Conversion of 2-methyl-4-styrylquinolines into 2,4-distyrylquinolines: synthesis, and spectroscopic and structural characterization of five examples.

Four new 2,4-distyrylquinolines and one 2-styryl-4-[2-(thiophen-2-yl)vinyl]quinoline have been synthesized using indium trichloride condensation reactions between aromatic aldehydes and the corresponding 2-methylquinolines, which were themselves prepared using Friedländer annulation reactions between mono- or diketones and (2-aminophenyl)chalcones: the products have all been fully characterized by spectroscopic and crystallographic methods. 2,4-Bis[(E)-styryl]quinoline, C25H19N, (IIa), and its dichloro analogue, 2-[(E)-2,4-dichlorostyryl]-4-[(E)-styryl]quinoline, C25H17Cl2N, (IIb), exhibit different orientations of the 2-styryl unit relative to the quinoline nucleus. In each of the 3-benzoyl analogues {2-[(E)-4-bromostyryl]-4-[(E)-styryl]quinolin-3-yl}(phenyl)methanone, C32H22BrNO, (IIc), {2-[(E)-4-bromostyryl]-4-[(E)-4-chlorostyryl]quinolin-3-yl}(phenyl)methanone, C32H21BrClNO, (IId), and {2-[(E)-4-bromostyryl]-4-[(E)-2-(thiophen-2-yl)vinyl]quinolin-3-yl}(phenyl)methanone, C30H20BrNOS, (IIe), the orientation of the 2-styryl unit is similar to that in (IIa), but the orientation of the 4-arylvinyl units show considerable variation. The thiophene unit in (IIe) is disordered over two sets of atomic sites having occupancies of 0.926 (3) and 0.074 (3). There are no hydrogen bonds of any kind in the structure of (IIa), but in (IId), a single C-H...O hydrogen bond links the molecules into cyclic centrosymmetric R22(20) dimers. A combination of C-H...N and C-H...π hydrogen bonds links the molecules of (IIb) into a three-dimensional framework structure. A combination of three C-H...π hydrogen bonds links the molecules of (IIc) into sheets, and a combination of C-H...O and C-H...π hydrogen bonds forms sheets in (IIe). Comparisons are made with the structures of some related compounds.

Synthesis, and spectroscopic and structural characterization of three new styrylquinoline-benzimidazole hybrids.

Three new 4-styrylquinoline-benzimidazole hybrids have been synthesized using a reaction sequence in which 2-methylquinoline precursors first undergo selective oxidation by selenium dioxide to form the corresponding 2-formylquinoline intermediates, followed by oxidative cyclocondensation reactions with benzene-1,2-diamine to yield the hybrid products. The formyl intermediates and the hybrid products have all been fully characterized using a combination of IR, 1H and 13C NMR spectroscopy, and high-resolution mass spectrometry, and the structures of the three hybrid products have been determined using single-crystal X-ray diffraction. Ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(4-chlorostyryl)quinoline-3-carboxylate, C27H20ClN3O2, (IIIa), and ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(2-methoxystyryl)quinoline-3-carboxylate, C28H23N3O3, (IIIb), both crystallize in the solvent-free form with Z' = 1, but ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(4-methylstyryl)quinoline-3-carboxylate, C28H23N3O2, (IIIc), crystallizes as a partial hexane solvate with Z' = 3, and the ester group in one of the independent molecules is disordered over two sets of atomic sites having occupancies of 0.765 (7) and 0.235 (7). The molecules of (IIIc) enclose continuous channels which are occupied by disordered solvent molecules having partial occupancy. In all of the molecules of (IIIa)-(IIIc), the styrylquinoline fragment is markedly nonplanar. Different combinations of N-H...O and C-H...π hydrogen bonds generate supramolecular assemblies which are two-dimensional in (IIIb) and (IIIc), but three-dimensional in (IIIa). Comparisons are made with the structures of some related compounds.

Characterising PvRBSA: an exclusive protein from Plasmodium species infecting reticulocytes.

BACKGROUND: Plasmodium vivax uses multiple ligand-receptor interactions for preferential invasion of human reticulocytes. Several of these ligands have been identified by in silico approaches based on the role displayed by their orthologs in other Plasmodium species during initial adhesion or invasion. However, the cell adhesion role of proteins that are exclusive to species that specifically invade reticulocytes (as P. vivax and P. cynomolgi) has not been evaluated to date. This study aimed to characterise an antigen shared between Plasmodium species that preferentially infect reticulocytes with a focus on assessing its binding activity to target cells. RESULTS: An in silico analysis was performed using P. vivax proteome data to identify and characterise one antigen shared between P. vivax and P. cynomolgi. This led to identification of the pvrbsa gene present in the P. vivax VCG-I strain genome. This gene is transcribed in mature schizonts and encodes a protein located on the parasite surface. rPvRBSA was antigenic and capable of binding to a population of reticulocytes with a different Duffy phenotype. Interestingly, the molecule showed a higher percentage of binding to immature human reticulocytes (CD71hi). CONCLUSIONS: This study describes for the first time, a molecule involved in host cell binding that is exclusive in reticulocyte-infecting Plasmodium species. This suggest that PvRBSA is an antigenic adhesin that plays a role in parasite binding to target cells.