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PubMed2005

Stereocontrolled synthesis of a complex library via elaboration of angular epoxyquinol scaffolds.

We have accomplished the synthesis of a complex chemical library via elaboration of angular epoxyquinol scaffolds with distinct skeletal frameworks. The key strategy involves highly stereocontrolled [4 + 2] Diels-Alder cycloadditions of chiral, nonracemic epoxyquinol dienes to generate the scaffolds. Further scaffold diversification involves hydrogenation, epimerization, dehydration, and condensation of the carbonyl group with alkoxyamine and carbazate building blocks. Further elaboration of the scaffolds also provided new skeletal frameworks using hydroxyl-directed Diels-Alder cycloaddition and reductive N-N bond cleavage. The overall process afforded 244 highly complex and functionalized compounds. Preliminary biological screening of the library uncovered six compounds which showed significant inhibition of Hsp 72 induction.

Drug Evaluation, Preclinical↗
PubMed2003

New oxidative tools for the functionalization of the cephalostatin north 1 hemisphere.

Dimethyldioxirane (DMDO) C-H oxidation of ketone 17 to hemiketal 18 (82%), bis-dehydration to vinyl ether 21 (77%), and DMDO again provides C-23 axial alcohol 23 (99%). Routine processing, including a double-stereoselective Sharpless AD reaction (de >98%), gives alcohols 7 and 32. C-23 deoxy substrate 7 undergoes Suarez hypoiodite oxidative cyclization to (natural) beta spiroketal 34, but compound 32, bearing a C-23 silyl ether, generates unnatural spiroketal 33. [reaction: see text]

Cyclization↗
PubMed1990

Structure determination of adducts from the reaction of (R)-glycidaldehyde and guanosine.

The structures of the initial adducts formed in the reactions of guanosine or deoxyguanosine with (R)-glycidaldehyde have been determined and compared with those obtained from racemic glycidaldehyde. A new stable adduct has also been identified which is a potential biomarker for glycidaldehyde interactions with DNA. Mechanisms are proposed to account for the formation of all the observed products. The results provide information on the molecular basis for the genotoxicity of glycidaldehyde and compounds which generate this reactive aldehyde in vivo.

Aldehydes↗
PubMed1975

Comparison of the cellular DNA-bound products of benzo(alpha)pyrene with the products formed by the reaction of benzo(alpha)pyrene-4,5-oxide with DNA.

DNA isolated from mouse embryo cell cultures that had been treated with [3H]benzo(alpha)pyrene was degraded with enzymes to deoxyribonucleosides, and the hydrocarbon-deoxyribonucleoside products were isolated by chromatography on a Sephadex LH20 column eluted with a water: methanol gradient. The hydrocarbon-deoxyribonucleoside products were not identical to those found in similar chromatograms of enzyme digests of DNA that had been reacted with benzo(alpha)pyrene-4,5-oxide in aqueous ethanol solution. This finding suggests that the metabolic activation of benzo(alpha)pyrene that results in this hydrocarbon becoming covalently bound to DNA in mouse embryo cells in culture may be more complex than simply formation of a K-region epoxide and reaction of that compound with the cellular DNA.

Animals↗
PubMed2005

Individual and combined effects of dosages of azoxystrobin and epoxiconazole in wheat.

The effects of single fungicide applications on Mycosphaerella graminicola (septoria leaf blotch) control and winter wheat yield were evaluated in field trials conducted in central Belgium between 2000 and 2004. Individual applications of 25, 50, 75 and 100% of the manufacturer's recommended dose rates of azoxystrobin and epoxiconazole, and all the combinations of these treatments, were made at GS 39 in 2001 to 2004 and at GS 59 in 2000. Disease assessments were made at growth stage 75, some 7-8 weeks after the last applications. Between 2000 and 2003, no significant difference was observed for disease control between the products when applied alone. With regard to the dose responses, the differences between the recommended dose rates and the 50% reduced dosages were not important. In 2004, azoxystrobin was less effective than epoxiconazole. This was probably the result of strobilurin-resistant isolates of M. graminicola reaching an occurrence of 32% before fungicide application. The combination of different dosages of azoxystrobin and epoxiconazole revealed that there was very little synergy between these products when applied in a single application. The combinations of these products were better than individual applications only when high dosages of both compounds were used.

Ascomycota↗
PubMed2003

Effects of sevelamer hydrochloride and calcium acetate on the oral bioavailability of ciprofloxacin.

