Hidayat Hussain

Journey Describing Applications of Oxone in Synthetic Chemistry

Hidayat Hussain,*,†,‡ Ivan R. Green, and Ishtiaq Ahmed †Department of Chemistry, University of Paderborn, Warburger Strasse 100, 33098 Paderborn, Germany ‡Department of Biological Sciences and Chemistry, College of Arts and Sciences, University of Nizwa, Birkat Al-Mouz, Nizwa 616, Sultanate of Oman Department of Chemistry and Polymer Science, University of Stellenbosch, P/Bag X1Matieland 7602, South Africa Karlsruhe Institute of Technology (KIT), DFG Centre for Functional Nanostructures, Wolfgang Gaede Strasse 1, 76131 Karlsruhe, Germany

Fruitful Decade for Antileishmanial Compounds from 2002 to Late 2011

2011 Hidayat Hussain,*,† Ahmed Al-Harrasi,*,† Ahmed Al-Rawahi,† Ivan R. Green,‡ and Simon Gibbons* †UoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, P.O. Box 33, Birkat Al Mauz, Nizwa 616, Sultanate of Oman ‡Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland, Stellenbosch 7600, South Africa Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, London WC1N 1AX, United Kingdom

Phenolic glycosides from Symplocos racemosa: natural inhibitors of phosphodiesterase I.

One new phenolic glycoside named benzoylsalireposide (1) along with one known phenolic glycoside named salireposide (2) have been isolated from Symplocos racemosa. Four other known compounds i.e. beta-amyrin (3), oleonolic acid (4), beta-sitosterol (5) and beta-sitosterol glycoside (6) were also isolated from this plant. The structure elucidation of the isolated compounds was based primarily on 1D- and 2D-NMR analysis, including COSY, HMQC, and HMBC correlations. The compound 1 and 2 showed inhibitory activity against snake venom phosphodiesterase I.

Xanthones and oxepino[2, 3-b]chromones from three endophytic fungi.

Three new metabolites, microsphaeropsones A-C (1-3) with a unique oxepino[2,3-b]chromen-6-one (ring-enlarged xanthone) skeleton, were isolated from the endophytic fungus Microsphaeropsis species, co-occurring with their putative biogenetic anthraquinoide precursors citreorosein (4) and emodin (5). From another Microsphaeropsis species, large amounts of fusidienol A (8 a), smaller amounts of emodin (5), the known aromatic xanthones 9 a and 9 b, the new 3,4-dihydrofusidienol A (8 b), and the new aromatic xanthone 9 c were isolated. The endophyte Seimatosporium species produced a new aromatic xanthone, seimatoxanthone A (10), and 3,4-dihydroglobosuxanthone A (12), closely related to alpha-diversolonic ester (13) from Microdiplodia sp.. The structures were determined mainly by extensive 1D and 2D NMR experiments and supported by X-ray single-crystal analysis of 1 and the oxidation product 7. The absolute configurations of the microsphaeropsones A-C (1-3) were established by comparison of the electronic and vibrational circular dichroism (ECD and VCD) spectra of 1 with time-dependent DFT (TDDFT) and DFT calculations by using either the solid-state structures or DFT-optimized geometries as inputs. Preliminary studies indicated that 1, 2, and enone 7 showed antibacterial, fungicidal, and algicidal properties.

Diversonol and Blennolide Derivatives from the Endophytic Fungus Microdiplodia sp.: Absolute Configuration of Diversonol

Chemical investigation of the fungal strain Microdiplodia sp. isolated from the shrub Lycium intricatum led to the isolation of four new compounds: a hexahydroxanthone (2), a 2,3-dihydrochroman-4-one (3), a 7-oxoxanthone derivative (4), and a 1,4-oxazepan-7-one (5). The relative configurations of the new compounds were determined by intensive NMR investigations, notably NOESY experiments at different temperatures. The absolute configurations of the well-known fungal metabolite diversonol (1) and of other xanthone derivatives (3, 4) were established by means of TDDFT ECD calculations. Most of the metabolites were biologically active, with antibacterial activity against Legionella pneumophila and/or antifungal activity against Microbotryum violaceum.

