Dgu 20a3r degassing unit

HPLC for obtaining the sulfoxide enantiomers was performed on a Shimadzu instrument composed of LC-10AT and LC-10AS pumps, a SPD-10A UV-VIS detector, a SIL-10A auto injector, a DGU-20A3R degassing unit, a CTO-20AC temperature controller and a SCL-10A system controller (Duisburg, Germany). The LCsolution software was used for instrument control and data acquisition. A Lux i-Cellulose 5 column (150 × 4.6 mm, 5 µm, Phenomenex, Aschaffenburg, Germany) containing cellulose tris(3,5-dichlorophenylcarabamate) as chiral selector in combination with methanol as mobile phase was used. The flow rate was 1.0 mL/min, the temperature was set at 20 °C and detection was carried out at 254 nm. 50 µL of the solutions of the sulfoxides prepared at a concentration of 1,2 mg/mL in methanol, were injected. A minimum of 20 runs were performed for each sulfoxide and the eluate containing the respective enantiomers were pooled followed by evaporation of the solvent under reduced pressure. The compounds were obtained as amorphous off-white to yellow solids. The purity of the isolated enantiomers was estimated by HPLC analysis using the same experimental set-up. The optical rotation of the purified enantiomers was determined in ethanol using a P2000 polarimeter from Jasco (Pfungstadt, Germany).

The HPLC system consisted of a Shimadzu binary gradient system with a DGU-20A3R degassing unit, SIL-20AC autosampler, CTO-20AC column oven and SPD-20A UV/VIS detector. The injection volume was 50 µl, and the separation was performed on a 250 × 4.6 mm S-5 µm YMC 30 HPLC column. The mobile phase consisted of methanol (solvent A) and tertiary butyl methyl ether (tBME, solvent B). The total flow was 1.3 ml min -1 , and the column temperature was adjusted to 29 °C. The gradient started with 90% solvent A and 10% solvent B. A linear gradient was applied up to 55% solvent A and 45% solvent B (45 min) followed by another linear gradient up to 45% solvent A and 55% solvent B (5 min). This ratio was held constant for 5 min before returning to the starting conditions (90% solvent A) within 2 min. The peaks were evaluated at 450 nm and 470 nm. The quantification was performed by an external calibration with standard solutions taking into account the internal standard. The limit of quantification (LOQ) determined by the signal to noise ratio was 0.03 µg ml -1 .