Reaction of diisopropoxytitanium(III) tetrahydroborate with selected organic compounds containing representative functional groups

Diisopropoxytitanium(III) tetrahydroborate, ((PrO)-Pr-1)(2)TiBH4), generated in situ in dichloromethane from diisopropoxytitanium dichloride and benzyltriethylammonium borohydride in a 1:2 ratio selectively reduces aldehydes, ketones, acid chlorides, carboxylic acids, and N-Boc-protected amino acids to the corresponding alcohols in excellent yield under very mild reaction conditions (-78 to 25 degrees C).

What makes a cell tick? The A, B and C of the matter

Nuclear lamina in an eukaryotic cell is primarily composed of the lamins A, B and C. The A type lamins are found only in differentiated cell types while the B type lamins are present both in differentiated and undifferentiated cells. Lamin B interacts with the inner nuclear membrane, In recent years there have been extensive studies on the relationship between the dynamic state of lamin B and the nuclear envelope integrity with respect to the fate of a particular cell, In this article, we have analysed the recent developments and have considered the sequence of events that might be contributing to the fate of a cell either to undergo normal cell division or uncontrolled cellular proliferation or apoptosis.

An ethnobotanical survey of medicinal plants in the Eastern Himalayan zone of Arunachal Pradesh, India

Aim of the study: The medicinal plants are integral source of easily available remedy used in rural healthcare system. This study was conducted among three major ethnic groups namely the Nocte, the Nyishi and the Adi in the Eastern Himalayan region of Arunachal Pradesh to evaluate their comparative knowledge on medicinal plants. Materials and methods: The three remote districts of Arunachal Pradesh namely the Tirap, the Dibang Valley and the Papum Pare were surveyed through interviewing of randomly selected 237 participants using semi-structured questionnaire and regular field visits to selected districts. Results: We recorded the traditional use of 74 medicinal plants species belonging to 41 taxonomic plant families used for treating a total of 25 different diseases/ailments. The informant consensus factor (ICF) values demonstrated that local people tend to agree more with each other in terms of the plants used to treat malaria (0.71), jaundice (0.62), urological problems (0.56), dermatological disorders (0.45), pain (0.30), and respiratory disorder (0.33), and while the general health (0.15) and gastro-intestinal disorders category (0.28) were found low ICF values. Conclusion: Of the total 74 species recorded, the highest number of medicinal plants (36 species) was reported from the Adi of Lower Dibang Valley followed by the Nocte of the Tirap (25 species) and the Nyishi ethnic groups of Papum Pare districts (13 species). In the present study, we found that the men, elder people and illiterate ones had better knowledge on medicinal plants as compared to women, younger and literate people. Findings of this documentation study can be used as an ethnopharmacological basis for selecting plants for future phytochemical and pharmaceutical studies. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Kinetics of copolyurethane network formation

Cure kinetics for the formation of copolyurethane networks of various compositions based on hydroxy-terminated polybutadiene(HTPB), poly(12-hydroxy stearic acid-co-TMP) ester polyol(PEP), and different isocyanates has been studied through viscosity build up during the cure reaction. The viscosity (N)-time (t) plots conform to the equation N = ae(bt), where a and b are empirical constants, dependent on the composition and the nature of the polyols and the isocyanates. The rate constants (b) for viscosity build up, evaluated from the slopes of dN/dt versus N plots at different temperatures, were found to vary significantly from 0.0073 to 0.25 min(-1); and the activation energies for gelation were found to be in the range 20 to 40 kJ mol(-1). The results have been interpreted in terms of the dependence of the rate constants on structural characteristics of the prepolymers. (C) 1997 John Wiley & Sons, Inc.

Synthesis of thiolactones using benzyltriethylammonium tetrathiomolybdate as sulfur transfer reagent

An interesting sulfur transfer reaction mediated by benzyltriethylammonium tetrathiomolybdate [(PhCH2NEt3)(2)MoS4] converts omega-halo acid chlorides to the corresponding thiolactones in moderate to good yields in one step. (C) 1997 Elsevier Science Ltd.

