Development and validation of a chiral LC-MS method for the enantiomeric resolution of (+) and (-)-medetomidine in equine plasma by using polysaccharide-based chiral stationary phases

The detection and separation of medetomidine enantiomers from the complex biological matrices poses a great analytical challenge, especially in the field of forensic toxicology and pharmacology. Couple of researchers reported resolution of medetomidine using protein-based chiral columns, but the reported method is quiet challenging and tedious to be employed for routine analysis. This research paper reported a method that enables the enantio-separation of medetomidine by using polysaccharide cellulose chiral column. The use of chiralcel OJ-3R column was found to have the highest potential for successful chiral resolution. Ammonium hydrogen carbonate was the ideal buffer salt for chiral liquid chromatography (LC) with electrospray ionization (ESI)+ mass spectrometry (MS) detection for the successful separation and detection of racemic compound. The method was linear over the range of 0 to 20 ng/mL in equine plasma and the inter-day precisions of levomedetomidine, dexmedetomidine were 1.36% and 1.89%, respectively. The accuracy of levomedetomidine was in the range of 99.25% to 101.57% and that for dexmedetomidine was 99.17% to 100.99%. The limits of quantification for both isomers were 0.2 ng/mL. Recovery and matrix effect on the analytes were also evaluated. Under the optimized conditions, the validated method can be adapted for the identification and resolution of the medetomidine enantiomers in different matrices used for drug testing and analysis.

Separation and identification of the epimeric doping agents - Dexamethasone and betamethasone in equine urine and plasma: A reversed phase chiral chromatographic approach

Chirality is one of the most important considerations when controlling doping. The epimeric corticosteroids dexamethasone and betamethasone are significantly potent and long-acting, and they are highly abused in equestrian sports. The scope of this study was to develop a simple and reliable analytical method for simultaneously identifying and separating regularly abused co-eluting corticosteroids in equine urine and plasma. In this paper, we present a simple and rapid method for the chiral separation and identification of epimeric mixtures of dexamethasone and betamethasone using a Thermo Q Exactive high resolution accurate mass spectrometer. The high resolution accurate mass spectrometer system provided extremely high sensitivity, enabling detection of each isomer at a very low concentration from complex biological matrices. Chromatographic separation was performed using amylose and cellulose chiral columns. Reversed phase media showed very good potential for providing a successful chiral resolution in LC-MS analysis. This study also focused on optimizing the mobile phase for elution strength, nature of the organic modifier, additives, and column temperature.

NIXANTPHOS: a highly active ligand for palladium catalyzed Buchwald–Hartwig amination of unactivated aryl chlorides

The NIXANTPHOS-based catalyst outperformed the parent ligand Xantphos in Pd catalyzed amination reaction of aryl chlorides at room temperature.

Mo(CO)6 as a Solid CO Source in the Synthesis of Aryl/Heteroaryl Weinreb Amides under Microwave-Enhanced Condition

The facile transformation of aryl/heteroaryl nonaflates into corresponding amides via Pd-catalyzed aminocarbonylation using Mo(CO)6 as a solid CO source under microwave-enhanced condition is reported. The method was found to be tolerant with respect to a diverse range of electronically biased aryl/heteroaryl nonaflates, and exceptional yields were obtained. The optimized protocol was further extended to a diverse range of amines.

A rapid and modified approach for C-7 amination and amidation of 4-methyl-7-nonafluorobutylsulfonyloxy coumarins under microwave irradiation

A rapid approach for the synthesis of an array of 4-methyl-7-substituted coumarins has been developed.