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Biomedical subjects

G Szöllösi

Publications and source records attributed to G Szöllösi.

12 recordsLinked to original sources
PubMed2001

Enantioselective Michael addition catalyzed by cinchona alkaloids.

Enantioselective Michael additions of cyclic beta-ketoesters to methyl vinyl ketone catalyzed by cinchona alkaloids were studied. The results revealed that the induced enantioselectivity was significantly influenced by both the structure of the catalyst and that of the substrate. Interesting differences in the effect of the structure of the alkaloid on the enantioselectivity of this reaction in the case of three beta-ketoesters were discovered. High enantioselectivities were obtained in the reaction of ethyl 2-oxocyclopentanecarboxylate and ethyl 2-oxocyclohexanecarboxylate (up to 83 and 80%, respectively) at a low cinchona:reactant ratio of 1:500. As the specific rotations of the product enantiomers were unknown, they were determined by optical rotation and chiral GC measurements and verified by NMR experiments.

Butanones↗
PubMed2001

Heterogeneous asymmetric reactions. Part 24. Heterogeneous catalytic enantioselective hydrogenation of the C==N group over cinchona alkaloid modified palladium catalyst.

The enantioselective hydrogenation of C==N-C group containing compounds over modified metal catalysts is as yet an uninvestigated research area. This work contains results obtained on the hydrogenation of 1-pyrroline-2-carboxylate esters and sodium salt over cinchona alkaloid-modified alumina-supported Pd catalyst. The effect of the reaction parameters and the structure of the alkaloid molecule on hydrogenation rate and enantioselectivity allowed us to assume that on the catalyst surface only a weak interaction exists between the modifier and the substrate, resulting in the low enantiomeric excesses (up to 20%) obtainable in these reactions.

Catalysis↗
PubMed2000

Asymmetric sonochemical reactions enantioselective hydrogenation of alpha-ketoesters over platinum catalysts.

The sonochemical enantioselective hydrogenation of different alpha-ketoesters to the corresponding hydroxy derivatives over cinchona modified Pt catalysts is described. Ultrasonic irradiation was found to be beneficial in improving the optical yields. Besides studying the reaction rates and enantioselectivities, the effect of ultrasonics on the catalyst-modifier system and the scale-up of the process will also be considered.

Journal Article↗
PubMed2000

Ultrasonics in chemoselective heterogeneous metal catalysis sonochemical hydrogenation of unsaturated carbonyl compounds over platinum catalysts.

The hydrogenation of unsaturated aldehydes was studied over ultrasonically pretreated silica supported platinum catalyst. In the hydrogenation of cinnamaldehyde a remarkable reaction rate and cinnamyl alcohol selectivity increase was observed. Using other unsaturated aldehydes the reaction rate and unsaturated alcohol selectivity increased moderately.

Journal Article↗
PubMed1999

Ultrasonics in heterogeneous metal catalysis: sonochemical chemo- and enantioselective hydrogenations over supported platinum catalysts.

Sonochemical chemo- and enantioselective hydrogenations over supported platinum catalysts are described. We disclose our results with respect to a sonochemical modification of the chemoselective hydrogenation of cinnamaldehyde over supported platinum catalysts, and the asymmetric hydrogenation of ethyl pyruvate promoted by various ultrasonic pretreatments. The ultrasonic pretreatment of the supported platinum catalysts was found to be highly beneficial in almost every case, improving both the catalytic activity and selectivity. The effect of additional experimental variables, such as hydrogen pressure, catalyst support, temperature and the ultrasonic insonation time were also studied. The enantioselectivity of the hydrogenation of ethyl pyruvate increased up to 97.1% ee. In the case of cinnamaldehyde hydrogenation, the selective preparation of cinnamyl alcohol became possible. The theoretical aspects of the working mechanisms in comparison with 'silent' reactions will also be provided.

Journal Article↗
PubMed1990

Combined peritoneal and haemodialysis therapy for chronic renal insufficiency.

Twenty-three patients with chronic uraemia were treated for an average of 8.5 months with intermittent peritoneal dialysis. When hypervolaemia developed and/or the volume of low-molecular weight substances increased, the therapy was complemented by one or two sessions of haemodialysis per week. The combined treatment was carried on for 4.1 months on average, in consequence of which the general condition improved, body weight reached the optimum, blood pressure diminished, turned normal and could be controlled by drugs. In the wake of the therapy carbamide nitrogen and creatinine levels dropped significantly, serum total protein and albumin values increased. At the close of the observation period 3 patients remained under combined therapy, 2 had undergone cadaveric kidney transplantation, 18 were transferred to chronic haemodialysis. Thoughts are evolved about the advisability of intermittent peritoneal dialysis and combined therapy in the care for uraemic patients.

Adult↗
PubMed1989

[Combination of peritoneal dialysis and hemodialysis in the treatment of chronic renal insufficiency].

In case of 23 patients, who had been treated for 8.5 (2-10) months with intermittent peritoneal dialysis, the peritoneal dialysis was supplemented once or twice a week by haemodialysis for 8.5 months. This combined way of treatment was favourable in cases of hypervolemia and/or of increased level of substances of small molecular weight. The average duration of this kind of treatment was 4.1 (1.5-11) months. In the course of treatment the general condition of the patients improved. When they regained their optimal bodyweight, their blood pressure got normalized or their hypertony decreased or it could be regulated by drug therapy. At the effect of this treatment, the carbamid nitrate and serum creatinin significantly decreased and the serum total protein and albumin levels increased. Two of the patients underwent cadaver kidney transplantation, and 18 of them have been treated by hemodialysis, 3 of them are being treated in this combined way even now. The authors discuss the role of intermittent peritoneal dialysis and that of the combined treatment in the management of uremic patients.

Humans↗