Microwave-assisted,rapid synthesis of 2-vinylquinolines and evaluation of their antimalarial activity

A rapid and efficient synthesis of 2-vinylquinolines via trifluoromethanesulfonamide-mediated olefination of 2-methylquinoline and aldehyde under microwave irradiation is reported. Biological evaluation of these scaffolds demonstrates that 2-vinylquinolines 3x-3z possess excellent antimalarial activities against chloroquine-resistant Dd2 strain of Plasmodium falciparum (IC₅₀ < 100 nM).     

Chloride selective calix[4]arene optical sensor combining urea functionality with pyrene excimer transduction

A neutral 2-site chloride selective compound has been developed (3), based on a 1,3-alternate tetrasubstituted calix[4]arene providing a preorganized supramolecular scaffold. The resultant supramolecular cavity is among the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signaling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion among a wide variety of anions tested. 3 has an association constant of 2.4 x 10(4) M(-1) with chloride. The suitability and advantages of ratiometric optical sensor compounds like 3 for use in practical sensor devices is discussed. 3 has an LOD of 8 x 10(-6) M with chloride in acetonitrile-chloroform (95:5 v/v). A dynamic fluorescence study revealed a response time of < 3 s. A recently developed and simple HPLC-based purification method complimented conventional organic work up methods to yield pure product.     

Homochiral tripodal imidazolium receptors: structural and anion-receptor studies

Two homochiral tripodal receptors were characterised by X-ray crystallography, the first examples for this class of imidazolium receptor. These receptors were also screened for anion recognition. Both receptors demonstrated selectivity towards chloride and bromide with binding constants as high as 16,000.     

Novel synthesis and characterisation of 3,3-dimethyl-5′-(2-benzothiazolyl)-spironaphth(indoline-2,3′-[3H]naphth[2,1-b] [1,4]oxazine) derivatives

Novel modified spirooxazines (SOs) with additional chelating groups were synthesised and the crystal structure of one of these was determined. UV-vis spectroscopic characterization of the photoisomerization of the SO derivatives shows that the photochromic behaviour is altered with Zn²⁺ coordination. In particular, addition of a group as in carboxylic acid 5 to the indole section of the SO increases the lifetime of the merocyanine Zn ²⁺ complex by 20-fold compared to the methylated indole 6.