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PubMed2002

[Decontamination of dental unit waterlines using disinfectants and filters].

Bacterial contamination of the dental unit water system can become a health problem for patients, particularly if they are immunodepressed. The present study has had the purpose of evaluating the effectiveness of methods of chemical decontamination using different disinfectants (peracetic acid, hydrogen peroxide, silver salts, chloramine T, glutaraldehyde T4) and methods of physical decontamination using synthetic membranes for the filtration of water. A preliminary removal procedure of the biofilm present in the waterline has been followed in a dental unit prepared on purpose for the research; subsequently different 2-week long maintenance procedures were applied using disinfectants injected by a pump and finally the bacterial contamination of the water flowing from the waterline was evaluated. The physical decontamination was performed using 0.22 mm membrane filters, which have been installed also in another dental unit, and the filtered water was analyzed to detect bacterial contamination. The preliminary procedure of biofilm removal succeeded obtaining germ-free water. Among the disinfectants used for the maintenance of the water quality only glutaraldehyde T4 was able to reduce the bacterial contamination under the limit suggested by the ADA. The membrane filter system was not able to purify the water, but when a disinfectant (peracetic acid) was used in the last part of the waterline good results were obtained. At present no decontamination system of dental waterline is available, and glutaraldehyde T4 seems to be the best disinfectant only if integrated with periodic biofilm removal for the maintenance of the water quality.

Biofilms↗
PubMed1995

[Antimalarial active 10 H-indolo(3,2-b)quinolin-11-yl-amine. 2. Chloroquine analogs].

The quinolones 1b and 1c react with tosylisocyanate to yield the tosylamino quinolines 2b and 2c, while 1a under the same conditions gives the carbamate 5. Decarboxylation of 5 affords 2a. The mono and bis alkylated products 3 and 6 are received from 2b. The N-tosyl derivatives 2b and 3 rearrange to form the C-tosyl compounds 7 by heating with polyphosphoric acid (PPA) while 2c is hydrolized to 8c. 8 are isolated either from 2 using sulfuric acid 90% or from the 11-chloro-quinolines 9 melting in a mixture of ammonium chloride and acetate. The chloroquine analogues 4 are obtained from the 9-hydrochlorides with the dihydrochloride of the novaldiamine base. The quaternary salt 10 prepared by methylation of 9b reacts with the base in ethanol to yield 11. 4c inhibits the multi-resistant Plasmodium falciparum strain K-1 stronger than chloroquine.

Aminoquinolines↗
PubMed2003

Investigation of the transition-metal- and acid-catalyzed reactions of beta-(N-tosyl)amino diazo carbonyl compounds.

A series of beta-(N-tosyl)amino diazo carbonyl compounds have been prepared by nucleophilic condensation of N-tosylimines with acyldiazomethanes. The diazo decomposition of these diazo carbonyl compounds under various catalytic conditions, including Rh(II) carboxylates, Cu(I) and Cu(II) complexes, PhCO(2)Ag/Et(3)N, TsOH, and SnCl(2).2H(2)O, has been investigated. It was found that, in most cases, the diazo decomposition gave preferentially 1,2-aryl migration product, but 1,2-hydride migration predominated when PhCO(2)Ag/Et(3)N was the catalytic system. Hammett correlation has been applied in the analysis of the electronic effects of 1,2-aryl migration. The factors that govern the migratory preference and the mechanistic aspects of the reaction are discussed.

Journal Article↗
PubMed2005

Zinc has ambiguous effects on chromium (VI)-induced oxidative stress and apoptosis.

Zinc is an important cellular antioxidant. We investigated its role in chromium-induced oxidative stress and apoptosis in human tumor cell line Hep-2. The measured parameters included intracellular labile zinc content (Zinquin-E fluorescence), cell viability (WST-1 assay), oxidative stress (spectrophotometry), mitochondrial potential (flow cytometry), caspase-3 activity, and PARP cleavage (immunofluorescence). We found that Hep-2 cells contain abundant labile zinc stores that may be depleted by the ionophore TPEN or increased by external zinc supplementation. Chromium (VI)-induced cytotoxicity and apoptosis were enhanced in zinc-depleted cells after 24 h, in particular at chromium (VI) concentrations of 50 and 150 micromol/l. On the other hand, elevated levels of labile zinc were able to protect against apoptosis induced by 10 micromol/l chromium (VI) but at higher chromium (VI) concentrations (50 and 150 micromol/l) acted synergistically, significantly enhancing oxidative stress and the course of apoptosis, possibly through oxidative stress and mitochondrial damage.

