Enantioselective synthesis of macrolactone core of the natural product Sch725674

An enantioselective synthesis of the macrolactone core of natural product Sch725674 was accomplished from furfural. Key reactions in assembly of the macrolactone are the use of furan as a but-2-ene-dione equivalent and ring closing metathesis. (C) 2014 Elsevier Ltd. All rights reserved.

Facile hydrothermal synthesis of carbon nanoparticles and possible application as white light phosphors and catalysts for the reduction of nitrophenol

We report a simple hydrothermal synthesis of highly reproducible carbon nanoparticles in a size range between 2 and 7 nmfroma single precursor sucrose without either surface passivating agents or acids and bases. The carbon nanoparticles can be used as white light phosphors, especially for ultraviolet light emitting diodes and metal-free catalyst for the reduction of nitrophenol.

Formal Synthesis of Actin Binding Macrolide Rhizopodin

Formal synthesis, of an actin binding macrolide rhizopodin was achieved in 19 longest linear steps. The key features of the synthesis include a stereoselective Mukaiyama aldol reaction, dual role of a Nagao auxiliary (first, as a chiral auxiliary of choice for installing hydroxy centers and, later, as an acylating agent to form an amide bond with an amino alcohol), late stage oxazole formation, and Stille coupling reactions.

An electrochemical method for the synthesis of few layer graphene sheets for high temperature applications

We demonstrate an electrochemical technique for the large scale synthesis of high quality few layer graphene sheets (FLGS) directly from graphite using oxalic acid (a weak acid) as the electrolyte. One of the interesting observations is that the FLGS are stable at least up to 800 degrees C and hence have potential application in solid oxide fuel cells as a gas diffusion layer.

Green ionothermal synthesis of hierarchical nanostructures of SnS2 and their Li-ion storage properties

Flower-like hierarchical architectures of layered SnS2 have been synthesized ionothermally for the first time, using a water soluble EMIM]BF4 ionic liquid (IL) as the solvent medium. At lower reaction temperatures, the hierarchical structures are formed of few-layered polycrystalline 2D nanosheet-petals composed of randomly oriented nanoparticles of SnS2. The supramolecular networks of the IL serve as templates on which the nanoparticles of SnS2 are glued together by combined effects of hydrogen bonding, electrostatic, hydrophobic and imidazolium stacking interactions of the IL, giving rise to polycrystalline 2D nanosheet-petals. At higher reaction temperatures, single crystalline plate-like nanosheets with well-defined crystallographic facets are obtained due to rapid inter-particle diffusion across the IL. Efficient surface charge screening by the IL favors the aggregation of individual nanosheets to form hierarchical flower-like architectures of SnS2. The mechanistic aspects of the ionothermal bottom-up hierarchical assembly of SnS2 nanosheets are discussed in detail. Li-ion storage properties of the pristine SnS2 samples are examined and the electrochemical performance of the sample synthesized at higher temperatures is found to be comparable to that reported for pristine SnS2 samples in the literature.

Novel synthesis of carbohydrate fused alpha-amino gamma-lactams and glycopeptides by NIS mediated ring opening of donor-acceptor substituted cyclopropanes

alpha-Amino gamma-lactams have been synthesized from carbohydrate derived cyclopropanecarboxylates using N-iodosuccinimide (NIS) and NaN3. Cyclopropane ring opening with NIS and NaN3 in different solvents has been studied. Reductive cyclization of the intermediate di-azides leads to the carbohydrate fused alpha-amino gamma-lactam and gamma-lactams. Additionally, the methodology has been successfully extended to the synthesis of a glycopeptide. (C) 2014 Elsevier Ltd. All rights reserved.

