Synthesis of Non-proteinogenic Amino-Acid Methyl Esters with Acid-Sensitive Side Chains from a Chiral Glycine Derivative

A superior chiral glycine derivative 1 (tert-butyl 2-(tert-butyl)-4-methoxy-2,5-dihydro-1,3-imidazole-1-carboxylate, BDI) for the synthesis of acid-sensitive and highly hindered α-amino-acid methyl esters is readily available by resolution methods. The heterocycle 1 is alkylated once and twice in the 5-position with very high diastereoselectivity, and the resulting products (2, 3) are hydrolyzed under very mild conditions to give methyl esters of the corresponding amino acids (6–10)

The Biological Stability of β-Peptides: No Interactions between α- and β-Peptidic Structures?

The use of peptides in pharmaceutical applications is always hindered by the rapid degradation of the peptides by enzymes. Recent work on β-peptides, peptides constructed entirely from β-amino acids, has shown that even the short-chain oligomers (6 or 7 residues) exhibit remarkably stable secondary structures. However, before certain applications of β-peptides can be considered, an information about their possible interactions or reactions with enzymes must be acquired.Ames tests (all negative) have now been performed on a selection of β-amino acids, which would be the result of the enzymatic degradation of a β-peptide. Furthermore, digestion experiments using a variety of peptidases and β-peptides have now shown that β-peptides, in sharp contrast to their α-peptide counterparts, undergo no degradation

Catalytic Enantioselective Reactions from Research to Application. Diarylmethanol-Containing Auxiliaries as a Study Case

Chiral auxiliaries – in the broadest possible definition of the term – can be obtained by Grignard reactions of Aryl-MgX with chiral esters R*CO2R. The products formed all contain a diarylmethanol structural moiety. They can be used in stoichiometric and catalytic enantioselective reactions, preferably as ligands on metal centers. They have also found applications for enantioselective inclusions, for solid-phase reactions, and for liquid-crystal preparations

Sequencing of β-Peptides by Mass Spectrometry

Seven ?-peptides containing up to 18 β2-, β3- and β2,3-amino acids have been subjected to ESI-tandem mass spectrometry (low-energy fragmentation, positive ions). From the fragment ions formed from the free β-peptides, as well as from the corresponding methyl esters (+14 U) and N-acetyl derivatives (+42 U), the known sequences of β-amino acids could be confirmed unambiguously with the program Sherpa. Thus, the commonly used MS-sequencing procedure for α-peptides can be adopted for β-peptides without modification. However, there are pronounced differences in the fragmentation patterns of the two types of peptides: the β-peptides disclose their relationship to Mannich bases in the mass-spectrometric experiment by the elimination of ammonia from the N-terminus (→ RCH=CH-CO-NH-R') and the occurence of retro-Mannich cleavage (cf. formation of HN=CHR + CH3CO-NH-R' from β-amino-acid residues)

Kristallistrukturanalyse von lösungsmitterfreiem Lithium-benzoat. Relevanz föur die Material-eigenschaften von Lithium-carboxylaten?

Anhydrous Li benzoate crystallizes from water as very thin, soft, and flexible platelets. The poor quality of these crystals rendered the data collection for the crystal structure determination very difficult. Anisotropic refinement did not reduce the R value below 0.1. The Li benzoate molecules form a two-dimensional polymeric structure consisting of a grid of lithium and carboxylate O-atoms, with the Ph groups forming kind of a covering layer on each side. The polymeric layers are stacked with phenyl CH groups pointing towards each other. Thus, very weak van-der-Waals forces hold the layers together. This structural feature is in agreement with the macroscopic properties of the crystals and probably causes Li carboxylates to be valuable components of high-temperature, high-performance greases (for instance in the vacuum technology). The structures of Li benzoate and of other Li carboxylates may also provide a clue for the fact that ionomers containing LiOOC groups are especially tough materials

Hoch effiziente, präparative chromatographische Enantiomerentrennung von 2-Phenyl-1,3-dioxin-4-onen an Cellulose-triacetat und Cuprat-Additionen zu β-Hydroxycarbonsäure-Derivaten

The 2-Phenyl-dioxinones 1 and 2 are resolved on cellulose-triacetate columns (medium pressure, eluent MeOH, separation factors α = 2.0–2.3, injection of g amounts). The enantiomerically pure formyl- and acetylacetate derivatives, thus available undergo diastereoselective (97–99% ds) 1,4-additions with CuCl-doped Grignard reagents or with cuprates to give the dioxanones 5,9, and 10. Eventually, 3-hydroxy-carboxylic acids, esters, and O-benzyl-protected acids (6, 8, 11–13) can be prepared with >96% enantiomeric excess; otherwise not readily available derivatives with a tertiary 3-hydroxy group are accessible by this route (see 11, 12). Two peculiar stereoselective reactions are reported: i) the inversion of configuration upon bromination of the dioxinone 2 ((–)-(R)-2 → (+)-(S)-4) and ii) the highly diastereoselective (91% ds) cleavage of the 2-phenyl-dioxanone 10 with D2/Pd-C(→13). Configurational assignments are based on nuclear Overhauser effects (NOE) and on chemical correlations

