Total Asymmetric Synthesis of 5-Deoxy-5-thio-l-allose

Abstract

The optically pure Diels-Alder adduct of furan to 1-cyanovinyl (1R)-camphanate was converted to methyl(methyl 5-bromo-5-deoxy-2,3-O-isopropylidene-β-l-allo-hexo-furanosid)uronate. Ester reduction, followed by HBr elimination afforded (+)-methyl 5,6-anhydro-2,3-O-isopropylidene-d-β-talo-hexofuranoside. Applying the method of Adley and Owen, (+)-methyl 5,6-dideoxy-5,6-epithio-2,3-O-isopropylidene-l-β-allo-hexofuranoside was obtained and acetolysed to give, after deprotection, (-)-5-deoxy-5-thio-l-allose.     

Nonparametric estimation in fractional SDE

Statistical Inference for Stochastic Processes - This paper deals with the consistency and a rate of convergence for a Nadaraya–Watson estimator of the drift function of a stochastic...     

Sulfur dioxide Plasma Treatment of the Clay (Laponite) Particles

Low temperature plasma treatment of the inorganic clay (Laponite) using sulfur dioxide (SO₂) as a process gas was carried out in order to graft the functional groups containing sulfur and oxygen (sulfonic acid groups) onto the inert clay surface. Conditions for SO₂ plasma modification were optimized by the measurement of the sulfur content as a function of the plasma power, gas flow rate and treatment time. It was found that the sulfur content increased with the increasing of the plasma power as well as the treatment time. Optical emission spectroscopy was presented in order to control the plasma phase and to characterize the different excitation processes of atomic species in SO₂ plasma under different discharge conditions. X-ray diffraction spectrometry, X-ray photoelectron spectroscopy, FTIR and thermal analysis measurements of grafted Laponite powder completed the characterization.     

DNA-polymer micelles as nanoparticles with recognition ability

The Watson-Crick binding of DNA single strands is a powerful tool for the assembly of nanostructures. Our objective is to develop polymer nanoparticles equipped with DNA strands for surface-patterning applications, taking advantage of the DNA technology, in particular, recognition and reversibility. A hybrid DNA copolymer is synthesized through the conjugation of a ssDNA (22-mer) with a poly(ethylene oxide)-poly(caprolactone) diblock copolymer (PEO-b-PCl). It is shown that, in water, the PEO-b-PCl-ssDNA(22) polymer forms micelles with a PCl hydrophobic core and a hydrophilic corona made of PEO and DNA. The micelles are thoroughly characterized using electron microscopy (TEM and cryoTEM) and small-angle neutron scattering. The binding of these DNA micelles to a surface through DNA recognition is monitored using a quartz crystal microbalance and imaged by atomic force microscopy. The micelles can be released from the surface by a competitive displacement event.     

An innovative antisolvent precipitation process as a promising technique to prepare ultrafine rifampicin particles

Many existing and new drugs fail to be fully utilized because of their limited bioavailability due to poor solubility in aqueous media (BCS drug classes II and IV). In this work, for accelerating dissolution of this kind of poorly water-soluble drugs, an antisolvent precipitation method that does not require the use of conventional volatile organic solvents is proposed. To demonstrate this technique, ultrafine particles of rifampicin were prepared using a room temperature ionic liquid (1-ethyl 3- methyl imidazolium methyl-phosphonate) as an alternative solvent and a phosphate buffer as an antisolvent.Rifampicin solubility was measured in various solvents (1-ethyl 3-methyl imidazolium methylphosphonate, water and phosphate buffer), showing the RTIL good solvency for the model drug: rifampicin solubility was found to be higher than 90 mg/g in RTIL at 30 °C and lower than 1 mg/g in water at 25 °C. Additionally, it was demonstrated that introduction of rifampicin solution in 1-ethyl 3- methyl imidazolium methyl-phosphonate into the aqueous solution antisolvent can produce particles in the submicron range with or without hydroxypropyl methylcellulose as the stabilizer. The ultrafine particles (280–360 nm) are amorphous with enhanced solubility and faster dissolution rate. To our knowledge, this is the first published work examining the suitability of using RTILs for ultrafine drug nanoparticles preparation by an antisolvent precipitation process.     

Twin-transformed lattice defects in γ-TiAl

We study the transformation of lattice defects in γ-TiAl upon intersection by deformation twins. A faulted dipole is chopped forming a dislocation loop faulted on the cube plane of the twin; faulted dipoles and twin loops may shrink at different rates. Dislocations with 1/2<110] and <011] Burgers vectors gliding on octahedral planes are transformed into configurations with low mobility on {010} plane. Elementary mechanisms involved in the transformation are considered and a pole mechanism for twin growth at forest dislocations is proposed.     

Random walk in random scenery and self-intersection local times in dimensions d ≥ 5

Let {S _k , k ≥ 0} be a symmetric random walk on , and an independent random field of centered i.i.d. random variables with tail decay . We consider a random walk in random scenery, that is . We present asymptotics for the probability, over both randomness, that {X _n > n ^β} for β > 1/2 and α > 1. To obtain such asymptotics, we establish large deviations estimates for the self-intersection local times process , where l _n (x) is the number of visits of site x up to time n.