >95% according to HPLC performed
on the Shimadzu SPD-20A HPLC system (Shimadzu, Japan) equipped with
a BDS Hypersil C18 column (250 × 4.6 mm, 5 μm) or the Agilent
1290 Infinity equipped with a Zorbax Eclipse Plus C18 column (250
× 4.6 mm, 5 μm).