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At least 1,063 records · Page 59Linked to original sources
PubMed2005

Unique Michael addition-initiated domino reaction for the stereoselective synthesis of functionalized macrolactones from alpha-nitroketones in water.

[reaction: see text]. A unique domino reaction of alpha-nitrocycloalkanones with alpha-alkyl alpha,beta-unsaturated aldehydes in aqueous base was discovered, leading to the one-pot synthesis of hitherto unknown functionalized, bridged, bicyclic lactones containing 10-, 11-, 13-, and 15-membered rings. The structures of these heterocyclic compounds, containing also an unusual 6-hydroxy-1,2-oxazine ring, were determined by spectral and single-crystal X-ray diffraction studies.

Aldehydes↗
PubMed1978

Biochemical pharmacology of the intestinal flora.

Animal and bacteriological techniques have been developed for clarifying the role of the flora in the metabolism of drugs and other exogenous compounds. In general the flora tends to catalyze reductive and hydrolytic reactions, some of which reverse the detoxification reactions normally occurring in the liver. These reactions and others have been implicated in the pharamacological or toxicological action of exogenous compounds. Only in a few instances, however, have practical consequences of these reactions been documented. The major challenge at present is to develop methods capable of further defining the implications of reactions due to the flora.

Animals↗
PubMed2003

A nonsteroidal glucocorticoid receptor antagonist.

Selective intracellular receptor antagonists are used clinically to ameliorate hormone-dependent disease states. Patients with Cushing's syndrome have high levels of the glucocorticoid, cortisol, and suffer significant consequences from this overexposure. High levels of this hormone are also implicated in exacerbating diabetes and the stress response. Selectively inhibiting this hormone may have clinical benefit in these disease states. To this end, we have identified the first selective, nonsteroidal glucocorticoid receptor (GR) antagonist. This compound is characterized by a tri-aryl methane core chemical structure. This GR-specific antagonist binds with nanomolar affinity to the GR and has no detectable binding affinity for the highly related receptors for mineralocorticoids, androgens, estrogens, and progestins. We demonstrate that this antagonist inhibits glucocorticoid-mediated transcriptional regulation. This compound binds competitively with steroids, likely occupying a similar site within the ligand-binding domain. Once bound, however, the compound fails to induce critical conformational changes in the receptor necessary for agonist activity.

Animals↗
PubMed1983

Nitroaromatic carcinogens in diesel soot: a review of laboratory findings.

The automobile industry plans to increase production of diesel-powered passenger cars because diesel engines provide better fuel economy than conventional gasoline engines. Diesel engines, however, produce more soot, and increased use of diesel cars will result in more discharge of diesel soot into the atmosphere. Recently, a new class of chemicals, called nitroaromatic compounds, have been identified in chemical extracts of diesel soot. Some of these nitroaromatic compounds produce mutations when tested in in vitro bacterial and mammalian cell assays, and cancer when tested in animals. Here, we review the relevance of these new laboratory findings to current deliberations over emission standards for particles from diesel cars.

Carbon↗
PubMed1996

Disinfection by-products in the chlorination of organic nitrogen compounds: by-products from kynurenine.

Volatile by-products in the chlorination of 3 humic acids as naturally-occurring substances and 37 nitrogen compounds normally found in excrement were analyzed, and as result kynurenine, a urinary metabolite of tryptophan was found a suitable model compound for dichloroacetonitrile-forming precursors. Possible pathways for the formation of chlorination by-products from kynurenine were also proposed by identification and kinetic properties of by-products decomposed further from each product.

Chromatography, Gas↗
PubMed1993

Vasorelaxant mechanism of the new vasodilator, FK409.

To define the vasorelaxation mechanism of FK409, we examined the effect of the compound on vascular tension and cyclic nucleotide levels in isolated rat thoracic aorta contracted with norepinephrine, and on activities of guanylate cyclase and cyclic GMP phosphodiesterase prepared from rat or rabbit thoracic aorta. FK409 (1 x 10(-9) to 1 x 10(-6) M), like nitroglycerin (1 x 10(-9) to 1 x 10(-6) M), produced a potent vasorelaxant effect associated with an increase in cyclic GMP content of the tissue. There was no change in cyclic AMP levels. The vasorelaxant effect of FK409 was independent of the integrity of the endothelium, and was unaffected by L-NG-monomethylarginine (0.1 mM) or oxyhemoglobin (1 microM). On the other hand, FK409 (3.2 x 10(-7) M) activated soluble guanylate cyclase, and the activating effect was completely inhibited by oxyhemoglobin (10 nM). Cyclic GMP phosphodiesterase was unaffected by FK409 (1 x 10(-7) to 1 x 10(-5) M). Furthermore, in rat aortic soluble fraction FK409 (3 mM) was found to liberate nitric oxide (NO) which was evaluated spectrophotometrically after diazotization of sulfanilic acid and coupling with N-(1-naphthyl)-ethylenediamine. The liberation occurred even in the absence of L-cysteine (5 mM), in contrast to the case with nitroglycerin (3 mM). These results suggest that the vasorelaxant effect of FK409 is associated with an increase in intracellular cyclic GMP, and that the cyclic GMP accumulation is due to activation of soluble guanylate cyclase. The enzyme activation is probably due to NO released from the compound molecule in the vascular smooth muscle cells.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2004

