Facile method for the synthesis of oseltamivir phosphate

A ten-step scheme for the preparation of an antiviral agent, ethyl (3R,4R,5S)-4-acetylamino-5-amino-3-(pent-3-yloxy)cyclohex-1-enecarboxylate phosphate, from (-)-shikimic acid was studied. The main parameters of the synthesis were determined and the optimal conditions for the preparation of the intermediate compounds were selected. The total yield of oseltamivir phosphate calculated based on (-)-shikimic acid was 27%.     

Estimation of the role of side reactions in the simulation of complexometric titration

A mathematical model was selected to describe the titration of metal ions with an arbitrary reagent in the presence of masking agents. The model takes into account the stepwise character of the complexation reaction and side reactions of protonation, hydrolysis and masking. The computed titration curves were in good agreement with the data of potentiometric titration. The corresponding program was used to optimize the titration conditions, to select promising titrants (other than complexones), and to predict systematic errors due to the shift of the titration jump in the presence of masking agents. Because of the last-named effect, the results of analysis may be underestimated several times     

Modification of the physicomechanical properties of metallic materials by formation of nanoscale intermetallic phases under ion implantation

The fundamental and technological aspects of application of nanosized intermetallic compounds as implanted layers have been considered. The existing theoretical and experimental data on the effect of ion implantation on the structural state and physicomechanical properties of surface layers of metals (nickel and titanium) have been analyzed. The common features and differences in the phase composition and distribution of the phases formed by implantation over the alloyed metal layers are demonstrated.     

Specific features of generation of the quasi-Schrödinger soliton in the CW mode-locked solid-state laser with a semiconductor saturable absorber

The mechanism of mode-locking in the cw solid-state laser with the saturable semiconductor switch caused by the formation of the quasi-Schrödinger soliton is investigated on the basis of the self-consistent laser field theory. The possible regimes of the quasi-soliton destabilization are studied: the sharp transition from the femtosecond to picosecond generation (“the picosecond collapse”), the self-oscillation instability, as well as the breakdown of the pulsed generation. The existence of multistable states and hysteresis phenomena upon the variation in the group-velocity dispersion and the pump power are shown.     

Effect of Stimulated Raman Scattering on Spectral Characteristics of Ultranarrow Pulses in a Mode-Locked Solid-State Laser

On the basis of numerical modeling, it is shown that the effect of the higher-order group-velocity dispersion is unable to account for the noticeable Stokes displacement of the generation spectrum in a LiSGaF laser with mode-locking due to self-focusing. The results of calculations indicate the determining influence of stimulated Raman scattering on the spectral characteristics of femtosecond pulses.     

Study of the effect of the fractionation of gas mixtures in the pathway through a mass spectrometer

A novel method was proposed for the investigation of the fractionation effect in a mass spectrometer. Experimental data obtained on a MI-1201AGM mass spectrometer in the analysis of gas mixtures composed of perfluoromethylcyclohexane and uranium hexafluoride are presented.     

Debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane

The debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetra-cyclo[5.5.0.0^3,11.0^5,9]dodecane by catalytic hydrogenolysis in a mixture of HCOOH with other RCOOH (R = Me, Et, Prⁱ) is accompanied by the N-formylation of the liberated secondary amino groups. The alkaline hydrolysis of the obtained products makes it possible to remove the formyl groups with the retention of the acetyl groups.     

Selective synthesis of triple-decker cyclohexylmethoxy-substituted europium phthalocyanine

Selective synthesis of substituded europium triphthalocyanine on the base of dilithium 2,3,9,10,16,17,23,24-octa(cyclohexylmethoxy)phthalocyanine was performed. The structure of the complex obtained was characterized by ¹H NMR spectroscopy, mass spectrometry, and UV-visible spectroscopy.     

Iterative scheduling algorithms based on the subdivision of the solution space into domains

Iterative multiprocessor scheduling algorithms are considered. The iterative algorithms make it possible to solve scheduling problems for a wide class of computer architectures but are very intricate from the computational point of view. To simplify the iterative algorithms, we propose an approach to their construction based on the subdivision of the space of correct schedules into disjoint domains, namely, an algorithm for constructing domains is proposed, the operations of the schedule transformations closed within the domains are introduced, and a technique for cutting off domains is developed. The approach developed also makes it possible to construct parallel algorithms with a low traffic of the exchange between parallel processes.