β- or γ-Site-selective C–H alkylation of aliphatic nitriles has been achieved using a decatungstate salt as the photocatalyst. The observed site selectivity was justified by a radical polar effect in ...transition states for hydrogen abstraction.
An efficient synthesis of cyclic thiocarbonates from epoxides and CS2 under mild reaction conditions was achieved when a KI–tetraethylene glycol complex was used as a readily available and economic ...catalyst. The effects of various glycols and alkali metal halides were investigated in the present work to clarify the importance of both KI and tetraethylene glycol. The reaction mechanisms for the synthesis of cyclic thiocarbonates are discussed on the basis of the stereochemistry of the products.
Efficient synthesis of cyclic thiocarbonates from epoxides and CS2 was achieved when a KI–tetraethylene glycol complex was used as an economic catalyst. The mechanism for this reaction is discussed on the basis of the stereochemistry of the products.
A photocatalytic synthesis of homoallyl ketones was achieved via a one-pot procedure starting from a Norrish Type I reaction of cyclopentanones, followed by a decatungstate-catalyzed hydroacylation ...of electron-deficient olefins by the resulting 4-pentenals. The site-selective formyl H-abstraction in the second step can be explained by radical polar effects in the transition state.
Despite extensive studies into the design of effective chiral catalysts for asymmetric halolactonizations, the development of highly enantioselective catalytic bromolactonization of ...4‐aryl‐4‐pentenoic acids, which is one of the benchmark reactions, has not been completely satisfactory. Herein, we report the use of BINOL‐derived chiral bifunctional sulfide catalysts to achieve highly enantioselective bromolactonizations of 4‐aryl‐4‐pentenoic acids. The importance of the bifunctional design of chiral sulfide catalysts was clearly demonstrated in the present study. Furthermore, the present catalytic asymmetric reaction system could be applied to highly stereoselective desymmetrizing bromolactonizations.
The highest reported enantioselective bromolactonization of 4‐aryl‐4‐pentenoic acids to produce optically active γ‐butyrolactones was accomplished via the use of chiral bifunctional sulfide catalysts bearing a hydroxy group.
The second largest epidemic of hand, foot, and mouth disease since 1982 occurred in 2017, which involved 6,173 cases in Osaka City, Japan. The main causative agent was coxsackievirus A6 (CV-A6). ...Phylogenetic analysis revealed that the detected CV-A6 strains belonged to genetic groups A3 and A4 in clade A.
In forests worldwide, Quercus is a major genus; however, the boundaries between the constituent species are relatively weak, and hybridization is reported frequently. In this study, we examined ...Quercus acuta and Quercus sessilifolia (subgenus Cyclobalanopsis), which have a putative hybrid—Q. x takaoyamensis. We investigated leaf morphological traits and microsatellites of Q. acuta and Q. sessilifolia in the area where the two species are both found. Although the leaf traits overlapped, the two species could be distinguished morphologically as demonstrated by principal component analysis based on a range of these traits. They were also genetically differentiated, with F ST = 0.104. However, they shared most of the alleles at all eight loci examined, and considerable genetic admixing was detected. Admixture analysis demonstrated that Q. acuta and Q. sessilifolia, respectively, contained 11 and 24 % of individuals with a probability of less than 0.9 of being correctly assigned to their species. Model-based testing showed that this admixing was created by not only shared ancestral polymorphism but also by hybridization. Effective population size and migration rate were estimated using the coalescent approach. We estimated 8.843 and 71.98 effective numbers of migrants per generation to Q. acuta and Q. sessilifolia, respectively. Theoretically, one to ten migrants per generation are required to prevent complete genetic differentiation. Based on the results of this study, it appears that genetic admixing, with sharing of most alleles, is probably common in the two species and is maintained by interspecific introgressive hybridization.
