RP-LC Determination of the cis-Isomer of Glimepiride in a Bulk Drug Substance

A rapid reversed-phase high-performance liquid chromatographic procedure is developed and validated for the resolution of the cis-isomer of 1-[[p-[2-(3-ethyl-4-methyl-2-oxo-3-pyrroline-1-carboxamido) ethyl] phenyl] sulfonyl]-3-(trans-4-methylcyclohexyl) urea, a dopamine agonist in bulk drugs. The cis-isomer and glimepiride were baseline resolved on a Waters Symmetry column (50 × 4.6 mm, 3.5 μm) using a mobile phase system containing water: tetrahydrofuran (75:25; v/v. The chromatographic resolutions between cis-isomer and glimepiride were found to be greater than two. The developed method was extensively validated and proved to be robust. The limit of detection and the limit of quantification of cis-isomer were 500 and 1,500 ng mL⁻¹, respectively, for 10 μL injection volume. The percentage recovery of the cis-isomer ranged from 97.3 to 102.0 in bulk drug samples of glimepiride. Glimepiride sample solution and mobile phase were found to be stable for at least 48 h. The proposed method was found to be suitable and accurate for the quantitative determination of the cis-isomer in bulk drugs.     

Validated Enantioselective LC Method, with Precolumn Derivatization with Marfey’s Reagent, for Analysis of the Antiepileptic Drug Pregabalin in Bulk Drug Samples

An enantioselective high-performance liquid chromatographic method, with precolumn derivatization with Marfey’s chiral reagent, sodium 2,4-dinitro-5-fluorophenyl-l-alanine amide, has been developed for resolution of the enantiomers of a new antiepileptic drug, pregabalin, in the bulk drug. The diastereomers of the pregabalin enantiomers were resolved to baseline on a reversed-phase ODS column with a 60:40 (v/v) mixture of aqueous 0.2% triethylamine (pH adjusted to 3.5 with dilute orthophosphoric acid) and acetonitrile as mobile phase. Resolution between the diastereomers was not less than five. The method was extensively validated and proved to be robust. The calibration plot was indicative of an excellent linear relationship between response and concentration over the range 750 (LOQ) to 7,500 ng L⁻¹ for the R enantiomer. The limits of detection and quantification of the R enantiomer were 250 and 750 ng L⁻¹, respectively, for an injection volume of 10 μL. Recovery of the R enantiomer from bulk drug samples of pregabalin ranged from 97.5 to 101.76%. Solutions of pregabalin in water and in the mobile phase were found to be stable for at least 48 h. The method was found to be suitable and accurate for quantitative determination of the R enantiomer in the bulk drug. It can be also used to test the stability of samples of pregabalin.     

Solvent-free sonochemical preparation of α-aminophosphonates catalyzed by 1-hexanesulphonic acid sodium salt

1-Hexanesulphonic acid sodium salt was found to be an efficient catalyst for the green synthesis of α-aminophosphonates by the coupling of aldehydes/ketone, an amine and triethyl phosphite under ultrasound irradiation at ambient temperature for appropriate time to furnish the desired product in good to excellent yield under solvent-free condition. This catalyst provides clean conversion; greater selectivity and easy workup make this protocol practical and economically attractive.     

Synthesis and biological activity of some fluorinated arylhydrazotriazoles

Potential biologically active derivatives of arylhydrazotriazole (3a–l) were prepared by the condensation reaction of diazonium salts using various aromatic amines (1a–l) and 1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl) ethanones (2). The synthesized products were obtained in 75–85% yield. All the synthesized products were having good-excellent antifungal activity as compared with standard (Fluconazole and Ketoconazole) drugs.     

Lithium bromide catalyzed solvent free method for synthesis of 2-substituted benzimidazoles and imidazopyridines

<正>The first successful lithium bromide mediated solvent free condensation of arylenediamine and esters to obtain 2-substituted benzimidazole and imidazopyridine in good to excellent yields is described.     

Synthesis of new 4-(4,5-diphenyl-1h-imidazol- 2-yl)tetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]quinolines from tetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]quinolines

Some new 4,5-diphenyl-1H-imidazole derivatives were synthesized in good yields by treating various tetrazolo[1,5-a]quinolines with benzil and ammonium acetate in glacial acetic acid.     

Cellulose sulphuric acid as a biodegradable and reusable catalyst for the Knoevenagel condensation

A green, mild and efficient method for Knoevenagel condensation of 3-formylchromone/2-chlroquinoline-3-carbaldehyde with active methylene compounds such as Meldrum’s acid/ethyl cyanoacetate using biosupported cellulose sulphuric acid (CSA) in the solid-state by grinding under solvent-free condition has been developed. This method provides several advantages including environmental friendliness, shor t reaction times, high yields and a simple work-up procedure. Moreover, the CSA was successfully reused for four cycles without significant loss of activity.     

Regiospecific oxidation of an alkyl group of aromatic amine to carbonyl group by DDQ in aq.medium

The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to be most simple, high yielding and novel method for oxidation of alkyl group of aromatic amine in to its carbonyl compound.     

An organocatalyzed facile and rapid access to α-hydroxy and α-amino phosphonates under conventional/ultrasound technique

In the present work, successful implementation of ultrasound irradiation for the rapid synthesis of α-hydroxy and α-amino phosphonates under solvent-free conditions is demonstrated. Use of a novel catalyst (i.e., camphor sulfonic acid) in combination with ultrasound technique is reported for the first time. Comparative study for the synthesis of α-hydroxy and α-amino phosphonates using conventional as well as ultrasonication method is discussed.