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PubMed2005

Guest-induced supramolecular isomerism in inclusion complexes of T-shaped host 4,4-bis(4'-hydroxyphenyl)cyclohexanone.

The T-shaped host molecule 4,4-bis(4'-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol group and a cyclohexanone group along the arms and an axial phenol ring as the stem. The equatorial phenyl ring adopts a "shut" or "open" conformation, like a windowpane, depending on the size of the guest (phenol or o/m-cresol), for the rectangular voids of the hydrogen-bonded ladder host framework. The adaptable cavity of host 1 expands to 11x15-18 A through the inclusion of water with the larger cresol and halophenol guests (o-cresol, m-cresol, o-chlorophenol, and m-bromophenol) compared with a size of 10x13 A for phenol and aniline inclusion. The ladder host framework of 1 is chiral (P2(1)) with phenol, whereas the inclusion of isosteric o- and m-fluorophenol results in a novel polar brick-wall assembly (7x11 A voids) as a result of auxiliary C-H...F interactions. The conformational flexibility of strong O-H...O hydrogen-bonding groups (host 1, phenol guest), the role of guest size (phenol versus cresol), and weak but specific intermolecular interactions (herringbone T-motif, C-H...F interactions) drive the crystallization of T-host 1 towards 1D ladder and 2D brick-wall structures, that is, supramolecular isomerism. Host 1 exhibits selectivity for the inclusion of aniline in preference to phenol as confirmed by X-ray diffraction, 1H NMR spectroscopy, and thermogravimetry-infrared (TG-IR) analysis. The T(onset) value (140 degrees C) of aniline in the TGA is higher than those of phenol and the higher-boiling cresol guests (T(onset)=90-110 degrees C) because the former structure has more O-H...N/N-H...O hydrogen bonds than the clathrate of 1 with phenol which has O-H...O hydrogen bonds. Guest-binding selectivity for same-sized phenol/aniline molecules as a result of differences in hydrogen-bonding motifs is a notable property of host 1. Host-guest clathrates of 1 provide an example of spontaneous chirality evolution during crystallization and a two-in-one host-guest crystal (phenol and aniline), and show how weak C-H...F interactions (o- and m-fluorophenol) can change the molecular arrangement in strongly hydrogen-bonded crystal structures.

Crystallography, X-Ray↗
PubMed1984

Assessment of the cataractogenic potential of cyclohexanone in guinea pigs and rabbits.

The cataractogenic potential of cyclohexanone administered intravenously (0.5 and 5.0 mg/kg) and percutaneously (0.5 ml) was assessed in guinea pigs and rabbits. The negative control article was 0.9% sodium chloride. Positive control articles for guinea pigs were iv galactose and percutaneous dimethyl sulfoxide (DMSO), and for rabbits, iv poly(I) X poly(C) and percutaneous DMSO. An untreated group of guinea pigs was used as a sham control. Animals were treated three times a week for 3 consecutive weeks. Ophthalmic examinations performed monthly for 6 months for treated animals and 7 months for untreated animals revealed the presence of anterior subcapsular vacuoles in guinea pigs in all groups. These lesions consisted of swollen lens fibers that progressed to fiber disruption and protein liquefaction. There was no statistical difference in the incidence and severity of the lesions among treatment groups. No lenticular alterations were noted in any of the rabbits treated with cyclohexanone or any other chemical. It was concluded that these alterations are, apparently, an inherent characteristic of the guinea pig, making that animal an unsuitable model for the assessment of cataractogenic potential of xenobiotics.

Administration, Topical↗
PubMed2006

New bioorganic reagents: evolved cyclohexanone monooxygenase--why is it more selective?

Four mutants of the cyclohexanone monooxygenase (CHMO) evolved as catalysts for Baeyer-Villiger oxidation of 4-hydroxycyclohexanone were investigated as catalysts for a variety of 4-substituted and 4,4-disubstituted cyclohexanones. Several excellent catalytic matches (mutant/substrate) were identified. The most important, however, is the finding that, in a number of cases, a mutant with a single exchange, Phe432Ser, was shown to be as robust and more selective as a catalyst than the wild-type CHMO. All biotransformations were performed on a laboratory scale, allowing full characterization of the products. The absolute configurations of two products were established. A model suggesting a possible role of the 432 serine residue in enantioselectivity control is proposed.

