1647-23-0Relevant articles and documents
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Collier,W.L.,Macomber,R.S.
, p. 1367 - 1369 (1973)
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Metallocene compounds, including the catalyst, the catalyst used in the process of olefin polymers, olefin homopolymers and copolymers and
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Paragraph 0186, (2017/11/01)
PROBLEM TO BE SOLVED: To solve shortcomings of metallocene compounds of the present technology standard and to provide metallocenes that increase desirable characteristics such as high melting point, high molar mass homopolymers and high molar mass copolymers, and do so at higher productivities when used as components of supported catalysts under industrially relevant polymerization conditions at temperatures of from 50 to 100°C.SOLUTION: Certain metallocene compounds are provided that, when used as a component in a supported polymerization catalyst under industrially relevant polymerization conditions, afford high molar mass homo polymers or copolymers like polypropylene or propylene/ethylene copolymers without the need for any α-branched substituent in either of the two available 2-positions of the indenyl ligands.
Total synthesis of the large non-ribosomal peptide polytheonamide B
Inoue, Masayuki,Shinohara, Naoki,Tanabe, Shintaro,Takahashi, Tomoaki,Okura, Ken,Itoh, Hiroaki,Mizoguchi, Yuki,Iida, Maiko,Lee, Nayoung,Matsuoka, Shigeru
supporting information; scheme or table, p. 280 - 285 (2010/09/03)
Polytheonamide B is by far the largest non-ribosomal peptide known at present, and displays extraordinary cytotoxicity (EC50 =68 pg ml -1 , mouse leukaemia P388 cells). Its 48 amino-acid residues include a variety of non-proteinogenic d- and l-amino acids, and the absolute stereochemistry of these amino acids alternate in sequence. These structural features induce the formation of a stable β-strand-type structure, giving rise to an overall tubular structure over 30A? in length. In a biological setting, this fold is believed to transport cations across the lipid bilayer through a pore, thereby acting as an ion channel. Here, we report the first chemical construction of polytheonamide B. Our synthesis relies on the combination of four key stages: syntheses of non-proteinogenic amino acids, a solid-phase assembly of four fragments of polytheonamide B, silver-mediated connection of the fragments and, finally, global deprotection. The synthetic material now available will allow studies of the relationships between its conformational properties, channel functions and cytotoxicity.
5-[4-(3,3-Dimethylbutoxycarbonyl)phenyl]-4-pentynoic acid and its derivatives inhibit ionotropic γ-aminobutyric acid receptors by binding to the 4'-ethynyl-4-n-propylbicycloorthobenzoate site
Hamano, Hiroshi,Nagata, Keiichi,Fukada, Nobuo,Shimotahira, Hiroshi,Ju, Xiu-Lian,Ozoe, Yoshihisa
, p. 665 - 674 (2007/10/03)
Acyclic noncompetitive antagonists of ionotropic γ-aminobutyric acid (GABA) receptors, bearing an ester or ether linkage, were designed, synthesized, and assayed for their inhibition of the specific binding of [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a radiolabeled noncompetitive antagonist, to rat brain and housefly head membranes. 5-[4-(3,3-Dimethylbutoxycarbonyl)phenyl]-4-pentynoic acid (DBCPP), a butyl benzoate analogue, was found to competitively inhibit the binding of [3H]EBOB in rat brain membranes, with an IC50 of 88 nM. The potency conferred by the p-substituent decreased in the order C=C(CH2)2COOH>C=C(CH2)2COOCH3>C=CH>Br. Pentyl phenyl ethers were equally potent compared with butyl benzoates, while phenyl pentanoates and benzyl butyl ethers were less potent. These compounds were generally less active in housefly head membranes than in rat brain membranes. The introduction of an isopropyl group into the 1-position of the 3,3-dimethylbutyl group of a butyl benzoate and two benzyl butyl ethers caused an increase in potency in housefly GABA receptors, whereas this modification at the corresponding position of other compounds led to an unchanged or decreased potency. In the case of rat receptors, this modification resulted in a decrease in potency except for a phenyl pentanoate. To confirm that DBCPP interferes with GABA receptor function, we performed whole-cell patch clamp experiments with rat dorsal root ganglion neurons in the primary culture. Repeated co-applications of GABA and DBCPP suppressed GABA-induced whole-cell currents with an IC50 of 0.54 μM and a Hill coefficient of 0.7. These findings indicate that DBCPP and its derivatives inhibit ionotropic GABA receptors by binding to the EBOB site and that there might be structural difference in the noncompetitive antagonist-binding site between rat and housefly GABA receptors. Copyright (C) 2000 Elsevier Science Ltd.