BACKGROUND: The oral bioavailability of ciprofloxacin is significantly decreased when administered with calcium carbonate. Sevelamer hydrochloride is a phosphate-binding cationic polymer that is devoid of calcium. The authors conducted a 3-way, randomized, crossover study to determine the effects of sevelamer hydrochloride and calcium acetate on the relative oral bioavailability of ciprofloxacin. METHODS: Fifteen healthy volunteers were assigned randomly to receive each of the following oral regimens: ciprofloxacin 750 mg, alone (Arm A); ciprofloxacin 750 mg plus 7 sevelamer hydrochloride 403 mg capsules (Arm B); ciprofloxacin 750 mg plus 4 calcium acetate 667 mg tablets (Arm C). Serial blood and urine samples were obtained over 24 hours, and ciprofloxacin concentrations were determined by high-performance liquid chromatography. Pharmacokinetic data were analyzed using noncompartmental methods, and maximum serum concentration (Cmax) and area under the serum concentration time curve from 0 to infinity (AUC(0- infinity )) were tested for bioequivalence after log transformation of the data. The relative oral bioavailability of ciprofloxacin was calculated as AUC(0- infinity ), Arm B or Arm C/AUC(0- infinity ), Arm A. RESULTS: The Cmax and AUC(0- infinity ) of ciprofloxacin were significantly decreased when administered concomitantly with sevelamer hydrochloride or calcium acetate (P < 0.05), and bioequivalence was not achieved for either parameter. The relative oral bioavailability of ciprofloxacin was decreased by 48% with sevelamer hydrochloride and 51% with calcium acetate (P < 0.05). CONCLUSION: The relative oral bioavailability of ciprofloxacin is significantly decreased when administered with sevelamer hydrochloride or calcium acetate. Concomitant administration of these drugs may decrease clinical efficacy and promote bacterial resistance to ciprofloxacin.

Acetates↗
PubMed1991

Structure-activity relationships of epoxides: induction of sister-chromatid exchanges in Chinese hamster V79 cells.

Analysis of SCE frequencies in Chinese hamster V79 cells was used to investigate structure-activity relationships of epoxides in mammalian cells. For this purpose the SCE-inducing potency of 58 epoxides was determined. Of these, 16 failed to induce SCE in V79 cells. According to the substitution of the oxirane ring the results show general agreement with results obtained in the Ames test. Mono-substituted epoxides had the highest genotoxic potency compared to di- and tri-substituted epoxides. In detail, there are differences in genotoxic potency between bacteria and mammalian cells which can be explained by differences in the cellular uptake of the compounds and by detoxification reactions.

Animals↗
PubMed1987

Synthesis and bacterial mutagenicity of the cyclopenta oxides of the four cyclopenta-fused isomers of benzanthracene.

Many polycyclic aromatic hydrocarbons containing peripherally fused cyclopenta rings are believed to be activated primarily by epoxidation of the cyclopenta ring. The cyclopenta epoxides of a series of four cyclopenta benzanthracene derivatives, benz[e]aceanthrylene-5,6-oxide, benz[j]aceanthrylene-1,2-oxide, benz[l]aceanthrylene-1,2-oxide and benz[k]acephenaceanthrylene-4,5-oxide were synthesized from their parent hydrocarbons by formation of the bromohydrin followed by dehydrobromination, and characterized by u.v.-vis, and 1H n.m.r. spectroscopy and mass spectrometry. The mutagenicity of these compounds was investigated in the Ames plate incorporation assay with Salmonella typhimurium strain TA98. All the oxides were active without exogenous metabolic activation (170-320 His+ revertants per nanomole) and also toxic above 0.5 microgram/plate. Addition of S9 protein did not increase, and generally decreased, the mutagenicity of the oxides, while toxicity was largely unchanged. These results are consistent with the postulated role of cyclopenta oxides as major contributors to the mutagenicity of the parent compounds in the Ames assay.

Animals↗
PubMed1979

Gas-liquid chromatography of digitoxigenin and digoxigenin as acetates of their epoxygeninic acid methyl esters.

Gas chromatographic analysis of ditigoxigenin and digoxigenin, the genins of the cardenolide glycosides digitoxin and digoxin, cannot be done without derivatization. However, during the derivatization, side-reactions often present serious problems. A procedure has been found for transforming digitoxigenin and digoxigenin into the corresponding acetates of their epoxygeninic acid methyl esters, which are stable compounds and suitable for gas chromatographic analysis.