Enzymatic resolution of dioxygenated dicyclopentadienes: Enantiopure hydrindanes, hydroisoquinolones, diquinanes and application to a synthesis of (+)-coronafacic acid

A 5, 10-dioxygenated-tricyclo[5.2.1.0(2,6)]decane derivative 6 has yielded to efficient enzymatic resolution to provide a range of chiral building blocks, whose absolute configuration has been determined through a total synthesis of naturally occuring (+)-coronafacic acid. (C) 1999 Elsevier Science Ltd. All rights reserved.

Enantiodivergent total synthesis of microcarpalide from L-tartaric acid

Stereoselective approach for the synthesis of both enantiomers of bio-active decanolactone microcarpalide is described from L-tartaric acid. The synthesis of the key intermediates en route to the natural product is achieved from L-tartaric acid involving the elaboration of gamma-hydroxy amide derived from tartaric acid and ring opening of an epoxide derived from tartaric acid. (C) 2011 Elsevier Ltd. All rights reserved.

Crystal structure of nonadentate tricompartmental ligand derived from pyridine-2,6-dicarboxylic acid: Spectroscopic, electrochemical and thermal investigations of its transition metal(II) complexes

The coordinating behavior of a new dihydrazone ligand, 2,6-bis(3-methoxysalicylidene) hydrazinocarbonyl]pyridine towards manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) has been described. The metal complexes were characterized by magnetic moments, conductivity measurements, spectral (IR, NMR, UV-Vis, FAB-Mass and EPR) and thermal studies. The ligand crystallizes in triclinic system, space group P-1, with alpha=98.491(10)degrees, beta=110.820(10)degrees and gamma=92.228(10)degrees. The cell dimensions are a=10.196(7)angstrom, b=10.814(7)angstrom, c=10.017(7)angstrom, Z=2 and V=1117.4(12). IR spectral studies reveal the nonadentate behavior of the ligand. All the complexes are neutral in nature and possess six-coordinate geometry around each metal center. The X-band EPR spectra of copper(II) complex at both room temperature and liquid nitrogen temperature showed unresolved broad signals with g(iso) = 2.106. Cyclic voltametric studies of copper(II) complex at different scan rates reveal that all the reaction occurring are irreversible. (C) 2011 Elsevier B.V. All rights reserved.

Synthesis and cation binding properties of new bile acid-based crown ethers

A series of bile acid-based crown ethers (7a-c,12 and 13) were easily constructed from readily available precursors. Measurement of association constants (K-a) with alkali metal picrates in CHCl3 showed that azacrown ethers 7a-c and Chola-Cuowns 12 and 13 show greater binding towards Rb+ and K+. The presence of the aromatic moieties showed subtle changes in the binding properties. Insight II minimized structures show very different conformations of aromatic units in 7a-b and 13.

Surface chemical studies on the competitive adsorption of poly(acrylic acid) and poly(vinyl alcohol) onto alumina

The adsorption of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) onto alumina has been studied as a function of pH, both individually and in the presence of each other. The adsorption density of PAA is found to decrease with an increase of pH while that of PVA shows the opposite trend. In a binary system containing PAA and PVA, the presence of PVA does not affect the adsorption of PAA onto alumina, but the addition of PAA diminishes the adsorption of PVA in the pH range investigated. The adsorption isotherm of PAA at acidic pH exhibits high-affinity Langmuirian behavior. The isotherms for PVA appear rounded and are of the low-affinity type, Once again the adsorption isotherms of PAA remain unaltered in the presence of PVA whereas those of PVA are significantly affected resulting in a lowering of the adsorption density consequent to PAA addition. A variation in the sequence of addition of PAA and PVA does not affect the adsorption behavior of either of the polymers, The electrokinetic behavior of alumina with PAA is hardly influenced by the addition of PVA, On the other hand, the electrophoretic mobility of alumina in the presence of PVA is significantly altered in the presence of PAA and closely resembles the trend observed with PAA alone. Desorption studies reveal that over 80% of PVA could be desorbed in the pH range 3-9 whereas in the case of PAA, the percent desorption increases from 20 to about 70% as the pH is increased from about 3 to 8. Solution conductivity tests confirm interaction of aluminum species and PAA in the bulk solution. FTIR spectroscopic data provide evidence in support of hydrogen bonding and chemical interaction in the case of the PAA-alumina system and hydrogen bonding with respect to the PVA-alumina interaction. (C) 1999 Academic Press.

