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PubMed2004

Saludimerines A and B, novel-type dimeric alkaloids with stereogenic centers and configurationally semistable biaryl axes.

The first biarylic bis-morphinanedienone alkaloids, saludimerines A (3a) and B (3b), isolated from a tree of Croton flavens (Euphorbiaceae) are described. These naturally occurring dimers of the known alkaloid salutaridine are joined together via a rotationally hindered biaryl axis, giving rise to atropo-diastereomers that are configurationally stable at room temperature but slowly interconvert in methanolic solution within several days. Their structures were established by spectroscopic methods and by partial synthesis, which was achieved by a highly atropo-diastereoselective biomimetic oxidative coupling of the monomeric precursor, salutaridine. Their axial configurations were elucidated by circular dichroism (CD) investigations, which succeeded despite the fact that the two atropo-diastereomers exhibit near-identical CD spectra. This remarkable phenomenon was rationalized by quantum chemical CD calculations. The configurational assignment of saludimerines A (3a) as P-axial and B (3b) as M was corroborated by atropisomer-specific NOE interactions between protons of the one molecular half with nuclei in the other.

Alkaloids↗
PubMed2004

A modular and concise total synthesis of (+/-)-daurichromenic acid and analogues.

A modular and concise total synthesis of (+/-)-daurichromenic acid has been accomplished in four steps from ethyl acetoacetate, ethyl crotonate, and trans,trans-farnesal. A series of analogues of this natural product, which has potent anti-HIV activity, were also prepared from ethyl or methyl acetoacetate and a series of readily available alpha,beta-unsaturated esters and aldehydes.

Anti-HIV Agents↗
PubMed2005

Mono- and beta,beta-double-Heck reactions of alpha,beta-unsaturated carbonyl compounds in aqueous media.

Optimized reaction conditions for the mono- and beta,beta-diarylation of electron-deficient alkenes in aqueous media catalyzed either by a p-hydroxyacetophenone oxime-derived palladacycle or by palladium(II) acetate under phosphine-free conditions and in the presence of (dicyclohexyl)methylamine as base are described. Regioselective monoarylation of unsubstituted and substituted alpha,beta-unsaturated carbonyl compounds takes place with aryl iodides at 120 degrees C in water. Aqueous N,N-dimethylacetamide (DMA), tetra-n-butylammonium bromide (TBAB) as additive, and the palladacycle as catalyst are the most efficient conditions for the coupling with aryl bromides, good stereoselectivities being also obtained in the arylation of crotonates and itaconates, whereas cinnamic derivatives afford lower steroselectivity, with the exception of cinnamic acid and nitrile. beta,beta-Diarylation of unsubstituted alpha,beta-unsaturated carbonyl compounds can be controlled by using higher loading of the palladacycle and can be performed in refluxing water for aryl iodides, whereas DMA must be used for aryl bromides. Microwave irradiation can be used in the monoarylation of tert-butyl acrylate with aryl iodides in water or the coupling between ethyl cinnamate and aryl bromides in aqueous DMA.

Journal Article↗
PubMed2005

Convenient access to new chiral ferroceno-(iso)quinolines.

[Chemical reaction: see text] New chiral pyridine derivatives possessing the planar chirality of the ferrocene have been prepared by means of an aldolization-crotonization reaction. This very simple reaction has been applied to the synthesis of isomers 1-4 that differ in the position of the nitrogen atom on the pyridine ring. Following the same procedure, asymmetric synthesis of 1 has been achieved using an enantiopure ferrocenylzinc intermediate. This method has also allowed the preparation of a chiral analogue of 2,2'-bipyridine.

Journal Article↗
PubMed2006

Density functional theory study of electroreductive hydrocoupling of alpha,beta-unsaturated carbonyl compounds.

[reaction: see text] The electroreductive hydrocoupling of methyl cinnamate, methyl crotonate, cumarin, and benzalacetone was studied by DFT (B3LYP/6-311++ G**) calculations. The computational outcomes for the transition states in the hydrocoupling of anion radicals generated by a one-electron transfer to the alpha,beta-unsaturated carbonyl compounds well agree with the diastereoselectivities in the experimental results previously reported.

Electrons↗
PubMed1996

Carbodications. 4.(1) Hydrogen Isotope Exchange of Crotonyl Cations in Superacid.

