Enantioselective Hydroalkenylation and Hydroalkynylation of Alkenes Enabled by a Transient Directing Group: Catalyst Generality through Rigidification.

The catalytic enantioselective synthesis of α-chiral alkenes and alkynes represents a powerful strategy for rapid generation of molecular complexity. Herein, we report a transient directing group (TDG) strategy to facilitate site-selective palladium-catalyzed reductive Heck-type hydroalkenylation and hydroalkynylation of alkenylaldehyes using alkenyl and alkynyl bromides, respectively, allowing for construction of a stereocenter at the δ-position with respect to the aldehyde. Computational studies reveal the dual beneficial roles of rigid TDGs, such as L-tert-leucine, in promoting TDG binding and inducing high levels of enantioselectivity in alkene insertion with a variety of migrating groups.

General Synthetic Approach to Diverse Taxane Cores.

Chemical synthesis of natural products is typically inspired by the structure and function of a target molecule. When both factors are of interest, such as in the case of taxane diterpenoids, a synthesis can both serve as a platform for synthetic strategy development and enable new biological exploration. Guided by this paradigm, we present here a unified enantiospecific approach to diverse taxane cores from the feedstock monoterpenoid (S)-carvone. Key to the success of our approach was the use of a skeletal remodeling strategy which began with the divergent reorganization and convergent coupling of two carvone-derived fragments, facilitated by Pd-catalyzed C-C bond cleavage tactics. This coupling was followed by additional restructuring using a Sm(II)-mediated rearrangement and a bioinspired, visible-light induced, transannular [2 + 2] photocycloaddition. Overall, this divergent monoterpenoid remodeling/convergent fragment coupling approach to complex diterpenoid synthesis provides access to structurally disparate taxane cores which have set the stage for the preparation of a wide range of taxanes.

Synthesis of the Aeromonas veronii strain Bs8 disaccharide repeating unit.

Presented herein is the synthesis of the Aeromonas veronii disaccharide repeating unit which has been achieved in 11 steps starting from d-fucose and d-galactosamine.

Time-resolved relaxation and fragmentation of polycyclic aromatic hydrocarbons investigated in the ultrafast XUV-IR regime.

Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10-100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we investigate three PAH molecules: fluorene, phenanthrene, and pyrene, using ultrafast XUV and IR laser pulses. Simultaneous measurements of the ion yields, ion momenta, and electron momenta as a function of laser pulse delay allow a detailed insight into the various molecular processes. We report relaxation times for the electronically excited PAH*, PAH+* and PAH2+* states, and show the time-dependent conversion between fragmentation pathways. Additionally, using recoil-frame covariance analysis between ion images, we demonstrate that the dissociation of the PAH2+ ions favors reaction pathways involving two-body breakup and/or loss of neutral fragments totaling an even number of carbon atoms.

Epistatic interaction of PDE4DIP and DES mutations in familial atrial fibrillation with slow conduction.

The genetic causes of atrial fibrillation (AF) with slow conduction are unknown. Eight kindreds with familial AF and slow conduction, including a family affected by early-onset AF, heart block, and incompletely penetrant nonischemic dilated cardiomyopathy (DCM) underwent whole exome sequencing. A known pathogenic mutation in the desmin (DES) gene resulting in p.S13F substitution (NM_001927.3:c.38C>T) at a PKC phosphorylation site was identified in all four members of the kindred with early-onset AF and heart block, while only two developed DCM. Higher penetrance for AF and heart block prompted a genetic screening for DES modifier(s). A deleterious mutation in the phosphodiesterase-4D-interacting-protein (PDE4DIP) gene resulting in p.A123T substitution (NM_001002811:c.367G>A) was identified that segregated with early-onset AF, heart block, and the DES mutation. Three additional novel deleterious PDE4DIP mutations were identified in four other unrelated kindreds. Characterization of PDE4DIPA123T in vitro suggested impaired compartmentalization of PKA and PDE4D characterized by reduced colocalization with PDE4D, increased cAMP activation leading to higher PKA phosphorylation of the ß2-adrenergic-receptor, and decreased PKA phosphorylation of desmin after isoproterenol stimulation. Our findings identify PDE4DIP as a novel gene for slow AF and unravel its epistatic interaction with DES mutations in development of conduction disease and arrhythmia.

Total Synthesis of the Photorhabdus temperata ssp. Cinereal 3240 Zwitterionic Trisaccharide Repeating Unit.

Zwitterionic carbohydrate modifications, such as phosphoethanolamine (PEtN), govern host-pathogen interactions. Whereas it is recognized that these modifications stimulate the host immune system, the purpose of PEtN modification remains largely descriptive. As an enabling step toward studying this carbohydrate modification, we report a synthesis of the P. temperata zwitterionic trisaccharide repeating unit. The 32-step synthesis was enabled by H-phosphonate chemistry to install the PEtN arm on a poorly reactive and sterically hindered C4-alcohol.

