Synthesis and in vitro evaluation of novel acyclic and cyclic nucleoside analogs with a thiadiazole ring.

THE SYNTHESIS OF SIX THIADIAZOLE NUCLEOSIDE ANALOGS IS REPORTED: 5-diacetylamino-1,2,4-thiadiazol-3-one (1), 5-amino-2- (tetrahydrofuran-2-yl)-1,2,4-thiadiazol-3-one (2), 5-amino-3-[(2'-hydroxyethoxy)methyl]-1,3,4-thiadiazol-2-one (3), 5-amino-3-(4'-hydroxy-2'-hydroxymethyl-butyl)-1,3,4-thiadiazole-2-thione (4), (R)-5-amino-3-(2',3'-dihydroxypropyl)-1,3,4-thiadiazole-2-thione (5), and (S)-5-amino-3-(2',3'-dihydroxypropyl)-1,3,4-thiadiazole-2-thione (6). The synthesis, characterization, and properties of these new synthesized thiadiazole derivatives are discussed. A dimerization of 5-amino-3H-1,3,4-thiadiazole-2-thione (14) by sodium nitrite resulting in di-(5-amino-1,3,4-thiadiazol-2-yl) disulfide (19) is also reported. The preliminary in vitro evaluation of these newly synthesized compounds is discussed.

Fluorescence properties and dipole moments of novel fused thienobenzofurans. Solvent and structural effects.

The electronic absorption, fluorescence excitation and emission spectra, and fluorescence quantum yields of novel fused thienobenzofurans, including thieno[3,2-b][1]benzofuran (1), [1]benzothieno[3,2-b]furan (2), and [1]benzothieno[3,2-b][1]benzofuran (3), were recorded in fourteen solvents of different polarities at room temperature. Compound 2 was not fluorescent. Experimental ground-state dipole moments of compounds 1-3 were measured in benzene at 298 K and compared with the corresponding theoretical dipole moment values. The solvent effects on the electronic absorption and fluorescence spectra of these thienobenzofurans were quantitatively investigated by means of solvatochromic correlations based on the Kawski-Chamma-Viallet and McRae equations. A weak negative solvatochromic behavior was found for these compounds, showing that their dipole moments are slightly lower in the excited singlet-state than in the ground-state. Kamlet-Abboud-Taft multiparameter relationships were also established for electronic absorption and fluorescence wavenumbers, and fluorescence quantum yields in most solvents, demonstrating the occurrence of specific solute-solvent interactions.

Luminescence and photophysical properties of benzo[a]phenothiazines--therapeutic, physico-chemical, and analytical applications.

Luminescence studies on a series of new 12H-benzo[a]phenothiazines (BPHTs), possessing potentially useful antitumor therapeutic properties, are reviewed. The electronic absorption and fluorescence spectral properties of BPHTs, as well as their triplet- and singlet-excited states luminescence quenching are reviewed. Ground-state and singlet-excited state dipole moments and solvatochromic relationships are also described for these compounds. Studies on the formation of inclusion complexes between BPHTs and cyclodextrins (CDs), including CD-enhanced fluorescence, and thermodynamic constants and molecular geometry of these complexes, are discussed. The BPHTs antitumor properties in relation to their pi-electron density, and the physico-chemical and analytical applications based on their fluorescence and photophysical properties are also presented. This review article is based on selected literature data published in the last ten years (1993-2004).

Solvatochromic correlations and ground- and excited-state dipole moments of curcuminoid dyes.

Experimental dipole moments of curcumin (1) and of its parent compound dicinnamoylmethane (2) were determined in dioxane and benzene, respectively. Theoretical dipole moments were calculated using a combination of the PPP method (pi-moment) and a vector sum of the sigma-bond moments (sigma-moment) as well as by the ZINDO/1 method. Solvatochromic correlations were used to obtain the experimental first excited singlet-state dipole moments. The experimental electronic absorption spectra were compared with the calculated transitions.