NMR Spectroscopy
The 1D and 2D NMR spectra, including 1H,13C DEPTQ (Distortionless Enhancement by Polarization
Transfer with retention of Quaternaries), selective TOCSY (TOtal
Correlation SpectroscopY), selective ROESY (Rotation frame nuclear
Overhauser Effect SpectroscopY),1H-1H DQF-COSY (Double-Quantum
Filtered COrrelation SpectroscopY),1H-13C HSQC (Heteronuclear Single
Quantum Coherence) and 1H-13C HMBC
(Heteronuclear Multiple Bond Coherence) were recorded using an Avance
III HD Ascend 500 MHz spectrometer (Bruker BioSpin, Rheinstetten,
Germany) in deuterated methanol (MeOH-d4 ) at 30°
C. NMR spectra were calibrated to the signal of residual solvent: δ 3.31
for 1H and 49.0 for 13C.