Urethane protected amino acid N-carboxyanhydrides and fluorides (U-NCAs and U2AAFs)

Summary In order to obtain peptide analogues containing a central pyrrolide bond, as potential mechanism-based inhibitors of the HIV-1 proteinase, activated derivatives of amino acids were required. Treatment of a N,N-bis(Boc) amino acid pyridinium salt with cyanuric fluoride in dichloromethane furnished the correspondingbis(Boc) amino acid fluoride (Boc₂AAF). Use of the Vilsmeier reagent in acetonitrile, instead of the cyanuric fluoride, led to a N-Boc amino acid N-carboxyanhydride (Boc-NCA). From a mixed N-Z,N-Boc amino acid salt a N-Z,N-Boc amino acid fluoride and a Z-NCA were respectively obtained. The very sensitive Young test showed that during the coupling of the N-benzoyl-L-Leucine N-carboxyanhydride or the N-benzoyl N-Boc-L-leucyl fluoride with ethyl glycinate the degrees of racemization were weak. Owing to the electronegativity and the small size of the fluorine atom, thebis(urethane) amino acid fluorides are efficient acylating agents for amines and pyrrole anions.     

Impact of a community-based bug-hunting campaign on Chagas disease control: a case study in the department of Jalapa,Guatemala

Chagas disease control requires an innovative approach to strengthen community participation in vector surveillance. This paper presents a case study of a community-based bug-hunting campaign in Guatemala. The campaign was implemented in 2007 in the following three stages: (i) a four week preparation stage to promote bug-hunting, (ii) a one week bug-hunting stage to capture and collect bugs and (iii) a 10 week follow-up stage to analyse the bugs and spray insecticide. A total of 2,845 bugs were reported, of which 7% were Triatominae vectors, such as Rhodnius prolixus and Triatoma dimidiata. The bug-hunting campaign detected a five-six-fold higher amount of vectors in one week than traditional community-based surveillance detects in one year. The bug-hunting campaign effectively detected vectors during a short period, provided information to update the vector infestation map and increased community and political awareness regarding Chagas disease. This approach could be recommended as an effective and feasible strategy to strengthen vector surveillance on a larger scale.     

Eradications and People: Lessons from the Plant Eradication Program in Galapagos

It is often argued that the benefit of eradication of an invasive species—a one-off injection of funds and the problem is solved—far outweighs the cost of a perennial control program. Furthermore, these are very attractive projects for funding agencies as outcomes are clear and easy to assess. Galapagos is in the early stage of the invasion process, with most alien species not yet naturalized and still restricted to gardens and farms. These species should be easy targets for early and cost-effective eradication projects, which would prevent many future problems. We review 30 plant eradication projects covering 23 potentially invasive species with limited distributions on four of the Galapagos Islands. Of the 30 projects, only four were successful: these were all less than 1 ha in net area, on land with a single owner and did not have persistent seed banks. Of the other 26 projects, most failed due to a lack of support from institutions that did not offer continuity of resources, from land owners who denied permission to carry out the work or from being too ambitious. As a result of these problems, 64.3% of the funding secured for the program was spent on discontinued projects. We highlight lessons learned to inform plant eradication programs in the future.     

DFT studies of the role of C-2-O-2 bond rotation in neighboring-group glycosylation reactions

Although the synthetic utility of the 1,2-trans relationship of the products of neighboring group participation is well established, it is still common to find glycosylation reactions where the stereochemical purity of the products is not 100%. As part of an ongoing series of density functional theory (DFT) studies of the factors that affect glycosylation reactions which are aimed at allowing synthetic chemists to achieve such selectivities, the structures of four oxacarbenium ions and eight methanol complexes of these ions were optimized for the prototypical ions 2-O-acetyl-3,4,6-tri-O-methyl-D-gluco- (1) and mannopyranos-1-yl (2). These studies corroborate the two-conformer hypothesis and further demonstrate that glycopyranosyl oxacarbenium ions exhibit facial selectivity that depends on, besides the inherent steric and Van der Waals effects, the conformational effect associated with the change from sp(2) to sp(3) hybridization at C-1 during nucleophilic attack and H-bonding between the incoming nucleophile and the electronegative atoms of the electrophile. Further studies based on systematic C-2-O-2 bond rotations found TSs that connect the monocyclic ions with the bicyclic ions associated with neighboring-group participation. It was also possible to find two TSs that connect nucleophilic attack at C-1 with C-2-O-2 bond rotation ultimately leading to 1,2-trans O-glycosides, that is, the probable TS that determines the stereochemistry of neighboring-group participation. Both of these TSs exhibit intramolecular H-bonding, which is considered the first step in proton transfer. It is further hypothesized that this coupling of proton transfer and nucleophilic attack is integral to glycosylation. It is further hypothesized that in many cases analogous intermolecular H-bonding is also favorable with the most likely acceptor the anion that is ion-paired to the oxacarbenium ion. These general features are found for both 1 and 2, but characteristic features of each isomer are found that provide further insights into the origins of stereoselectivity.     