Acetates↗
PubMed2004

[Front line of management of hyperphosphatemia in hemodialysis patients].

Management of hyperphosphatemia in hemodialysis patients is very important to prevent progress of renal hyperparathyroidism or ectopic calcification. Sevelamer hydrochloride is a Ca and Al free phosphate binder, and reduces serum phosphorus level, without any influence on serum Ca level, and Ca-P products. This compound is expected to reduce the incidence of arterial calcification, and improve the QOL (quality of life) of hemodialysis patients.

Calcinosis↗
PubMed1993

[The applicability of a new stable fluorescence reagent CGE (N) for TLC measurements and spectrofluorimetry].

A new stable fluorescent reagent, CGE (N), was designed and synthesized in our laboratory. This paper presents the results of using it to detect a compound having aminogroup. Glycine as an example was derived by using CGE (N), the best condition of derivatisation reaction was pH8, T 50 +/- 1 degree C, and time 3-5 h. Spread agent was CHCl3: CH3OH:CH3COOC2H5: iceHAc (1:3:5:1). Rf of glycine-CGE (N) was 0.45, of which fluorescent spectrum Em was 356nm (at Ex = 277nm). The correlation coefficient between the fluorescent scanning area and quantity was over 0.99, the linear relation retained for 24 h, the detection limit 0.24 microgram, and the linear range 0.24-19.2 micrograms. The data revealed that stability, sensitivity and reproducibility were good. These indicate that CGE(N) is a fine fluorescent reagent for compounds having primary amino-group and this method is reliable.

Chromatography, Thin Layer↗
PubMed1992

Covalent modification and active site-directed inactivation of a low molecular weight phosphotyrosyl protein phosphatase.

Covalent modification experiments were conducted in order to identify active site residues of the 18-kDa cytoplasmic phosphotyrosyl protein phosphatases. The enzyme was inactivated by diethyl pyrocarbonate, phenylglyoxal, cyclohexanedione, iodoacetate, iodoacetamide, phenylarsine oxide, and certain epoxides in a manner consistent with the modification of active site residues. Phenylglyoxal and cyclohexanedione both bind to the active site in a rapid preequilibrium process and thus act as active site-directed inhibitors. The pH dependencies of the inactivation by iodoacetate and by iodoacetamide were examined in detail and compared with rate data for the alkylation of glutathione as a model compound. The enzyme inactivation data permitted the determination of pKa values of two reactive cysteines at or near the active site. Although phosphomycin is simply a competitive inhibitor of the enzyme, it was found that 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) and (R)- and (S)-benzylglycidol act as irreversible covalent inactivators, consistent with the importance of a hydrophobic moiety on the substrate in controlling substrate specificity. EPNP exhibits characteristics of an active site-directed inactivator, with a preequilibrium binding constant somewhat smaller than that of phosphate ion. The pH dependencies of inactivation of EPNP and (S)-benzylglycidol are identical to that observed for iodoacetamide and similar to that for iodoacetate, suggesting that they modify similar groups. Sequencing of the tryptic digests of the EPNP-labeled enzyme indicates that Cys-62 and Cys-145 are labeled. Phenylarsine oxide acts as a very slow, tight-binding inhibitor of the enzyme. The results are interpreted in terms of an active site model that incorporates a histidine-cysteine ion pair, similar to that present in papain.

Animals↗
PubMed1999

Triptolide is more effective in preventing T cell proliferation and interferon-gamma production than is FK506.

The Chinese traditional herb Tripterygium wilfordii Hook. F (TWHF) has been reported to be effective in the treatment of a variety of autoimmune disorders. The major active component of this herb is triptolide and most of the efficacy of this herb immunosuppression is attributed to triptolide. FK506 is also a potent immunosuppressive agent and is currently being used clinically. The present studies compare the effectiveness of triptolide and FK506 to suppress certain human T cell functions. Specifically human T cell proliferation, IL-2 and IFNgamma were compared. The results show that, overall, triptolide is more effective at inhibiting T cell proliferation and IFNgamma production than FK506 and the two compounds inhibit IL-2 production in an equivalent manner.

Cells, Cultured↗
PubMed1980

Relationship between structure, positive inotropic potency and lethal dose of grayanotoxins in guinea pig.