The title ion reacts in 1:1 DF-SbF(5) and exchanges up to five protium atoms with deuterium. The incorporation of label was measured by GC-MS analysis of the methyl crotonate formed by methanol quenching. The isotopomer distribution at about 60% conversion, which shows a minimum for the d(1) and a maximum for the d(4) species, indicates that the intermediate dication with the second charge at C(3) loses a proton faster from C(4) than from C(2). Formation of the pentadeuteriocrotonyl cation indicates that the 1,4-dication (acyl primary alkyl) or the 1,2-dication must intervene in the process. Computer modeling of the kinetics for the multiple exchange process to fit the experimental deuterium distribution allowed determination of the relative rate constants and isotope effects (KIEs) for the formation of the carbocations from alkenoyl cations (beta-secondary KIE) and elimination from carbodications to alkenoyl cations (primary KIE). An exceptionally large beta-secondary KIE of ca. 2.0/hydrogen was found for the formation of the dication. A small primary isotope effect of ca. 1.5 was found for elimination from the dications to the alkenoyl cations. Elimination from the 1,3-acylalkyl dication to form the nonconjugated 3-butenoyl cation is 6-7 times faster than elimination to the conjugated 2-butenoyl cation. The rate ratio for the conversion of 3-butenoyl cation to the 1,4-dication (primary alkyl cation) and 1,3-dication (secondary alkyl cation) is (0.025-0.030):1, whereas the relative rate of the formation of the 1,2-acylalkyl dication (the alternative route of achieving pentadeuteration) is zero.

Journal Article↗
PubMed1998

Formation of Macrocyclic Ethers by Free Radical Cyclization: Effects of Chain Length, Substituents, and Solvents.

Free radical reduction by tributylstannane of omega-iodopolyoxaalkyl acrylates derived from tri-, tetra-, penta-, hexa-, and heptaethylene glycols gives mixtures of uncyclized reduction products and macrocyclic ethers formed by endo cyclization. The rate constants for cyclization of the intermediate radicals at 80 degrees C in benzene were determined under carefully defined conditions to be 15 x 10(4), 13 x 10(4), 5.1 x 10(4), 10 x 10(4) and 3.6 x 10(4) s(-) (1), for formation of the 12-, 15-, 18-, 21- and 24-membered rings, respectively. These values indicate that the presence of oxygen atoms in the chains increases the rate by a factor of 10-30 by comparison with the previously reported cyclization of alkenyl species. The rate constants at 80 degrees C in benzene and the endo/exo ratio for reductive cyclizations of the methacrylate, crotonate, cinnamate, maleate, and fumarate esters of 8-iodo-3,6-dioxaoctanol have been determined. The reduction of the 8-iodo-3,6-dioxaoctyl acrylate in solvents of varying polarity indicated that the cyclization rate has a relatively low solvent dependence.

Journal Article↗
PubMed1998

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides(1).

Benzonitrile oxides undergo 1,3-dipolar cycloaddition reactions with methyl cinnamate to produce the 5-phenyl and 4-phenyl regioisomers in approximately an 80:20 ratio. However, use of N,N-diethylcinnamide as the dipolarophile unexpectedly resulted in the formation of the 5-phenyl and 4-phenyl regioisomers in a 23:77 ratio. Studies have shown that this phenomena occurs only for tertiary cinnamides. In addition, it has been demonstrated that the phenyl group of tertiary cinnamides is not essential for the reversal of regioselectivity since crotonamides produce the same results and trends as the cinnamides. However, since acrylates and acrylamides both produce the 5-carbonyl regioisomers, it can be concluded that the beta-substituent is playing a key role for the unexpected results by possibly increasing steric interactions between the dipole and dipolarophile in the transition state. Transition state energies were calculated for the regioisomeric cycloadduct pairs derived from several crotonamides as well as methyl crotonate. These calculations indicate that steric factors are indeed responsible for the reversal of regioselectivity.

Journal Article↗
PubMed2001

The first total synthesis of (-)-solanapyrone E based on domino Michael strategy.

[figure: see text] A phytotoxin, solanapyrone E, has been synthesized from the decalone prepared by the domino Michael reaction of the kinetic enolate of optically pure acetylcyclohexene with methyl crotonate. After several transformations on the decalone ring, condensation of a methyl acetoacetate equivalent installed a pyrone moiety and introduction of a hydroxymethyl unit into the pyrone ring furnished solanapyrone E.

Alternaria↗
PubMed2002

Synergistic catalysis of anthrone Diels-Alder reactions.