Tuning nuclearity of clusters by positional change of functional group: Synthesis of polynuclear clusters, crystal structures and magnetic properties

Four neutral polynuclear magnetic clusters, (Mn6Mn2Na2I)-Mn-III-Na-II(N-3)(8)(mu(1)-O)(2)(L-1)(6)(CH3OH)(2)] (1), (Mn6Na2I)-Na-III(N-3)(4)(mu(4)-O)(2)(L-2)(4)(CH3COO)(4)] (2), Ni-5(II)(N-3)(4)(HL1)(4)(HCOO)(2)(CH3OH)(2)(H2O)(2)]center dot 2CH(3)OH (3) and (Ni4Na2I)-Na-II(N-3)(4)(HL2)(6)]center dot 2CH(3)OH (4) have been synthesized using tetradentate ligands H2L1-2 along with azide as a co-ligand. H2L1-2 are the products formed in situ upon condensation of 2-hydroxy-3-methoxybenzaldehyde with 1-aminopropan-2-ol and 1-aminopropan-3-ol, respectively. Single crystal X-ray diffraction and bond valence sum calculation showed that complex 1 is composed of both Mn-III and Mn-II. Complex 3 contains coordinated formate, which was formed upon in situ oxidation of methanol. The magnetic study over a wide range of temperatures of all the complexes (1-4) showed that 1 and 2 are antiferromagnetic whereas other two (3-4) are predominantly ferromagnetic. The estimated ground states of the complexes are S approximate to 3(1), S = 4(2), S = 5(3) and S approximate to 4(4), respectively. (C) 2014 Elsevier B.V. All rights reserved.

An Approach to a Bislactone Skeleton: A Scalable Total Synthesis of (+/-)-Penifulvin A

An efficient and scalable total synthesis of the architecturally challenging sesquiterpenoid (+/-)-penifulvin A has been accomplished via a 12-step sequence with an overall yield of 16%. For the construction of this structurally complex tetracyclic molecule, the key steps used included 1,4-conjugate addition, a Pd(0) catalyzed cross-coupling reaction between an enol phosphate and trimethyl aluminum, Claisen rearrangement using the Johnson orthoester protocol, Ti(III)-mediated reductive epoxide opening-cyclization, Lewis acid catalyzed epoxy-aldehyde rearrangement, and finally a substrate controlled oxidative cascade lactonization process.

Morphology controlled synthesis of wurtzite ZnS nanostructures through simple hydrothermal method and observation of white light emission from ZnO obtained by annealing the synthesized ZnS nanostructures

A controllable synthesis of phase pure wurtzite (WZ) ZnS nanostructures has been reported in this work at a low temperature of similar to 220 degrees C using ethylenediamine as the soft template and by varying the molar concentration of zinc to sulphur precursors as well as by using different precursors. A significant reduction in the formation temperature required for the synthesis of phase pure WZ ZnS has been observed. A strong correlation has been observed between the morphology of the synthesized ZnS nanostructures and the precursors used during synthesis. It has been found from Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) image analyses that the morphology of the ZnS nanocrystals changes from a block-like to a belt-like structure having an average length of similar to 450 nm when the molar ratio of zinc to sulphur source is increased from 1 : 1 to 1 : 3. An oriented attachment (OA) growth mechanism has been used to explain the observed shape evolution of the synthesized nanostructures. The synthesized nanostructures have been characterized by the X-ray diffraction technique as well as by UV-Vis absorption and photoluminescence (PL) emission spectroscopy. The as-synthesized nanobelts exhibit defect related visible PL emission. On isochronal annealing of the nanobelts in air in the temperature range of 100-600 degrees C, it has been found that white light emission with a Commission Internationale de I'Eclairage 1931 (CIE) chromaticity coordinate of (0.30, 0.34), close to that of white light (0.33, 0.33), can be obtained from the ZnO nanostructures obtained at an annealing temperature of 600 degrees C. UV light driven degradation of methylene blue (MB) dye aqueous solution has also been demonstrated using as-synthesized nanobelts and similar to 98% dye degradation has been observed within only 40 min of light irradiation. The synthesized nanobelts with visible light emission and having dye degradation activity can be used effectively in future optoelectronic devices and in water purification for cleaning of dyes.

