Synthesis of α-hydroxyalkyl dehydroazepanes via catalytic enantioselective borylative migration of an enol nonaflate

A Pd-catalyzed borylative migration methodology for cyclic enol perfluorosulfonates was applied to the synthesis of the corresponding 7-membered, azepane ring system. Throughout the optimization, it was shown that the reaction is sensitive to the nitrogen protecting group as well as the type of base and solvent. The resulting cyclic allylboronate reacts stereoselectively with aldehydes for the synthesis of novel α-hydroxyalkyl dehydroazepanes in good yield and enantioselectivity over two steps. We highlight the utility of this methodology with an efficient synthesis of the de novo 7-membered ring analogue of the piperidine alkaloid β-conhydrine.     

Protein–ligand docking using FFT based sampling: D3R case study

Fast Fourier transform (FFT) based approaches have been successful in application to modeling of relatively rigid protein–protein complexes. Recently, we have been able to adapt the FFT methodology to treatment of flexible protein–peptide interactions. Here, we report our latest attempt to expand the capabilities of the FFT approach to treatment of flexible protein–ligand interactions in application to the D3R PL-2016-1 challenge. Based on the D3R assessment, our FFT approach in conjunction with Monte Carlo minimization off-grid refinement was among the top performing methods in the challenge. The potential advantage of our method is its ability to globally sample the protein–ligand interaction landscape, which will be explored in further applications.     

Comparison of irradiated foil measurements with activation calculations and HPGe simulations

Theoretical activation calculations for Fe, Ni, and stainless steel foils were compared against irradiated foil measurements from a critical assembly. Calculated/experiment values spanning 0.62–1.31 showed that the restricted approach used here is insufficient for experiment planning, with the collapsed cross-section being the primary source of error. The effect of decay time on gamma-ray spectroscopy measurement reliability was investigated using a Monte Carlo HPGe detector model. Simulations showed no correlation with decay time, absent interferences. Specific interferences for Fe-59 (Ni) and Co-60 (stainless steel) activation product ratios suggested optimal measurement windows having respective decay times of 9–11 days and 4–7 days.     

Allenyl esters as quenching agents for ruthenium olefin metathesis catalysts

In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification.     

Synthesis,characterization and energetic properties of novel 1-methyl-1,2,4-triazolium N-aryl/N-pyridinyl ylids

Synthesis, characterization and energetic properties of novel, nitrogen-rich 1-methyl-1,2,4-triazolium N-aryl/N-pyridinyl ylids 3a–m are reported.     

Syntheses and photophysical properties of some 5(2)-aryl-2(5)-(4-pyridyl)oxazoles and related oxadiazoles and furans

A number of 5-aryl-2-(4-pyridyl)oxazoles, a 2-aryl-5-(4-pyridyl)oxazole, the related oxadiazole and furan, several 2-(4-pyridyl)cycloalkano[d]oxazoles, and many of their quaternary salts were prepared. No single standard synthesis was effective for preparation of more than a few of the 25 free bases described; methods often unique to a base were employed. Minor variations in structure sometimes produced large differences in absorption and emission wavelengths, as well as in the magnitude of the extinction coefficient. The salts are of interest as laser dyes, scintillation fluors, biological stains, and shifters for luminescent solar concentrators.     

Electrostatic water models

The possiblity of creating a useful model for the electrostatic potential around the water molecule is examined from two different starting points. It is suggested that the simplest and most accurate model will have three point charges on the nuclei together with a diffuse Gaussian charge centered near the nuclear center of the charge. This will represent the lone-pair cloud, include the penetration effects, and improve the representation of the electron density. The alternative use of atomic dipoles is explored but seen to be less effective.     

The crank moments weighted by the parity of cranks

In this note, we introduce the 2kth crank moment \(\mu _{2k}(-1,n)\) weighted by the parity of cranks and show that \((-1)^n \mu _{2k}(-1,n)>0\) for \(n\ge k \ge 0\). When \(k=0\), the inequality \((-1)^n \mu _{2k}(-1,n)>0\) reduces to Andrews and Lewis’s inequality \((-1)^n(M_e(n)-M_o(n))>0\) for \(n\ge 0\), where \(M_e(n)\) (resp. \(M_o(n)\)) denotes the number of partitions of n with even (resp. odd) crank. Several generating functions of \(\mu _{2k}(-1,n)\) are also studied in order to show the positivity of \((-1)^n\mu _{2k}(-1,n)\).     

Limit theorems for the median deviation

Summary In this paper, we obtain a strong law and central limit theorem for the median deviation under only very mild smoothness conditions on the underlying distribution. Under an additional condition implied by symmetry, we derive a weak Bahadur representation for the median deviation and establish the asymptotic equivalence of the median deviation and the semi-interquartile range.