Synthesis of 6R(β)-tritylaminopenicillanic-3R(β)-alcohol,a versatile stereoisomer of natural β-lactams

In an attempt to rationalize a synthesis of penicillin analogs modified at C(3), we have isolated the 3R(β)-carbinolamide derivative 4a. The trityl substituent on N(6′) seems to be responsible for the inversion of configuration which occurs at C(3) during the acid hydrolysis of the isocyanate intermediate. An hydrogen bond is formed on the β-face of the bell-shaped bicyclic skeleton between the N(6′)-nitrogen lone pair and the C(3) hydroxyl group. On standing, the carbinolamide analog slowly isomerizes to its expanded bicyclic isomer 4b , but the starting material may be easily recovered by treatment with acid. The postulated intermediate during isomerization, i.e., the open aldehyde form, does not accumulate. Substitutions of the hydroxyl group at C(3) lead to a variety of compounds with the biologically active 3S(α) configuration. These may be used to study the importance of the carboxyl group of penicillins in their interaction with β-lactamases at the molecular level.     

Contribution of cyclodextrins in the development of different pharmaceutical formulations of a new matrix metalloproteinase inhibitor

Ro 28-2653 is a new synthetic inhibitor of matrix metalloproteinases. The ability of these enzymes to degrade various components of the extracellular matrix seems to play a major role in tumors progression and is potentially effective against bronchial remodeling in asthma and BPCO. Ro 28-2653 is very poorly soluble in water. This low solubility estimated at about 0.56 μg/ml in water at 25 °C gives rise to difficulties in pharmaceutical formulation of oral, injectable or nebulizable solutions. The purpose of our study is to prepare and to characterize inclusion complexes between Ro 28-2653 and cyclodextrins and to investigate the biopharmaceutical repercussion of the inclusion of the active substance. The complex formation was investigated by phase solubility studies. ¹H-NMR spectroscopy and molecular modeling studies were carried out to elucidate the structure of the inclusion complex between Ro 28-2653 and cyclodextrin. Oral, intravenous and nebulizable solutions of Ro 28-2653 were developed with cyclodextrin. The in vivo studies were performed on healthy sheep for the pharmacokinetic evaluation of the oral and intravenous formulations while the nebulization of the complex solution was studied by using an asthma model in mouse.     

PROFLAVINE MEDIATED PHOTOINACTIVATION OFBACTERIOPHAGE φX174 AND ITS ISOLATED DNA: EFFECTS OF AGENTS MODIFYING VARIOUS PHOTOCHEMICAL PATHWAYS

Abstract. Thiols and disulfides protect both φX174 phage and its isolated DNA from the lethal action of proflavine plus light. The protective ability of these compounds appears to be attributed to the -SH or the -S-S- group and the property to interact with the proflavine-phage DNA complex. The phage inactivation efficiency per proflavine bound to DNA is reduced by 50 to 30% upon addition of cysteine or cystamine. Substances that affect the lifetime of singlet oxygen modify the rate of phage photoinactivation in the presence of proflavine; the inactivation rate is decreased by N^-₃ and increased by D₂O. Irradiation under N₂ atmosphere markedly decreases the phage photosensitization by proflavine. Irradiation with monochromatic light of 440 nm is less efficient than irradiation with light of 440 nm plus 360 nm, and the difference is more pronounced in N₂ than in air. These results are discussed in relation to various possible photochemical pathways.     

ESR STUDY OF ORIENTED TRIPLET MOLECULES GENERATED BY EXCITATION WITH POLARIZED LIGHT

Abstract— The lowest-lying triplet states of a variety of aromatic molecules and complexes have been generated by the irradiation of these compounds in solvent glasses with plane-polarized light. Measurements of the allowed (Δ M=± 1) ESR transitions clearly demonstrate that the triplets so formed are oriented with respect to the external magnetic field. By this method the triplet zero-field splitting parameters, D and E , can be evaluated simply and reliably. Intramolecular energy transfer is postulated to explain the triplet spectra of Zn( o -phen)₂(NO₃)₂ and Zn( o -phen)₃(NO₃)₂. It was observed that in triplet-triplet energy transfer from benzophenone to naphthalene there is no apparent orientation requirement between the donor and acceptor molecules. Further areas of significance and application of this technique are suggested.     

