Vipul P. Rane

Design, Synthesis and Utilization of 1- Substituted Sulphonyloxy-2-Phenyl Benzimidazole as a Novel Peptide Coupling Reagents

Highly efficient coupling reagents, N-methanesulphonyloxy-2-phenyl benzimidazole and N - p-toluenesulphonyloxy-2-phenyl benzimidazole were designed, synthesized and successfully applied in peptide coupling reactions. Their efficiency was evaluated by synthesizing a number of structurally different amides and peptides as well. The distereomeric purity was examined by HPLC. Also the optical rotations of all the synthesized peptides were measured and found to be quite matching with corresponding values in literature. After completion of reaction, the N-hydroxy 2-phenyl benzimidazole which was the starting material for the synthesis of reagents could be easily isolated during the work up by acid base treatment and could be re-used without significant loss in reactivity. Also the intermediate in the reaction sequence was isolated and characterized by mass and (1)H NMR which could help to comment about the probable mechanism.

VALIDATED CHIRAL LC METHOD FOR DEXRABEPRAZOLE ON REVERSE PHASE AMYLOSE BASED STATIONARY PHASE

A simple, rapid and robust LC method was developed and validated for the enantiomeric separation of dexrabeprazole in bulk drug and formulation. The enantiomers of dexrabeprazole were resolved on a Chiralpak AD-RH (amylose based stationary phase) column using a mobile phase consisting of water: acetonitrile (50:50, v/v) at a flow rate of 0.5 ml min -1. The resolution between the enantiomers was found to be more than 1.5 in optimized method. The developed method was extensively validated and proved to be robust. The calibration curve for (S)-enantiomer showed excellent linearity over the concentration range of 0.05 µg ml-1 (LOQ) to 1 µg ml-1. The limit of detection and limit of quantification for (S)-enantiomer were 0.015 µg ml -1 and 0.05 µg ml-1, respectively. The percentage recovery of the (S)-enantiomer ranged between 97 to 101 % in bulk drug samples of dexrabeprazole. The proposed method was found to be suitable and accurate for quantitative determination of (S)-enantiomer in bulk drug substance.

Development and Validation of the Chiral Liquid Chromatography Method for Separation of Enantiomeric Impurity in Novel Oxazolidinone Antibacterial Agent WCK 4086

A highly stereo-specific liquid chromatographic method was developed and validated for the quantification of enantiomeric impurity (R-enantiomer) in novel oxazolidinone antibacterial agent (WCK 4086), a drug substance. The separation was achieved on Chiralpak AD-H (amylose-based chiral stationary phase) using a mobile phase consisting of n-hexane:2-propanol:methanol:trifluoroacetic acid (80:10:10:0.4, v/v/v/v) at a flow rate of 1.0 mL min-1. Chromatographic resolution between two enantiomers was found to be more than 2.0. Method was extensively validated for the quantification of R-enantiomer in WCK 4086 and proved to be robust. Method was found to be highly specific as all other related impurities were separated from the enantiomers. The calibration curve for R-enantiomer showed an excellent linearity over the concentration range of 1-5 μg mL-1. Limit of quantitation (LOQ) and limit of detection (LOD) for R-enantiomer were 0.009 μg and 0.003 μg, respectively. Average recovery of the R-enantiomer was in the range of 94.55-109.67%. Analytical solutions were found to be stable up to 70 h at room temperature. Developed method was found to be specific, sensitive, precise and accurate for quantitative determination of R-enantiomer in WCK 4086 and useful for controlling the enantiomeric impurity in drug substance used for preclinical studies.