[reaction: see text] The combination of an amine base and Lewis acid (Li+) leads to synergistic catalysis of the Diels-Alder reaction of anthrone with methyl crotonate and some other less reactive dienophiles. These cycloadditions either do not occur with the individual catalysts used separately or they are greatly accelerated by the combined catalysts. DMSO solvent allows the use of LiCl as the Lewis acid source and can provide greater control of subsequent conversion to Michael adduct.

Journal Article↗
PubMed2002

Synthesis of enantiomerically pure 2,2,3,4,5-pentasubstituted pyrrolidines by phenylsulfanyl migration.

[reaction: see text] Enantiomerically pure 2,2,3,4,5-pentasubstituted pyrrolidines can be prepared, in high overall yield, from alpha,beta-unsaturated esters. Asymmetry is introduced via a Michael addition, and additional stereogenic centers are introduced by an aldol reaction. A novel stereospecific ring-forming reaction, proceeding via a thiiranium (episulfonium) ion, yields pyrrolidines from beta-hydroxy sulfides. In this manner, 2,2,3,4,5-pentasubstituted pyrrolidines, containing three contiguous stereogenic centers around the ring, can be prepared in 44% overall yield from ethyl crotonate.

Journal Article↗
PubMed2003

The remarkable ability of lithium ion to reverse the stereoselectivity in the conjugate addition of Li[BuCuI] to a chiral N-crotonyl-2-oxazolidinone.

[reaction: see text] The influence of lithium ions on the conjugate addition of the monoorganocuprate reagent, Li[BuCuI], to a chiral crotonate has been investigated. The results show that iodotrimethylsilane (TMSI) is crucial for the asymmetric conjugate addition of the copper reagent, but only in THF or when 12-crown-4 is used. The reaction is thought not to involve any halosilane in any critical steps in the organocopper mechanisms conducted in Et(2)O.

Journal Article↗
PubMed1998

Inhibition of tissue repair by spironolactone: role of mineralocorticoids in fibrous tissue formation.

Mineralocorticoids have been implicated in promoting fibrous tissue formation in various organs. In the present study, we sought to address the potential contribution of mineralocorticoids to fibrous tissue formation using a skin pouch model which has proved valuable for the analysis of inflammatory and wound healing responses. Skin pouches were induced in rats by administration of a phorbol ester, croton oil (0.5 ml of a 1% solution). After 2 weeks, rats were killed and intact pouch tissue collected. Pouch weights of control and aldosterone-treated (0.75 microg/h via osmotic minipump) rats were similar (3.33 +/- 0.44 g vs. 3.70 +/- 0.28 g respectively). However, pouch weights were reduced by more than 50% in spironolactone-treated (25 mg/day powdered in food) animals (1.62 +/- 0.22 g and 1.27 +/- 0.23 g respectively in aldosterone and spironolactone alone groups). To ascertain the effects of different treatments on collagen accumulation, hydroxyproline concentration was measured. Compared with controls, hydroxyproline concentration was significantly reduced following spironolactone treatment (17.1 +/- 0.08 vs. 7.5 +/- 2.0 microg/mg dry wt, respectively, p < 0.01). This response to spironolactone was negated by coadministration of aldosterone (hydroxyproline concentration was 18.6 +/- 2.1 microg/mg dry wt). Following bilateral adrenalectomy, spironolactone reduced pouch weight and hydroxyproline concentration, which was not the case for adrenalectomy alone. Two week aldosterone administration in uninephrectomized rats on high salt diet was deemed ineffective in modulating pouch development (pouch wet wts were 3.48 +/- 0.4 g vs. 3.00 +/- 0.19 g in controls and aldosterone-treated rats, respectively). Mineralocorticoid receptor expression in pouch tissue was demonstrated by RT/PCR. Furthermore, NADP+-dependent 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) activity was detected in pouch tissue, together with lower levels of NAD+-dependent 11beta-HSD2. Spironolactone (p < 0.05) significantly reduced 11beta-HSD1 activity compared with controls. Thus, fibrous tissue possesses requisite components of MC action, and antagonism of mineralocorticoid receptors by spironolactone attenuates its formation. Pouch formation is under the influence of circulating MC and, we would like to propose, is also mediated through corticosteroids generated de novo at the site of tissue repair.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1999

Breast and cervical cancer screening: knowledge, attitudes and behavior among schoolteachers in Italy.

