The application of nitrido manganese reagents to the synthesis of protected N-methyl D-fucosamine

A synthesis of protected D-fucosamine and N-methyl fucosamine from D-galactose is described. The synthesis is carried out in ten steps and includes the amination reaction of D-fucal with an easily prepared Mn≡N reagent

Capturing Fleeting Intermediates in a Catalytic C-H Amination Reaction Cycle

We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C–H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C–H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes

Thermokarst processes increase the supply of stabilizing surfaces and elements (Fe, Mn, Al, and Ca) for mineral–organic carbon interactions

The stabilizing properties of mineral–organic carbon (OC) interactions have been studied in many soil environments (temperate soils, podzol lateritic soils, and paddy soils). Recently, interest in their role in permafrost regions is increasing as permafrost was identified as a hotspot of change. In thawing ice-rich permafrost regions, such as the Yedoma domain, 327–466 Gt of frozen OC is buried in deep sediments. Interactions between minerals and OC are important because OC is located very near the mineral matrix. Mineral surfaces and elements could mitigate recent and future greenhouse gas emissions through physical and/or physicochemical protection of OC. The dynamic changes in redox and pH conditions associated with thermokarst lake formation and drainage trigger metal-oxide dissolution and precipitation, likely influencing OC stabilization and microbial mineralization. However, the influence of thermokarst processes on mineral–OC interactions remains poorly constrained. In this study, we aim to characterize Fe, Mn, Al, and Ca minerals and their potential protective role for OC. Total and selective extractions were used to assess the crystalline and amorphous oxides or complexed metal pools as well as the organic acids found within these pools. We analyzed four sediment cores from an ice-rich permafrost area in Central Yakutia, which were drilled (i) in undisturbed Yedoma uplands, (ii) beneath a recent lake formed within Yedoma deposits, (iii) in a drained thermokarst lake basin, and (iv) beneath a mature thermokarst lake from the early Holocene period. We find a decrease in the amount of reactive Fe, Mn, Al, and Ca in the deposits on lake formation (promoting reduction reactions), and this was largely balanced by an increase in the amount of reactive metals in the deposits on lake drainage (promoting oxidation reactions). We demonstrate an increase in the metal to C molar ratio on thermokarst process, which may indicate an increase in metal–C bindings and could provide a higher protective role against microbial mineralization of organic matter. Finally, we find that an increase in mineral–OC interactions corresponded to a decrease in CO2 and CH4 gas emissions on thermokarst process

Система автоматического регулирования температуры в производственном помещении

САР температуры в помещении необходима для быстрого восстановления температурного режима в помещении чего не обеспечивает существующее центральное отопление.Позволяет улучшить качество регулирования температурного баланса. Цель работы – Оснащение воздушного отопительного агрегата системой автоматического управления. В процессе исследования проводились Анализ работы САУ вентиляционных систем, анализ построения САР температуры вентиляционных систем. В результате исследования Была разработана структурная и функциональная схемы САР температуры отопительного агрегата, а также алгоритм управления САР.ACS of temperature is indoors necessary for fast restoration of temperature condition in what doesn't provide the existing central heating. Allows to improve quality of regulation of temperature balance. The aim of the work is Vehicle air heating unit automatic control system. In the process of investigation the Analysis of the work of the ACS ventilation systems, analysis of building SAR temperature ventilation systems. The study was developed by structural and functional scheme of the SAR temperature of the heating unit and the control algorithm of the SAR

Stochastic dynamics of correlations in quantum field theory: From Schwinger-Dyson to Boltzmann-Langevin equation

The aim of this paper is two-fold: in probing the statistical mechanical properties of interacting quantum fields, and in providing a field theoretical justification for a stochastic source term in the Boltzmann equation. We start with the formulation of quantum field theory in terms of the Schwinger - Dyson equations for the correlation functions, which we describe by a closed-time-path master ($n = \infty PI$) effective action. When the hierarchy is truncated, one obtains the ordinary closed-system of correlation functions up to a certain order, and from the nPI effective action, a set of time-reversal invariant equations of motion. But when the effect of the higher order correlation functions is included (through e.g., causal factorization-- molecular chaos -- conditions, which we call 'slaving'), in the form of a correlation noise, the dynamics of the lower order correlations shows dissipative features, as familiar in the field-theory version of Boltzmann equation. We show that fluctuation-dissipation relations exist for such effectively open systems, and use them to show that such a stochastic term, which explicitly introduces quantum fluctuations on the lower order correlation functions, necessarily accompanies the dissipative term, thus leading to a Boltzmann-Langevin equation which depicts both the dissipative and stochastic dynamics of correlation functions in quantum field theory.Comment: LATEX, 30 pages, no figure

I. Enantioselective synthesis of (+)-zaragozic acid C. II. Nitridomanganese(V) complexes: design, preparation, and use as novel nitrogen atom-transfer reagents

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. An enantioselective synthesis of the potent squalene synthase inhibitor (+)-zaragozic acid C is described. Zaragozic acid C constitutes one member of a family of natural products which possess a unique, highly functionalized 2,8-dioxabicyclo[3.2.1]octane core. An efficient route has been delineated which allows for the preparation of multigram quantities of this structural unit. Conversion of the bicyclooctane to the target molecule requires installing three carboxylic acids at C(8), C(9), and C(10), which has been accomplished by simultaneous oxidation of the corresponding tri-aldehyde. Additional highlights and supporting studies from this work include: (1) the use of [...] for the stereoselective reduction of ynones to trans enones; (2) an investigation of the diastereoselective dihydroxylation of [gamma]-alkoxy-[alpha,beta]-unsaturated ketones; (3) the effect of amine cosolvents on the nucleophilic addition of TMSC[...]CLi to a key dioxabicyclooctanone intermediate; and (4) stereospecific formation of the C(5) quaternary center by a chelation-controlled ketone addition reaction. The chemical transformations which have been developed should prove useful for the preparation of synthetic and semi-synthetic analogues of this important class of molecules. The design and preparation of novel nitridomanganese(V) Schiff base-derived complexes which function as nitrogen atom-transfer reagents for olefin amination has been described. X-ray crystallography has been employed to establish the structures of these unique [...] complexes, ORTEP figures of which are presented. The utility of these reagents has been demonstrated in reactions with silyl enol ethers and carbohydrate glycals to give [alpha]-amino ketones and 2-amino saccharides, respectively. Yields for these processes typically range from 60-80%, and, in all cases, the olefin starting material is employed as the limiting reagent. Moreover, the amine products isolated are conveniently protected as their N-trifluoroacetyl derivatives. Efforts to prepare additional reagents which display nitrogen transfer activity with unfunctionalized alkenes have led to the development of mild, efficient, and general protocols for the preparation of Mn[...]N systems. These complexes function competently as nitrogen transfer agents with styrene

Intermolecular sp3-C–H Amination for the Synthesis of Saturated Azacycles

The preparation of substituted azetidines and larger-ring, nitrogen-containing saturated heterocycles is enabled through efficient and selective intermolecular sp3-C–H amination of alkyl bromide derivatives. A range of substrates is demonstrated to undergo C–H amination and subsequent sulfamate alkylation in good to excellent yield. N-Phenoxysulfonyl-protected products can be unmasked under neutral or mild basic conditions to yield the corresponding cyclic 2° amines. The preparative convenience of this protocol is demonstrated through gram-scale and telescoped multi-step procedures. Application of this technology is highlighted in a nine step total synthesis of an unusual azetidine-containing natural product, penaresidin B