A New Class of Phenazines with Activity against a Chloroquine Resistant Plasmodium falciparum Strain and Antimicrobial Activity

New phenazines were synthesized by oxygenation of 1- and 2-naphthol with transition metal peroxo complexes and in situ reaction with 1,2-diamines. The title compounds were evaluated for in vitro antimalarial activity against Plasmodium falciparum and chloroquine-resistant strains. Phenazines 12, 27, and 28 were most prominent in growth inhibition. In vivo protection against cerebral malaria was observed with the phenazines 11, 12, 20, and 27, whereas partial protection was provided by 19.

Hetero-Diels-Alder reactions of cyclic ketone derived enamide. A new and efficient concept for the asymmetric Robinson annulation.

Chiral enamides, easily prepared in one step from a cyclic ketone and an oxazolidinone, are successfully employed in high-yielding, endo, and facially selective Hetero-Diels-Alder reactions involving activated oxadienes and Sievers reagent as catalyst. From the resulting bicyclic heteroadducts, a novel and efficient asymmetric modification for the Robinson annulation of cyclic monoketones is described.

Pyrenocines J–M: Four new pyrenocines from the endophytic fungus, Phomopsis sp.

Four new pyrenocines, named pyrenocines J-M (1-4), were isolated from an endophytic fungus, Phomopsis sp, by a bioassay-guided method. The structures of the new compound have been assigned from ¹H and ¹³C NMR spectra, DEPT, and by 2D COSY, HMQC, and HMBC experiments. Preliminary studied showed that compounds 1, 2 and 4 showed good antifungal, antibacterial, and algicidal properties, while compound 3 had good antibacterial and algicidal properties.

meta-Chloroperbenzoic acid (mCPBA): a versatile reagent in organic synthesis

The synthetic uses of different peroxides for organic synthesis have been widely studied. Among these peroxides, meta-chloroperbenzoic acid (mCPBA) is an efficient oxidizing reagent and have been used for many oxidative transformations. mCPBA is widely used for chemical transformations such as the oxidation of carbonyl compounds, iminoindolines, olefins, imines, alkanes, silyl enol ethers, N- and S-heterocycles, active methylene groups, fluoromethylated allylic bromides, cyclic acetals, N-substituted phthalimidines, selenides, furans and phosphates. The purpose of this review is to collect and discuss the synthetic applications of meta-chloroperbenzoic acid (mCPBA) over the past few decades.

Characterization and DNA binding studies of unexplored imidazolidines by electronic absorption spectroscopy and cyclic voltammetry

UV-Vis spectroscopic behavior of four imidazolidine derivatives i.e., [5-benzylideneimidazolidine-2,4-dione (NBI), 5-(2-hydroxybenzylidene)imidazolidine-2,4-dione (HBI), 5-(4-methoxybenzylidene)imidazolidine-2,4-dione (MBI) and 5-(3,4-di-methoxybenzylidene)imidazolidine-2,4-dione (DBI)] was studied in a wide pH range. Spectroscopic response of the studied compounds was found sensitive to pH and the attached substituents. Incited by anti-tumor activity, structural miscellany and biological applications of imidazolidines, the DNA binding affinity of some novel derivatives of this class of compounds was examined by cyclic voltammetry (CV) and UV-Vis spectroscopy at pH values of blood (7.4) and lysosomes (4.5). The CV results showed the following order of binding strength: KNBI (6.40×10(6)M(-1))>KHBI (1.77×10(5)M(-1))>KMBI (2.06×10(4)M(-1))>KDBI (1.01×10(4)M(-1)) at pH 7.4. The same order was also obtained from UV-Vis spectroscopy. The greater affinity of NBI justified its preferred candidature as an effective anti-cancer drug. The DNA binding propensity of these compounds was found comparable or greater than most of the clinically used anticancer drugs.