New Chiral Ortho-P,S-Difunctionalized Aromatic Compounds

Abstract

A new method to prepare enantioenriched sulfinates was developed to obtain optically active ortho-methylsulfinyl(phenylphosphonates). It consists of a diastereoselective oxidation of sulfenates to sulfinates. Additionally, preliminary results concerning the synthesis of ortho-phophonylated benzylic thiol derivatives via a new P═S to P═C [1,4]-rearrangement and a first synthetic application of these compounds are also described.     

A diastereoselective C–C bond formation at C-5 of d-gulose. A convenient approach to (5S)-5-C-alkyl-β-l-lyxo-hexofuranoses

A flexible approach to the stereoselective synthesis of (5S)-5-C-methyl- and (5S)-5-C-ethyl-β-l-lyxo-hexofuranoses 15a, 22 starting from 1,2:5,6-di-O-isopropylidene-α-d-gulofuranose 3 as the source of chirality is described. The corresponding C-5 alkyl groups were introduced via a Wittig olefination followed by Pd/C-mediated hydrogenation of the conformationally restricted alkenes in a highly diastereoselective manner.     

The preparation of the 239Np tracer from 243Am and the purification of the stock solution

The present work describes preparation of ²³⁹Np tracer from ²⁴³Am stock solution and the purification of this solution from ferric cation. The method of the preparation of tracer involves stabilization of Np(IV) by ascorbic acid and ferric nitrate, separation of ²³⁹Np from ²⁴³Am by extraction chromatography and determination of recoveries of ²³⁹Np by means of gamma spectroscopy. We used the commercially available sorbents TEVA^®Resin for the ²³⁹Np preparation and DGA Resin for ²⁴³Am purification. All sorbents were purchased from Eichrom Industries, Inc. The first eluate from the column can be stored for a future preparation of the tracer and fraction with ²³⁹Np will be used to monitor radiochemical yield of ²³⁷Np.     

Stereoselective total synthesis of protected sulfamisterin and its analogues

The stereoselective synthesis of sulfamisterin I and its unnatural analogues II and V in their protected form was achieved through a common strategy. The Wittig reaction of aldehydes VIII and IX with the C₁₄ hydrophobic side-chain X served as the key C-C connecting transformation. Subsequent functional group inter-conversions in the coupling products XI and XX completed the total synthesis.     

Application of umbelliferone molecularly imprinted polymer in analysis of plant samples

The molecularly imprinted polymers (MIPs) were synthesised and the influence of the type of porogen, the nature of sample solvent, and the binding capacity of material were tested by high-performance liquid chromatography (HPLC). Umbelliferone was used as the template for imprint formation. Methacrylic acid was used as the monomer and acetonitrile, ethanol, and chloroform as porogen. Non-imprinted polymers (NIPs) were prepared by the same procedure. The highest value of the specific binding capacity (269 μg of umbelliferone per 100 mg of polymer) was obtained for polymers prepared in chloroform as porogen and methanol/water (φ _r = 1: 1) as the sample solvent. The group-selective MIP was used as sorbent for the SPE pre-treatment of umbelliferone from plant extracts prior to HPLC analysis. Analysis of the spiked samples showed good recoveries (> 77 %). The limit of detection, limit of determination, and repeatability of the method were also calculated.     

DNA Interaction with 17α‐Ethinylestradiol Studied Using Electrochemical Biosensors and Biosensing in Solution

The synthetic estrogen 17α‐ethinylestradiol (EE2) is an active component of oral contraceptives. It is considered as an endocrine disrupting compound that, once incorporated into an organism, affects the hormonal balance of animals and humans. In this study we characterized the DNA‐EE2 interaction using an electrochemical biosensor and biosensing in solution phase with the double stranded DNA from salmon sperm and deoxyguanosine monophosphate (dGMP). Differential pulse voltammetry method has been applied based on voltammetric anodic responses of the deoxyguanine (dGuo) and deoxyadenine (dAdo) as well as EE2 in the medium of phosphate buffer solution pH 7.0. Binding of EE2 to the nucleobases leads to a decrease of their anodic signals. Association constant for DNA‐EE2 interaction has been estimated to be about 1.1 ? 10³ L mol^?1 and 1.4 ? 10³ L mol^?1 for dGuo and dAdo responses, respectively. The association is reversible as indicated by decrease of the EE2 response in pure buffer solution due to leaching of EE2 from the surface attached DNA. The DNA‐EE2 association has been confirmed also by UV‐vis spectrometric experiments.     

Photokinetic,Biochemical and Structural Features of Chimeric Photoactive Yellow Protein Constructs

Of the 10 photoactive yellow protein (PYPs) that have been characterized, the two from Rhodobacter species are the only ones that have an additional intermediate spectral form in the resting state (λ_max = 375 nm), compared to the prototypical Halorhodospira halophila PYP. We have constructed three chimeric PYP proteins by replacing the first 21 residues from the N‐terminus (Hyb1PYP), 10 from the β4–β5 loop (Hyb2PYP) and both (Hyb3PYP) in Hhal PYP with those from Rb. capsulatus PYP. The N‐terminal chimera behaves both spectrally and kinetically like Hhal PYP, indicating that the Rcaps N‐terminus folds against the core of Hhal PYP. A small fraction shows dimerization and slower recovery, possibly due to interaction at the N‐termini. The loop chimera has a small amount of the intermediate spectral form and a photocycle that is 20 000 times slower than Hhal PYP. The third chimera, with both regions exchanged, resembles Rcaps PYP with a significant amount of intermediate spectral form (λ_max = 380 nm), but has even slower kinetics. The effects are not strictly additive in the double chimera, suggesting that what perturbs one site, affects the other as well. These chimeras suggest that the intermediate spectral form has its origins in overall protein stability and solvent exposure.     

Superbeads: immobilization in "sweet" chemistry

Enzymatic oligosaccharide synthesis using recombinant glycosyltransferases is able to overcome the difficulties associated with chemical methods. Nonetheless, sugar nucleotide regeneration cycles are necessary for the glycosylation. The multistep enzyme reaction can be efficiently carried out on superbeads that are prepared by immobilizing multienzyme mixtures on bead support through fused binding domains.     

Ion transmission in an electrospray ionization-mass spectrometry interface using an S-lens

We present the design and performance of an in-house built electrospray ionization-mass spectrometry (ESI-MS) interface equipped with an S-lens ion guide. The ion source was designed specifically for our ion beam experiments to investigate the chemical reactivity and deposition of the clusters and nanoparticles. It includes standard ESI-MS interface components, such as nanoelectrospray, ion transfer capillary, and the S-lens. A custom design enables systematic optimization of all relevant factors influencing ion formation and transfer through the interface. By varying the ESI voltage and flow rate, we determined the optimal operating conditions for selected silica emitters. A comparison of the pulled silica emitters with different tip inner diameters reveals that the total ion current is highest for the largest tip, whereas a tip with the smallest diameter exhibited the highest transmission efficiency through the ESI-MS interface. Ion transmission through the transfer capillary is strongly limited by its length, but the loss of ions can be reduced by increasing the capillary voltage and temperature. The S-lens was characterized over a wide range of RF frequencies and amplitudes. Maximum ion current was detected at RF amplitudes greater than 50 V peak-to-peak (p/p) and frequencies above 750 kHz, with a stable ion transmission region of about 20%. A factor of 2.6 increase in total ion current is observed for 650 kHz as RF amplitudes reach 400 V p/p. Higher RF amplitudes also focus the ions into a narrow beam, which mitigates their losses when passing through the ion guide.