O privacy, where art thou?

In last issue's column, John Abowd and Lars Vilhuber discussed the interplay between science, confidentiality, and the public good and outlined some of the data access modalities, in particular a synthetic data model implemented by the Cornell Virtual Research Data Center. In this month's column, Saki Kinney and Alan Karr from the National Institute of Statistical Sciences give details about how access is operationalized and offer practical guidelines and considerations for researchers seeking access to confidential data from government agencies.     

4‐Methyltetrahydropyran (4‐MeTHP): Application as an Organic Reaction Solvent

4‐Methyltetrahydropyran (4‐MeTHP) is a hydrophobic cyclic ether with potential for industrial applications. We herein report, for the first time, a comprehensive study on the performance of 4‐MeTHP as an organic reaction solvent. Its broad application to organic reactions includes radical, Grignard, Wittig, organometallic, halogen‐metal exchange, reduction, oxidation, epoxidation, amidation, esterification, metathesis, and other miscellaneous organic reactions. This breadth suggests 4‐MeTHP can serve as a substitute for conventional ethers and harmful halogenated solvents. However, 4‐MeTHP was found incompatible with strong Lewis acids, and the C?O bond was readily cleaved by treatment with BBr₃. Moreover, the radical‐based degradation pathways of 4‐MeTHP, THP and 2‐MeTHF were elucidated on the basis of GC‐MS analyses. The data reported herein is anticipated to be useful for a broad range of synthetic chemists, especially industrial process chemists, when selecting the reaction solvent with green chemistry perspectives.     

Image Defogging Framework Using Segmentation and the Dark Channel Prior

Foggy images suffer from low contrast and poor visibility problem along with little color information of the scene. It is imperative to remove fog from images as a pre-processing step in computer vision. The Dark Channel Prior (DCP) technique is a very promising defogging technique due to excellent restoring results for images containing no homogeneous region. However, having a large homogeneous region such as sky region, the restored images suffer from color distortion and block effects. Thus, to overcome the limitation of DCP method, we introduce a framework which is based on sky and non-sky region segmentation and restoring sky and non-sky parts separately. Here, isolation of the sky and non-sky part is done by using a binary mask formulated by floodfill algorithm. The foggy sky part is restored by using Contrast Limited Adaptive Histogram Equalization (CLAHE) and non-sky part by modified DCP. The restored parts are blended together for the resultant image. The proposed method is evaluated using both synthetic and real world foggy images against state of the art techniques. The experimental result shows that our proposed method provides better entropy value than other stated techniques along with have better natural visual effects while consuming much lower processing time.     

Hydrogen bonding between aromatic H and F groups leading to a stripe structure with R‐ and S‐columns: the crystal structure of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone and comparison with its 1‐aroylnaphthalene analogues

In the molecule of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone, C₁₉H₁₅FO₃, (I), the dihedral angle between the plane of the naphthalene ring system and that of the benzene ring is 85.90 (5)°. The molecules exhibit axial chirality, with either an R‐ or an S‐stereogenic axis. In the crystal structure, each enantiomer is stacked into a columnar structure and the columns are arranged alternately to form a stripe structure. A pair of (methoxy)C—H...F hydrogen bonds and π–π interactions between the benzene rings of the aroyl groups link an R‐ and an S‐isomer to form a dimeric pair. These dimeric pairs are piled up in a columnar fashion through (benzene)C—H...O=C and (benzene)C—H...OCH₃ hydrogen bonds. The analogous 1‐benzoylated compound, namely (2,7‐dimethoxynaphthalen‐1‐yl)(phenyl)methanone [Kato et al. (2010). Acta Cryst. E 66 , o2659], (II), affords three independent molecules having slightly different dihedral angles between the benzene and naphthalene rings. The three independent molecules form separate columns and the three types of column are connected to each other via two C—H...OCH₃ hydrogen bonds and one C—H...O=C hydrogen bond. Two of the three columns are formed by the same enantiomeric isomer, whereas the remaining column consists of the counterpart isomer. In the case of the fluorinated 1‐benzoylated naphthalene analogue, namely (2,7‐dimethoxynaphthalen‐1‐yl)(4‐fluorophenyl)methanone [Watanabe et al. (2011). Acta Cryst. E 67 , o1466], (III), the molecular packing is similar to that of (I), i.e. it consists of stripes of R‐ and S‐enantiomeric columns. A pair of C—H...F hydrogen bonds between R‐ and S‐isomers, and C—H...O=C hydrogen bonds between R(or S)‐isomers, are also observed. Consequently, the stripe structure is apparently induced by the formation of R...S dimeric pairs stacked in a columnar fashion. The pair of C—H...F hydrogen bonds effectively stabilizes the dimeric pair of R‐ and S‐enantiomers. In addition, the co‐existence of C—H...F and C—H...O=C hydrogen bonds makes possible the formation of a structure with just one independent molecule.     

Systematic approach to the chemical synthesis of arabidopyrones,the unique α-pyrones of Arabidopsis metabolites

Abstract

Total synthesis of two arabidopyrones, iso-arabidopyl alcohol (1) and iso-arabidopic acid (2) isolated from Arabidopsis thaliana was achieved for the first time using Claisen condensation and Wittig reaction as the key steps. In addition, arabidopic acid (4) was synthesized from the methyl ester of arabidopyl alcohol (3). Thus, chemical synthesis of the unique natural α-pyrones 1–4 was accomplished with a short synthetic route by a systematic approach from readily available substances.     