Differences in the vascular selectivity and tolerance between the NO donor/beta-blocker PF9404C and nitroglycerin.

The vascular selectivity of PF9404C ((2'S),(2S)-3-isopropylamine,1-[4-(2,3-dinitroxy)propoxymethyl]-phenoxy-2'-propanol), a new beta-blocker with nitric oxide (NO)-donor and vasodilator properties, was studied in different rabbit arteries and veins. Phenylephrine (10(-6) M) or 35 mM K+ were used to pre-contract the arteries and veins prior to study the relaxant effects of PF9404C and nitroglycerin. The potency of both drugs to depress the phenylephrine-induced contraction was greater than that shown in the blockade of the K(+)-evoked contraction in most of the vessels studied, with the exception of the central ear artery. PF9404C exhibited about three-fold higher potency than nitroglycerin to relax the majority of the vessels studied, especially when they were contracted with K+, and showed a certain selectivity of action for the renal artery. PF9404C produced autotolerance but this effect was about 20-fold less pronounced than that observed with nitroglycerin. Cross-tolerance in those preparations pre-exposed to PF9404C that were relaxed later on with nitroglycerin was much greater than autotolerance. The tolerance for nitroglycerin was practically abolished in the presence of N-acetylcysteine. However, this was not the case for PF9404C. These results indicate that, although sharing the property of being NO donors, PF9404C and nitroglycerin show a different profile in causing vasodilation; furthermore, the tolerance to this effect is lesser for PF9404C and seems to be mediated by a mechanism different to that of nitrates. This makes PF9404C a nice pharmacological tool to further develop novel NO-donor compounds with a lesser degree of vascular tolerance than those now available.

Adrenergic beta-Antagonists↗
PubMed2001

Two intermediates in the synthesis of decahydroisoquinolines with NMDA and AMPA receptor antagonist activity.

In 6-methyl-N-(4-nitrobenzoyl)-5,6-dihydropyridin-2(1H)-one, C(13)H(12)N(2)O(4), (I), the piperidone ring is in a distorted half-chair conformation. In 8-methoxy-3-methyl-N-(4-nitrobenzoyl)-1,2,3,4,5,6,7,8-octahydroisoquinoline-1,6-dione, C(18)H(20)N(2)O(6), (II), the heterocyclic ring is in a slightly distorted half-boat conformation, while the other six-membered ring is in a distorted chair conformation. Compound (II) presents a strong intramolecular C-H...O hydrogen bond. In both (I) and (II), the molecules interact through C-H...O interactions.

Crystallography, X-Ray↗
PubMed2007

Effect of substituents at the 5-position of the pyridine ring of imidacloprid on insecticidal activity against Periplaneta americana.

The insecticidal activities of imidacloprid derivatives with a wide range of substituents at the 5-position on the pyridine ring against American cockroaches, Periplaneta americana (L.), were measured by injection with and without synergists propyl 2-propynyl phenylphosphonate and piperonyl butoxide. The log(1/MLD) value (MLD = minimal lethal dose in mol) without synergists was 7.96 for the methyl derivative, and the values were lower for other derivatives. Synergists enhanced the potencies of all the compounds tested. Considering these compounds and those with other substituents at this position, the region for maximum activity was predicted to be in the conjunction of the pyridyl 6-chlorine atom with a lipophilic small group in the 5-position.

Animals↗
PubMed2005

Ni(II)-Bis[(R,R)-N,N'-dibenzylcyclohexane-1,2-diamine]Br2 catalyzed enantioselective Michael additions of 1,3-dicarbonyl compounds to conjugated nitroalkenes.

A highly enantioselective Michael addition of 1,3-dicarbonyl compounds to nitroalkenes has been developed that employs a newly developed Ni(II)-(bis)diamine based catalyst. The reaction scope includes substituted and unsubstituted malonates, beta-ketoesters, and nitroalkenes bearing aromatic and aliphatic residues. Ease of synthesis of this complex is noteworthy.

Alkenes↗
PubMed2002

Structural features of azidopyridinyl neonicotinoid probes conferring high affinity and selectivity for mammalian alpha4beta2 and Drosophila nicotinic receptors.