Enantioselective total synthesis of macrosphelides A and E

Enantioselective synthesis of 16-membered trilactone macrolides, macrosphelide A and E from (S)-lactic acid is described. Key features of the synthesis include the utility of a hitherto unexplored beta-ketophosphonate derived from lactic acid and Yamaguchi lactonization leading to the title compounds. (C) 2011 Elsevier Ltd. All rights reserved.

Fluorescence and visual sensing of nitroaromatic explosives using electron rich discrete fluorophores

Several pi-electron rich fluorescent aromatic compounds containing trimethylsilylethynyl functionality have been synthesized by employing Sonogashira coupling reaction and they were characterized fully by NMR (H-1, C-13)/IR spectroscopy. Incorporation of bulky trimethylsilylethynyl groups on the peripheral of the fluorophores prevents self-quenching of the initial intensity through pi-pi interaction and thereby maintains the spectroscopic stability in solution. These compounds showed fluorescence behavior in chloroform solution and were used as selective fluorescence sensors for the detection of electron deficient nitroaromatics. All these fluorophores showed the largest quenching response with high selectivity for nitroaromatics among the various electron deficient aromatic compounds tested. Quantitative analysis of the fluorescence titration profile of 9,10-bis(trimethylsilylethynyl) anthracene with picric acid provided evidence that this particular fluorophore detects picric acid even at ppb level. A sharp visual detection of 2,4,6-trinitrotoluene was observed upon subjecting 1,3,6,8-tetrakis (trimethylsilylethynyl) pyrene fluorophore to increasing quantities of 2,4,6-trinitrotoluene in chloroform. Furthermore, thin film of the fluorophores was made by spin coating of a solution of 1.0 x 10(-3) M in chloroform or dichloromethane on a quartz plate and was used for the detection of vapors of nitroaromatics at room temperature. The vapor-phase sensing experiments suggested that the sensing process is reproducible and quite selective for nitroaromatic compounds. Selective fluorescence quenching response including a sharp visual color change for nitroaromatics makes these fluorophores as promising fluorescence sensory materials for nitroaromatic compounds (NAC) with a detection limit of even ppb level as judged with picric acid.

Synthesis and Degradation of Sorbitol-Based Polymers

A new class of biodegradable copolyesters was synthesized by the catalyst-free melt condensation of sorbitol with citric acid, tartaric acid, and sebacic acid. The resulting polymers were designated as poly(sorbitol citric sebacate) p(SCS)] and poly(sorbitol tartaric sebacate) p(STS)]. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, H-1-NMR spectroscopy, and differential scanning calorimetry analysis. Porous spongelike scaffolds were prepared with a salt-leaching technique and characterized with scanning electron microscopy. Tensile testing of the p(SCS) and p(STS) polymers showed that they exhibited a wide range of mechanical properties. The Young's modulus and tensile strengths of the polymers ranged from 1.06 +/- 0.12 to 462.65 +/- 34.21 MPa and from 0.45 +/- 0.04 to 20.32 +/- 2.54 MPa, respectively. In vitro degradation studies were performed on disc-shaped polymer samples. The half-life of the polymers ranged from 0.54 to 38.52 days. The percentage hydration of the polymers was in the range 9.36 +/- 1.26 to 78.25 +/- 1.91, with sol contents of 2-14%. At any given polymer composition, the Young's modulus and tensile strength of p(SCS) was higher than that of p(STS), whereas the degradation rates of p(SCS) was lower than that of p(STS). This was attributed to the structural difference between the citric and tartaric monomers and to the degree of crosslinking. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2861-2869, 2011

Beckmann rearrangement of ketoximes on solid metaboric acid: a simple and effective procedure

When ketoximes admixed with solid metaboric acid (formed from boric acid at 100degreesC/0.1 Torr) are heated (similar to 140degreesC/7-42 h), the corresponding amides or lactams are produced in excellent yields (62-92%) via the Beckmann reaction. Aromatic aldoximes undergo both dehydration to the nitrile as well as (non-stereospecific) rearrangement under the above conditions. The absence of solvent, and the mildness and low toxicity of boric acid, characterise the present procedure. CO. 2002 Elsevier Science Ltd. All rights reserved.