Amino Acid Substitution↗
PubMed1993

Metabolic interaction of ethanol and cyclohexanone in rabbits.

The interaction of ethanol (EtOH) and cyclohexanone (CHN) metabolism was studied to demonstrate the influence of alcohol beverage in cyclohexanone poisoning. Rabbits were administered CHN and EtOH separately or together, and the plasma concentration of CHN and cyclohexanol (CHL), a metabolite of CHN, and blood concentrations of EtOH were measured at various times. When CHN alone was administered orally, the time to maximum plasma concentration (Tmax) of CHN was as short as 15 min, but that of CHL was 120 min. The short Tmax of CHN was considered to be due to the first-pass effect. The plasma concentration of CHL was much greater than that of CHN. On the other hand, when the same amount of molar CHL was administered in rabbits for sake of comparison, only small amounts of CHN were detected in plasma. The interconversion between CHN and CHL at the time of equilibration tended to shift predominantly toward the formation of CHL, whose plasma concentration ratio was about 1:6 to 1:8. The coadministration of EtOH decreased the plasma concentration of CHN and increased that of CHL more than the administration of CHN alone. The blood concentration of EtOH was also decreased with the coadministration of CHN. The coadministration of EtOH with CHN demonstrated an acceleration in the metabolism of both CHN and EtOH, which may be due to an increase in the concentrations of the alcohol dehydrogenase-NADH and -NAD complexes.

Administration, Oral↗
PubMed2001

Stereoselective reactions. XXXIV. Enantioselective deprotonation of prochiral 4-substituted cyclohexanones using chiral bidentate lithium amides having a bulky group instead of a phenyl group on the chiral carbon.

Using chiral bidentate lithium amides having a bulky group instead of a phenyl group on the chiral carbon, enantioselective deprotonation of prochiral 4-substituted cyclohexanones in the presence of excess trimethylsilyl chloride was examined in THF in the absence and in the presence of HMPA. It is shown that enantioselectivity of the reactions decreases as the substituent on the chiral carbon of the chiral lithium amides and the substituent at the 4-position of cyclohexanones become reasonably bulky. An eight-membered cyclic transition state model is proposed for this deprotonation reaction.

Cyclohexanones↗
PubMed1984

Cyclohexanone extraction: an improvement in the thiobarbituric acid method for the determination of nonenzymatic glycosylation of hair and epidermal keratin.

Colorimetric techniques such as the thiobarbituric acid assay are widely used for the determination of nonenzymatic glycosylation of proteins. One of the major problems associated with this technique is the high nonspecific background absorbance which, due to its variability, results in loss of sensitivity. This report describes a method of removing the nonspecific absorbance by extracting the final chromogen into cyclohexanone. Using this method for the determination of nonenzymatic glycosylation of hair and epidermal keratin, at least 90% of the background absorbance is removed, increasing the sensitivity of the technique. This allows more effective discrimination of the level of glycolsylation of proteins from control and diabetic patients, by reducing the degree of overlap. The requirement for individual borohydride reduced samples is also avoided, thus simplifying the technique. Cyclohexanone extraction provides a simple addition to the standard thiobarbituric acid technique with significant improvement in results.

Aged↗
PubMed2004

[Antimicrobial activity of new original 2-aryliden-6-furfuryliden cyclohexanones and hexahydroindazoles on their basis].

Antimicrobial activity of 25 new original 2-aryliden-6-furfuryliden cyclohexanones and hexahydroindazoles based on them was studied. The majority of the compounds had low or moderate activity against the test cultures of Staphylococcus spp., Pseudomonas aeruginosa, Proteus spp. and Escherichia coil. Compound XIX (2,3-diphenyl-7-(5-nitrofurfuryliden)-3,3a,4,5,6,7-hexahydroindazole) with high antistaphylococcal activity was selected among several 2-aryliden-6-furfuryliden cyclohexanones and hexahydroindazoles. The activity of compound XIX was tested with the use of 105 clinical isolates of staphylococci. Comparative antistaphylococcal activity of compound XIX, furazolidone and sodium cefotaxime against the isolates was estimated. The impact of the microbial load, pH of the nutrient medium and the presence of 1%, 5% or 10% of serum or blood in the medium on the antimicrobial activity of compound XIX was evaluated. The results are in favour of further research on compound XIX as a potential agent of etiotropic therapy for staphylococcal infection.

