Synthesis of Unnatural Selenocystines and beta-Aminodiselenides via Regioselective Ring-Opening of Sulfamidates Using a Sequential, One-Pot, Multistep Strategy

A variety of N-alkyl-beta-aminodiselenides have been synthesized in high yield from sulfamidates under mild reaction conditions using potassium selenocyanate and benzyltriethylammonium tetrathiomolybdate ([BnNEt3](2)MoS4) in a sequential, one-pot, multistep reaction. The tolerance of multifarious protecting groups under the reaction conditions is discussed. The methodology was successfully extended to the synthesis of selenocystine,3,3'-dialkylselenocystine, and 3,3'-diphenylisoselenocystine and their direct incorporation into peptides.

Synthesis of cyclohexylideneacetaldehyde 2-, 3- and 4-methylcyclohexylideneacetaldehyde

Cyclohexanone and 2-, 3- and 4-methylcyclohexanones have been condensed with acetylene to give the respective 1-ethinylcyclohexanola. The 1-ethinylcyclohexanols were hydrogenated to the respective 1-vinyl- and 1-ethylcyclohexanols. The 1-vinylcyclohexanols have been treated with phosphorus tribromide to give the corresponding rearranged β-cyclohexylidenethyl bromides which have been converted to the pyridinium salts. The latter were treated with p-nitrosodimethylaniline and alkali (Krohnke's method) to give the corresponding nitrones which were hydrolyzed to the corresponding aldehydes. The 1-ethinyl-, 1-vinyl- and 1-ethylcyclohexanols prepared were subjected to pharmacological tests.

Synthesis, aggregation behavior and cholesterol solubilization studies of 16-epi-pythocholic acid (3 alpha,12 alpha,16 beta-trihydroxy-5 beta-cholan-24-oic acid)

Synthesis, aggregation behavior and in vitro cholesterol solubilization studies of 16-epi-pythocholic acid (3 alpha,12 alpha,16 beta-trihydroxy-5 beta-cholan-24-oic acid, EPCA) are reported. The synthesis of this unnatural epimer of pythocholic acid (3 alpha,12 alpha,16 alpha-trihydroxy-5 beta-cholan-24-oic acid, PCA) involves a series of simple and selective chemical transformations with an overall yield of 21% starting from readily available cholic acid (CA). The critical micellar concentration (CMC) of 16-epi-pythocholate in aqueous media was determined using pyrene as a fluorescent probe. In vitro cholesterol solubilization ability was evaluated using anhydrous cholesterol and results were compared with those of other natural di-and trihydroxy bile acids. These studies showed that 16-epi-pythocholic acid (16 beta-hydroxy-deoxycholic acid) behaves similar to cholic acid (CA) and avicholic acid (3 alpha,7 alpha,16 alpha-trihydroxy-5 beta-cholan-24-oic acid, ACA) in its aggregation behavior and cholesterol dissolution properties. (C) 2010 Elsevier Inc. All rights reserved.

Synthesis and characterization of metal substituted AlxCr1-x(acetylacetonate)(3) single-source precursors for their application to MOCVD of thin films

A detailed study, involving the synthesis of a single-source precursor containing two metal ions sharing the same crystallographic site, has been undertaken to elucidate the use of such a single-source precursor in a CVD process for growing thin films of oxides comprising these two metals, ensuring a uniform composition and distribution of metal ions. The substituted complexes Cr1-xAlx(acac)(3), where acac = acetyl-acetonate, have been prepared by a co-synthesis method, and characterized using UV-Vis spectroscopy. TGA/DTA measurements, and single crystal X-ray diffraction at low temperature. All the studied compositions crystallize in the monoclinic space group P2(1)/c with Z = 4 in the unit cell. It was observed that the ratio (Al:Cr) of the site occupancy for the metal ions, obtained from single crystal refinement, is in agreement with the results obtained from complexometric titrations. All the solid state structures have the metal in an octahedral environment forming six-membered chelate rings. M-O acac bond lengths and disorder in the terminal carbon have been studied in detail for these substituted metal-organic complexes. One composition among these was chosen to evaluate their suitability as a single-source precursor in a LPMOCVD process (low-pressure metal-organic chemical vapour deposition) for the deposition of a substituted binary metal oxide thin film. The resulting thin films were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. (C) 2010 Elsevier Ltd. All rights reserved.

Synthesis and Isolation of 5,6-Dihydro-4H-1,3-Oxazine Hydrobromides by Autocyclization of N-(3-Bromopropyl)amides

5,6-Dihydro-4H-1,3-oxazine hydrobromides have been synthesized by the nucleophilic autocyclo-O-alkylation of N-(3-bromopropyl)amides under neutral conditions in chloroform. It is found that electron-donating amide alpha-substituents influence the autocyclization efficiency.

Synthesis of Functionalized Dihydrothiophenes from Doubly Activated Cyclopropanes Using Tetrathiomolybdate as the Sulfur Transfer Reagent

A number of doubly activated cyclopropanes were synthesized starting from various substituted bromosulfonium bromides in good yield. Regioselective ring-opening of cyclopropanes with tetrathiomolybdate as the sulfur transfer reagent gave dihydrothiophenes in excellent yield.

