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.

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.

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.

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.

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.

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.

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.

The serotype distribution of Campylobacter in patients with diarrhoea in Kuwait.

Fifty one strains of Campylobacter jejuni/coli isolated from patients with diarrhoea, at the Amiri Hospital, Hawally, Kuwait were classified on the basis of the heatstable-HS-antigens and the heat-labile-HL-antigens, by using 20 and 23 hyperimmune antisera for the two methods, respectively. The ages of the patient ranged from 3 months to 60 years, and 72.6% of the strains were from children less than 4 years. With the number of antisera used 78.4% of the HS antigens and 96.1% of the HL antigens could be identified. About half of the strains had one of five HS antigens (4, 8, 13, 5 or 25) and 70.5% of the strains had one of five HL antigens (1, 36, 2, 6, or 21). The study shows that the most common HS and HL antigens among Campylobacter strains from Kuwait also are the most frequent antigens of strains from other parts of the world. A limited number of antisera are sufficient to identify the majority of the strains.

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.

Salmonella osteomyelitis in a patient with systemic lupus erythematosus.

This paper describes a case of osteomyelitis due to Salmonella bovis morbificans in a patient with systemic lupus erythematosus (SLE) on long-term corticosteroid therapy. Although the organism was susceptible in vitro to chloramphenicol, ampicillin and co-trimoxazole, therapy with any of these drugs became impossible due to severe allergic reactions. A prolonged course of trimethoprim coupled with surgical debridement cured the lesion. The serum concentration of trimethoprim 24 hours after administration of a single oral dose of 300 mg was over four times the minimum inhibitory concentration (MIC) of the Salmonella sp. involved. These results indicate that trimethoprim may be effective in the treatment of Salmonella osteomyelitis.

Septicaemia in a teaching hospital in Kuwait--II: Factors influencing the outcome in III episodes.

The case fatality rate (CFR) among III episodes of septicaemia in Kuwait was 22.5%. It increased with age but was not influenced by sex. Gram-negative, polymicrobial and hospital-acquired septicaemia carried a high mortality rate. Due to the influence of the more common, but less fatal salmonella infections, however, mortality from septicaemia caused by Gram-negative bacteria was lower than that reported from more developed countries. Patients with underlying conditions, such as malignancy, chronic liver disease, diabetes mellitus, renal transplant and conditions requiring surgery, as well as those with unknown sources of infection or infection originating from the respiratory tract or from surgical wounds had high mortality rates. The chances of survival increased with the use of appropriate antibiotic therapy and the absence of underlying disease. None of the patients with underlying conditions survived after receiving inappropriate therapy as compared with 50% who were previously healthy. The changing aetiology and the emergence of immuno compromised patients are possible causes for the failure to reduce significantly the mortality from septicaemia in Kuwait.

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.

Antimicrobial treatment of Flavobacterium meningosepticum infection.

A six-month-old boy in hospital developed septicaemia and meningitis due to Flavobacterium meningosepticum type A. Although the organism was susceptible to amikacin, chloramphenicol and sulphonamides when tested by the disc diffusion method, therapy with these drugs was ineffective. Intravenous therapy with cotrimoxazole gave complete recovery. Various strains of flavobacteria including F. meningosepticum type B were isolated from the environment. Antimicrobial susceptibilities of patients and environmental strains against chloramphenicol, sulphonamides and rifampicin showed no correlation between disc diffusion results and minimum inhibitory concentration (MIC). On the other hand, all the strains were found by both methods to be susceptible to amikacin, erythromycin, clindamycin and trimethoprim. Disc diffusion method should be supplemented with determination of MIC when testing antimicrobial susceptibility of Flavobacterium sp.