Liposomalization of hydroxyphenyl fluorescein as a reagent for detecting highly reactive oxygen species

It has been shown that lifestyle-related diseases and aging are related to reactive oxygen species (ROS), and many studies have reported on the direct detection of ROS. The topical fluorescence reagent 2,7-dichlorodihydrofluorescein (DCDHF) is used to measure oxidation. However, there are problems regarding its stability, and its similar sensitivity to ROS cannot be easily distinguished. In this study, we used hydroxyphenyl fluorescein (HPF), which is a novel fluorescence probe with high stability against light that undergoes specific reactions with highly ROS (hROS). We examined the specificity for hROS of HPF solution and liposomal HPF in different reactions. HPF containing high cholesterol liposomes (HC-H-lipo) maintained its ability to tolerate light scattering energy, dependent on the turbidity of this solution, but DCDHF did not. In the reaction with hydroxyl radicals, the fluorescein concentration in HC-H-lipo was increased compared with that in HPF solution. In contrast, in the reaction with peroxynitrite, HC-H-lipo was inhibited. It was confirmed that HC-H-lipo that reacted specifically with hydroxyl radicals was able to distinguishably detect hydroxyl radicals. It was regarded to be useful as an examination kit. Tissue disorder induced by sodium valproate (SV) was one of the prepared murine disease models. The reactivity ratio of HC-H-lipo with serum to that of HPF solution was markedly different between the normal group (30%) and SV group (70%). In conclusion, HC-H-lipo cannot only simply and directly detect ROS but can also selectively detect ROS type. This nanocarrier is expected to be used as a novel diagnosis method.     

Flavonoid metabolism: the synthesis of phenolic glucuronides and sulfates as candidate metabolites for bioactivity studies of dietary flavonoids

Epidemiological studies indicate that flavonoid intake is inversely associated with the risk of coronary heart disease, yet the mechanisms responsible for their bioactivity are still a matter of debate. Based on the rapid and extensive metabolism of most flavonoids, their health effects most likely result from the biological activity of their metabolites. However, a lack of commercially available compounds/standards has prevented the study of metabolite bioactivity and resulted in a focus on non-physiologically relevant precursor/parent structures. This paper details the synthesis of a series of phenolic glucuronide 1a–e and sulfate 2a–e derivates as candidate metabolites for use as reference compounds in metabolic profiling studies and for the exploration of flavonoid bioactivity.     

Divergent total synthesis of penaresidin B and its straight side chain analogue

The divergent synthesis of penaresidin B and its straight side chain analogue was accomplished by constructing an azetidine ring via S_N2 type cyclization of protected 2,3-syn-3,4-syn-4-amino-1,3-dihydroxyhept-6-en-2-yl mesylate and late-stage introduction of an alkyl side chain via olefin cross-metathesis of 4-allylazetidine with readily available terminal alkenes. This synthetic route would be useful to synthesize penaresidin side chain analogues.     

Silane Coupling Agent Modifies the Mechanical Properties of a Chitosan Microfiber

Chitosan microfibers are widely used in medical applications because they have favorable inherent properties. However, their mechanical properties require further improvement. In the present study, a trimethoxysilane aldehyde (TMSA) crosslinking agent was added to chitosan microfibers to improve their tensile strength. The chitosan microfibers were prepared using a coagulation method. The tensile strength of the chitosan microfibers was improved by crosslinking them with TMSA, even when only a small amount was used (less than 1%). TMSA did not change the orientation of the chitosan molecules. Furthermore, aldehyde derived from TMSA did not remain, and siloxane units were formed in the microfibers.     

Control of the Single‐Molecule Magnet Behavior of Lanthanide‐Diarylethene Photochromic Assemblies by Irradiation with Light

Lanthanide‐based extended coordination frameworks showing photocontrolled single‐molecule magnet (SMM) behavior were prepared by combining highly anisotropic Dy^III and Ho^III ions with the carboxylato‐functionalized photochromic molecule 1,2‐bis(5‐carboxyl‐2‐methyl‐3‐thienyl)perfluorocyclopentene (H₂dae), which acts as a bridging ligand. As a result, two new compounds of the general formula [{Ln^III₂(dae)₃(DMSO)₃(MeOH)} ? 10 M eOH]_n (M=Dy for 1 a and Ho for 2 ) and two additional pseudo‐polymorphs [{Dy^III₂(dae)₃(DMSO)₃(H₂O)} ? x MeOH]_n ( 1 b ) and [{Dy^III₂(dae)₃(DMSO)₃(DMSO)} ? x MeOH]_n ( 1 c ) were obtained. All four compounds have 2D coordination‐layer topologies, in which carboxylate‐bridged Ln₂ units are linked together by dae^2? anions into grid‐like frameworks. All four compounds exhibited a strong reversible photochromic response to UV/Vis light. Moreover, both 1 a and 2 show field‐induced SMM behavior. The slow magnetic relaxation of 1 a is influenced by the photoisomerization reaction leading to the observation of the cross‐effect: photocontrolled SMM behavior.