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.

Amide Functionalized Microporous Organic Polymer (Am-MOP) for Selective CO2 Sorption and Catalysis

We report the design and synthesis of an amide functionalized microporous organic polymer (Am-MOP) prepared from trimesic acid and p-phenylenediamine using thionyl chloride as a reagent. Polar amide (CONH) functional groups act as a linking unit between the node and spacer and constitute the pore wall of the continuous polymeric network. The strong covalent bonds between the building blocks (trimesic acid and p-phenylenediamine) through amide bond linkages provide high thermal and chemical stability to Am-MOP. The presence of a highly polar pore surface allows selective CO2 uptake at 195 K over other gases such as N-2, Ar, and O-2. The CO2 molecule interacts with amide functional groups via Lewis acid base type interactions as demonstrated through DFT calculations. Furthermore, for the first time Am-MOP with basic functional groups has been exploited for the Knoevenagel condensation reaction between aldehydes and active methylene compounds. Availability of a large number of catalytic sites per volume and confined microporosity gives enhanced catalytic efficiency and high selectivity for small substrate molecules.

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.

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.

Rare-earth carboxylates, Ln(2)(III)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O Ln = Ce, Pr and Nd]: synthesis, structure and properties

A new series of inorganic-organic hybrid framework compounds, Ln(2)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O, (Ln = Ce, Pr and Nd), have been prepared employing a hydrothermal method. Malic acid and fumaric acid form part of the structure. The malate units connect the lanthanide centers forming Ln-O-Ln two-dimensional layers, which are cross-linked by the fumarate units forming the three-dimensional structure. Extra framework water molecules form a dimer and occupy the channels. The water molecules can be reversibly adsorbed. The dehydrated structure did not show any differences in framework structure/ connectivity. The presence of lattice water provides a pathway for proton conductivity. Optical studies suggest an up-conversion behavior involving more than one photon for a neodymium compound.

In-situ Stabilization of Tin Nanoparticles in Porous Carbon Matrix derived from Metal Organic Framework: High Capacity and High Rate Capability Anodes for Lithium-ion Batteries

It is a formidable challenge to arrange tin nanoparticles in a porous matrix for the achievement of high specific capacity and current rate capability anode for lithium-ion batteries. This article discusses a simple and novel synthesis of arranging tin nanoparticles with carbon in a porous configuration for application as anode in lithium-ion batteries. Direct carbonization of synthesized three-dimensional Sn-based MOF: K2Sn2(1,4-bdc)(3)](H2O) (1) (bdc = benzenedicarboxylate) resulted in stabilization of tin nanoparticles in a porous carbon matrix (abbreviated as Sn@C). Sn@C exhibited remarkably high electrochemical lithium stability (tested over 100 charge and discharge cycles) and high specific capacities over a wide range of operating currents (0.2-5 Ag-1). The novel synthesis strategy to obtain Sn@C from a single precursor as discussed herein provides an optimal combination of particle size and dispersion for buffering severe volume changes due to Li-Sn alloying reaction and provides fast pathways for lithium and electron transport.

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.

Enantiospecific Total Synthesis of Macrolactone Sch 725674

The enantiospecific total synthesis of 14-membered macrolactone Sch 725674 was accomplished from tartaric acid. Key reactions in the synthesis include the Ley's dithiaketalization of an alkynone derived from the bis-Weinreb amide of tartaric acid, Boord olefination, and ring-closing metathesis of an acrylate ester.

3 `-Amino-5 `-carboxymethy1-3 `,5 `-dideoxy nucleosides for the synthesis of fully amide-linked RNA mimics

A convenient protocol is developed for the synthesis of 3 `-N-(fluorenylmethoxycarbonyl)-amino]-5 `-carboxymethyl derivatives of all four natural ribonucleosides from cheap chiral pool compound glucose. Synthesis of fully amide-linked RNA analogues of small oligonucleotides containing, for the first time, all four nucleoside amino acids using standard solid phase Fmoc-chemistry is described. (C) 2014 Elsevier Ltd. All rights reserved.

Design and Synthesis of New Benzimidazole-Carbazole Conjugates for the Stabilization of Human Telomeric DNA, Telomerase Inhibition, and Their Selective Action on Cancer Cells

Cell-permeable small molecules that enhance the stability of the G-quadruplex (G4) DNA structures are currently among the most intensively pursued ligands for inhibition of the telomerase activity. Herein we report the design and syntheses of four novel benzimidazole carbazole conjugates and demonstrate their high binding affinity to G4 DNA. Si nuclease assay confirmed the ligand mediated G-quadruplex DNA protection. Additional evidence from Telomeric Repeat Amplification Protocol (TRAP-LIG) assay demonstrated efficient telomerase inhibition activity by the ligands. Two of the ligands showed IC50 values in the sub-micromolar range in the TRAP-LIG assay, which are the best among the benzimidazole derivatives reported so far. The ligands also exhibited cancer cell selective nuclear internalization, nuclear condensation, fragmentation, and eventually antiproliferative activity in long-term cell viability assays. Annexin V-FITC/PI staining assays confirm that the cell death induced by the ligands follows an apoptotic pathway. An insight into the mode of ligand binding was obtained from the molecular dynamics simulations.

Synthesis of 5,6-dihydro-4H-1,3-thiazine containing peptide mimics from N-(3-hydroxypropyl)thioamides and epimerization studies

The first synthesis of 1,3-thiazine fused peptide mimics is described from N-(3-hydroxypropyl)thioamides under MsCl/NEt3 conditions. The method is amenable to oligopeptidomimics with polar and apolar side chains. Substantial epimerization occurs at chiral C(2) exo methines in non-Pro fused mimics even under neutral conditions. H-1 NMR and crystal structure analyses indicate that the Thi analogues primarily associate with each other through intermolecular hydrogen bonds, involving the nitrogen of 1,3-thiazine and the N-H of the fused residue, which may be the basis for enamination-racemization process in these peptide mimics. (C) 2014 Elsevier Ltd. All rights reserved.

Useful approach to the synthesis of aryl thio- and selenoglycosides in the presence of rongalite

A simple, mild, and cost effective methodology has been developed for the synthesis of aryl thio-and selenoglycosides from glycosyl halides and diaryl dichalcogenides. Diaryl dichalcogenides undergo reductive cleavage in the presence of rongalite (HOCH2SO2Na) to generate a chalcogenide anion in situ followed by reaction with glycosyl halides to furnish the corresponding aryl thio- and selenoglycosides in excellent yields. Using this protocol, synthesis of 4-methyl-7-thioumbelliferyl-beta-D-cellobioside (MUS-CB), a fluorescent non-hydrolyzable substrate analogue for cellulases has been achieved. (C) 2014 Elsevier Ltd. All rights reserved.

Improved Erlenmeyer Synthesis with 5-Thiazolone and Catalytic Mn(II) Acetate. Crystal Structure Confirmation of the Reaction Stereochemistry

2-Phenylthiazolin-5-one (5, a thioazlactone) condenses with various aldehydes in the presence of the mild base Mn(II) acetate as catalyst in CH2Cl2 solution. This leads to the corresponding Erlenmeyer reaction products (6) in excellent yields in the case of aromatic aldehydes and moderate yields in others. The mildness of the reaction conditions is apparently enabled by the aromaticity of the (putative) intermediate thiazolone anion. The structure and stereochemistry (Z) of the product derived from i-BuCHO was confirmed by single crystal X-ray diffraction. This study overcomes key limitations of the classical Erlenmeyer synthesis and also introduces the relatively nontoxic Mn(II) acetate as a reagent in heterocyclic chemistry.