Synthetic Phosphoethanolamine Cellobiose Promotes Escherichia coli Biofilm Formation and Congo Red Binding.

Urinary tract infections (UTIs) are caused by bacteria growing in complex, multicellular enclosed aggregates known as biofilms. Recently, a zwitterionic cellulose derivative produced in Escherichia coli (E. coli) was determined to play an important role in the formation and assembly of biofilms. In order to produce a minimal, yet structurally defined tool compound to probe the biology of the naturally occurring polymer, we have synthesized a zwitterionic phosphoethanolamine cellobiose (pEtN cellobiose) and evaluated its biofilm activity in the Gram-negative bacterium E. coli, a pathogen implicated in the pathogenesis of UTIs. The impact of synthetic pEtN cellobiose on biofilm formation was examined via colorimetric assays which revealed an increase in cellular adhesion to an abiotic substrate compared to untreated samples. Additionally, Congo red binding assays indicate that culturing E. coli in the presence of pEtN cellobiose enhances Congo Red binding to bacterial cells. These results reveal new opportunities to study the impact glycopolymers have on cellular adhesion in Gram-negative pathogens.

Leveraging Stereoelectronic Effects in Biofilm Eradication: Synthetic ß-Amino Human Milk Oligosaccharides Impede Microbial Adhesion As Observed by Scanning Electron Microscopy.

Alongside Edward, Lemieux was among the earliest researchers studying negative hyperconjugation (i.e., the anomeric effect) or the preference for gauche conformations about the C1-O5 bond in carbohydrates. Lemieux also studied an esoteric, if not controversial, theory known as the reverse anomeric effect (RAE). This theory is used to rationalize scenarios where predicted anomeric stabilization does not occur. One such example is the Kochetkov amination where reducing end amines exist solely as the ß-anomer. Herein, we provide a brief account of Lemieux's contributions to the field of stereoelectronics and apply this knowledge toward the synthesis of ß-amino human milk oligosaccharides (ßΑ-HMOs). These molecules were evaluated for their ability to inhibit growth and biofilm production in Group B Streptococcus (GBS) and Staphylococcus aureus. While the parent HMOs lacked antimicrobial and antibiofilm activity, their ß-amino derivatives significantly inhibited biofilm formation in both species. Field emission gun-scanning single electron microscopy (FEG-SEM) revealed that treatment with ß-amino HMOs significantly inhibits bacterial adherence and eliminates the ability of both microbes to form biofilms.

Methicillin-resistant Staphylococcus aureus (MRSA): antibiotic-resistance and the biofilm phenotype.

Staphylococcus aureus (S. aureus) is an asymptomatic colonizer of 30% of all human beings. While generally benign, antibiotic resistance contributes to the success of S. aureus as a human pathogen. Resistance is rapidly evolved through a wide portfolio of mechanisms including horizontal gene transfer and chromosomal mutation. In addition to traditional resistance mechanisms, a special feature of S. aureus pathogenesis is its ability to survive on both biotic and abiotic surfaces in the biofilm state. Due to this characteristic, S. aureus is a leading cause of human infection. Methicillin-resistant S. aureus (MRSA) in particular has emerged as a widespread cause of both community- and hospital-acquired infections. Currently, MRSA is responsible for 10-fold more infections than all multi-drug resistant (MDR) Gram-negative pathogens combined. Recently, MRSA was classified by the World Health Organization (WHO) as one of twelve priority pathogens that threaten human health. In this targeted mini-review, we discuss MRSA biofilm production, the relationship of biofilm production to antibiotic resistance, and front-line techniques to defeat the biofilm-resistance system.

Surveillance of antibacterial resistance in Staphylococcus aureus isolated in Kuwaiti hospitals.

OBJECTIVE: To investigate the prevalence of antibiotic resistance among Staphylococcus aureus isolated in Kuwaiti hospitals. MATERIALS AND METHODS: S. aureus were isolated and identified following standard microbiological methods. Antibacterial susceptibility test was performed by disk diffusion and the measurement of minimum inhibitory concentration with E-test strips. RESULTS: A total of 1,846 S. aureus isolates were analyzed from 13 hospitals between 1 March and 30 October 2005. They were isolated from 1,765 (95.6%) inpatients and 81 (4.4%) outpatients. Methicillin resistance was detected in 588 (32.0%) of the isolates. The methicillin-resistant S. aureus (MRSA) consisted of 461 (78%) multiresistant and 127 (22%) nonmultiresistant isolates. The nonmultiresistant MRSA consisted of epidemic MRSA-15 and community-associated MRSA. The community-associated MRSA was detected in all hospitals with MRSA, indicating its establishment in Kuwaiti hospitals. The proportion of isolates resistant to gentamicin, kanamycin, erythromycin, tetracycline, ciprofloxacin, fusidic acid and trimethoprim was higher among MRSA than methicillin-susceptible S. aureus (MSSA) isolates. Twenty-four and 22% of MRSA and MSSA isolates, respectively, expressed reduced susceptibility to vancomycin (minimum inhibitory concentration = 3-4 mg/l). CONCLUSION: The study revealed the presence of methicillin resistance in 32% of S. aureus isolated in Kuwaiti hospitals and revealed an increase in the number of MRSA and MSSA with reduced susceptibility to vancomycin.