The higher toxicity of neonicotinoid insecticides such as N-(6-chloropyridin-3-ylmethyl)-2-nitroiminoimidazolidine (imidacloprid) to insects than mammals is due in large part to target site specificity at the corresponding nicotinic acetylcholine receptors (nAChRs). We propose that neonicotinoids with a protonated N-unsubstituted imine or equivalent substituent recognize the anionic subsite of the mammalian alpha4beta2 nAChR whereas the negatively charged (delta(-)) tip of the neonicotinoid insecticides interacts with a putative cationic subsite of the insect nAChR. This hypothesis can be tested by using two photoaffinity probes that differ only in the N-unsubstituted imine vs negatively charged (delta(-)) tip. Synthesis methodology was developed for compounds combining three moieties: pyridin-3-ylmethyl or 6-chloropyridin-3-ylmethyl and their 4- and 5-azido analogues; imidazolidine, 4-imidazoline or 4-thiazoline; and N-unsubstituted imine, nitroimine, cyanoimine, or nitromethylene. Structure-activity studies compared displacement of [(3)H]nicotine binding in mammalian alpha4beta2 nAChR and [(3)H]imidacloprid binding in Drosophila nAChR. Preferred compounds are N-(5-azido-6-chloropyridin-3-ylmethyl) with 2-iminothiazoline for alpha4beta2 (K(i) = 0.47 nM) and with 2-nitroiminothiazoline or 2-nitromethyleneimidazolidine for Drosophila (K(i) = 0.72-3.9 nM).

Animals↗
PubMed1975

4-Nitrocatechol production from rho-nitrophenol by rat liver.

Time course studies of rho-nitroanisole O-demethylation revealed formaldehyde production in excess of rho-nitrophenol (PNP) and 4-nitrocatechol (NTC) formation by rat liver microsomes. This indicated that these products (PNP, NTC) were metabolised further. The hydroxylation reaction PNP yields NTC showed substrate and product inhibition and a requirement for reduced nicotinamide adenine dinucleotide phosphate and O2 and was localized in liver microsomes. It was strongly activated by ascorbic acid, cysteine, adenosine triphosphate or hydroxylamine in vitro and enhanced by phenobarbital treatment in vivo. Mercapturic derivatives were metabolized to the corresponding hydroxy compounds with the same speed as their parent compounds. Both PNP and NTC were metabolized to the corresponding glucuronide and sulfate conjugates. On the other hand, the PNP or NTC glucuronides and sulfates were metabolized with liver microsomes to PNP and NTC.

Adenosine Triphosphate↗
PubMedDate not supplied

A computer automated study of the structure-mutagenicity relationships of non-fused-ring nitroarenes and related compounds.

A quantitative structure-activity analysis of the mutagenicity of non-fused-ring nitroaromatic compounds is reported. The analysis is performed on the basis of substructural fragment descriptors according to a recently developed methodology acronymed CASE (computer automated structure evaluation). The compounds of the data base were reclassified as mutagens or nonmutagens n the basis of probabilistic considerations. The mutagenic potencies of these agents were calculated through a multivariate regression analysis using fragments as descriptors. A good correlation with experimental values is obtained.

Benzene Derivatives↗
PubMed1981

[Synthesis and in vitro antibacterial activity of N-methylnitrone and nitrovinyl derivatives of some N-substituted 2-chloroindol-3-carboxaldehydes].

N-methylnitrones and nitrovinyl derivatives from 1-substituted-2-chloroindol-3-carboxaldehydes were synthesized and evaluated for their in vitro antibacterial activity. Some nitrovinyl derivatives displayed good in vitro activity against Gram-positive bacteria; the compound (II e), 1-(o-chlorobenzyl)-2-chloro-3-(2-nitroethenyl)indole, was more active than nitrofurantoin against Staphylococcus aureus and Streptococcus pyogenes. Some structure-activity relationships are discussed.

Anti-Bacterial Agents↗
PubMed1975

Pharmacological studies on 1-nitro-9-alkyl acridine derivatives. II. Chronic action.

Encouraging results of preclinical pharmacologic analysis prompted the following study on the chronic action of 1-nitro-9-(diethylaminopropylamino)-acridine (compound C-410) and 1-nitro-9-(diethylaminoethylamino)-acridine (compound C-516). Neither compound had an appreciable effect on quantitative regeneration of peripheral formed blood elements. Liver and kidney function tests were not significantly affectd. Histopathologic studies showed involutive changes in the lymphatic tissues and slight degenerative lesions in parenchymal organs and nuclei. However, these changes were not severe enough to cause functional disturbances or to impair reproductivity.

Acridines↗