Mercury 300 mhz nmr spectrometer

Solution ¹H-NMR spectra (300 MHz) were recorded on Varian Mercury 300 MHz NMR spectrometer (Varian Inc., Palo Alto, CA, USA) for clonidine. Chemical shifts are reported relative to CDCl₃ (δ 7.26 ppm) for ¹H-NMR spectra. The ¹H NMR data are presented as follows: Chemical shift, multiplicity and integration.
Solid state NMR (ssNMR) was performed using a Varian 400 MHz VNMRS wide bore spectrometer (Varian Inc., Palo Alto, CA, USA) operating at a ¹H frequency of 399.76 MHz, a ¹³C frequency of 100.53 MHz. CPMAS ¹³C spectra were acquired using a 4 mm double-resonance probe (Varian Inc., Palo Alto, CA, USA).
Spectra of (Na⁺cafa⁻) and (Hlin⁺Cl⁻) were acquired under spinning at 5 kHz. That of (Hlin⁺)(cafa⁻) was acquired at 8 kHz, and that of Hcafa was acquired at 13 kHz spinning. The spectrum of (Hlin⁺Cl⁻) was compared with a CPTOSS spectrum (not shown) to identify spinning sidebands. A recycle delay of 4 s was used for Hcafa, while a 5 s delay was used for (Na⁺cafa⁻) and (Hlin⁺Cl⁻), and 6 s for (Hlin⁺)(cafa⁻). A contact time of 3.5 ms was used for Hcafa and (Na⁺cafa⁻), 1.5 ms was used for (Hlin⁺Cl⁻), and 3.0 ms was used for (Hlin⁺)(cafa⁻). A total of 128 transients were acquired of (Na⁺cafa⁻), 1280 of (Hlin⁺Cl⁻), 172 of (Hlin⁺)(cafa⁻), and 8192 of Hcafa. The ¹³C spectra were referenced to TMS using the carbonyl signal of glycine at 176.04 ppm.

The melting points of the compounds prepared in this investigation were recorded on a Thermocouple digital melting point apparatus (Mettler Toledo LLC, Columbus, OH, USA). Their IR spectra were recorded as powders using a Bruker VERTEX 70 FT-IR Spectrometer (Bruker Optics, Billerica, MA, USA) equipped with a diamond attenuated total reflectance (ATR) accessory. For column chromatography, we used the Merck kieselgel 60 (0.063–0.200 mm) (Merck KGaA, Frankfurt, Germany) as stationary phase. The NMR spectra were obtained as DMSO-d₆ solutions using Varian Mercury 300 MHz NMR spectrometer (Varian Inc., Palo Alto, CA, USA) and the chemical shifts are quoted relative to the residual proton signal in the deuterated solvent. The mass spectra were recorded at an ionization potential of 70 eV using Waters Synapt G2 Quadrupole Time-of-flight mass spectrometer (Waters Corp., Milford, MA, USA) at the University of Stellenbosch. The synthesis and analytical data of compounds 1a–d, which are known have been described before [18 (link)].

Hyaluronic acid (MW 130 kDa) was purchased from LifeCore Biomedical (Chaska, MN, USA). 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole hydrate (HOBt), DL-Dithiothreitol (DTT), Cysteamine hydrochloride, 2,2′-Dithiodipyridine, 4-Nitrophenyl chloroformate were purchased from Sigma-Aldrich (St. Louis, MO, USA). Dialysis membranes used for purification were purchased from Spectra Por-6 (MWCO 3500, Pomona, CA, USA). All solvents were of analytical quality. Nuclear Magnetic Resonance (NMR) spectroscopy experiments were performed with a Varian Mercury 300 MHz NMR Spectrometer (Palo Alto, CA, USA). All spectrophotometric analysis was carried out on Shimadzu UV-3600 plus UV-VIS-NIR spectrophotometer (Kyoto, Japan).