A lipophilic hexaporphyrin assembly supported on a stannoxane core

Lipophilic hexaporphyrin free-base and copper-metalated assemblies supported on a Sn6O6 core have been synthesized and characterized. The nuclease activity of the copper derivative has been studied.     

Synthesis of a core trisaccharide building block for the assembly of N-glycan neoconjugates

A short and high yielding synthesis of a core trisaccharide 1 as the key building block in the assembly of a library of N-glycan neoconjugates is presented. The β-d-Manp-(1→4)-d-GlcpNAc linkage was introduced by inversion of the C-2 position of a β-glucoside. The glucosyl donor was efficiently synthesised following a recently published one-pot strategy. 2-Naphthylmethyl and benzylidene-acetal protection in the terminal mannose permitted selective liberation of main branching sites for subsequent glycosylation. A C5 azido linker attached to the anomeric position, which is stable throughout the synthesis, will allow for the posterior immobilisation of deprotected glycans on a microarray surface.     

Towards the total synthesis of FD-838: modular enantioselective assembly of the core

A rapid assembly of the tetracyclic core of FD-838, featuring a catalytic asymmetric Stetter reaction, is described.     

Radical carboazidation: expedient assembly of the core structure of various alkaloid families

A procedure for one-pot intermolecular radical addition of 2-iodoesters to terminal alkenes followed by azidation of the radical adduct has been developed. This sequential reaction represents an alkene carboazidation process. Its efficacy is demonstrated by the two-step preparation of various lactams such as pyrrolidinones, pyrrolizidinones, and indolizidinones. An easy access to spirolactams bearing an amino-substituted quaternary carbon center is also described. These compounds are important building blocks for the synthesis of numerous alkaloids such as, for instance, FR901483.     

Templated assembly of organic-inorganic materials using the core shell structure of the P22 bacteriophage

Biomimetic chemistry offers new approaches to supramolecular materials synthesis and assembly. We have demonstrated that an assembled viral protein cage, comprising an organic core-shell structure, can be used as a template for the size constrained synthesis of Fe(2)O(3). Particle nucleation is directed by the inner scaffold protein layer, while the size constraints are determined by the outer capsid layer.     

Directed reductive amination of beta-hydroxy-ketones: convergent assembly of the ritonavir/lopinavir core

An efficient procedure for the directed reductive amination of beta-hydroxy-ketones (3) for the stereoselective preparation of 1,3-syn-amino alcohols (6) is reported. The operationally simple protocol uses Ti(iOPr)4 for coordination of the intermediate imino alcohol (5) and PMHS as the reducing agent. The method was expanded to an asymmetric aldol reductive amination sequence to allow a highly convergent synthesis of the hydroxy-amine core of the HIV-protease inhibitors ritonavir and lopinavir. [reaction: see text].     

Synthesis of bis-indole carboxamides as G-quadruplex stabilizing and inducing ligands

The design and synthesis of a series of bis‐indole carboxamides with varying amine containing side chains as G‐quadruplex DNA stabilising small molecules are reported. Their interactions with quadruplexes have been evaluated by means of Förster resonance energy transfer (FRET) melting analysis, UV/Vis spectroscopy, circular dichroism spectroscopy and molecular modelling studies. FRET analysis indicates that these ligands exhibit significant selectivity for quadruplex over duplex DNA, and the position of the carboxamide side chains is of paramount importance in G‐quadruplex stabilisation. UV/Vis titration studies reveal that bis‐indole ligands bind tightly to quadruplexes and show a three‐ to fivefold preference for c‐kit2 over h‐telo quadruplex DNA. CD studies revealed that bis‐indole carboxamide with a central pyridine ring induces the formation of a single, antiparallel, conformation of the h‐telo quadruplex in the presence and absence of added salt. The chirality of h‐telo quadruplex was transferred to the achiral ligand (induced CD) and the formation of a preferred atropisomer was observed.     

Chemical assembly of a new heterometallic trimethylacetate cluster with the Co6Ni2 core

Co-thermolysis of the tetranuclear trimethylacetate clusters M₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ (M = Co or Ni; the reagent ratio was 1 : 1) in decalin (2 h, 170 °C) afforded the octanuclear heterometallic cluster Co₆Ni₂(₄-O)₂(₂-OOCCMe₃)₆(₃-OOCCMe₃)₆, which exhibits ferromagnetic properties at 10—8 K.     

Facile room-temperature assembly of the 1,2,4-oxadiazole core from readily available amidoximes and carboxylic acids

A one-pot ambient-temperature procedure for the synthesis of 3,5-disubstituted-1,2,4-oxadiazoles from amidoximes and carboxylic acids under superbase-promoted conditions is reported.     

Enzymatic resolution of chroman-4-ol and its core analogues with Burkholderia cepacia lipase

A convenient protocol for lipase resolution of chroman-4-ol and its analogues (six- and seven-membered rings with O, S, SO₂) has been elaborated. The structure of substrates has minor influence on the efficiency of resolution.     

Convenient access to bis-indole alkaloids. Application to the synthesis of topsentins

Topsentins and related bis-indole alkaloids may be efficiently synthesized through an addition/oxidation sequence leading to 2-(3-indolylcarbonyl)-imidazole derivatives followed by a Pd-catalyzed heteroarylation with the appropriate 3-stannylindoles.     