Antioxidants↗
PubMed1998

Chloramine-T in high-specific-activity radioiodination of antibodies using N-succinimidyl-3-(trimethylstannyl)benzoate as an intermediate.

Monoclonal antibodies C215 and MOv18 have been radiohalogenated, using a single-batch method employing N-succinimidyl-3-(trimethylstannyl)benzoate, m-MeATE. Labelling to the stannyl ester was optimized using chloramine-T as oxidizing agent. The results show that the stannyl ester is effectively labelled with short reaction times giving reproducible yields from 85% to 95%. Subsequent antibody conjugation, 10 to 80 microg MAb, resulted in biologically active, labelled antibodies with overall radiochemical yields of 50% to 80%, with corresponding specific activities of 490-50 kBq(125I)/microg.

Antibodies↗
PubMed2002

Novel chemistry of alpha-tosyloxy ketones: applications to the solution- and solid-phase synthesis of privileged heterocycle and enediyne libraries.

New synthetic technologies for the preparation and elaboration of alpha-tosyloxy ketones in solution- and on solid-phase are described. Both olefins and ketones serve as precursors to these relatively stable chemical entities: olefins via a novel one-pot epoxidation, arylsulfonic acid displacement, and oxidation sequence, and ketones by direct exposure to arylsulfonic acids in the presence of diacetoxy iodobenzene. Reaction of these substrates with O-, S-, or N-centered nucleophiles leads to incorporation of the nucleophile with concomitant expulsion of the sulfonate, while exposure to bis-functional nucleophiles furnishes annulated heterocyclic systems. In addition, the reactions of carbon-centered nucleophiles with alpha-tosylyloxy ketones are also explored. The collated data for all these nucleophiles provide compelling evidence for the proposal that different reaction pathways are followed when alpha-tosyloxy ketones are engaged by "hard" versus "soft" nucleophiles. The accessibility and site-selectivity of the chemistry demonstrated herein offer the promise of an expanded use for this moiety in solid-phase library construction, in particular, and in the field of organic synthesis, in general.

Alkynes↗
PubMed2006

The hydrogenation/transfer hydrogenation network: asymmetric hydrogenation of ketones with chiral eta6-arene/N-Tosylethylenediamine-ruthenium(II) catalysts.

Chiral eta6-arene/N-tosylethylenediamine-Ru(II) complexes, known as excellent catalysts for asymmetric transfer hydrogenation of aromatic ketones in basic 2-propanol, can be used for asymmetric hydrogenation using H2 gas. Active catalysts are generated from RuCl[(S,S)-TsNCH(C6H5)CH(C6H5)NH2](eta6-p-cymene) in methanol, but not 2-propanol, or by combination of Ru[(S,S)-TsNCH(C6H5)CH(C6H5)NH](eta6-p-cymene) and CF3SO3H or other non-nucleophilic acids. This method allows, for the first time, asymmetric hydrogenation of simple ketones under acidic conditions. Hydrogenation of base-sensitive 4-chromanone and its derivatives with the S,S catalyst proceeds in methanol with a substrate-to-catalyst molar ratio of 1000-3000 (10 atm) to 7000 (100 atm), giving (S)-4-chromanols with 97% ee quantitatively. The reaction can be achieved even on a 2.4 kg scale. The mechanistic rationale for the catalytic efficiency is presented.

Alcohols↗
PubMed2005

Highly regioselective Diels-Alder reactions toward oroidin alkaloids: use of a tosylvinyl moiety as a nitrogen masking group with adjustable electronics.

[reaction: see text] The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels-Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence.

Alkaloids↗