Effects of sex steroids and their inhibitors on endocrine parameters and gender growth differences in Eurasian perch (Perca fluviatilis) juveniles.

Sex steroid inhibitors were used to characterize the effects of 17beta-estradiol (E2) and testosterone (T) on the sexual growth dimorphism of Eurasian perch juveniles. In experiment 1, growth responses to different doses of either E2 (25, 50, 75, and 100 mgkg(diet)-1) or fadrozole (Fa; 50 and 100 mgkg(diet)-1) were compared in triplicate tanks of 30 fish each during 85 days. In experiment 2, five diets containing (50 mgkg(diet)-1) Tamoxifen (Ta), Flutamide (Flu), Fa, E2, and T were tested in triplicate tanks of 20 fish each during 90 days. Steroid supplementation or inhibition increased or decreased E2 and T plasma levels. Moreover, E2 treatment induced a higher plasma vitellogenin level but decreased triidothyronine levels. Brain aromatase activity (AA) was lower in Fa-treated fish than in other groups. In experiment 1, E2 supplementation did not promote growth, but high doses had negative effects as did Fa. In experiment 2, a greater growth response was observed only in E2-treated females in relation to higher food intake (FI) not feeding efficiency. Fa also promoted growth and FI both in females and males during the last month of the experiment. Other treatments did not affect growth, but T treatment decreased FI in males. In conclusion, the results did not provide clear evidence for E2 action on sexual growth dimorphism, but showed that testosterone may decrease growth in males by decreasing food intake in Eurasian perch. Therefore, the acceleration of male-to-female growth differences with age may not be a result of promotion of growth in females by estrogens, but a consequence of a reduction in growth by increased secretion of androgens in males.

Strongyloidiasis: challenges in diagnosis and management in non-endemic Kuwait.

Among immunocompromised individuals, hyper-infection with Strongyloides stercoralis may occur and lead to fatal strongyloidiasis. To clinicians and laboratory diagnosticians in non-endemic countries such as Kuwait, this severe infection poses a particular problem. The clinical histories and signs and symptoms of four Kuwaiti cases of S. stercoralis hyper-infection were reviewed. Each of the four was found not only to have lived in an area where S. stercoralis was endemic but also to have been treated with immunosuppressive steroids (for medical problems unrelated to the nematode infection). When they presented with undiagnosed hyper-infections their clinical features were confusing. Three of the cases, all with low eosinophil counts, died but the other, who was treated with thiabendazole, survived. In the light of these observations, healthy medical examinees who had recently moved from endemic zones were checked for asymptomatic S. stercoralis infection, both by stool examination and ELISA-based serology. Of 381 stool samples investigated over a 3-month period, 183 (48%) were found positive for helminths, 7% for S. stercoralis. Of 198 individuals from endemic zones who were screened after another medical examination, 71 (35.8%) were found positive for intestinal helminth parasites, including one (1.45%) infected with S. stercoralis. Although ELISA appear reliable in making a presumptive diagnosis of strongylodiasis, the results of such assays are not very specific and are best interpreted in conjunction with the patient's clinical status. The concurrent administration of anthelminthics to patients prescribed steroids who, because they live or have lived in an area where S. stercoralis is endemic, are at risk of infection with the nematode, should be considered.

Additional case of Ramichloridium mackenziei cerebral phaeohyphomycosis from the Middle East.

In this report we describe a case of cerebral phaeohyphomycosis involving a 56-year-old Egyptian male who worked as a mason in Kuwait for 6 years. Computerized tomography scan of the brain revealed presence of a large abscess in the left occipital lobe. Aspirated pus from the abscess showed branched, septate, hyphae with light brown pigmentation. Cultured pus grew the fungus Ramichloridium mackenziei. Despite amphotericin B (1 mg kg(-1) per day) therapy for 2 weeks, the patient expired. The isolate was later found to be resistant to amphotericin B ( > 32 microg ml(-1)). Antifungal susceptibility testing to other agents was also performed.