Formation of different gold nanocrystal core-resin shell structures through the control of the core assembly and shell polymerization

The formation of different Au nanocrystal core-resin shell structures through the control of the nanocrystal assembly and shell polymerization is investigated. 4-Mercaptophenol is employed together with formaldehyde as the resin monomers. 4-Mercaptophenol molecules bond to the surface of Au nanocrystals so that the resultant phenolic resin can intimately encapsulate Au nanocrystals. The morphologies of the obtained structures are determined by the nanocrystal assembly and the monomer polymerization behaviors, which are controlled by the solution pH as well as the monomer amounts. At pH = 8-9, Au nanorods are assembled and fused together under hydrothermal conditions in a preferential end-to-end manner. The fused structures are coated with a layer of resin, with the thickness controlled by the supplied amounts of the monomers. At pH = ～10, Au nanorods are coated with resin of controllable thicknesses and separated from each other. The resin-coated Au nanorods are stable in both aqueous and nonaqueous solutions. At pH = ～12, Au nanorods are coated with a thin layer of resin and assembled together in a side-by-side manner. A similar assembly and resin coating behavior is also observed with Au nanopolyhedrons. Moreover, plasmonic-fluorescent bifunctional structures are readily produced by incorporating CdTe nanocrystals in the resin shell that is coated on Au nanocrystals, owing to the presence of a number of thiol groups in the resin shell.     

The biosynthetic gene cluster for the antitumor rebeccamycin: characterization and generation of indolocarbazole derivatives

Rebeccamycin, a halogenated natural product of the indolocarbazole family, is produced by Saccharothrix aerocolonigenes ATCC39243. Several rebeccamycin analogues, which target DNA topoisomerase I or II, have already entered clinical trials as anticancer drugs. Using as a probe an internal fragment of ngt, a Saccharothrix aerocolonigenes gene encoding an indolocarbazole N-glycosyltransferase, we isolated a DNA region that directed the biosynthesis of rebeccamycin when introduced into Streptomyces albus. Sequence analysis of 25.6 kb revealed genes for indolocarbazole core formation, halogenation, glycosylation, and sugar methylation, as well as a regulatory gene and two resistance/secretion genes. Heterologous expression of subsets of these genes resulted in production of deschloro-rebeccamycin, 4'-demethyldeschloro-rebeccamycin, and deschloro-rebeccamycin aglycone. The cloned genes should help to elucidate the molecular basis for indolocarbazole biosynthesis and set the stage for the generation of novel indolocarbazole analogues by genetic engineering.     

Rapid assembly of the functionalized tricyclic core of umbellactal through domino metathesis involving ROM-RCM of a norbornene derivative

A novel approach to the construction of the functionalized core structure of the anticancer diterpene umbellactal is described using a domino metathesis protocol involving ROM-RCM of an appropriately constructed norbornene derivative.     

Ag@C core/shell structured nanoparticles: controlled synthesis, characterization, and assembly

Silver nanoparticles with tunable sizes were encapsulated in a carbonaceous shell through a green wet chemical route-the catalyzed dehydration of glucose under hydrothermal condition. In this one-pot synthesis, glucose was used as the reducing agent to react with Ag+ or Ag(NH3)2+, and it also served as the source of carbonaceous shells. The effects of hydrothermal temperature, time, and the concentrations of reagents on formation of the final nanostructures were systematically studied. The presence of competitive molecules poly(vinyl pyrrolidone) was found to be able to relieve the carbonization process, to incorporate themselves into carbonaceous shell, and to make the carbonaceous shell colorless. All these approaches provided diverse means to tailor the Ag@C nanostructures. By evaporation of the solvents gradually in a moist atmosphere, the monodispersed nanoparticles could self-assemble into arrays. Transmission electron microscopy, scanning electron microscopy, and UV-vis extinction spectra and surface-enhanced Raman spectra were used to characterize the core/shell nanostructures. These Ag@C core/shell nanoparticles have hydrophilic, organic-group-loaded surfaces and characteristic optical properties, which indicated their promising applications in optical nanodevices and biochemistry.     

Stereocontrolled assembly of the C3/C3' dideoxy core of lomaiviticin A/B and congeners

The dideoxy core (23) of lomaiviticinone and congener 15 were derived starting from (-)-quinic acid in a stereocontrolled fashion.     

Isolation and structure of rebeccamycin - a new antitumor antibiotic from nocardia aerocoligenes

The isolation and structure elucidation of rebeccamycin 1, a new antitumor agent from $\text{Nocardia}$$\text{Aerocoligenes}$, is described. The NMR spectra of 1 and its peracetate 2 are discussed.     

A study on the synthesis of structural analogs of bis-indole alkaloid caulerpin: a step-by-step synthesis of a cyclic indole-tetramer

The syntheses of structural isomers of bis-indole alkaloid caulerpin are investigated. Construction of the caulerpin skeleton is based on the Fisher indolization reaction of the appropriate cyclooctane-diones or cyclooctanone. In addition, a step-by-step synthesis of one isomer from possible four cyclic indole-tetramers has first been described.