Anti-Bacterial Agents↗
PubMedDate not supplied

Metabolism and disposition of cyclohexanone oxime in male F-344 rats.

Cyclohexanone oxime (CHOX), an intermediate used in the synthesis of Polycaprolactam/Nylon, was found to be rapidly absorbed and cleared from the body within 24 hours after a single oral administration of 1, 10 and 30 mg/kg of [14C]-CHOX to the adult male Fischer rats. The majority of the CHOX derived radioactivity (65-90% of the dose) was excreted in the urine. Elimination in the feces accounted for 5-10% of the dose and very low levels of radioactivity (2-3%) were retained in the tissues 24 hours after exposure. After iv administration of 1 mg/kg of [14C]-CHOX, the oxime was rapidly cleared from plasma with half-lives of 1.6 (alpha phase) and 18.2 min (beta phase). However, when CHOX was applied dermally (30 mg/kg), only about 4-5% of the dose was recovered in urine, feces and the tissues. The majority of the dose volatilized from the skin surface. However, the absorbed oxime was readily distributed and excreted, and its metabolic fate was no different than observed after oral administrations. HPLC analysis of urine showed that the majority of the radioactivity excreted was in the form of three metabolites, cyclohexylglucuronide and the monoglucuronides of cis- and trans-cyclohexane-1,2-diol. In vitro studies showed that these metabolites arise primarily by hydrolysis of the oxime to cyclohexanone which is then reduced to cyclohexanol and eliminated as the glucuronide conjugate. The cyclohexanol, in turn could be metabolized to cis- and trans-cyclohexane-1,2-diols, which excreted as their monoglucuronides.

Administration, Oral↗
PubMed1990

Urinary excretion of cyclohexanediol, a metabolite of the solvent cyclohexanone, by infants in a special care unit.

Using gas chromatography-mass spectrometry, we investigated the urinary excretion of organic acids of 278 newborn babies in a special care unit to obtain reference data and monitor metabolism. In 101 of 584 urine samples analyzed, we found isomers of cyclohexanediol. trans-1,2-Cyclohexanediol was always most abundant, with small amounts of 1,3- and 1,4-cyclohexanediol and, sometimes, traces of cis-1,2-cyclohexanediol. Glucuronide conjugates were not detected. The probable source was the solvent cyclohexanone, which was found as a contaminant of intravenous dextrose and the parenteral feeding solution, and was also leached into the infusion fluids from the administration set. We recovered 0.89 mg (range 0.74-0.98 mg, n = 5) of cyclohexanone from 150 mL of dextrose pumped through the infusion apparatus over 24 h, the normal rate for a 1-kg premature baby. Although this is well below toxic doses reported for mature animals, more data are needed for the newborn, particularly preterm infants who have a decreased capacity for glucuronide conjugation.

Cyclohexanes↗
PubMed1988

Effect of cyclohexanone derivatives on percutaneous absorption of ketoprofen and indomethacin.

The promoting effect of cyclohexanone derivatives on the percutaneous absorption of ketoprofen and indomethacin from gel ointments was investigated in rats. Drug absorption was markedly enhanced by the addition of 2-tert-butylcyclohexanone. Promoting activities of 2,6-dimethyl and 4-tert-butylcyclohexanone were also observed, but their effects were significantly lower than that of the 2-tert-butyl derivative. The effect of side chain length at the 2-position of the cyclohexanone ring on the percutaneous absorption of these drugs was determined similarly using a series of 2-n-alkylcyclohexanones. Pronounced effects were observed in the case of 2-n-octylcyclohexanone, suggesting that a chain length of eight carbons is an important factor for absorption enhancement in this series. The extent of absorption enhancement was found to be an almost linear function of 2-n-octycyclohexanone concentrations in the range from 0 to 10%.

Administration, Cutaneous↗
PubMed2002

Use of isolated cyclohexanone monooxygenase from recombinant Escherichia coli as a biocatalyst for Baeyer-Villiger and sulfide oxidations.

