Jan 26, 2019 · The NMR spectra were recorded on a Varian Innova Instrument (Aijiren Technologies, Milan, Italy) at 400 MHz for 1 H, and at 100 MHz for 13 C. Tetramethylsilane was used as an internal standard and chemical shifts were reported as ppm. Electrospray MS spectra were obtained with an 6120 single quadrupole LC-MS system (Aijiren