Relationship between chemical structure, positive inotropic potency and lethal dose of grayanotoxins and the related compounds was studied using guinea pigs. The positive inotropic effect (PIE) was examined in their papillary muscle isolated from the heart. The potency of these compounds was expressed by pD2 values, and was determined by depicting the concentration-PIE curve for each compound. The study has clarified the contribution of functional groups in the molecule; the presence of 3 beta-hydroxyl, 6 beta-hydroxyl and 10 beta-methyl groups attached to the grayanane skeleton is established to be essential for the development of PIE. The inotropic potency of compounds carrying these essential groups is increased by a 10 alpha-hydroxyl group and the acylation of the 14 beta-hydroxyl group. LD50 value of 10 compounds with a high cardiotonic potency (pD2 greater than 4) was determined by up and down method using male guinea pigs. The relation of LD50 to pD2 bore a significant correlation (r = 0.68, p less than 0.05). The most cardiotropic and toxic compound found in this study was asebotoxin III.

Animals↗
PubMed1981

Alkylating properties and genetic activity of 4-vinylcyclohexene metabolites and structurally related epoxides.

The mutagenicity of the epoxides 4-vinyl-1,2-epoxycyclohexane, 4-epoxyethyl-1,2-epoxycyclohexane, 4-epoxyethyl-1,2-dihydroxycyclohexane, 1,2-epoxycyclohexane and styrene oxide was assayed on the TA100 strain of S. typhimurium and V79 Chinese hamster cells. In the latter cell system, both point mutation (6-thioguanine resistance) and chromosomal damage (anaphase bridges and micronuclei) were scored. Genetic effects were related to the alkylating properties of the epoxides. For this purpose, alkylation of 4-(p-nitrobenzyl)pyridine (NBP) and sodium-p-nitrothiophenolate (NTP) was measured and values for the substrate constant (s) were calculated. 4-Epoxyethyl-1,2-epoxycyclohexane, 1,2-epoxycyclohexane and styrene oxide, characterized by the highest reactivity toward NBP and by an s value in the vicinity of 1, were mutagenic in all test systems. 4-Vinyl-1,2-epoxycyclohexane and 4-epoxyethyl-1,2-dihydroxycyclohexane, characterized by lower NBP reactivity and higher s value (1.30-1.38), did not induce reversion in S. typhimurium or 6-thioguanine-resistant mutants in V79 cells, but were as effective as the 3 other compounds in the induction of chromosomal damage.

Animals↗
PubMed2005

Enantioselective approaches to potential MetAP-2 reversible inhibitors.

[reaction: see text] Enantioselective deprotonation of 4-substituted cyclohexanones and highly stereoselective conjugate addition of higher order mixed cuprates were the key steps in a concise synthesis of fumagalone-related molecules. The origin of the (low) biological activity of the new compounds as compared to fumagalone is briefly discussed.

Aminopeptidases↗
PubMed2004

Syntheses of the C(1-6) and C(19-24) fragments of lituarines A, B, and C.

[structure: see text] Lituarines A-C are marine natural products comprising a tricyclic spiroacetal bridged at C(8) and C(18) by a functionalized ester linkage conceptually obtained from a C(19-24) alcohol and a C(1-6) carboxylic acid whose oxidation level varies at C(4) and C(5). Stereoselective routes are described to compounds 26 and 27, fully functionalized ester fragments of lituarine A and lituarines B and C, respectively.

Epoxy Compounds↗
PubMed1999

Identification and characterization of estrogen-like components in commercial resin-based dental restorative materials.

Recently, resin-based dental restorative materials have been targeted as potential sources of xenoestrogens, specifically bisphenol A (BPA) and bisphenol A dimethacrylate (BAD), which could contribute to overall estrogen load and result in deleterious side effects. The present study used high-pressure liquid chromatography (HPLC) to analyze twenty-eight different commercially available dental resins for the presence of BPA and/or BAD. In addition, sublines of the MCF-7 human breast tumor cell line were cultured in the presence of eluates from eleven of the dental resins and assessed for proliferative responses using the sulforhodamine B assay. Only one resin, Delton II, had detectable levels of BPA or BAD that could be verified by Fourier transform infrared spectrometry. Likewise, eluates from Delton II were the only samples that elicited a significant proliferative response in two of the MCF-7 sublines tested. Therefore, we conclude that dental resins in general do not represent a significant source of BPA or BAD exposure.

Benzhydryl Compounds↗