A. Naidu

Development and validation of a highly sensitive and robust LC-MS/MS with electrospray ionization method for simultaneous quantitation of itraconazole and hydroxyitraconazole in human plasma: application to a bioequivalence study.

A highly sensitive and specific LC-MS/MS method has been developed for simultaneous estimation of itraconazole (ITZ) and hydroxyitraconazole (OH-ITZ) with 500 microL of human plasma using fluconazole as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique. Solid phase extraction process was used to extract ITZ, OH-ITZ and IS from human plasma. The total run time was 3.0 min and the elution of ITZ, OH-ITZ and IS occurred at 2.08 min, 1.85 min and 1.29 min, respectively; this was achieved with a mobile phase consisting of 0.2% (v/v) ammonia solution:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a HyPurity C(18) (50 mm x 4.6 mm, 5 microm) column. The developed method was validated in human plasma with a lower limit of quantitation of 0.50 ng/mL for both ITZ and OH-ITZ. A linear response function was established for the range of concentrations 0.5-263 ng/mL (r>0.998) for both ITZ and OH-ITZ. The intra- and inter-day precision values for ITZ and OH-ITZ met the acceptance as per FDA guidelines. ITZ and OH-ITZ were stable in the battery of stability studies, viz., bench-top, auto-sampler, dry extract and freeze/thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans.

Simultaneous estimation of four proton pump inhibitors—lansoprazole, omeprazole, pantoprazole and rabeprazole: development of a novel generic HPLC-UV method and its application to clinical pharmacokinetic study

A highly selective, sensitive and accurate HPLC method has been developed and validated for the estimation of four proton-pump inhibitors (PPI), lansoprazole (LPZ), omeprazole (OPZ), pantoprazole (PPZ) and rabeprazole (RPZ), with 500 microL human plasma using zonisamide as an internal standard (IS). The sample preparation involved simple liquid-liquid extraction of LPZ, OPZ, PPZ and RPZ and IS from human plasma with ethyl acetate. The baseline separation of all the peaks was achieved with 0.1% triethylamine (pH 6.0):acetonitrile (72:28, v/v) at a flow rate of 1 mL/min on a Zorbax C(8) column. The total chromatographic run time was 11.0 min and the simultaneous elution of IS, OPZ, RPZ, PPZ and LPZ occurred at approximately 2.42, 4.45, 5.02 and 9.37 min, respectively. The method was proved to be accurate and precise at linearity range of 20.61-1999.79 ng/mL with a correlation coefficient (r) of >or=0.999. The limit of quantitation for each of the PPI studied was 20.61 ng/mL. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits as per the FDA guidelines. The developed assay method was applied to a pharmacokinetic study in human volunteers.

Quantification of montelukast, a selective cysteinyl leukotriene receptor (CysLT1) antagonist in human plasma by liquid chromatography–mass spectrometry: validation and its application to a human pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of montelukast (MTK) in human plasma with liquid chromatography coupled to tandem mass spectrometry with electro spray ionization in the positive-ion mode. Liquid-liquid extraction was used to extract MTK and amlodipine (internal standard, IS) from human plasma. Chromatographic separation was achieved with 10 mM ammonium acetate (pH 6.4): acetonitrile (15:85, v/v) at a flow rate of 0.50 mL/min on a Discovery HS C(18) column with a total run time of 3.5 min. The MS/MS ion transitions monitored were 586.10 --> 422.10 for MTK and 409.20 --> 238.30 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.25 ng/mL and linearity was observed from 0.25 to 800 ng/mL. The intra-day and inter-day precisions were 5.97-8.33 and 7.09-10.13%, respectively. This novel method has been applied to a pharmacokinetic study of MTK in humans.

Novel Procedure for the Synthesis of 1‐Hydroxy‐1,1‐bisphosphonic Acids using Phenols as Medium

Abstract A facile synthetic route for the synthesis of bisphosphonates in phenols is described. Preparations of some of bisphosphonates, which are presently in clinical use such as risedronic acid and alendronate sodium, are synthesized following this new, simple method. This procedure can be useful for the synthesis of this class of bone‐resorptive inhibitors in bulk quantities.

Highly sensitive method for the determination of ropinirole with a lower limit of quantitation of 3.45 pg/mL in human plasma by LC-ESI-MS/MS: application to a clinical pharmacokinetic study.

A highly sensitive, rapid assay method has been developed and validated for the estimation of ropinirole (RPR) in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive-ion mode. A solid-phase process was used to extract RPR and citalopram (internal standard, IS) from human plasma. Chromatographic separation was operated with 0.2% ammonia solution:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Hypurity C(18) column with a total run time of 3.2 min. The MS/MS ion transitions monitored were 261.2 --> 114.2 for RPR and 325.1 --> 209.0 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 3.45 pg/mL and the linearity was observed from 3.45 to 1200 pg/mL. The intra-day and inter-day precisions were in the range of 4.71-7.98 and 6.56-8.31%, respectively. This novel method has been applied to a pharmacokinetic study of RPR in humans.

Development and validation of a sensitive LC-MS/MS method with electrospray ionization for quantitation of zafirlukast, a selective leukotriene antagonist in human plasma: application to a clinical pharmacokinetic study.

