One-pot Synthesis, Molecular Modeling and In Vitro Antibacterial Activity of Novel 3-(1,3,4-Oxadiazol-2-yl) Quinoxaline 1,4-Dioxide and Pyrazolyl Analogs.

The new 1,3,4-oxadiazolylquinoxaline ring system was synthesized by the condensation of the quinoxaline 1,4-dioxide acid hydrazide 6 with acetyl chloride in one-pot synthesis. In which the hydrazide was refluxed in excess of acetyl chloride, acetic anhydride or acetic acid in the presence of phosphorus oxychloride forming the 1,3,4-oxadiazolylquinoxaline ring system. Molecular modeling studies have been performed to evaluate their recognition at the hDHFR binding-pocket as potential hDHFR inhibitors.

Photoionization of psoralen derivatives in micelles: Imperatorin and alloimperatorin.

The fluorescence properties of psoralen derivatives, 8-methoxypsoralen (8-MOP), imperatorin (IMP) and alloimperatorin (ALLOI), were investigated in various solvent and micellar solutions. The variation in intensity and maxima of the fluorescence in micellar solutions suggest that psoralens are located in the micelle-water interface region. Radical cations and hydrated electrons were generated by photoionization in micellar solution upon excitation at 266 nm.

Photoreactivity of psoralen derivatives in micelles: the roles of hydrophobicity and heavy atom substitution.

Intersystem crossing quantum yields of two psoralen derivatives, bromopsoralen (BrMOP) and hexylpsoralen (8-HOP) were measured in ethanol and water by means of laser flash photolysis. Compared to 8-methoxypsoralen (8-MOP), the triplet quantum yields of BrMOP and 8-HOP in ethanol are increased by a factor of 5 and 30, respectively, while BrMOP in aqueous solution shows a twofold enhancement with respect to 8-MOP. Radical cations and hydrated electrons were generated by photoionization in micellar solution upon excitation at 266nm.

Ultraviolet photoionization of the photosensitizers khellin and visnagin in aqueous solution and in micelles: one-photon ionization is a minor process.

One-photon ionization, leading to formation of hydrated electrons and radical cations, has been proposed as a possible mechanism of action of some sensitizers in photobiology. In this contribution, we have investigated this proposal for the compounds khellin and visnagin, used in photomedical applications. Nanosecond transient absorption spectroscopy covering a wide range of laser pulse energies was employed to measure the formation of radical cations and hydrated electrons in aqueous solution and in cationic (CTAB) as well as anionic (SDS) micellar solutions.