Synthesis of taxanes - The carvone approach; A simple, efficient stereo- and enantio-selective synthesis of the functionalised A ring

A highly stereo- and enantio-selective methodology for the construction of the chiral functionalised A-ring of taxanes, starting from (R)-carvone employing a short, simple and efficient sequence is described.

Synthesis and esterolytic chemistry of some (dialkylamino) pyridine-functionalized micellar aggregates. Evidence of catalytic turnover

Four new (dialkylamino)pyridine-functionalized surfactants have been synthesized. Micelles were generated either from the surfactant alone in aqueous buffer (pH 8.5 or 9.0) or by comicellization in 1 x 10(-3)-1 x 10(-4) M aqueous micellar cetyltrimethylammonium bromide (CTABr) solution at pH 8.5 or 9.0. Such aggregates were used to cleave p-nitrophenyl alkanoates or p-nitrophenyl diphenylphosphate. The nucleophilic reagents and the second-order ''catalytic'' rate constants toward esterolysis of the substrate p-nitrophenyl octanoate (at 25 degrees C, pH 9.0) were [cat.] = 1 x 10(-4) M, [CTABr] = 1 x 10(-3) M, and k(cat.) = 440.13 M(-1) s(-1) for 1b, [cat.] = 5 x 10(-4) M, [CTABr] = 5 x 10(-4) M, and k(cat.) = 30.8 M(-1) s(-1) for 1c, [cat.] = 5 x 10(-4) M, [CTABr] = 5 x 10(-3) M, and k(cat.) = 183.64 M(-1) s(-1) for 2a, and [cat.] = 3 x 10(-4) M and k(cat.) = 54.1 M(-1) s(-1) for 2b. The catalytic systems, especially 1b/CTABr and 2a/CTABr, also conferred significantly greater reactivity toward the esters derived from alkanoic acids of moderate chain length (C-6-C-10) during hydrolytic cleavages relative to their shorter and longer counterparts. Importantly, the catalytic systems comprising the coaggregates of either neutral 1b and CTABr (1:10) or anionic 2a and CTABr (1:10) conformed to the Michaelis-Menten kinetic scheme and demonstrated turnover behavior in the presence of excess substrate.

Synthesis, Thermotropic Behavior, and Permeability Properties of Vesicular Membranes Composed of Cationic Mixed-Chain Surfactants

In order to elucidate the role of the linkage region that connects polar headgroups with hydrophobic segments in a lipid monomer, cationic mixed-chain amphiphiles containing acyl and alkyl hydrophobic segments connected at the level of Me(2)N(+) headgroups 2a-d were synthesized. Related dialkyldimethyl-ammonium ion surfactants 1a-e and diacyl systems 3a-c were also synthesized. Despite mismatch in the connector region, amphiphiles 2a-d form bilayer vesicles like their dialkyl and diacyl counterparts, as revealed by electron microscopy. Introduction of an ester connector function between the polar and hydrophobic parts raises the phase transition temperature (T-m), transition enthalpies, and resistance to ion permeation. Consideration of energy minimized conformations points toward the importance of differences in the depth of chain penetration into the putative bilayer.

Synthesis of Co(II), Ni(II) and Cu(II) Complexes from Schiff base Ligand and Reactivity Studies with Thermosetting Epoxy Resin

A hybrid thermosetting maleimido epoxy compound 4-(N-maleimidophenyl) glycidylether (N-MPGE) containing Co(II), Ni(II) and Cu(II) ions was prepared by curing N-MPGE and tetradentate Schiff base Co(II), Ni(II) and Cu(II) complexes. The curing polymerization reaction of N-MPGE with metal complexes as curing agents was studied. The cured samples were studied for thermal stability, chemical (acid/alkali/solvent) and water absorption resistance and homogeneity of the cured systems. The tetradentate Schiff base, 3-(Z)-2-piperazin-1-yl-ethylimino]-1,3-dihydro indol-2-one was synthesized by the condensation of Isatin (Indole-2, 3-dione) with 1-(2-aminoethyl)piperazine (AEP). Its complexes with Co(II), Ni(II) and Cu(II) have been synthesized and characterized by microanalysis, conductivity, Uv-Visible, FT-IR, TGA and magnetic susceptibility measurements. The spectral data revealed that the ligand acts as a neutral tetradentate Schiff base and coordinating through the azomethine nitrogen, two piperazine nitrogen atoms and carbonyl oxygen.

Synthesis and vesicle formation from novel pseudoglyceryl dimeric lipids. Evidence of formation of widely different membrane organizations with exceptional thermotropic properties

Eight new bis-cationic dimeric lipids 2a-h have been synthesized; TEM of their aqueous dispersions confirmed the vesicle formation and from the thermal, spectroscopic, DLS and XRD studies it has been revealed that they form three different kinds of membranous aggregate depending on the m-value.

Synthesis based on cyclohexadienes. Part-27. Synthesis of functionalized tricyclo[5.2.2.0(1,5)]undecanes

A new methodology for the construction of tricyclo[5.2.2.0(1,5)]undecanes is described from indane-4-carboxylic acids. Birch reduction of indane-4-carboxylic acids followed by conjugation and cycloaddition with alpha-chloroacrylonitrile and hydrolysis lead to the tricyclic compounds 36 and 48 which are intermediates in the eremolactone synthesis.