Efficient synthesis of (3R,3aS,6aR)- hexahydrofuro[2,3-b]furan-3-ol from glycolaldehyde

A one-step diastereoselective (up to 98:2) synthesis of the bis-furan alcohol of Darunavir and other HIV drug candidates has been achieved utilizing the novel cyclization of glycolaldehyde and 2,3-dihydrofuran. The cycloaddition was catalyzed by a variety of catalysts including those formed from tin(II) triflate and common chiral ligands such as BINAP and Evans's box ligands. An efficient and unique enzymatic process enhanced the enantiomeric purity to provide the target in optically pure form.     

The random <Emphasis Type="Italic">k</Emphasis> cycle walk on the symmetric group

We study the random walk on the symmetric group \(S_n\) generated by the conjugacy class of cycles of length k. We show that the convergence to uniform measure of this walk has a cut-off in total variation distance after \(\frac{n}{k}\log n\) steps, uniformly in \(k = o(n)\) as \(n \rightarrow \infty \). The analysis follows from a new asymptotic estimation of the characters of the symmetric group evaluated at cycles.     

ROC-curve approach for determining the detection limit of a field chemical sensor

The detection limit of a field chemical sensor under realistic operating conditions is determined by receiver operator characteristic (ROC) curves. The chemical sensor is an ion mobility spectrometry (IMS) device used to detect a chemical marker in diesel fuel. The detection limit is the lowest concentration of the marker in diesel fuel that obtains the desired true-positive probability (TPP) and false-positive probability (FPP). A TPP of 0.90 and a FPP of 0.10 were selected as acceptable levels for the field sensor in this study. The detection limit under realistic operating conditions is found to be between 2 to 4 ppm (w/w). The upper value is the detection limit under challenging conditions. The ROC-based detection limit is very reliable because it is determined from multiple and repetitive sensor analyses under realistic circumstances. ROC curves also clearly illustrate and gauge the effects data preprocessing and sampling environments have on the sensor's detection limit.     

Hydrothermal Synthesis and Crystal Structure of a New Manganese（Ⅱ） Complex with 2,4-Pyridine-dicarboxylic Acid and 2,2′-Bipyridine Ligands

A new metal-organic complex [Mn2（PDC）2（bipy）2（H2O）2] （H2PDC = 2,4-pyridine-dicarboxylic acid, bipy = 2,2′-bipyridine） 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. The compound crystallizes in triclinic, space group P ^-1 with a = 7.376（3）, b = 9.990（4）, c = 11.950（5） A^°, α= 75.217（5）, β = 78.052（5）, γ = 70.655（5）°, V = 796.0（5）A^°3, C34HE6Mn2N6O10, Mr = 788.49, De = 1.645 g/cm^3,μ（MoKa） = 0.866 mm^-1, F（000） = 235, Z = 1, the final R = 0.0425 and wR = 0.0700 for 1971 observed reflections （I 〉 2σ（I））. In the crystal structure, the manganese atom is six-coordinated by two carboxylate oxygen atoms from two different PDC ligands, one aqua ligand, and three nitrogen atoms from 2,2′-bipy and PDC ligands, giving a distorted octahedral geometry. It exhibits a three-dimensional supramolecular network defined by O-H…O hydrogen-bonding interactions.     

Fast liquid chromatography separation and multiple‐reaction monitoring mass spectrometric detection of neurotransmitters

We describe here the fast LC‐MS/MS separation of a mixture of neurotransmitters consisting of dopamine, epinephrine, norepinephrine, 3,4‐dihydroxybenzylamine (DHBA), salsolinol, serotonin, and γ‐aminobutyric acid (GABA). The new UltiMate® 3000 Rapid Separation system (RSLC) was successfully coupled to the 4000 QTRAP mass spectrometer operating in multiple‐reaction monitoring (MRM) mode. The separation was attained using a 100 mm length, 2.2 μm particle size Acclaim column at a flow rate of 0.5 mL/min. The column back pressure was 350 bar, while the total run time including column re‐equilibration was 5.2 min. The peak resolution was minimally affected by the fast separation. The RSLC‐MRM separation was found to have a precision range based on peak area for 50 replicate runs of 2–5% CV for all analytes, and the reproducibility of the retention time for all analytes was found to range from 0–2% CV. The described method represents an almost seven times shorter analysis time of neurotransmitters using LC/MRM which is very useful in screening large quantities of biological samples for various neurotransmitters.     

Operational Properties of Two Integral Transforms of Fourier Type and their Convolutions

In this paper we present the operational properties of two integral transforms of Fourier type, provide the formulation of convolutions, and obtain eight new convolutions for those transforms. Moreover, we consider applications such as the construction of normed ring structures on L₁(\mathbbR)L_{1}({\mathbb{R}}), further applications to linear partial differential equations and an integral equation with a mixed Toeplitz-Hankel kernel.