Enzymatic resolution of bicyclic 1-heteroarylamines using Candida antarctica lipase B

Candida antarctica lipase B has been used to kinetically resolve a structurally diverse series of bicyclic 1-heteroaryl primary amines by enantioselective acetylation. High yields of either enantiomer could be obtained with excellent enantioselectivity (90-99% ee), while the undesired enantiomer could, in some cases, be recycled by thermal racemization. The absolute stereochemistry of the products was confirmed by an X-ray crystal structure.     

Effect of the Reaction Medium on Radical Copolymerization

.In contrast to early investigations on radical copolymerization [1], abounding experimental data accumulated during the last two decades has made it possible to establish an unequivocal effect of the reaction medium in at least some monomer systems.     

Surface analysis of a cold leg section of an SS316-lithium loop

Compatibility studies of austenitic stainless steel AISI 316 with liquid lithium for fusion application have shown that a porous ferritic layer is formed on the surface of the steel in the hot leg of a loop experiment due to depletion of alloying elements. The concentration profiles of the removed elements across the cross section of the tube reveal a pronounced step between the austenite matrix and the porous ferrite which is not expected in a normal diffusion process. The removed elements are partly deposited on the surface of the cold leg.In this study we looked at the boundary between the nickel rich deposit and the original matrix of a section of the cold (435 °C) leg. On the surface of the austenite, the expected grain boundary attack of lithium was observed. Additionally, to a depth of about one grain size, chromium and molybdenum were depleted and lithium seemed to also have attacked the bulk material, resulting in a splitting up into smaller grains with decomposed concentrations of the alloying elements, i.e. iron with large amounts of nickel and iron with chromium and small nickel amounts.In this paper a suggestion is put forward describing a reaction mechanism leading to the porous layer in the hot leg as a result of the instability of AISI 316 and its decomposition into two phases under the influence of liquid lithium.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Bicyclic [b]‐heteroannulated pyridazine derivatives. 9. cyclization reactions of 4,4‐dimethyl‐ and 4‐phenyltetrahydropyridazine‐3,6‐dione 3‐hydrazones with esters of keto dicarboxylic acids

Bis(ethoxycarbonyl)alkylidene derivatives 4 and 5 of the respective title hydrazones were obtained in the reactions with diethyl oxomalonate, diethyl oxosuccinate, diethyl 2‐oxoglutarate, and diethyl oxalo‐propionate as mixtures of geometric isomers with high predominance of one of them. On heating at 160‐200° without any solvent or on refluxing in ethanol 4 cyclized to yield the corresponding pyri‐dazino[6, 1‐c]triazines 6 , whereas heating of 5 gave, depending on the chain length, the corresponding pyra‐zolylpyridazines 8b and 8d or the pyridazinylpyridazine 8c . X‐ray analysis was used to determine the structures of 6 and 8 ; the unit cell of 6c was found to accommodate 16 molecules representing four conforma‐tional varieties. The different behavior of 4 and 5 in the cyclization reactions was interpreted in terms of the tautomeric equilibrium which was shifted towards the enamine form in 4 , and towards the imine form, in 5 . Transmission of a long‐range chirality effect in 4d and 5a‐d manifested itself in the ¹H nmr spectra as the magnetic non‐equivalence of the CH₂ protons in one or both ester ethyl groups.     

Cross depolarization: Two-dimensional heteronuclear dipolar powder pattern

A new two-dimensional depolarization pulse sequence is applied on the static powder sample of ferrocene. The transient oscillations during the first stage of the depolarization process are used for the modulation of magnetization during the evolution period giving the dipolar coupling/chemical shift resolved spectrum.     

Physico-chemical changes taking place in gamma irradiated bovine globulins studied by thermal analysis

Structural transformations induced in gamma and alpha globulins under influence of gamma irradiation using doses of 2.5 and 24 kGy were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG, DTG). Thermal decomposition of the globulins irradiated in water suspensions occurs at higher temperatures, in comparison to the reference non-irradiated samples. This was related to formation of covalent linkages in the irradiated proteins, apart to chemical changes induced in amino-acids. Essential modification of thermal decomposition was detected already after irradiation with a dose of 2.5 kGy performed for water suspensions. Irradiation of solid native proteins induces decrease in decomposition temperature and gives evidence of proteins degradation.     

Does Maternal Treatment with Zidovudine Affect Changes in Mandibles of Newborns? Laser Induced Fluorescence Study

The influence of antiretroviral drug zidovudine treatment during pregnancy on mandible development in newborn rats was studied. The fluorescence of mandibles from 7-, 14- and 28-days old individuals was measured by means of fiber-optical fluorescence analyzer with 407 nm laser excitation. Obtained results revealed disturbing effect of maternal zidovudine administration on mandible fluorescence intensity which should decrease with bone development. Small changes in fluorescence of porphyrin forms are maintaining in the first month of newborns life while the changes observed in 440–585 nm range disappear.