Domino reactions of 5-deoxy-5-iodo-d-xylo- and -l-arabinofuranose derivatives with organometallic reagents. A way towards polyfunctionalized building-blocks

Domino reactions involving metal-halogen exchange, furanose ring-opening and nucleophilic addition from 3-O-benzyl-5-deoxy-5-iodo-1,2-O-isopropylidene-α-d-xylofuranose and the epimeric l-arabino derivative with various organometallic reagents are reported. In anhydrous conditions, with a large excess of organolithium or Grignard reagents, vicinal diols are obtained with good yields and a fair diastereoselectivity. Interestingly, with α-trimethylsilyl organolithium reagents, the fragmentation of the furanose ring to the substituted pent-4-enal is followed by a Peterson olefination giving dienic compounds in a four-step one-pot process.     

Synthesis and Crystal Structures of Novel Copper(I) Complexes of a Phosphanylborane

The novel copper iodide clusters [Cu₃(μ‐I)(μ₃‐I)₂(PH₂BH₂·NMe₃)₃] ( 2 ) and [Cu₄(μ‐I)₂(μ₃‐I)₂(PH₂BH₂·NMe₃)₃] ( 3 ) were synthesized by treating CuI with the primary phosphine (H₂PBH₂·NMe₃). The novel features of both compounds, which have been characterized by X‐ray crystallography, are the unsymmetrical constitution of the copper iodide core due to the influence of the monodentate phosphorus ligand. This results in copper atoms with different coordination numbers within the compound. Complex 2 , the major product of the reaction, contains a distorted octahedral Cu₃I₃‐core, in which one vertex is missing. Complex 3 was isolated as a by‐product and is composed of a Cu₄I₄‐core in a distorted octahedral coordination.     

Development and validation of a fast RP-HPLC method for determination of methotrexate entrapment efficiency in polymeric nanocapsules

A rapid and effective isocratic chromatographic procedure is successfully developed to determinate methotrexate (MTX) entrapment efficiency (EE) in polymeric nanocapsules using reversed-phase high-performance liquid chromatography. The method employed a RP-C(18) Shimadzu Shim-pack CLC-ODS (150 mm x 4.6 mm, 5 microm) column with mobile phase constituted by a mixture of water-acetonitrile-tetrahydrofuran (65:30:5 v/v/v; pH 3.0) at a flow rate of 0.8 mL/min. The eluate is monitored with a UV detector set at 313 nm. The parameters used in the validation process are: linearity, specificity, precision, accuracy, and limit of quantitation (LOQ). The linearity is evaluated by a calibration curve in the concentration range of 10-50 microg/mL and presented a correlation coefficient of 0.9998. The polymers (PLA or PLA-PEG), oil, and surfactants used in the nanocapsule formulation did not interfere with analysis and the recovery was quantitative. The intra and inter-day assay relative standard deviation were less than 0.72%. Results are satisfactory, and the method proved to be adequate for the determination of methotrexate in nanocapsules formulations.     

A method to find generators of a semi-simple Lie group via the topology of its flag manifolds

In this paper we continue to develop the topological method to get semigroup generators of semi-simple Lie groups. Consider a subset \(\Gamma \subset G\) that contains a semi-simple subgroup \(G_{1}\) of G. If one can show that \( \Gamma \) does not leave invariant a contractible subset on any flag manifold of G, then \(\Gamma \) generates G if \(\mathrm {Ad}\left( \Gamma \right) \) generates a Zariski dense subgroup of the algebraic group \(\mathrm {Ad}\left( G\right) \). The proof is reduced to check that some specific closed orbits of \(G_{1}\) in the flag manifolds of G are not trivial in the sense of algebraic topology. Here, we consider three different cases of semi-simple Lie groups G and subgroups \(G_{1}\subset G\).     

Modified locus equations categorize stop place in a perceptually realistic time frame

Slope and y-intercepts of locus equations have previously been shown to successfully classify place of articulation for English voiced stop consonants when derived from measurements at vowel onset and vowel midpoint. However, listeners are capable of identifying English voiced stops when less than 30 ms of vowel is presented. The present results show that modified locus equation measurements made within the first several pitch periods of a vowel following an English voiced stop were also successful at classifying place of articulation, consistent with the amount of vocalic information necessary for perceptual identification of English voiced stops /b d g/.     

High Spin and Anisotropic Molecules Based on Polycyanometalate Chemistry

 This paper points out some recent achievements in the chemistry and physics of high spin and anisotropic molecules based on polycyanometalate complexes. Following a step by step synthetic strategy and using a localized electron orbital model, isotropic high spin molecules were obtained with ground spin states ranging from S = 9/2 to 27/2. In the same way, anisotropic molecules with various nuclearities (bi, tri, tetra, hexa, and hepta-nuclear complexes) have been synthesized. Mixing these two approaches, it has been possible to obtained anisotropic high spin molecules that behave as single molecule magnets. The paper reviews some of the steps that lead to these findings and some of the prospects opened in the field of single molecule magnets.     

Rational functions with linear relations

We find all polynomials over a field such that and are linear and . We also solve the same problem for rational functions , in case the field is algebraically closed.