Two-step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter

A new two-step procedure for the synthesis of MoS2 nanotubes using lead as a growth promoter is reported. In the first step, molybdenum suboxide nanowhiskers containing a small amount of lead atoms were created by exposing a pressed MoS2+Pb mixture to highly compressed shock-heated argon gas, with estimated temperatures exceeding 9900 K. In the second step, these molybdenum suboxide nanowhiskers served as templates for the sulfidization of the oxide into MoS2 nanotubes (by using H2S gas in a reducing atmosphere at 820 degrees C). Unlike the case of WS2 nanotubes, the synthesis of a pure phase of MoS2 nanotubes from molybdenum oxide has proven challenging, due mostly to the volatile nature of the latter at the high requisite reaction temperatures (>800 degrees C). In contrast, the nature and apparent reaction mechanism of the method reported herein are amenable to future scale-up. The high-temperature shockwave system should also facilitate the synthesis of new nanostructures from other layered materials.

Mechanochemical Synthesis of Amide Functionalized Porous Organic Polymers

Two porous organic polymers decorated with the amide functionality were synthesized mechanochemically and their properties were compared with the ones prepared by conventional solution mediated method. All the POPs were subjected to gas and water vapor sorption studies. The mechanochemically synthesized POPs have less surface area and show moderate adsorption properties compared to the solution mediated POPs. The amide based POPs show remarkable stability in water and concentrated acids.

Design and synthesis of new low band gap organic semiconductors for photovoltaic applications

Donor-acceptor (D-A) conjugated polymers have attracted a good deal of attention in recent years. In D-A systems, the introduction of electron withdrawing groups reduces E-g by lowering the LUMO levels whereas, the introduction of electron donating groups reduces E-g by raising the HOMO levels. Also, conjugated polymers with desired HOMO and LUMO energy levels could be obtained by the proper selection of donor and acceptor units. Because of this reason, D-A conjugated polymers are emerging as promising materials particularly for polymer light emitting diodes (PLEDs) and polymer solar cells (PSCs). We report the design and synthesis of four new narrow band gap donor-acceptor (D-A) conjugated polymers, PTCNN, PTCNF, PTCNV and PTCNO, containing electron donating 3,4-didodecyloxythiophene and electron accepting cyanovinylene units. The effects of further addition of electron donating and electron withdrawing groups to the repeating unit of a D-A conjugated polymer (PTCNN) on its optical and electrochemical properties are discussed. The studies revealed that the nature of D and A units as well as the extent of alternate D-A structure influences the optical and the electrochemical properties of the polymers. All the polymers are thermally stable up to a temperature of 300 degrees C under nitrogen atmosphere. The electrochemical studies revealed that the polymers possess low-lying HOMO energy levels and low-lying LUMO energy levels. In the UV-Vis absorption study, the polymer films displayed broad absorption in the wavelength region of 400-700 nm. The polymers exhibited low optical band gaps in the range 1.70 - 1.77 eV.

Total synthesis of the indole alkaloids henrycinol A and B

The total synthesis of new indole alkaloids henrycinol A and B were accomplished starting from L-tryptophan methyl ester. The key step is a stereochemically flexible Pictet-Spengler reaction governed by the presence or absence of an N-allyl group in the tryptophan precursor. The natural products henrycinol A and B were synthesized in good overall yield in eight and nine steps, respectively. (C) 2014 Elsevier Ltd. All rights reserved.

Total synthesis of (+)-anamarine

An enantiospecific total synthesis of polyhydroxy delta-pyrone natural product (+)-anamarine is accomplished. The main features of the synthesis include the stereoselective reduction of the ketone obtained by the desymmetrization of the bis-dimethyl amide of tartaric acid and further elaboration involving asymmetric Brown's allylation and ring closing metathesis. (C) 2014 Elsevier Ltd. All rights reserved.

Toward the total synthesis of a lagunamide B analogue

Lagunamides, isolated from a marine cyanobacterium Lyngbya majuscule found in Singapore, showed very potent activities against Plasmodium falciparum and murine leukemia cell line (P388). Herein, a concise synthetic approach toward the total synthesis of a lagunamide B analogue is discussed. Macrolactonization, HWE-olefination, and modified Crimmin's aldol are some of the key reactions featured in this synthesis. (C) 2014 Elsevier Ltd. All rights reserved.