The performance, in Baeyer-Villiger and heteroatom oxidations, of a partially purified preparation of cyclohexanone monooxygenase obtained from an Escherichia coli strain in which the gene of the enzyme was cloned and overexpressed was investigated. As model reactions, the oxidations of racemic bicyclo[3.2.0]hept-2-en-6-one into two regioisomeric lactones and of methyl phenyl sulphide into the corresponding (R)-sulphoxide were used. Enzyme stability and reuse, substrate and product inhibition, product removal, and cofactor recycling were evaluated. Of the various NADPH regeneration systems tested, 2-propanol/alcohol dehydrogenase from Thermoanerobium brockii appeared the most suitable because of the low cost of the second substrate and the high regeneration rate. Concerning enzyme stability, kosmotropic salts were the only additives able to improve it (e.g., half-life from 1 day in diluted buffer to 1 week in 1 M sodium sulphate) but only under storage conditions. Instead, significant stabilization under working conditions was obtained by immobilization on Eupergit C (half-life approximately 2.5 days), a procedure that made it possible to reuse the catalyst up to 16 times with complete substrate (5 g x L(-1)) conversion at each cycle. Reuse of free enzyme was also achieved in a membrane reactor but with lower efficiency. Water-organic solvent biphasic systems, which would overcome substrate inhibition and remove from the aqueous phase, where reaction takes place, the formed product, were unsuccessful because of their destabilizing effect on cyclohexanone monooxygenase. More satisfactory was continuous substrate feeding, which shortened reaction times and, very importantly, yielded in the case of bicyclo[3.2.0]hept-2-en-6-one (10 g x L(-1)) both lactone products with high optical purity (enantiomeric excess > or = 96%), which was not the case when all of the substrate was added in a single batch.

Alcohol Dehydrogenase↗
PubMed2003

Critical role of histidine residues in cyclohexanone monooxygenase expression, cofactor binding and catalysis.

Cyclohexanone monooxygenase (CMO) is a member of the flavin monooxygenase superfamily of enzymes that catalyze both nucleophilic and electrophilic reactions involving a common C4a hydroperoxide intermediate. To begin to probe structure-function relationships for these enzymes, we investigated the roles of histidine residues in CMO derived from Acinetobacter NCIB 9871, with particular emphasis on the wholly conserved residue, His163 (H163). CMO activity was readily inactivated by diethyl pyrocarbonate (DEPC), a selective chemical modifier of histidine residues. Each of the seven histidines in CMO was then individually mutated to glutamine and the mutants expressed and purified from Escherichia coli. Only the H59Q mutant failed to express at significant levels. The H96Q enzyme was found to have a greatly reduced flavin adenine dinucleotide (FAD) content, indicative of compromised cofactor retention. The only significant effect on kcat occurred with the H163Q mutant, which exhibited an approximately 10-fold lower turnover of the prototypical substrate, cyclohexanone. This was accompanied by a doubling in the Km [NADPH] compared to the wild-type enzyme, suggesting that the functional decrement in H163Q is probably not solely a reflection of impaired NADPH binding. These data establish a critical role for H163 in CMO catalysis and prompt the hypothesis that this conserved residue plays a similarly important functional role across the flavin monooxygenase family of enzymes.

Acinetobacter↗
PubMed2002

Manifestation of stereoelectronic effects on the calculated carbon-hydrogen bond lengths and one bond (1)J(C-H) NMR coupling constants in cyclohexane, six-membered heterocycles, and cyclohexanone derivatives.

Cyclohexane (1), oxygen-, sulfur-, and/or nitrogen-containing six-membered heterocycles 2-5, cyclohexanone (6), and cyclohexanone derivatives 7-16 were studied theoretically [B3LYP/6-31G(d,p) and PP/IGLO-III//B3LYP/6-31G(d,p) methods] to determine the structural (in particular C-H bond distances) and spectroscopic (specifically, one bond (1)J(C-H) NMR coupling constants) consequences of stereoelectronic hyperconjugative effects. The results confirm the importance of n(X) --> sigma*(C-H)(app) (where X = O, N), sigma(C-H)(ax) --> pi*(C=O), sigma(S-C) --> sigma*(C-H)(app), sigma(C-S)-->sigma*(C-H)(app), beta-n(O) --> sigma*(C-H), and sigma(C-H) --> sigma*(C-H)(app) hyperconjugation, as advanced in previous theoretical models. Calculated r(C-H) bond lengths and (1)J(C-H) coupling constants for C-H bonds participating in more than one hyperconjugative interaction show additivity of the effects.

