The Synthesis of Natural Acetylenic Compounds from Stereum hirsutum

The regioselective synthesis of two new acetylenic compounds, sterehirsutinal ( 1 ) and sterehirsutinol ( 2 ), isolated recently from culture medium of the fungus Stereum hirsutum, is reported.     

Conceptual polymorphism of entropy into the history: extensions of the second law of thermodynamics towards statistical physics and chemistry during nineteenth–twentieth centuries

After the birth of thermodynamics’ second principle—outlined in Carnot's Réflexions sur la puissance motrice du feu (1824)—several studies provided new arguments in the field. Mainly, they concerned the thermodynamics’ first principle—including energy conceptualisation—, the analytical aspects of the heat propagation, the statistical aspects of the mechanical theory of heat. In other words, the second half of nineteenth century was marked by an intense interdisciplinary research activity between physics and chemistry: new disciplines applied to the heat developed in the form of analytical, mechanical and statistical theories. Inside all these theories, entropy—the brand-new function that Clausius coined in his Mechanical theory of heat—started to play a central epistemic role. In the present paper, we analyse some steps of the historical process of conceptualisation of such function from 1850 to 1902. Particularly, we retrace the historical–foundational path that—starting from Clausius’ Second Law—lead Boltzmann and Gibbs to their distinguished formulations of statistical entropy. As usual, our research has been unrolled through the analyses of primary sources and by leaning on critical readings of the secondary literature. As for the methodological approach, text analysis of historical documents constituted our privileged modus operandi. This paper is the expression of a collaborative historical research program focused on the thermodynamic foundations of physics–chemistry relationship; early results have already been published by the same authors upon the concepts of reversibility––and––thermal equilibrium.

     

Structural basis for the potential antitumour activity of DNA-interacting benzo[kl]xanthene lignans

The biological properties and possible pharmacological applications of benzo[kl]xanthene lignans, rare among natural products and synthetic compounds, are almost unexplored. In the present contribution, the possible interaction of six synthetic benzo[kl]xanthene lignans and the natural metabolite rufescidride with DNA has been investigated through a combined STD-NMR and molecular docking approach, paralleled by in vitro biological assays on their antiproliferative activity towards two different cancer cell lines: SW 480 and HepG2. Our data suggest that the benzo[kl]xanthene lignans are suitable lead compounds for the design of DNA selective ligands with potential antitumour properties.     

Phospholipid-based nonlamellar mesophases for delivery systems: Bridging the gap between empirical and rational design

Phospholipids are ubiquitous cell membrane components and relatively well-accepted ingredients due to their natural origin. Phosphatidylcholine (PC) in particular offers a promising alternative to monoglycerides for lyotropic liquid crystalline (LLC) delivery system applications in the food, cosmetics and pharmaceutical industries, provided its strong tendency to form zero-mean curvature lamellar mesophases in water can be overcome. Higher negative curvatures are usually reached through the addition of a third lipid component, forming a ternary diagram phospholipid/water/oil.     

Selective epoxidation of monoterpenes with H2O2 and polymer-supported methylrheniumtrioxide systems

A convenient and efficient synthesis of monoterpene epoxides by application of heterogeneous poly(4-vinylpyridine)/methyl rhenium trioxide (PVP/MTO) and polystyrene/methyl rhenium trioxide (PS/MTO) systems is described. Even highly sensitive terpenic epoxides were obtained in excellent yield. Environment friendly, easily available, and low cost H₂O₂ was used as oxidant. Catalysts were stable systems for at least five recycling experiments.     

Degradation kinetic (D100) of lycopene during the thermal treatment of concentrated tomato paste

Heat treatments can cause degradation in tomatoes of lycopene which has important antioxidant effects. No information about decimal reduction time (D₁₀₀) of lycopene is available. D-value is the time required at a given temperature to reduce 90% of the molecule. This study for the first time determine the kinetic of lycopene thermal degradation. The content was measured at regular intervals of pasteurization using canned tomato paste to determinate D value. Microbiological analysis was carried out to verify product stability after packaging. Yeasts, molds and lactic acid bacteria were determined. The pasteurization time allowed to observe a loss of the red color. Lycopene content, after an increase at 8 min, decreased at 32 min of pasteurization. D₁₀₀ value was calculated at 75 min; a diminution of 90% in lycopene content in the concentrated tomato paste was observed. Microbiological analysis confirmed the stability of products after 8 min of pasteurization.     

Finite-Order Formulation of Vinogradov's C-Spectral Sequence

The C-spectral sequence was introduced by A. M. Vinogradov in the late Seventies as a fundamental tool for the study of the algebro-geometric properties of jet spaces and differential equations. A spectral sequence arises from the contact filtration of the modules of forms on jet spaces of a fibring (or on a differential equation). In order to avoid serious technical difficulties, the order of the jet space is not fixed, i.e., computations are performed on spaces containing forms on jet spaces of any order. In this paper we show that there exists a formulation of Vinogradov's C-spectral sequence in the case of finite-order jet spaces of a fibred manifold. We compute all cohomology groups of the finite-order C-spectral sequence. We obtain a finite-order variational sequence which is shown to be naturally isomorphic with Krupka's finite-order variational sequence.     

Effect of copper salts on peptide bond formation using peptide thioesters

[reaction: see text] In the present paper, systematic studies revealed that Cu(I) salts in general and Cu(II) salts under certain circumstances promote effective reaction between peptide thiol esters and the N-terminal amino function of a second peptide segment to give the native amide bond for both solution- and solid-phase syntheses. Chiral integrity was retained. Reaction conditions were optimized and applied to the synthesis of a small protein, the identity of which was confirmed by NMR analysis.     

A novel group of highly hydroxylated steroids from the starfish Protoreaster nodosus

Thre novel polyhydroxylated sterols, 5-cholestane-3β,6,8,15,16β,26-hexol, 5-cholestane-3β,6,7,8,15,16β,26-heptol and 5-cholestane-3β,4β,6,7,8,15,16β,26-octol, have been isolated from the Pacific Starfish Protoreaster nodosus and their structures have been established through extensive ¹H NMR and ¹³C NMR studies, chemical transformations and related spectroscopic data.