Enantiomeric Separation and Thermodynamic investigation of (R)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)- [1,3,4]-thiadiazole, a Key Intermediate of Nafithromycin

Abstract

A selective and precise chiral high performance liquid chromatography method for the separation of (R)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)-[1, 3, 4]-thiadiazole (RE) has been developed and validated. It is an intermediate of a novel antibiotic nafithromycin. Nafithromycin is a ketolide class antibiotic being developed to treat community acquired bacterial pneumonia. Enantiomeric separation was achieved on Chiralpak IA column using mobile phase consisting of n-hexane and ethanol in the ratio of (15:85; v/v) with the resolution of more than 3. Separation was achieved at flow rate of 1.0 mL min⁻¹ and column temperature 30°C. The eluent was monitored at 254 nm. The developed method was validated as per the guideline. The method was found to be selective, precise, accurate and linear. Limit of detection and limit of quantification of the undesired enantiomer (S)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)- [1, 3, 4]-thiadiazole (SE) was 0.11 and 0.35 μgmL⁻¹ respectively. Recovery of the SE was found to be in the range of 104.52 % and 105.83 %. The impact of thermodynamic parameters on the chiral separation was evaluated.

Key words:

• Enantiomer
• chiral purity
• key intermediate
• HPLC
• validation
• nafithromycin