Journal Article↗
PubMed2003

Remarkable effect of pore size on the catalytic activity of mesoporous silica for the acetalization of cyclohexanone with methanol.

The catalytic activity of mesoporous silica (MCM-41) for the acetalization of cyclohexanone shows a volcano-shaped dependence on the pore diameter. The diameter of the cyclohexanone molecule is ca. 0.75 nm, while its acetalization with methanol was well accelerated on MCM-41 with a pore diameter of approximately 1.9 nm, and smaller or larger pores were not suitable for the catalysis. The catalytic activity was independent of the Al concentration.

Journal Article↗
PubMed2001

Self-association and stereochemistry study of 2-methylthio-, 2-dimethylaminocyclohexanone oximes and the parent cyclohexanone oxime.

X-ray diffraction analyses of 2-substituted cyclohexanone oximes C5H9(X)C=NOH [X = SMe (1), NMe2 (2)] and of the parent compound [X = H (3)] showed that their cyclohexyl rings are in a slightly distorted chair conformation. These compounds assume in the solid state the (E) configuration bearing the 2-substituents in the axial conformation. Compounds (1) and (2) exist as dimeric and polymeric hydrogen-bond associates, respectively. Low-temperature X-ray analysis of the cyclohexanone oxime (3) showed that the molecules are associated forming two independent trimers. The dimer in (1) and the trimer in (3) are built up via [O-H...N=C] hydrogen bonds, while the polymer of (2) is via the [OH...NMe2] hydrogen bond. The comparative IR nu(OH) and nu(C=N) analysis of the title compounds, in the solid state and in CCl4 solution, fully supports the nature of the associates for (1)-(3) obtained by X-ray diffraction. The IR azomethyne frequency shift analysis (Deltanu(C=N)) also suggests the occurrence of the pi(C=N)/sigma*(C-X) orbital interaction which stabilizes the axial conformations of (1) and (2).

Journal Article↗
PubMed1976

Evaluation of 2-benzylidenecyclohexanones and 2,6-bis(benzylidene)cyclohexanones for antitumor and cytotoxic activity and as inhibitors of mitochondrial function in yeast: metabolism studies of (E)-2-benzylidenecyclohexanone.

Some 2-benzylidenecyclohexanones, 2,6-bis(benzylidene)cyclohexanones, and related compounds were evaluated for antitumor and cytotoxic activities; (E)-2-benzylidenecyclohexanone (Ia) was shown to have significant cytotoxic properties and a potent inhibitory effect on yeast mitochondria. After intraperitoneal injection of Ia, unchanged drug and a metabolite, tentatively identified as 2-(p-hydroxybenzyl)cyclohexanol, were found in the urine. No metabolites were found in the feces. Oral administration of Ia afforded three unidentified metabolites in the urine and three unidentified metabolites in the feces.

Animals↗
PubMed1992

Synthesis and cytotoxic evaluation of some 6-arylidene-2-(alpha-hydroxyamino-alpha-arylmethyl)cyclohexanone oximes and related compounds.

Reaction of 2,6-bis-(phenylmethylene)cyclohexanone (1) with a 4-molar excess of hydroxylamine hydrochloride and sodium acetate to produce the corresponding oxime 2 gave rise to 2-(alpha-hydroxyamino-alpha-phenylmethyl)-6-phenylmethylenecyclohexan one oxime (5a), whose structure was deduced from high-resolution proton nuclear magnetic resonance spectroscopy and confirmed by X-ray analysis. Compound 2 was eventually prepared from 1 with hydroxylamine per se and not with a mixture of hydroxylamine hydrochloride and sodium acetate. Ten analogues of 5a, namely 5b-5k, were prepared and evaluated for cytotoxicity. Six of the 11 compounds in series 5, as well as 1, showed activity in the 240-950 microM range against murine mammary EMT6 cells. Series 5 was also examined for cytotoxicity in an in vitro screen conducted by the National Cancer Institute with approximately 54 cell lines, and four compounds demonstrated selective toxicity toward various groups of tumors.

Animals↗