The study explores knowledge, attitudes and behavior regarding screening for breast and cervical cancers. All female teachers in primary and secondary schools in Crotone and in Cassino (Italy) received a questionnaire on demographic and socioeconomic characteristics, clinical history, knowledge, behavior and attitudes about breast and cervical cancer and related screening procedures. A response rate of 65% was achieved. Knowledge on effectiveness of mammography and pap test in finding related cancers was widely spread in the sample. Only about 30% and 50% had respectively undergone their last mammogram and pap test according to the recommended time interval. Having been examined by a physician in the previous year and having had a screening CBE or a screening pap smear in the past three years were significantly more likely in women who underwent mammography for screening purposes in the past two years. Pap smear in the previous three years was significantly more likely in women in their forties, with a higher family income and in those who had been examined by a physician in the previous year. The results strongly recommend continued emphasis of physicians on education of women regarding mammography and pap smear.

Adult↗
PubMed2003

Modulatory effect of henna leaf (Lawsonia inermis) on drug metabolising phase I and phase II enzymes, antioxidant enzymes, lipid peroxidation and chemically induced skin and forestomach papillomagenesis in mice.

Henna leaf (Lawsonia inermis), commonly known as Mehndi is cultivated throughout India and is a very popular natural dye to color hand and hair. It is an integral part of indigenous culture, and is also known for its medicinal value. The effect of 200 and 400 mg/kg body weight of 80% ethanolic extract of the fresh leaves of Lawsonia inermis were examined on drug metabolizing phase-I and phase-II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase and lipid peroxidation in the liver of 7 weeks old Swiss albino mice. Also anticarcinogenic potential of Henna leaf extract was studied adopting the protocol of benzo(a)pyrene induced forestomach and 7,12 dimethylbenz(a)anthracene (DMBA)-initiated and croton oil-promoted skin papillomagenesis. Our primary findings reveal the 'duel-acting' nature of henna leaf as deduced from its potential to induce only the phase-II enzyme activity, associated mainly with carcinogen detoxification in liver of mice and inhibit the phase I enzyme activities. The hepatic glutathione S-transferase and DT-diaphorase specific activities were elevated above basal (p < 0.005) level by Lawsonia inermis extract treatment. With reference to antioxidant enzymes the investigated doses were effective in increasing the hepatic glutathione reductase (GR), superoxide dismutase (SOD) and catalase activities significantly (from p < 0.05 to p < 0.005) at both the dose levels. Reduced glutathione (GSH) measured as non-protein sulphydryl was found to be significantly elevated in liver (p < 0.005) and in all the extrahepatic organs studied (from p < 0.05 to p < 0.005). Among the extrahepatic organs examined (forestomach, kidney and lung) glutathione S-transferase and DT-diaphorase level were increased in a dose independent manner (from p < 0.05 to p < 0.005). Chemopreventive response was measured by the average number of papillomas per mouse (tumor burden) as well as percentage of tumor bearing animals and tumor multiplicity. There was a significant inhibition of tumor burden in both the tumor model systems studied (from p < 0.01 to p < 0.001). Tumor incidence was also reduced by both the doses used in our experiment in both the model systems.

Animals↗
PubMed2003

Comparison of two in vitro dendritic cell maturation models for screening contact sensitizers using a panel of methacrylates.

Allergen-induced emigration and maturation of dendritic cells (DC) are pivotal steps in sparking off allergic contact dermatitis. In vitro models, reflecting these steps, may provide tools for assessment of sensitizing capacities of putative contact allergens. Here, we evaluated the applicability of such models for a panel of methacrylate congeners, the sensitizing properties of which were established previously in clinical and experimental animal studies. First, using interleukin-4 (IL-4)/granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced, blood monocyte-derived DC, hapten-induced up-regulation of maturation/ activation markers, including CD80, CD83, CD86, chemokine receptors CXCR4 and CCR5, as well as the drug resistance related molecules P-glycoprotein (Pgp) and lung resistance protein (LRP), were monitored by flow cytometry. Of note, whereas CD86 and CXCR4 were most sensitive in discriminating between the contact sensitizers and irritants included in the panel, i.e. sodium dodecyl sulphate (SDS) and croton oil (CO), assessment of CD83 and LRP expression reflected the relatively lower sensitizing capacity of methyl methacrylate. Second, using ex vivo skin explant cultures, allergen-induced LC migration from epidermal to basal membranous and dermal skin structures was most reliably monitored by CDla, as compared with Pgp, LRP, HLA-DR or CD54 staining. The extent of CD1a+ LC migration was found to closely correlate with the sensitizing capacities of the panel of test compounds. These results support the view that both in vitro models can provide valuable data on contact sensitizing properties, and add chemokine receptors and drug resistance related molecules to the list of DC membrane markers revealing allergenic signaling.

Cell Movement↗