Non-aqueous capillary electrophoretic enantioseparation of N-derivatized amino acids using cinchona alkaloids and derivatives as chiral counter-ions

A non-aqueous capillary electrophoretic method developed with quinine and tert.-butyl carbamoylated quinine as chiral selectors for the enantioseparation of N-protected amino acids was applied to the investigation of other quinine derivatives as chiral additives. The optimum composition of the background electrolyte was found to be 12.5 mM ammonia, 100 mM octanoic acid and 10 mM chiral selector in an ethanol-methanol (60:40, v/v) mixture. Under these conditions, a series of chiral acids, as various benzoyl, 3,5-dinitrobenzoyl and 3,5-dinitrobenzyloxycarbonyl amino acid derivatives were investigated with regards to selectand-selector relationships and enantioselectivity employing quinine, quinidine, cinchonine, cinchonidine, tert.-butyl carbamoylated quinine, tert.-butyl carbamoylated quinidine, dinitrophenyl carbamoylated quinine and cyclohexyl carbamoylated quinine as chiral selector.     

TRIPLET STATE STUDIES OF FLAVlNS BY ELECTRON PARAMAGNETTC RESONANCE-III

Abstract— A continuation of studies is presented on the excited triplet state of flavins using EPR techniques. Detailed experiments are reported on the triplet state of flavin-mono-nucleotide (FMN) and flavin-adenine-dinucleotide (FAD). Action spectra of triplet yield are explained in terms of the optical absorption for FMN and FAD. Effects of light saturation, concentration quenching and oxygen on the triplet state are discussed. It is suggested that the rate constant k ₃ for the intersystem crossover from the excited singlet to the triplet state is increased by oxygen and quenchers such as KI. Detailed kinetic studies are presented on the formation of the triplet state.     

TRIPLET STATE STUDIES OF FLAVINS BY ELECTRON PARAMAGNETIC RESONANCE—I

Abstract— The triplet state of flavin derivatives and d-amino acid oxidase was observed by electron paramagnetic resonance at 77°K.
Flavin triplets (Δ m =± 2) originate from the isoalloxazine ring and are resonant at 1560 guass.The half-life of the FMN triplet in 1 N HCl is 15 nisec.This life-time is prolonged indirectly by the presence of paramagnetic species, such as oxygen or free radicals.
The flavin triplet state is pH dependent.In neutral solution the nlaximum triplet yield is obtained and the longest life-time is observed.The triplet state is affected by intra-and inter-molecular complex formation, FAD is partially quenched by indirectly substituted adenine.Tryptophan quenches completely the FMN triplet.The FAD triplet of d-amino acid oxidase is enhanced but the life-time is shortened relative to a pure FAD solution.     

Enantiomeric separation of N-protected amino acids by non-aqueous capillary electrophoresis with dimeric forms of quinine and quinidine derivatives serving as chiral selectors

A simple method for analysis of anatoxin-a in aqueous samples was developed using solid-phase microextraction (SPME) and high-performance liquid chromatography (HPLC) with fluorescence detection. Anatoxin-a was derivatized to a fluorogenic agent on the surface of the SPME fiber. In the method an SPME fiber was immersed for 30 min in the aqueous sample. The fluorogenic derivatizing reagent (4-fluoro-7-nitro-2,1,3-benzoxadiazole, 1.0 mg/ml in methanol) was dropped or sprayed onto the fiber containing extracted analytes. The fiber was then heated for 10 min in an empty vial at 70 degrees C in a waterbath to promote derivatization. The derivatives formed on the fiber were desorbed in a SPME-HPLC interface. The interface was filled with methanol-1 mM hydrochloric acid (7:3, v/v) before inserting of the fiber into the interface. For desorption, the fiber was inserted in the interface for 5 min. For anatoxin-a in an aqueous sample, the calibration curve showed linearity in the range of 50-1500 ng/ml and the limit of detection of anatoxin-a was 20 ng/ml. No interferences were found, and the time for analysis was 55 min for one sample.