Reactions of pentaammineruthenium complexes with 1,2- and 1,4-dicyanobenzene and cyanobenzamides: evidences of neighboring group participation

The spectral (UV-Vis and IR) and electrochemical behavior of the nitrile bonded complexes [Ru(NH₃)₅L]²⁺ (L = 1,4-dicyanobenzene (1,4-dcb), 1,2-dicyanobenzene (1,2-dcb)), [Ru(NH₃)₅(NHC(OH)-bz-4-CN)]³⁺, [Ru(NH₃)₅(NHC(O)-bz-2-CN)]²⁺ and [Ru(NH₃)₅(NH(C)NHC(O)bz)]³⁺ (NH(C)NHC(O)-bz = 3-imino-1-oxo-isoindoline) are described. Oxidation of [Ru(NH₃)₅L]²⁺, at 0 ? pH ? 6, is followed by hydrolysis of the coordinated nitrile to give amide complexes in which the amide is through the nitrogen, with pH-dependent rate constants. The estimated values of the rate constant of hydrolysis (k_obs) at 25 °C are 2.9 × 10⁻³ s⁻¹ for [Ru(NH₃)₅(1,4-dcb)]³⁺ and 5.6 × 10⁻³ s⁻¹ for [Ru(NH₃)₅(1,2-dcb)]³⁺ at pH 4.65. Reduction of [Ru(NH₃)₅(NHC(O)-bz-4-CN)]²⁺ and [Ru(NH₃)₅(NHC(O)-bz-2-CN)]²⁺ is followed by two reactions, one is an aquation forming [Ru(NH₃)₅(OH₂)]²⁺ and free ligand, and the other an intramolecular linkage isomerization forming [Ru(NH₃)₅(NC-bz-4-NH₂C(O))]²⁺ and [Ru(NH₃)₅(NC-bz-2-NH₂C(O))]²⁺. The oxidized1,2-cyanobenzamide complex [Ru(NH₃)₅(NHC(OH)-bz-2-CN)]³⁺ undergoes an amide to nitrile intramolecular linkage isomerization, followed by a cyclization reaction resulting in [Ru(NH₃)₅(NH-(C)(HN-C(O)-2-bz))]³⁺ ((NH-(C)(HN-C(O)-2-bz)) = 3-imino-1-oxo-isoindoline bonded through the exocyclic nitrogen) (pK_a = 4.3). The rates of these reactions, which occur with neighboring group participation, increase with acidity. The reduced form, [Ru(NH₃)₅(NH-(C)(HN-C(O)-2-bz))]²⁺, is relatively substitution inert.     

Constituting ‘Asian women’: Political representation,identity politics and local discourses of participation

Political representation of ethnicized and other identities is a complex process, whereby identities are constructed and shaped through the competing claims of different collectivities. In the article I explore this process through a case study of a local authority community development project for Asian women. The analysis demonstrates that institutions are not neutral spaces in which contestations over collectivity are played out, but exert a constitutive impact upon the identities produced. Current theories of fluidity and instability in identities mean that collective identities must be staked strategically and contingently, determinant upon the political strategies appropriate within given institutional contexts.     

A pollution incident at a Qiaoxiang village in China: the role of migration in civic organization and political participation

Through an analysis of a pollution-based incident at Refinery-G in an infamous Qiaoxiang town in Fujian, China, this paper analyses how transnational migrants participate in and influence the public management activities in their hometowns. This paper underscores four factors driving civic and political participation that emerged during the revelation, resistance, negotiation and settlement of this incident: (1) the role of the ‘leisured’ villager; (2) the role of overseas Chinese in caring for the developmental path of their hometown; (3) the role of independent civic organizations; and (4) the role of the news media in shaping public opinion. Qiaoxiang's civic participation is both more active and more effective. With the development and globalization of modern communication technology and low-cost and convenient communication and transportation systems, it is possible for overseas migrants to influence public management activities in their hometown through civic organization and political participation.     

National interests and international collaboration: tensions and ambiguity among Finns towards usages of tissue samples

Recent trends in biobanking indicate that the practices associated with the collection and use of human tissue samples and related health information are increasingly becoming premised on networks of biobanks. These networks and partnerships often involve international collaborations, as well as public–private partnerships. This article reports on the results of a study of people's attitudes towards biobanking and the biomedical use of tissue samples in Finland. Three approaches were used to study these attitudes: a population-based survey, focus group interviews among members of patient organizations and short interviews with research participants. In particular, we look at the attitudes of respondents in these three studies towards the use of tissue samples and use them as a catalyst to discuss two dimensions of biomedical research: public/private and domestic/international. Our discussion highlights how notions of value related to the use of tissue samples vary and provide contrasting perspectives and ambiguity that people may have towards various types of research partnerships and the benefits that may arise from them.     

Biomass transportation model and optimum plant size for the production of ethanol

A detailed model based on a non-dimensional transportation factor is developed to assess the economics of biomass collection, transportation, and storage. The optimum plant size for bio-refineries is investigated; ethanol production from corn stover via dilute acid hydrolysis is presented as a case study. The conversion of straight-line, farm-to-plant distances to road distances via a winding factor leads to a shift in the distribution of transportation distances towards shorter hauls. The capital investment scaling exponent was calculated using the model developed at the National Renewable Energy Laboratory (Aden et al., NREL/TP-510-32438, 2002) and found to be 0.7. The cost of the delivered corn stover is proportional to the square root of the inverse of the farmer participation; as a consequence, bio-fuel producers intending to use agricultural residues as feedstock should work towards a farmer participation of fifty percent. Costs associated with storage represent a significant portion of the production cost.