Novel selenium-mediated cyclisations

The present work describes the selenium-mediated cyclofunctionalisations of alkenes. Three different areas are reported herein. Chapter 2 reports syntheses of several substrates for carbocyclisation reactions and use of selenium and Lewis acids resulting in various dihydronaphthalenes. These dihydronaphthalenes then acted as substrates for second ring forming reactions. This novel tandem double cyclisation comprises a carboannulation, a Friedel-Crafts reaction and a rearrangement. This cascade sequence has been proven to be a useful tool in the selective synthesis of dihydronaphthalenes and benzofluorenes from easily accessible stilbenes and provides fast access to polycyclic ring systems in a single step. Chapter 3 describes electrophilic selenium-mediated reactions which have been used to cyclise a range of /-keto esters to corresponding biaryl compounds under very mild conditions. The products were formed by a carboannulation via addition/elimination sequence and a subsequent rearrangement of range of alkyl and aryl groups. The key starting materials stilbene /-keto esters were readily prepared by Heck coupling and hydrolysis followed by condensation with potassium ethyl malonate. Chapter 4 describes work on catalytic selenium reagents with stoichiometric amount of hypervalent iodine to convert a range of stilbene carboxylic acids into their corresponding isocoumarins. The work also describes the selective synthesis of dihydroisocoumarins using diphenyl disulfide and dimethyl diselenide

A cost effective preparative thin layer chromatography cleanup method for high performance liquid chromatography analysis of aflatoxins B1, B2 and G2

Aflatoxins are the by-products of fungal metabolism and common contaminants in feed. To keep their level below permissible limits, various assays have been developed. Currently, High Performance Liquid Chromatography (HPLC) with fluorescence detection of toxins is most widely used method but the cleanup methods requiring specific gadgets have increased the cost of the assay. Thin Layer Chromatography (TLC) is effective and economical but it only gives semi quantitative determination for aflatoxin.This study explores the preparative potential of TLC as cleanup method for HPLC analysis of toxin. Standard aflatoxins solutions containing 10 ng of B1, 2.5 ng of B2 and 2.5 ng of G2 were spotted on silica plates and then extracted using chloroform and acetone (4:1). The extracted toxins were resolved and quantified on HPLC using fluorescent detection. The results showed 81, 79 and 60% mean recovery of aflatoxin B1, B2 and G2, respectively. This method was proved equivocally comparable to other methods of aflatoxins cleanup and thus can be used as an alternative cost effective cleanup method

1-Azido-N′-(phenylsulfonyl)methan­imid­amide

In the title compound, C7H7N5O2S, the aromatic ring is oriented at dihedral angles of 79.46 (2) and 89.17 (2)°, respectively, with respect to the amino­(azido)­methyl and the S(6) six-membered ring motif generated by an intra­molecular N—H⋯O inter­action [N⋯O = 2.8901 (15) Å]. Inter­molecular N—H⋯O hydrogen bonds [N⋯O = 2.9177 (15) and 2.9757 (15) Å] generate an infinite one-dimensional network along the base vector (010)

Frequency of hepatitis E and Hepatitis A virus in water sample collected from Faisalabad, Pakistan

Hepatitis E and Hepatitis A virus both are highly prevalent in Pakistan mainly present as a sporadic disease. The aim of the current study is to isolate and characterized the specific genotype of Hepatitis E virus from water bodies of Faisalabad, Pakistan. Drinking and sewage samples were qualitatively analyzed by using RT-PCR. HEV Genotype 1 strain was recovered from sewage water of Faisalabad. Prevalence of HEV and HAV in sewage water propose the possibility of gradual decline in the protection level of the circulated vaccine in the Pakistani population