High concentrations of tropospheric ozone remain a concern, and strategies to reduce the precursors of ozone, volatile organic compounds (VOCs) and nitrogen oxides, have been established in many ...countries. In this study, chassis dynamometer experiments were conducted for 25 late model gasoline passenger vehicles in the Japanese market to evaluate VOC emission trends. Tailpipe emissions were collected and analyzed using gas chromatography mass spectrometer and flame ionization detector, and liquid chromatography–mass spectrometry (LC-MS). Results showed that tailpipe VOC emissions increased linearly with vehicle mileage due to deterioration of the three-way catalysis converter used to purify the toxic components in vehicle emissions. Distance normalized total VOC emissions showed that port injection mini-sized vehicles were effective in decreasing tailpipe VOC emissions because of their low vehicle weight. The VOC composition of tailpipe emissions was dependent on the fuel type (regular or premium gasoline). VOC emissions from hybrid vehicles were similar to those of other vehicles because cooling of the three-way catalysis converter during battery operations sometimes tended to reduce catalyst effectiveness during engine operations. However, it can also be assumed that each manufacturer is aware of this phenomenon and is taking action. Further monitoring of hybrid vehicles is warranted to ensure that these vehicles remain an effective means of mitigating air pollution.
We have revealed that in Caenorhabditis elegans, non-sulfated chondroitin is required for normal cell division and cytokinesis at an early developmental stage, whereas heparan sulfate is essential ...for embryonic morphogenesis in the later stages of development. To clarify the roles of chondroitin sulfate and heparan sulfate in early embryogenesis in mammals, we generated glucuronyltransferase-I (GlcAT-I) knock-out mice by gene targeting. GlcAT-I is an enzyme required for the synthesis of both chondroitin sulfate and heparan sulfate. Here we report that mice with a deletion of GlcAT-I showed remarkable reduction of the synthesis of chondroitin sulfate and heparan sulfate and embryonic lethality before the 8-cell stage because of failed cytokinesis. In addition, treatment of wild-type 2-cell embryos with chondroitinase ABC had marked effects on cell division, although many heparitinase-treated embryos normally developed to blastocysts. Taken together, these results suggest that chondroitin sulfate in mammals, as with non-sulfated chondroitin in C. elegans, is indispensable for embryonic cell division.
HS (heparan sulfate) is synthesized by HS co-polymerases encoded by the EXT1 and EXT2 genes (exostosin 1 and 2), which are known as causative genes for hereditary multiple exostoses, a dominantly ...inherited genetic disorder characterized by multiple cartilaginous tumours. It has been thought that the hetero-oligomeric EXT1-EXT2 complex is the biologically relevant form of the polymerase and that targeted deletion of either EXT1 or EXT2 leads to a complete lack of HS synthesis. In the present paper we show, unexpectedly, that two distinct cell lines defective in EXT1 expression indeed produce small but significant amounts of HS chains. The HS chains produced without the aid of EXT1 were shorter than HS chains formed in concert with EXT1 and EXT2. In addition, biosynthesis of HS in EXT1-defective cells was notably blocked by knockdown of either EXT2 or EXTL2 (EXT-like), but not of EXTL3. Then, to examine the roles of EXTL2 in the biosynthesis of HS in EXT1-deficient cells, we focused on the GlcNAc (N-aetylglucosamine) transferase activity of EXTL2, which is involved in the initiation of HS chains by transferring the first GlcNAc to the linkage region. Although EXT2 alone synthesized no heparan polymers on the synthetic linkage region analogue GlcUAbeta1-3Galbeta1-O-C2H4NH-benzyloxycarbonyl, marked polymerization by EXT2 alone was demonstrated on GlcNAcalpha1-4GlcUAbeta1-3Galbeta1-O-C2H4N-benzyloxycarbonyl (where GlcUA is glucuronic acid and Gal is galactose), which was generated by transferring a GlcNAc residue using recombinant EXTL2 on to GlcUAbeta1-3Galbeta1-O-C2H4NH-benzyloxycarbonyl. These findings indicate that the transfer of the first GlcNAc residue to the linkage region by EXTL2 is critically required for the biosynthesis of HS in cells deficient in EXT1.
The genus Chromobacterium consists of 7 recognized species. Among those, only C. violaceum, commonly found in the soil and water of tropical and subtropical regions, has been shown to cause human ...infection. Although human infection is rare, C. violaceum can cause life-threatening sepsis, with metastatic abscesses, most frequently infecting those who are young and healthy.
We recently identified a case of severe bacteremia caused by Chromobacterium haemolyticum infection in a healthy young patient following trauma and exposure to river water, in Japan. The patient developed necrotizing fasciitis that was successfully treated with a fasciotomy and intravenous ciprofloxacin and gentamicin.
C. haemolyticum should be considered in the differential diagnosis of skin lesions that progressively worsen after trauma involving exposure to river or lake water, even in temperate regions. Second, early blood cultures for the isolation and identification of the causative organism were important for initiating proper antimicrobial therapy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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