The application of integrated environmental management to improve storm water quality and reduce marine pollution at Jeffreys Bay (South Africa)

It is projected that by 2025 three-quarters of the world’s population will live in the coastal zone. This is an alarming statistic, with a consequently significant impact on small coastal towns and the adjacent marine environments. Developing communities within the coastal zone of South Africa have proved to be a significant pollution source of storm water. Studies have shown that storm water that is deposited in the ocean will be trapped in the near shore marine environment causing poor seawater quality over a large distance. Furthermore, this can pose a significant threat to the health of recreational users and important marine ecosystems. In Jeffreys Bay storm water quality is thought to pose a threat to the maintenance of the international Blue Flag status for its beach. The aim of the current project was to investigate the main sources of storm water and subsequent marine pollution at Jeffreys Bay and to develop an appropriate management strategy using the integrated environmental management framework. In order to achieve this objective, it was also necessary to determine the current quality of water at various points within the catchment and near shore marine environment. Even though the storm water was found to be severely contaminated no evidence existed for a negative impact on the marine environment. None the less, a precautionary approach was adopted and a risk assessment employed in order to consider potential impacts on the marine and aquatic environment, human health and socio-economic welfare within the town. Significant sources of storm water contamination included grey water, domestic solid waste disposal and informal ablution. These significant aspects were investigated further and it was found that solid waste management in the catchment was poor with significant quantities of waste, primarily (76%) from domestic sources, being disposed of illegally. A study of sanitation management showed inadequacies where up to 58% of the residents from the informal settlements disposed of their grey water into open spaces. The ratio of residents to toilets in these areas was 28:1, therefore supporting the outcome of the risk assessment. Due to the fact that all the significant aspects were related to anthropogenic waste, an integrated waste management plan (IWMP) was developed that would not only facilitate the reduction of pollution of storm water, but would also allow for sustainable community-based development

The investigation of the production environment factors through the prism of the game process

У сучасному світі широко використовується гейміфікація, як один з найбільш ефективних підходів в навчанні. Гейміфікація застосовується з метою залучення користувачів, підвищення їхньої зацікавленості у вирішенні прикладних завдань. Однією з найбільш ефективних методик виступає ділова гра. У процесі її моделювання визначається проблемна ситуація, і мета гри полягає в пошуку шляхів її вирішення. Ділові ігри застосовуються як в освітній, так і діловій сферах. Важливе значення ділових ігор полягає також в тому, що вони сприяють встановленню відносин співробітництва викладача і студентів, обумовлюють формування позитивного емоційно-психологічного клімату на заняттях. Розроблена і впроваджена в навчальний процес робота "Office Explorer" - це візуальний інструмент у вивченні впливу факторів виробничого середовища і трудового процесу на стан здоров'я людини і навколишнього середовища. Створена така універсальна програма, яка в ігровій формі доступно, не нав'язливо донесе інформацію до студента, заставить проаналізувати, засвоїти, зробити правильні висновки, обрати необхідні засоби і заходи захисту від впливу шкідливих чинників виробничого середовища і трудового процесу. Програма "Office Explorer" об'єднала в собі всі ці вимоги до комп'ютерних лабораторних робіт і стала незамінним інструментом в засвоєнні знань і практичних навичок з дисциплін "Безпека життєдіяльності" та "Основ охорони праці". Реалізований підхід є найсучаснішим рішенням висвітленої проблеми сучасних заходів навчання та оцінювання знань студентів ВНЗ. Використання цього підходу дозволяє автоматизувати навчальний процес, а також готує майбутнього спеціаліста до умов вирішення реальних проблем. Використання подібних робіт при різних формах навчання дуже важливо і необхідно в сучасних умовах.In the modern world, gaming is widely used as one of the most effective approaches in the teaching. Gaming is used to attract users, increase their interest in solving applied problems. One of the most effective techniques is the business game. In the process of its simulation, the problem situation is determined, and the purpose of the game is to find ways to solve it. Business games are applied both in educational and business spheres. The importance of business games is also that they contribute to the establishment of relations between the teacher and students, which determine the formation of a positive emotional and psychological climate in the classes. The "Office Explorer" work developed and implemented in the educational process is a visual tool in studying the influence of the working environment factors and the working process on the condition of human health and the environment. The Office Explorer program combines all these requirements with computer labs and has become an indispensable tool in acquiring knowledge and practical skills in the disciplines "Security of Life" and "Fundamentals of Occupational Safety". The implemented approach is the most up-to-date solution of the illuminated problem of modern educational measures and assessment of students' knowledge of universities. Using this approach allows you to automate the learning process, as well as prepare a future specialist for the conditions for solving real problems. The using of such works in various forms of training is very important and necessary in the modern conditions