A highly sensitive and specific LC-MS/MS method has been developed and validated for the estimation of zafirlukast (ZFK) with 500 microL human plasma using valdecoxib as an internal standard (IS). The API-4,000 LC-MS/MS was operated under multiple reaction-monitoring mode using the electrospray ionization technique. The assay procedure involved extraction of ZFK and IS from human plasma with ethyl acetate. The resolution of peaks was achieved with 10 mm ammonium acetate (pH 6.4):acetonitrile (20:80, v/v) on a Hypersil BDS C(18) column. The total chromatographic run time was 2.0 min and the elution of ZFK and IS occurred at approximately 1.11 and 1.58 min, respectively. The MS/MS ion transitions monitored were 574.2 --> 462.1 for ZFK and 313.3 --> 118.1 for IS. The method was proved to be accurate and precise at a linearity range of 0.15-600 ng/mL with a correlation coefficient (r) of >or=0.999. The method was rugged with 0.15 ng/mL as lower limit of quantitation. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits as per the FDA guidelines. The developed assay method was applied to a pharmacokinetic study in human volunteers following oral administration of 20 mg ZFK tablet.

Identification, isolation and characterization of impurities of clindamycin palmitate hydrochloride

Clindamycin palmitate hydrochloride is a water soluble hydrochloride salt of the ester of clindamycin and palmitic acid. It is inactive in vitro, rapid in vivo hydrolysis converts this compound to the antibacterially active clindamycin. Total 12 impurities at levels ranging from 0.05% to 0.5% were detected by isocratic reverse-phase high performance liquid chromatography (HPLC) using RI detector. The molecular weights of impurities were determined by LC-MS analysis. Two impurities were starting materials and the remaining impurities were isolated from crude samples/enriched mother liquors using reverse-phase preparative HPLC. Based on the spectral data the structures of these impurities were characterized as, clindamycin palmitate sulphoxides alpha-/beta-isomers (impurity I); clindamycin laurate (impurity II); lincomycin palmitate (impurity III); clindamycin myristate (impurity IV); epiclindamycin palmitate (impurity V); clindamycin palmitate 3-isomer (impurity VI); clindamycin pentadecanoate (impurity VII); clindamycin B-palmitate (impurity VIII); clindamycin heptadecanoate (impurity IX) and clindamycin stearate (impurity X). Structural elucidation of all impurities by spectral data ((1)H NMR, (13)C NMR, MS and IR) and formation of these impurities have been discussed in detail.

L-Proline-Catalyzed Synthesis of Novel 5-(1H-Indol-3-yl-methylene)-thiazolidine-2,4-dione Derivatives as Potential Antihyperglycemic Agents

Abstract Knoevenagel condensation between indole-3-aldehyde 1 and an active methylene group containing 2,4-thiazolidinedione 2 in refluxing toluene using L-proline as a catalyst yielded 3, which on alkylation using 2 equivalents of alkylating agent under phase-transfer-catalyzed (PTC) conditions using K2CO3 as a base in dimethylformamide gave N,NI-symmetrically disubstituted 5-(1H-indol-3ylmethylene)-thiazolidine-2,4-diones 4. Alternately, 4 can be synthesized by condensing 5 and 6 in a single step. Using this synthetic strategy, N,NI-unsymmetricallydisubstituted derivatives 9a–f were prepared either by condensing 6 with N-substituted-2,4-thiazolidinedione 5 to obtain 7 followed by alkylation under PTC conditions or condensing 6 with N-unsubstituted- 2,4-thiazolidinedione 2 to yield 8 followed by alkylation under PTC conditions. The latter are the dehydro analogs of the dihydro-N-substituted-5-(1H-indol-3-yl-methylene)-thiazolidine-2,4-diones, which are potential antihyperglycemic agents.

NOVEL, RECYCLABLE, AND THERMALLY STABLE TASK-SPECIFIC IONIC LIQUID (TBA ACETATE) MEDIUM/CATALYST FOR THE SYNTHESIS OF INDOLYLIDINECYCLIC-1,3- AND -1,4-DIKETONES

Abstract A simple and efficient synthesis of indolylidinethiazolidnediones (3) and indolylidinecyclic-1,3-diketones (5) has been developed by reaction of indole-3-aldehyde (1) with thiazolidinedione (2) or cyclic-1,3-diketones (4) using tetra butyl ammonium acetate (TBAA) melt as novel, cost-effective, and recyclable ionic liquid under solvent-free green conditions at 100 °C for 15–20 min without additional use of catalyst. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Improved Synthesis of Cefdinir and Its Polymorphic Form, an Antibacterial Active Pharmaceutical Ingredient

Abstract New methods for the preparation of Cefdinir 1 and its polymorphic form Sesqui hydrate 1a are described. The synthesis of 2‐mercaptobenzothiazolyl (Z)‐2‐(2‐amino‐4‐thiazolyl)‐2‐acetoxyiminoacetate 4 was affected by using triphenylphosphine and triethylamine, and acylation of 7‐amino‐3‐vinylcephem‐4‐carboxylic acid 5 followed by deprotection with K2CO3 in the presence of ammonium chloride in the same pot yielded crude Cefdinir. Purification of crude Cefdinir through resin and treatment of the resulting wet product with trifluoroacetic acid gave highly pure TFA salt of Cefdinir 6, which on neutralization afforded 1a in excellent yield. The impurity profiling of this compound has also been discussed.