Wyniki wyszukiwania - Biblioteka Nauki

1

Środki ochrony roślin o budowie chiralnej

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Morzycka B. , Morzycki J. W.

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tom [Z] 57, 9-10

855--876

EN

The agrochemical industry is continuously searching for new active compounds to combat pests. The main aim of this research is to develop new substances with lower application rates, increased selectivity and decreased undesired ecological impact. Most synthetic agrochemicals with chiral structure are marketed as racemates even though the desired biological activity may be derived from only one enantiopure isomer. However, some newly introduced compounds are marketed as the most biologically active stereoisomers. When agrochemicals have chiral structures, efforts should be made to define the mode of action, toxicity, and metabolic pathway of each enantiopure isomer. If there are large differences in the biological activities of individual stereoisomers, it is desirable to use only the most active one. In this review article some stereochemical aspects of several groups of important agrochemicals including aryloxypropanoate herbicides, acylanilides, triazine herbicides, ureas and cyanoacrylates, triazole fungicides, morpholine derivatives, organochlorine insecticides, pyrethroid insecticides, pheromones and antifeedants, and organophosphorus compounds, will be discussed.

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Wspomnienia o profesorze Jerzym Suszce i szkic jego dokonań naukowych

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Antkowiak W. Z.

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tom [Z] 52, 7-8

473-509

EN

A quarter of a century has already passed since the most distinguished Polish pioneer in both natural products chemistry and stereochemistry, scientist meritorious for chemistry education, Professor Jerzy Suszko, passed away. He was born in Silesia near Teschen in 1889 and studied at the Polytechnic of Prague where he finished his PhD thesis under the auspices of Paul Rabe at the age of 24. After World War I he took on research work at the Jagielloński University in Cracow collaborating with Karol Dziewoński at the beginning. Next, after passing a habilitation examination and spending three years at the Univerity of Lvov, he moved to Poznań, where he spent the second half of his life, working as a professor and the Head of the Organic Chemistry Department of the University of Poznań. Furthermore, he was to become the Head of the Laboratory of Alkaloids of the Institute of Organic Chemistry of the Polish Academy of Sciences. He also held some highly responsible and a Dean of the Mathematical and Natural Science Faculty for a few years. The main scientific achievements of Professor Jerzy Suszko were concerned with the chemistry of physiologically active natural products and with the spatial structure of organic molecules. From among the natural products, the alkaloids and especially those of cinchona bark were the most intensively studied mainly because of their pharmacological properties. His synthetic and structural studies analysed all the most reactive and stereochemically important fragments of the molecules of quinine and related alkaloids. This resulted analogues differing by the kind of substituent in the quinoline moiety as well as the corresponding stereoisomers. Further significant achievements in the same field comprised, among others, the elaboration of a convenient method of a reverse conversion of quinotoxine (the product of an acid treatment of quinine but also occurring as the key intermediate in the quinine synthesis) and related toxins to the natural cinchona alkaloids, the determination of the pattern of rearrangement within the vicinal amino-alcohol fragment, and the discoveries in the chemistry of derivatives with a modified vinyl side chain, especially those being intramolecular ethers. The structure and conversion studies of other alkaloids concerned those occurring in the genera Papaver (codeine and rheadine), Lupinus and Cortinarius. At the beginning of the thirties, J. Suszko, proposed a new method of determining the molecular symmetry, especially in the case of fused-ring polycyclic aromatic hydrocarbons. This method was next verified mainly on naphthalene molecules and was based on the binding of two identical chiral substituents to the ring system in different positions followed by an analysis of the resulting stereochemical mixture. Other stereochemical studies concerning stereocontrolled syntheses, conformation stability and configuration determination were carried out on various cyclic apliphatic hydrocarbons, including bornane derivatives. Professor Jerzy Suszko educated a great number of graduated students both in chemistry and pharmacy. From about forty people who got their PhD degrees under his scientific supervision many later reached the highest levels in their scientific careers. He was a founding member of the Polish Chemical Society and was very much engaged in its activities during his whole life. He served in some responsible offices therein, including the President of the Society. He was also a member of several foreign scientific societies, including the American Chemical Society.

3

Stereokontrolowana synteza tlenowych analogów penicylin i cefalosporyn

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Łysek R. , Furman B. , Borsuk K. , Chmielewski M.

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tom [Z] 57, 5-6

391--433

EN

Synthesis of oxacephalotin and oxacephamandol which are more active then natural, containing sulfur congeners, and isolation of clavulanic acid, a patent inhibitor of (3-lactamase enzymes, directed attention of academic and industrial laboratories to the synthesis of oxygen analogs of penicillins and cephalosporins. The present review directs attention to the stereocontrol of a desired configuration in the formation of the bridgehead carbon atom. Five possible methods leading to basic skeletons of the title compounds are discussed (Scheme 1). Three of them involve nucleophilic substitution at C-4 of the azetidin-2-ones performed as inter or intramolccular process, and two of them involve cycloaddition reactions between ketenes and iminoethers, or between vinyl ethers and isocyanates. Owing to the general application stereospecificity, and high asymmetric induction, the last method seems to be most advantageous. The weak point of the nucleophilic substitution methodology is that a nuclcophilc enters 3-substituted azetidin-2-one ring preferentially anti to the existing substituent or if there is no substitutent at C-3, stereoselectivity in generation of a new stereogcnic center at C-4 is low. All methods arc illustrated by examples taken from the literature.