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31.
Laurence MenguyBruno Drouillat Jérome MarrotFrançois Couty 《Tetrahedron letters》2012,53(35):4697-4699
Various functionalized azetidines were oxidized with mCPBA or hydrogen peroxide, to produce the corresponding N-oxide and study its fate in the [1,2] Meisenheimer rearrangement. This ring expansion leading to isoxazolidines occurs readily, without trapping of the transient N-oxide. Starting with azetidines bearing a nitrile or an ester group at C-2, the rearrangement is regioselective. However, a varying amount of epimerization on the migrating radical is observed, which can also be observed with the related [1,2] Stevens rearrangement. 相似文献
32.
João M. Batista Jr. Andrea N.L. BatistaMassuo J. Kato Vanderlan S. BolzaniSilvia N. López Laurence A. NafieMaysa Furlan 《Tetrahedron letters》2012,53(45):6051-6054
A reinvestigation of the monoterpene chromane ester enriched fraction from Peperomia obtusifolia using chiral chromatography led to the identification of a minor peak, which was elucidated by NMR and HRMS as fenchyl-3,4-dihydro-5-hydroxy-2,7-dimethyl-8-(3″-methyl-2″-butenyl)-2-(4′-methyl-1′,3′-pentadienyl)-2H-1-benzopyran-6-carboxylate, the same structure assigned to two other fenchyl esters described previously, pointing out a stereoisomeric relationship among them. Further NMR analysis revealed that it was actually a mixture of two compounds, whose absolute configurations were determined by VCD measurements. Although, almost no vibrational transitions could be assigned to the chiral chromane, the experimental VCD spectrum was largely opposite to that obtained for the average experimental VCD [(2S,1?R,2?R,4?S + 2R,1?R,2?R,4?S)/2] for fenchol derivatives. These results allowed us to assign the putative compounds as a racemic mixture of the chiral chromane esterified with the monoterpene (1S,2S,4R)-fenchol, which had not been identified in our early work. 相似文献
33.
Shahali Y Sutra JP Haddad I Vinh J Guilloux L Peltre G Sénéchal H Poncet P 《Electrophoresis》2012,33(3):462-469
Italian cypress (Cupressus sempervirens, Cups) pollen causes allergic diseases in inhabitants of many of the cities surrounding the Mediterranean basin. However, allergens of Cups pollen are still poorly known. We introduce here a novel proteomic approach based on double one‐dimensional gel electrophoresis (D1‐DE) as an alternative to the 2‐DE immunoblot, for the specific IgE screening of allergenic proteins from pollen extracts. The sequential one‐dimensional combination of IEF and SDS‐PAGE associated with IgE immunoblotting allows a versatile multiplexed immunochemical analysis of selected groups of allergens by converting a single protein spot into an extended protein band. Moreover, the method appears to be valuable for MS/MS identification, without protein purification, of a new Cups pollen allergen at 43 kDa. D1‐DE immunoblotting revealed that the prevalence of IgE sensitization to this allergen belonging to the polygalacturonase (PG) family was 70% in tested French allergic patients. In subsequent triple one‐dimensional gel electrophoresis, the Cups pollen PG was shown to promote lectin‐based protein‐protein interactions. Therefore, D1‐DE could be used in routine work as a convenient alternative to 2‐DE immunoblotting for the simultaneous screening of allergenic components under identical experimental conditions, thereby saving considerable amounts of sera and allergen extracts. 相似文献
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35.
Maria A Girault JP Saatov Z Harmatha J Dinan L Lafont R 《Journal of chromatographic science》2005,43(3):149-157
Ecdysteroid glycosides are found in both animals and plants. The chromatographic behavior of these molecules is characteristic, as they appear much more polar than their corresponding free aglycones when analyzed by normal-phase high-performance liquid chromatography (HPLC), whereas the presence of glycosidic moieties has a very limited (if any) impact on polarity when using reversed-phase HPLC. Biological activity is greatly reduced because the presence of this bulky substituent probably impairs the interaction with ecdysteroid receptor(s). 2-Deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, which has been isolated from the dried aerial parts of Silene nutans (Caryophyllaceae), is used as a model compound to describe the rationale of ecdysteroid glycoside purification and identification. 相似文献
36.
Guinot C Malvy DJ Latreille J Ezzedine K Galan P Tenenhaus M Ambroisine L Hercberg S Tschachler E 《Photochemistry and photobiology》2005,81(4):934-940
Phototype classifications were initially developed in an attempt to predict the skin reactions of patients to phototherapy and are now widely used to advise individuals with regard to sun protection. A transversal study was conducted on the SU.VI.MAX cohort to estimate the frequency of sun-reactive skin features in a large, general adult population-based sample, and to describe the associations between these features. The data were collected 3 years after the beginning of the SU.VI.MAX nutritional intervention study on 4912 volunteers (2868 women aged 35-60 years and 2044 men aged 45-60 years). A multiple correspondence analysis was performed to study the associations between the features. The results showed that these features correspond to a one-dimensional phenomenon, which allowed us to establish a score to summarize skin sensitivity to sun exposure. Furthermore, we found a link between gender and phototype using the Césarini classification (phototype > or = IV: 37% of women, 47% of men). The analysis of the relationship with sun-reactive skin features and the score revealed the same trend. Phenotypic evaluation appears to be a good estimator of skin sensitivity to sun exposure for clinical screening or for use in research, and is easy to collect at a lower cost. Moreover, the sun sensitivity difference between gender should be considered in education about photoprotection. 相似文献
37.
Michèle Postel Félix Tomi Henri Li Kam Wah Laurence Mordenti Patricia Guillaume 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):453-457
Abstract Fe(NO)2XL and Fe(NO)X2L nitrosyl iron complexes, X = Cl, I, and L = HMPA, dppe, PPh3, activate molecular O2 to yield nitrato complexes. The phosphorous ligand is decisive for the oxidative power of these nitrates: with HMPA or dppe, oxygen transfer occurs only to phosphines. On going from HMPA to PPh3 the single nitrato complex obtained, Fe(NO)2X(OPPh3)2 selectively epoxidizes cyclohexene, and this is the first example of oxygen transfer from a nitrato ligand to an olefin. 相似文献
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39.
Chalcones may be cyclised to the corresponding flavanones by stirring with KF-celite suspended in methanol at reflux. This method gives consistently higher conversion than other reported procedures and its utility is illustrated by the synthesis of the linear prenylated flavanone bavachinin. 相似文献
40.
Laurence E. Burgess 《合成通讯》2013,43(12):2181-2191
The preparation of immunosuppressant SR-31747 is described. Attempts to install the Z-allyl amine included Lindlar partial hydrogenation and vinyl stannane methodologies. Ultimately, the Wittig olefination of aldehyde 12, with the ylide derived from β-aminoethyl phosphonium salt 13 proved successful. 相似文献