Crohn's disease presenting as pyogenic liver abscess with review of previous case reports.

A 40-yr-old male doctor from India presented with pyogenic liver abscesses as the first manifestation of Crohn's disease. The Crohn's disease itself was limited to the appendix and the adjacent cecum and could be diagnosed only 6 months after the presentation with liver abscess. This single case highlights three unusual features of Crohn's disease, and stresses the importance of meticulous search for a cause for pyogenic liver abscess when it occurs in an otherwise healthy adult.

Community-acquired bacteraemic Acinetobacter pneumonia with survival.

A 65 year old man was admitted with segmental consolidation of the left upper lobe after having stayed in a hotel for 2 days. He deteriorated rapidly on conventional antibiotic therapy and required ventilatory support. Acinetobacter calcoaceticus var. anitratus was grown from the sputum and blood cultures, which was treated with a combination of anti-pseudomonal agent, aminoglycoside and cotrimoxazole. He made a slow but remarkable recovery from the pneumonia. Acinetobacter is a rare potentially fatal cause of community-acquired pneumonia.

Foot infections in diabetics: the antibiotic choice.

The authors studied 59 diabetics with foot infections to determine the organisms responsible and the sensitivity to antibiotics. All infections were polymicrobial (aerobic and anaerobic). On average 3.2 isolates per culture were obtained from the depth of the infection. The commonest organisms in order of frequency were: Staphylococcus aureus, beta-hemolytic streptococci, Proteus sp., Bacteroides sp., enterococci, Klebsiella sp. and Pseudomonas aeruginosa. A combination of piperacillin and cloxacillin is recommended as initial therapy for foot infections in diabetic patients because it was found to be effective for 73% of the causative microorganisms.

Use of an alkaline phosphatase-labeled synthetic oligonucleotide probe for detection of Campylobacter jejuni and Campylobacter coli.

A commercially available synthetic nucleic acid probe (SNAP) conjugated to alkaline phosphatase was compared with standard culture techniques for detecting Campylobacter species. The SNAP was able to detect either 5 ng of C. jejuni DNA or 10(5) CFU of bacteria. The SNAP could also detect DNA extracted from 10(5) CFU in mock-infected stool samples. The SNAP detected C. jejuni and C. coli but showed no reactivity with C. laridis, C. fetus subsp. fetus, C. fetus subsp. venerealis, C. fennelliae, "C. upsaliensis," C. cinaedii, C. fecalis, C. hyointestinalis, C. mucosalis, or Helicobacter (Campylobacter) pylori. The SNAP also showed no cross-reactivity with other enteric pathogens. When applied to pure cultures, the SNAP detected 55 clinical isolates of C. jejuni and 11 clinical isolates of C. coli, with an accuracy of 100%. When applied directly to clinical specimens, the SNAP detected Campylobacter spp. in 19 of 23 culture-positive stool specimens (sensitivity, 82.6%; specificity, 100%). Pure cultures of the Campylobacter strains isolated from the four probe-negative, culture-positive stool specimens gave positive reactions with the SNAP. While the SNAP had excellent sensitivity and specificity for isolated bacterial colony isolates, the main limitation to the Campylobacter probe detection kit may be the sensitivity limit on direct detection of Campylobacter organisms in stools.

Enterotoxigenicity and frequency of Campylobacter jejuni, C. coli and C. laridis in human and animal stool isolates from different countries.

Campylobacter jejuni and C. coli strains were collected during three different years from adult patients with enterocolitis in Sweden (n = 372) from 49 patients in Kuwait, and Campylobacter strains from hens from Mexico, Pakistan and Sweden (n = 107) and Swedish pigs (n = 47). C. jejuni was the predominant species in human and hen isolates, and C. coli in pigs C. coli was significantly more common in human isolates from Sweden, and more common in hen isolates from Pakistan, than in hens from Sweden and Mexico. C. laridis was only isolated from pigs (17%) and was in no case enterotoxigenic. Both in human and hen isolates, C. jejuni strains were more enterotoxigenic than C. coli strains. C. jejuni strains from Swedish hens were less enterotoxigenic than those from Pakistan and Mexico (P less than 0.001), and strains from pigs were less enterotoxigenic than those from hens (P less than 0.001). We conclude that C. jejuni are more often enterotoxigenic and possibly more virulent than c. coli and C. laridis. The relative frequency of C. jejuni and C. coli in humans and animals differs from one country to another.

Urinary tract infection caused by Shigella sonnei: a case report.

We report a case of severe urinary tract infection caused by Shigella sonnei in a 3-year-old girl with vesico-ureteric reflux and no history of dysentery. Treatment with co-trimoxazole in a dose of 48 mg/kg for 10 days was given and the infection was eradicated. Possible sources of infection are discussed.