N-Bromoamides as versatile catalysts for aziridination of olefins using chloramine-T

N-Bromoamides catalyze effectively the aziridination of electron-deficient as well as electron-rich olefins using chloramine-T (N-chloro-N-sodio-p-toluenesulfonamide) as a nitrogen source under ambient conditions to afford the corresponding aziridines in good to excellent yields.     

Baseline studies of radon/thoron concentration levels in and around the Lambapur and Peddagattu areas in Nalgonda district, Andhra Pradesh, India

Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×10¹ and (6.7±0.3)×10¹ Bq/m³, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution.     

A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL^?1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 10⁴ L mol^?1 cm^?1 and 0.0435 mg cm^?2, respectively for method C, and their respective values for method D are 2.9 × 10⁴ L mol^?1 cm^?1 and 0.0156 mg cm^?2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.     

Information-theoretic approaches to SVM feature selection for metagenome read classification

Analysis of DNA sequences isolated directly from the environment, known as metagenomics, produces a large quantity of genome fragments that need to be classified into specific taxa. Most composition-based classification methods use all features instead of a subset of features that may maximize classifier accuracy. We show that feature selection methods can boost performance of taxonomic classifiers. This work proposes three different filter-based feature selection methods that stem from information theory: (1) a technique that combines Kullback-Leibler, Mutual Information, and distance information, (2) a text mining technique, TF-IDF, and (3) minimum redundancy-maximum-relevance (mRMR). The feature selection methods are compared by how well they improve support vector machine classification of genomic reads. Overall, the 6mer mRMR method performs well, especially on the phyla-level. If the number of total features is very large, feature selection becomes difficult because a small subset of features that captures a majority of the data variance is less likely to exist. Therefore, we conclude that there is a trade-off between feature set size and feature selection method to optimize classification performance. For larger feature set sizes, TF-IDF works better for finer-resolutions while mRMR performs the best out of any method for N=6 for all taxonomic levels.     

Regioselective cobalt-catalyzed addition of sulfides to unactivated alkenes

A novel method to synthesize tertiary alkyl/aryl sulfides in a mild and regioselective manner from unactivated alkenes using cobalt catalysis is described. The methodology is compatible with sensitive functionalities and is successful with several different types of alkenes and sulfides.     

Azopyrazolobenzylidene derivatives of 4‐amino‐1,2,4‐triazol‐3‐ones. Synthesis of 4‐{[4‐(3,5‐dimethyl‐1H‐pyrazol‐4‐yl)diazenyl]‐benzylidene}amino‐2‐aryl‐5‐methyl‐3H‐[1,2,4]‐triazol‐3‐ones

The Schiff bases 3a‐h obtained from 4‐amino‐1,2,4‐triazol‐3‐ones 1a‐h when subjected to Japp‐Klingemann reaction yielded the corresponding 3‐{2‐[(2‐aryl‐5‐methyl‐3H‐[1,2,4]‐triazol‐3‐one‐4‐yl)]‐iminophenyl}‐pentane‐2,4‐diones 4a‐h . These diones on cyclisation with N₂H₄ yielded the title compounds 5a‐h . The energetics of the Keto‐enol tautomers of the diones was calculated by semiemperical calculations using AM1 and PM3 methods. All these compounds were screened for their antimicrobial activity against few microbes and most of them exhibited fungal inhibition more than the reference drugs used.     

Preparation and electrical conductivity of organoheterobimetallic-maleonitriledithiolates

The new complexes [PhHg]₂[M(mnt)₂] [M = Ni^II, Cu^II, Zn^II or Pd^II; mnt^2– = 1,2-dicyano-1,2-ethylenedithiolate (maleonitriledithiolate)] have been characterized spectroscopically and magnetically and their solid phase conductivity measured. All compounds exhibit solid phase _rt in the 1.29 × 10^–12–5.68 × 10^–10 S cm^–1 range and semiconduct in the 313–383 K range.     

Sensitive and selective spectrophotometric methods for the determination of pheniramine maleate in bulk drug and in its formulations using sodium hypochlorite

Two simple, selective and sensitive spectrophotometric methods are described for the determination of pheniramine maleate (PAM) in pure and dosage forms. The method is based on the reaction of PAM with hypochlorite in the presence of Kolthoff buffer (phosphate-borate) of pH 7.0 to form the chloro derivative of PAM, destruction of the excess hypochlorite by nitrite ion (the chloro derivative of drug is unaffected under the optimized conditions) followed by the oxidation of iodide with the chloro derivative of PAM to iodine (I ₃ ^? which is either measured directly at 355 (method A) or reacted with starch to form a blue chromogen measurable at 590 nm (method B). The optimum conditions that affect the reaction were ascertained, and under these conditions linear relationship was obtained in the concentration ranges of 2–50 and 1–25 μg/mL PAM in methods A and B, respectively. The calculated molar absorptivity values are 7.26 × 10³ and 1.28 × 10⁴ L/(mol cm) for method A and method B, respectively. Sandell’s sensitivity values, limits of detection (LOD) and quantification (LOQ) are calculated as per ICH guidelines. The proposed methods were applied successfully to the determination of PAM in tablets and injection with good accuracy and precision and without interferences from common additives. The results obtained by the proposed methods were compared favourably with those of the reference method. The accuracy and reliability of the proposed methods were further checked by recovery studies via standard addition procedure.     

Syntheses of nucleosides with 2′-spirolactam and 2′-spiropyrrolidine moieties as potential inhibitors of hepatitis C virus NS5B polymerase

To discover novel nucleosides as potential antiviral agents, 2′-spirolactam and 2′-spiropyrrolidine-containing nucleoside analogs were envisioned. Efficient synthetic routes were developed with an epoxide opening as the key step to establish the quaternary center at the 2′ position, leading to the design and synthesis of uridine analogs 8 and 21, prodrugs 13–16, and cytidine analog 11.