Enantioselective Peptide Synthesis by Using the Optically Active Polymer Containing the 1-Benzyl-3-Hydroxy-5-Isobutyl-Hydantoin Structure

The polymer containing the 1-benzyl-3-hydroxyhydantoin structure was prepared from styrene and 1-chloromethylhydantotin in order to achieve not only the act as acyl activating polymeric ester but the selective reaction using the D, L-amino acid seter. For the enantioselective peptide senthesis, the 1-benzyl-3-hydroxyhydantoin as a model compound and the 1-bernzyl-3-hydroxyhydantoin type polymer were allowed to act by two methods-the active ester method and the additive method using N, N\u27-dicyclohexylcarbodiimide (DCC). Optical yield was appreciated in 45%

Acetohydroxamic Acid for Peptide Synthesis

The ester derivatives of acetohydroxamic acid md N, N-diacetyl hydroxylamine, N, O-diacetyl hydroxylamine and triacetyl hydroxylamine were assured to be capable of being used as activated esters. At first, evaluation of acyl activating ability was made by reacting the above compounds with amine, and it was shown that all of them worked to yield amides with excellent conversion and that, among them, triacetyy hydroxylamine was most powerfull, where acetylation of amines went through its imide carbonyl group. Furthemore, dipeptide synthesis was found to accomplish without any racemization and in a good yield by use of acetohydroxamic acid. Next syntheses of polymers containing hydroxamic acid structure were carried out by the following routes. (a) methyl methacrylate was copolymerized with N-methacrylobenzyloxyamine and the copolymer obtained was debenzylated, (b) N-methacrylo-N, O-diacetyl hydroxylamine was polymerized, followed by hydrolysis and copolymers with styrene or methyl methacrylate were deacylated. The polymer obtained by route (a) was converted to the activated polymer ester of N-blocked diglycine and removal of the protecting group would provide a method for preparation of cyclic diglycine

Polymers Having Stable Radicals : Electrochemical and Chemical Behaviors of the Polymer Having Nitroxyls.

As a part of this series on polymers having stable radicals, evaluation of oxidation-reduction potentials by polarography and oxidative reactivities toward hydrazine and hydrazobenzene has been dealt with on nitroxyl stable radicals. Poly (4-methacryloyloxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl) (III) as a polymer having stable radicals, and its prototypes, 4-oxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl (I) and 4-isobutyroyloxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl (II), have been employed for purpose of the study. The electrode reactions of (I) in a range of pH. 8.0-10.1 in aqueous media were observed to be quasi-reversible and the reduction half-wave potentials (E_) being between 0.120-0.200 V (vs. SCE) depending on pH.. In the other pH. regions, the reactions seemed to be irreversible and the reduction halfwave potentials depended uPon pH. as well. In addition, polarographic data in a non-aqueous medium ensured that all the nitroxyls (I), (II) and (III) might have the same redox potential values. The oxidation reactions, using (I), (II), and (III), on hydrazine and hydrazobenzene have been performed, of which extent was pursued spectrophotometrically. From the kinetics, it was elucidated that, (1) the reactions were bimolecula, (2) the rate determinant steps were in the first hydrogen abstraction and, (3) the reactions with hydrazine were reaction controlled (ΔE ; 11.2-11.3 Kcal/mol) while the reactions with hydrazobenzene were diffusion controlled (ΔE ; 5.9-3.9 Kcal/mol). Thermodynamic analysis indicated that the case of reaction with hydrazobenzene differed mechanistically whether the reactant was monomeric (II)or polymeric (III) (ΔS^‡ : -17.9 e. u., (II) ; -21.8 e.u., (III), at 20℃ in THF)and that a steric hindrance presumably took place in the latter

Source reduction for prevention of methylene chloride hazards: cases from four industrial sectors

BACKGROUND: Source reduction, defined as chemical, equipment and process changes that intervene in an industrial process to eliminate or reduce hazards, has not figured as a front-line strategy for the protection of workers' health. Such initiatives are popular for environmental protection, but their feasibility and effectiveness as an industrial hygiene approach have not been well described. METHODS: We investigated four cases of source reduction as a hazard prevention strategy in Massachusetts companies that had used methylene chloride, an occupational carcinogen, for cleaning and adhesive thinning. Three cases were retrospective and one was prospective, where the researchers assisted with the source reduction process change. Data were collected using qualitative research methods, including in-depth interviews and site visits. RESULTS: Motivated by environmental restrictions, a new worker health standard, and opportunity for productivity improvements, three companies eliminated their use of methylene chloride by utilizing available technologies and drop-in substitutes. Aided by technical assistance from the investigators, a fourth case dramatically reduced its use of methylene chloride via process and chemistry changes. While the companies' evaluations of potential work environment impacts of substitutes were not extensive, and in two cases new potential hazards were introduced, the overall impact of the source reduction strategy was deemed beneficial, both from a worker health and a production standpoint. CONCLUSION: The findings from these four cases suggest that source reduction should be considered potentially feasible and effective for reducing or eliminating the potential hazards of methylene chloride exposure. Especially when faced with a hazard that is both an environmental and worker health concern, companies may chose to change their processes rather than rely on local exhaust ventilation equipment or personal protective equipment that might not be as effective, might transfer risk and/or not be integrated with financial goals. However, technical assistance sensitive to environmental and health and safety impacts as well as production issues should be provided to guide companies' source reduction efforts

What is the state of the art in energy and transport poverty metrics? A critical and comprehensive review

This review investigates the state of the art in metrics used in energy (or fuel) and transport poverty with a view to assessing how these overlapping concepts may be unified in their measurement. Our review contributes to ongoing debates over decarbonisation, a politically sensitive and crucial aspect of the energy transition, and one that could exacerbate patterns of inequality or vulnerability. Up to 125 million people across the European Union experience the effects of energy poverty in their daily lives. A more comprehensive understanding of the breadth and depth of these conditions is therefore paramount. This review assessed 1,134 articles and critically analysed a deeper sample of 93. In terms of the use of metrics, we find that multiple indicators are better than any single metric or composite. We find work remains to be conducted in the transport poverty sphere before energy poverty metrics can be fully unified with those of transport poverty, namely the stipulation of travel standards. Without such standards, our ability to unify the metrics of both fields and potentially alleviate both conditions simultaneously is limited. The difficulties in defining necessary travel necessitate the further use of vulnerability lenses and holistic assessments focused on energy and transport services