Efficient and selective synthesis of glycofuranosyl azides and nucleosides from cyclic 1,2-thiocarbonate sugars

[reaction: see text] Cyclic 1,2-thiocarbonate sugars are convenient starting materials for the selective and efficient preparation of glycofuranosyl azides and nucleosides by regio- and stereoselective thiocarbonate ring-opening.     

Supramolecular Inclusion Hosts Based on Amino Acid Compound Sources: Design, Synthesis and Crystalline Inclusion Behaviour. X-Ray Crystal Structures of Two Inefficient Host Compounds

A new design of crystalline hosts derived from amino acids, characterised by an amino- ethanol functional unit or its carbonamide structural derivative and appended aromatic residues including secondary substituents, is reported. The syntheses of corresponding compounds (1–15) are described. Crystalline inclusion formation is shown and discussed with reference to structural parameters of the host molecules. X-Ray crystal structures of compounds 3 and 11 have been determined in order to suggest reasons for their failure to show inclusion ability.     

Synthesis of polyhydroxycyclohexanes and relatives from (-)-quinic acid

An efficient and versatile strategy for the synthesis of polyhydroxycyclohexanes and related compounds 3-6 is reported. The successful synthesis of these analogues has been achieved from a common intermediate, quinic acid derived lactone 2, rapidly accessible from cheap and commercially available (-)-quinic acid (1) as a chiral template. A practical route involving stereocontrolled epoxide formation and hydrolysis has been developed for the synthesis of 2,3-trans analogues 3 and 4. The preparation of the 2,3-cis analogues 5 and 6 has been realized by diasteroselective oxidation of a 5,6-double bond.     

Fentanyl and its analogue N-(1-phenylpyrazol-3-yl)-N-[1-(2-phenylethyl)-4-piperidyl]propanamide: 1H- and 13C-NMR spectroscopy,X-ray crystallography,and theoretical calculations

The oxalate salts and free bases of fentanyl and N-[1-(2-phenylethyl)-4-piperidyl]-N-(1-phenyl-4-pyrazolyl)propanamide, a new lead compound for long-acting analgesia, have been characterized by (1)H- and (13)C-NMR spectroscopy. The crystal structure of the hydrochloride of N-[1-(2-phenylethyl)-4-piperidyl]-N-(1-phenyl-4-pyrazolyl)propanamide monohydrate has been determined. Two centrosymmetrically related cations, joined through C(phenyl)-H em leader pi contacts, encapsulate a large void that contains pairs of anions and bridged water molecules into a zero-dimensional (0D) supramolecular motif. The cations are linked to this framework via N(+)H em leader Cl(-) contacts. GIAO/B3LYP calculations have been carried out to compare the experimental (13)C chemical shifts with the absolute shieldings thus calculated. The protonation of both molecules takes place on the piperidine ring (axial protonation), as has been verified both in the solid state (X-ray) and in solution (NMR).     

Novel fused D-A dyad and A-D-A triad incorporating tetrathiafulvalene and p-benzoquinone

Novel fused donor-acceptor dyad (TTF-Q or D-A) and acceptor-donor-acceptor triad (Q-TTF-Q or A-D-A) incorporating the donor tetrathiafulvalene (TTF) and the acceptor p-benzoquinone (Q) have been synthesized. The solution UV-vis spectra of these molecules display a low-energy absorption band that is attributed to an intramolecular charge transfer between both antagonistic units. The presence of reversible oxidation and reduction waves for the donor and acceptor moieties was shown by cyclic voltammetry, in agreement with the ratio TTF/quinone(s) units. The successive generation from these compounds of the cation radical and anion radical obtained upon (electro)chemical oxidation and reduction, respectively, was monitored by optical and ESR spectroscopies. The anion radical Q-TTF-Q(-.) triad was demonstrated to be a class II mixed-valence system with the existence of a temperature-dependent intramolecular electron transfer. The crystallographic tendency of these fused systems to overlap in mixed stacks of alternating A-D-A units is also discussed.     

One teflon-like channelled nanoporous polymer with a chiral and new uninodal 4-connected net: sorption and catalytic properties

Zn(C17H8F6O4) is the first example of a fluoro-lined nanotube organo-inorganic 3D polymeric chiral structure, which possesses two different types of isolated channels, one of them being laid out with a double spiral of CF3-groups from the ligand molecule; the structure is a new uninodal 4-connected net that only exists when bent ligands connect the centres, and the compound exhibits selective sorption and catalytic chiral recognition properties.     

Hydrogen-bonded self-assemblies in a polychlorotriphenylmethyl radical derivative substituted with six meta-carboxylic acid groups

The synthesis, self assembly and magnetic properties of a polychlorotriphenylmethyl radical, substituted with six meta-carboxylic groups, are reported showing that radical-radical hydrogen bonds in the solid state yield to very weak intermolecular ferromagnetic interactions.     

Multistability in a BEDT-TTF based molecular conductor

The low dimensional organic conductor (BEDT-TTF)(2)Br(1.3)I(1.1)Cl(0.6) [BEDT-TTF = bis(ethylenedithio)tertathiafulvalene] is shown to be a unique molecular solid that exists in three crystalline polymorphic forms (alpha'-, alpha' "-, beta' '-phase) and, surprisingly, is able to adopt the same metal-like beta' '-phase at both low (T < 185 K) and high (T > 395 K) temperatures. Several crystals of the alpha'- and alpha' "-phases have been studied using three different techniques: dc-conductivity measurements, ESR spectroscopy, and X-ray diffraction analysis. All these techniques show the existence of the reversible semiconductor <--> metal (alpha' " <--> beta' ') phase transition at both high and low temperatures as well as the alpha' <--> alpha' " phase transition at high temperatures. The phase transitions of these polymorphs are characterized by huge hysteresis and dramatic changes in the transport and magnetic properties. Based on ab initio calculations, it is suggested that dipole-dipole interactions can play a key role in the rich polymorphism of this molecular solid.