Syntheses and Study of New 2-Hydroxy-5,6-Dihydro-2H-1,4-Oxazines by NMR and X-ray Crystallography

The preparation of six new 2-hydroxy-5,6-dihydro-2H-[1,4]-oxazines and four oxazino-oxazine type structures is described. The structures of four of these compounds were established by X-ray crystallographic analyses.     

Stereoselective allylation and reduction of N-tert-butanesulfinyl-α-keto aldimines

A simple methodology for the synthesis of N-tert-butanesulfinyl-α-keto aldimines from both α-keto aldehydes and carboxylic esters has been developed. The addition of an in situ formed allyl indium reagent to these chiral imines was also studied. The addition took place in a sequential manner, first to the imine group with excellent diastereoselectivity and then to the carbonyl group with lower diastereoselectivity. Ruthenium-catalyzed ring closing metathesis of the resulting 5-aminoocta-1,7-dien-4-ol derivatives provided access to 6-aminocyclohex-3-enols. Reduction of the α-keto aldimines led to N-tert-butanesulfinyl-1,2-aminoalcohols as a 1:1 diastereomeric mixture.     

Flavonoid glycosides from Persea caerulea. Unraveling their interactions with SDS‐micelles through matrix‐assisted DOSY,PGSE, mass spectrometry,and NOESY

Two flavonoid glycosides derived from rhamnopyranoside ( 1 ) and arabinofuranoside ( 2 ) have been isolated from leaves of Persea caerulea for the first time. The structures of 1 and 2 have been established by ¹H NMR, ¹³C NMR, and IR spectroscopy, together with LC–ESI–TOF and LC–ESI–IT MS spectrometry. From the MS and MS/MS data, the molecular weights of the intact molecules as well as those of quercetin and kaempferol together with their sugar moieties were deduced. The NMR data provided information on the identity of the compounds, as well as the α and β configurations and the position of the glycosides on quercetin and kaempferol. We have also explored the application of sodium dodecyl sulfate (SDS) normal micelles in binary aqueous solution, at a range of concentrations, to the diffusion resolution of these two glycosides, by the application of matrix‐assisted diffusion ordered spectroscopy (DOSY) and pulse field gradient spin echo (PGSE) methodologies, showing that SDS micelles offer a significant resolution which can, in part, be rationalized in terms of differing degrees of hydrophobicity, amphiphilicity, and steric effects. In addition, intra‐residue and inter‐residue proton–proton distances using nuclear Overhauser effect build‐up curves were used to elucidate the conformational preferences of these two flavonoid glycosides when interacting with the micelles. By the combination of both diffusion and nuclear Overhauser spectroscopy techniques, the average location site of kaempferol and quercetin glycosides has been postulated, with the former exhibiting a clear insertion into the interior of the SDS‐micelle, whereas the latter is placed closer to the surface. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal diffusivity study of cheese fats by thermal lens detection

In this paper we used thermal lens spectrometry to determine the thermal diffusivity of cheese fats. We have used equal concentrations of cheese fats from oaxaca, chihuahua, gouda, manchego and mozzarella cheeses at 42°C temperature. The two lasers mismatched mode experimental configuration was used with a He-Ne laser, as a probe beam and an Ar⁺ laser as the excitation one. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression to the experimental data in order to obtain the thermal diffusivity of the cheese fat samples. This measured thermal property may contribute to a better understanding of the cheese fats quality, which is very important in food industry.     

Electrophoretic behavior of individual nuclear species as determined by capillary electrophoresis with laser-induced fluorescence detection

We determined the feasibility of using capillary electrophoresis with postcolumn laser-induced fluorescence (CE-LIF) detection to characterize electrophoretic properties of isolated cell nuclei and impurities present in nuclear fractions. These fractions were isolated from NS-1 mouse hybridoma cells, stained with hexidium iodide, a DNA intercalating dye, and analyzed by CE-LIF detection. The corresponding electropherograms display two features: (i) broad peaks (6-90 s wide) caused by the cell culturing media and by free-DNA intercalated with hexidium iodide, and (ii) a large number of narrow peaks (180 ms wide), resulting from DNA associated with individual intact or disrupted nuclei. We confirmed that the narrow peaks were not caused by contaminating mitochondria. The overall electrophoretic mobility range of disrupted nuclei is 0 to -5 x 10(-4)cm(2)/Vs, while intact nuclei seem to have mobilities in the -1.5 to -3.5 x 10(-4)cm(2)/Vs range. Furthermore, the highly sensitive CE-LIF method reveals a high abundance of disrupted nuclei that cannot be directly observed by confocal microscopy.     

First intermolecular cyclopropanation of Fischer dialkylaminocarbene complexes. Synthesis of 1-aminocyclopropanecarboxylic acid derivatives

[reaction: see text] The first cyclopropanation reaction of olefins with Fischer dialkylaminocarbene complexes is presented. The reaction yields 1-aminocyclopropanecarboxylic acid derivatives in a single step, usually with high diastereoselectivity. An approach to the asymmetric version of this reaction is also presented. The synthetic utility of the procedure is exemplified by the synthesis of both cycles of metanoproline in a single step. In addition, the synthesis of the first Fischer carbene containing a halocarbonyl group is reported.     

Singularity in the thermal boundary resistance between superfluid (4)He and a solid surface

We report new measurements in four cells of the thermal boundary resistance R between copper and (4)He below but near the superfluid-transition temperature T(lambda). For 10(-7)< or =t identical to 1-T/T(lambda))< or =10(-4) fits of R = R(0)t(-x(b))+R(B) to the data yielded x(b) approximately equal to 0.18, whereas a fit to theoretical values based on the renormalization-group theory yielded x(b) = 0.23. Alternatively, a good fit of the theory to the data could be obtained if the amplitude of the prediction was reduced by a factor close to 2. The results raise the question whether the boundary conditions used in the theory should be modified.     

Electrochemical treatment of textile dyes and their analysis by high-performance liquid chromatography with diode array detection

Several textile dyes were individually exposed to electrochemical treatment. Chromaticity variation and the formation of degradation products were followed using a UV spectrophotometer and HPLC with diode array detection. Dyes studied belong to the azo (color index, C.I. 15,510), methine (C.I. 48,013), indigo (C.I. 73,040), natural (C.I. 75,760) and arylmethane (C.I. 42,000) classes. Aliquots of the solutions treated at constant potential were analyzed and compared with control dye solutions. The final electrolysis solutions obtained by using different electrode materials: Pt, Ti and diamond presented different chromatograms. It was found that the novel (in this application) diamond electrode is efficient in studying the degradation of various dyes. Possible fragmentation and molecule moiety rearrangement are proposed as a result of the electrochemical treatment.