The role of charge distribution on the antimalarial activity of artemisinin analogues

In this work the calculated nuclear quadrupole coupling constants (NQCC; chi) of 17O in artemisinin and some of its derivatives and the effects of charge density due to the nature of ligands on NQCC of 17O were investigated. All calculations were performed at the HF/3-21G level using the Gaussian 98 program. The results show that the O-O linkage has a characteristic role in the antimalarial activity of artemisinin. In addition, various substitutions on C4 change the charge density on these oxygens and consequently change the pharmaceutical effect of artemisinin. Our results suggest that due to a larger charge density on O1, the heme iron approaches the endoperoxide moiety at the O1 position with preference to the O2 position.     

The facile and efficient Michael addition of indoles and pyrrole to alpha,beta-unsaturated electron-deficient compounds catalyzed by aluminium dodecyl sulfate trihydrate [Al(DS)3].3H2O in water

Aluminium dodecyl sulfate trihydrate [Al(DS)3].3H2O is easily prepared and can be used as a Lewis acid surfactant catalyst in water to conduct the highly efficient Michael addition of indoles and pyrrole to alpha,beta-unsaturated electron-deficient compounds at room temperature.     

Synthesis of N-1-(Indanyloxymethyl) and N-1-(4-Hydroxybut-2-enyloxymethyl) Analogues of the HIV Drugs Emivirine and GCA-186

A series of Emivirine and GCA-186 analogues substituted at N-1 with indan-1-yloxymethyl (6a–6c) and indan-2-yloxymethyl (6d–6f) were synthesized by reaction of the corresponding bis(indanyloxy)methans with uracils having 5-ethyl or 5-isopropyl and 6-benzyl or 6-(3,5-dimethylbenzyl) substituents. A route to the corresponding N-1 substituted 4-hydroxybut-2-enyloxymethyl analogue was also devised. All newly synthesized compounds showed potent activity against wild-type HIV-1, the most active compound being 5-ethyl-1-(indan-1-yloxymethyl)-6-(3,5-dimethylbenzyl)uracil (6b), which was 50-fold more active than Emivirine.     

An efficient and chemoselective method for protection of thiols catalyzed by aluminumdodecatungstophosphate (AlPW12O40), as a highly water tolerant Lewis acid catalyst

Protection of various thiols with diphenylmethanol was achieved in high yields at room temperature using catalytic amounts of AlPW₁₂O₄₀ in CH₂Cl₂. In the presence of this catalyst, protection of SH versus OH was achieved with high chemoselectivity and yields. The catalyst can be easily recovered and reused. Deprotection of DPM thioethers was also achieved using molecular iodine at reflux in CH₂Cl₂ in high yields.     

A New ent‐Kaurane Diterpene from Stems of Alibertia macrophylla K. Schum. (Rubiaceae)

Phytochemical investigations of the stems of a specimen of Alibertia macrophylla led to the isolation and characterization of the new diterpene ent‐kaurane‐2β,3α,16α‐triol ( 1 ), along with triterpenes 2 – 8 , iridoids 9 – 12 , and phenolic acids 13 – 15 . The structure of 1 was established based on spectroscopic studies (¹H‐ and ¹³C‐NMR, IR, and HR‐ESI‐MS). This is the first report of the isolation of a diterpene from the Alibertia genus in Rubiaceae.     

Preparation and coordination complex of the first imine-bridged tetrathiafulvalene-pyridine donor ligand

The first imine-bridged pyridyltetrathiafulvalene building block (TTF-CH=N-Py, 1) has been synthesized via the Schiff base condensation of formyltetrathiafulvalene and 2-aminopyridine. The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [CuII(hfac)2(TTF-CH=N-Py)] (2) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center, thus making this ligand an attractive precursor for the assembly of pi-d systems.     

Adsorptive stripping voltammetric analysis of 2,4,6-tri(2′pyridyl)-1,3,5-triazine at a mercury electrode

The redox behaviour of adsorbed species of 2,4,6-tri(2-pyridyl)-1,3-5-triazine (TPTZ) at the surface of a mercury electrode was examined using cycling voltammetry. Based on the adsorption and accumulation of TPTZ at the charged mercury surface cathodic adsorptive stripping voltammetry (CSV) is applied for the trace determination of TPTZ using a differential pulse (DP) technique. Experimental and operational parameters for the quantitative analysis of TPTZ are optimized and the detection limit was found to be 3×10^–9 mol/l. The effect of some interferences, e.g. organic compounds, cations and anions, are investigated.     

Facile,one-pot,four-component synthesis of a new series of imidazo[1,2-a]pyridines in presence of TPAB in EtOH under reflux conditions

Research on Chemical Intermediates - A convenient, regioselective, novel, and elegant one-pot, four-component reaction was designed for synthesis of a series of new of imidazo[1,2-a]pyridines using...