Evaluation of asymmetric Diels-Alder approaches for the synthesis of the cyclohexene subunit of CP-225,917 and CP-263,114

Asymmetric synthesis of a functionalised cyclohexenone required for total synthesis of CP-225,917 and CP-263,114 is reported, using a Lewis acid-promoted Diels-Alder reaction between a 2-silyloxy-1,3-diene and a dienophile bearing an oxazolidinone auxiliary. A novel method for appendage of the exocyclic malonate unit, via cyclopropane ring opening, is also described.     

Determination of total arsenic in serum and packed cellsof patients with renal insufficiency

In order to investigate the arsenic level in serum and packed cells of patients with renal insufficiency, total arsenic (As) concentrations were determined with hydride generation atomic absorption spectrometry (HGAAS) in serum (S) and packed cells (PC) of 31 non-dialyzed patients. The accuracy of the method was tested by the analysis of arsenic in 3 certified reference materials. Patients showed a three-fold increase of arsenic concentrations in serum and a two-fold increase of arsenic in packed cells compared with controls. Patients (n=10) with higher serum creatinine (>2.0 mg/dL), urea (>0.70 g/L) and urinary protein (mean ±SD: 1.12±0.82 g/L) showed higher arsenic concentrations (5.8±3.3 g/L in serum and 18.0±16.7 g/kg in packed cells) compared with those with lower creatinine (<1.6 mg/dL), urea (<0.6 g/L) and urinary protein (mean ±SD: 0.27±0.82 g/L) (n=16, serum arsenic 1.2±1.2 g/L, packed cells arsenic 2.6±1.9 g/kg). The significant differences (both p<0.001) in S and PC-arsenic levels of patients in group I and II implies a relationship between the arsenic level and the degree of chronic renal insufficiency.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday     

Ethynylgold(I) complexes

Reactions between R₃PAuCl, NaOEt, and HCCR′ under mild conditions produce R₃PAuCCR′ in excellent yield. When R′ = H, a second step leading to the formation of R₃PAuCCAuPR₃ can take place. Exchange reactions of ethynyl for chloride between the ethynylgold complexes and HgCl₂, cis-[PtCl₂L₂cis-[PtCl₂(CO)L], and R₂″PAuCl have been monitored, revealing R₃PAuCCR′ to be useful alkynylating agents. In the reaction with cis-[PtCl₂(CO)L], the first substitution step is non-specific.     

The structures,binding energies and vibrational frequencies of Ca3 and Ca4 — An application of the CCSD(T) method

Summary The Ca₃ and Ca₄ metallic clusters have been investigated using state-of-the-artab initio quantum mechanical methods. Large atomic natural orbital basis sets have been used in conjunction with the singles and doubles coupled-cluster (CCSD) method, a coupled-cluster method that includes a perturbational estimate of connected triple excitations, denoted CCSD(T), and the multireference configuration interaction (MRCI) method. The equilibrium geometries, binding energies and harmonic vibrational frequencies have been determined with each of the methods so that the accuracy of the coupled-cluster methods may be assessed. Since the CCSD(T) method reproduces the MRCI results very well, cubic and quartic force fields of Ca₃ and Ca₄ have been determined using this approach and used to evaluate the fundamental vibrational frequencies. The infrared intensities of both thee mode of Ca₃ and thet ₂ mode of Ca₄ are found to be small. The results obtained in this study are compared and contrasted with those from our earlier studies on small Be and Mg clusters.Dedicated to Prof. Klaus Ruedenberg on the occasion of his 70th birthday     

Thermo-Reversible Cellulose Micro Phase-Separation in Mixtures of Methyltributylphosphonium Acetate and γ-Valerolactone or DMSO

We have identified cellulose solvents, comprised of binary mixtures of molecular solvents and ionic liquids that rapidly dissolve cellulose to high concentration and show upper-critical solution temperature (UCST)-like thermodynamic behaviour - upon cooling and micro phase-separation to roughly spherical microparticle particle-gel mixtures. This is a result of an entropy-dominant process, controllable by changing temperature, with an overall exothermic regeneration step. However, the initial dissolution of cellulose in this system, from the majority cellulose I allomorph upon increasing temperature, is also exothermic. The mixtures essentially act as ‘thermo-switchable’ gels. Upon initial dissolution and cooling, micro-scaled spherical particles are formed, the formation onset and size of which are dependent on the presence of traces of water. Wide-angle X-ray scattering (WAXS) and ¹³C cross-polarisation magic-angle spinning (CP-MAS) NMR spectroscopy have identified that the cellulose micro phase-separates with no remaining cellulose I allomorph and eventually forms a proportion of the cellulose II allomorph after water washing and drying. The rheological properties of these solutions demonstrate the possibility of a new type of cellulose processing, whereby morphology can be influenced by changing temperature.     

Twisted Heisenberg Doubles

We introduce a twisted version of the Heisenberg double, constructed from a twisted Hopf algebra and a twisted pairing. We state a Stone–von Neumann type theorem for a natural Fock space representation of this twisted Heisenberg double and deduce the effect on the algebra of shifting the product and coproduct of the original twisted Hopf algebra. We conclude by showing that the quantum Weyl algebra, quantum Heisenberg algebras, and lattice Heisenberg algebras are all examples of the general construction.     

BioMOFs: Metal–Organic Frameworks for Biological and Medical Applications

The class of highly porous materials called metal–organic frameworks offer many opportunities for applications across biology and medicine. Their wide range of chemical composition makes toxicologically acceptable formulation possible, and their high level of functionality enables possible applications as imaging agents and as delivery vehicles for therapeutic agents. The challenges in the area encompass not only the development of new solids but also improvements in the formulation and processing of the materials, including tailoring the morphology and surface chemistry of the frameworks to fit the proposed applications.