Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. XI. Synthesis of 2H-pyrano[3,2-g]benzothiazole derivatives

Cycloaddition of dichloroketene to N,N-disubstituted 6-aminomethylene-5,6-dihydro-2-phenylbenzothiazol-7-(4H)ones gave in good yield N,N-disubstituted 4-amino-3,3-dichloro-3,4,5,6-tetrahydro-8-phenyl-2H-pyrano[3,2-g]benzothiazol-2-ones II, which are derivatives of the new heterocyclic system 2H-pyrano[3,2-g]benzothiazole. Dehydrochlorination with triethylamine of II afforded N,N-disubstituted 4-amino-3-chloro-5,6-dihydro-8-phenyl-2H-pyrano[3,2-g]benzothiazol-2-ones III in good to moderate yield. The dimethylamino adduct was dehydrochlorinated in high yield by refluxing in toluene, whereas the diisopropylamino adduct gave in low yield 6-(2,2-dichloroethylidene)-5,6-dihydro-2-phenylbenzothiazol-7-(4H)one with the triethylamine treatment. The dehydrochlorinated product IIId (NR₂ = pyrrolidino) was obtained directly in low yield by cycloaddition of dichloroketene to the corresponding enaminone. Full aromatisation of IIIa,g [NR₂ = N(CH₃)₂ and N(CH₃)C₆H₅, respectively] to the corresponding N,N-disubstituted 4-amino-3-chloro-8-phenyl-2H-pyrano-[3,2-g]benzothiazol-2-ones was accomplished with DDQ in refluxing benzene.     

Reaction of sulfene with heterocyclic N,N-disubstituted α-aminomethyleneketones. IX. Synthesis of 1,2-oxathiino[6,5-e]indole derivatives

The polar 1,4-cycloaddition of sulfene to N,N-disubstituted 5-aminomethylene-1,5,6,7-tetrahydro-1-methylindol-4-ones occurred only in the case of aliphatic N-substitution to give, generally in good yield, 4-dialkylamino-3,4,5,6-tetrahydro-7-methyl-7H-1,2-oxathiino[6,5-e]indole 2,2-dioxides IV. Full aromatization of IVa (4-NR₂ = dimethylamino) with DDQ in refluxing benzene gave in low yield 7-methyl-7H-1,2-oxathiino-[6,5-e]indole 2,2-dioxide, whereas the same reaction of IVe (4-NR₂ = morpholinyl) with excess DDQ afforded in low yield 7-methyl-4-morpholinyl-7H-1,2-oxathiino[6,5-e]indole 2,2-dioxide.     

2‐(4′‐Pyridyl‐N‐oxide)‐Substituted Hemithioindigos as Photoresponsive Guests for a Super Aryl‐Extended Calix[4]pyrrole Receptor

We report the synthesis of two 2‐(4′‐pyridyl‐N‐oxide)‐substituted hemithioindigos (HTIs). We probed their photoisomerization by using UV/Vis and ¹H NMR spectroscopy techniques. Light irradiation at λ=450 nm provoked the isomerization of the HTI Z isomer to the E counterpart to a large extent (≈80 % at the photostationary state). ¹H NMR titration experiments revealed the formation of thermodynamically and kinetically stable 1:1 inclusion complexes of the (Z)‐HTI isomers with a super aryl‐extended host (association constant>10⁴ m ^?1). Photoirradiation at λ=450 nm of the inclusion complexes induced the isomerization of the bound HTI N‐oxide to afford the (E)‐HTI?calix[4]pyrrole complex. We determined accurate association constant values for the 1:1 inclusion complexes of the (Z)‐ and (E)‐HTI isomers by using isothermal titration calorimetry experiments. The results showed that the stability constants of the (E)‐HTI complexes were 2.2–2.8‐fold lower than those of the (Z)‐HTI counterparts, which explains the lack of light‐induced release of the former to the bulk solution.     

Reaction of 2-dimethylaminomethylene-1,3-diones with Dinucleophiles. IV. Synthesis of 5,7-dihydrothiopyrano[3,4-c]pyrazol-4(1H)-ones, 5H-Thiopyrano[4,3-d]isoxazol-4(7H)-one and 6H-Thiopyrano[3,4-d]pyrimidin-5(8H)-ones

The reaction of 2H-thiopyran-3,5(4H,6H)-dione with N,N-dimethylformamide dimethyl acetal gave in good yield 4-dimethylaminomethylene-2H-thiopyran-3,5(4H,6H)dione (II), which afforded 1-substituted 5,7-dihydrothiopyrano[3,4-c]pyrazol-4(1H)-ones with aliphatic and aromatic hydrazines, 5H-thiopyrano[4,3-d]isoxazol-4(7H)-one (IV) with hydroxylamine hydrochloride and 2-substituted 6H-thiopyrano[3,4-d]pyrimidin-5(8H)-ones with amidines and guanidines, generally in satisfactory yields. 4-(t-Butylhydrazonoformyl)-2H-thiopyran-3,5(4H,6H)-dione was isolated as an intermediate in the reaction of II with t-butylhydrazine, whereas formamidine gave with II 4-iminoformyl-2H-thiopyran-3,5(4H,6H)-dione as the sole product. The isoxazole IV isomerized easily with sodium methoxide to 3,4,5,6-tetrahydro-5,5-dihydroxy-3-oxo-2H-thiopyrano-4-carbonitrile.     

Synthesis of Uniform,Monodisperse, Sophorolipid Twisted Ribbons

Control over size monodispersity in chiral self‐assembled systems is important for potential applications like templating, tissue engineering or enantioselective chromatography, just to cite a few examples. In this context, it was reported that the saturated form of sophorolipids (SL), a bioderived glycolipid, are able to form self‐assembled twisted ribbons in water at neutral pH. Here, we show the possibility to control their size dispersion, generally between 10 and 40 nm after synthesis to a value of 13.5±1.5 nm, by a simple dialysis step eliminating the excess of NaCl. We use transmission electron microscopy under cryogenic conditions (cryo‐TEM) combined with small angle neutron scattering (SANS) to characterize the ribbon dispersion both visually and statistically. Two negative controls show the importance of salt in the aggregation process of the ribbons.     

Some Remarks on the Definition of Boltzmann, Shannon and Kolmogorov Entropy

We give an alternative definition of Shannon and Kolmogorov-Sinai entropies based on the Boltzmann formula S = k log W. We prove the equivalence of those new definitions with the traditional ones using some tools from Information Theory such as information function and empirical entropy. Lecture held in the Seminario Matematico e Fisico on November 29, 2004 Received: April 2005     

The effect of operating conditions on the physicochemical characteristics of whey protein–based systems

The uptake of proteins is highly recommended, mainly for athletes, elderly people and patients with serious diseases like dysphagia. In this work, whey proteins were used for producing two kinds of aqueous materials: suspensions of proteins, in the native form, and gels, obtained by protein denaturation. In the first system, proteins are used as interfacial active ingredients or as thickening agents of the aqueous phase, whereas in the second one they are used as structuring agents. These protein-based materials show very different rheological and microstructural behaviour even at the same concentration. In the case of an undenatured system, a growing protein fraction resulted in an increased dimension of their aggregates and all investigated systems exhibited a liquid-like behaviour with a viscosity independent of shear rate and well described by a Krieger-Dougherty model. In the case of thermally denatured systems, it has been observed that, at increasing protein content, aggregates evolve towards a continuous gel network with a fractal behaviour. Both systems have been modelled, according to their specific behaviour, with the aim of proposing equations suitable to relate macroscopic properties and microstructure, useful for designing new food products with predictable properties for different industrial uses.

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