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111.
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Hans Jürgen Rosenkranz Barbara Winkler-Lardelli Hans-Jürgen Hansen Hans Schmid 《Helvetica chimica acta》1974,57(3):887-916
It is shown that treatment of indolines like 4a-methyl-1,2,3,4,4a,9a-hexahydrocarbazole ( 1 ) and even indoline-alkaloids like 5 or 6 (cf. scheme 1) with KMnO4 in boiling acetone solution leads to the indolenines 10, 29 and 33 , respectively, and, in relatively high yields, to N,N′- or C,N-coupling products (cf. schemes 2 and 5). The results of the oxidation of 6- or 8-methoxy-indolines are shown in schemes 3 and 4, respectively. Analogous ‘dimeric’ dehydrogenation products are observed when tetrahydroquinolines ( 8 and 9 , resp.) are treated with KMnO4 (cf. schemes 7 and 8, resp.). The formation of the bis-compounds is almost certainly due to the coupling of two intermediate indolenyl or tetrahydroquinolyl radicals. The cleavage of the hydrazine derivatives 11 or 17 (scheme 9) also leads to ‘dimeric’ C,N-coupling products. By heating the hydrazine derivative 17 with aqueous HCl, a complete cleavage into indoline 2 and the indolenines 16 and 20 is observed. The reaction is rationalized in scheme 10. So far no naturally occurring alkaloids related to the above mentioned C,N-coupling products have been found. 相似文献
113.
Sem DS Bertolaet B Baker B Chang E Costache AD Coutts S Dong Q Hansen M Hong V Huang X Jack RM Kho R Lang H Ma CT Meininger D Pellecchia M Pierre F Villar H Yu L 《Chemistry & biology》2004,11(2):185-194
Genomics-driven growth in the number of enzymes of unknown function has created a need for better strategies to characterize them. Since enzyme inhibitors have traditionally served this purpose, we present here an efficient systems-based inhibitor design strategy, enabled by bioinformatic and NMR structural developments. First, we parse the oxidoreductase gene family into structural subfamilies termed pharmacofamilies, which share pharmacophore features in their cofactor binding sites. Then we identify a ligand for this site and use NMR-based binding site mapping (NMR SOLVE) to determine where to extend a combinatorial library, such that diversity elements are directed into the adjacent substrate site. The cofactor mimic is reused in the library in a manner that parallels the reuse of cofactor domains in the oxidoreductase gene family. A library designed in this manner yielded specific inhibitors for multiple oxidoreductases. 相似文献
114.
Rudolf Schmid Marco Cereghetti Bernd Heiser Peter Schnholzer Hans-Jürgen Hansen 《Helvetica chimica acta》1988,71(4):897-929
The axially dissymmetric diphosphines (?)-(R)- and (+)-(S)-(6-6′-dimethylbiphenyl-2,2′-diyl)bis(diphenyl-phosphine) ((?)-(R)- 10 and (+)-(S)- 10 ; ‘BIPHEMP’) have been synthesized, starting from (R)- and (S)-6,6′-dimethylbiphenyl-2,2′-diamine ((R)- and(S)- 16 ), respectively, via Sandmeyer reaction, liathiation, and phosphinylation. Moreover, racemic 4,4′- dimethyl- and 4,4′-bis(dimethylamino)-substituted analogues 11 and 12 respectively, and the 6,6′-bridged analogues 1,11-bis(diphenylphosphino)-5,7-dihydrodibenz[c,e]oxepin (13) were synthesized and resolved into optically pure (R)- and(S)-enantiomers via complexation with di-μ-chlorob is {(R)-2-[1-(dimethylamino)ethyl]pheny-C? N}dipalladium(II) ((R)- 18 ). The molecular structures of the diphosphines (S)- 10 and (R)- 13 and of two derived cationic Rh(I) complexes,[Rh((S)- 10 )(nbd)]BF4 and [Rh((R)- 13 )(nbd)]BF 4 were determined by x-ray analyses. Absolute configurations were established for (+)-(S)- 10 by X-ray analyses of both the free diphosphine and of the derived Rh(I) complex, and for (?)-(R)- 13 by X-ray analysis of the derived Rh(I) complex. Configurational assignments for the substituted BIPHEMP analogues 11 12 were achieved by means of 1H-NMR comparisons. The BIPHEMP ligand 10 and analogues 11 , 12 and 13 are the first examples of optically active bis(triaylphosphines) containing the axially dissymmetric biphenyl moiety. All these new diphosphines proved to be excellent asymmetry-inducing ligands in Rh(I)-catalyzed isomerizations of N,N-diethylnerylamine affording citronellat enamine of 98-99% ee. 相似文献
115.
The air-gap electrode has been used in kinetic chemical analysis, illustrated by the assay of the activities of the enzymes urease and arginase. The determinations are based on monitoring the initial reaction rates of the selective release of ammoniacal nitrogen, which in the arginine—arginase system was ensured by adding excess of urease. The reaction rates measured are in the range 2.5 · 10-5—1.5 · 10-3M min-1; the relative standard deviation is ca. 2.8 %. 相似文献
116.
Timonov proposes an algorithm for global maximization of univariate Lipschitz functions in which successive evaluation points are chosen in order to ensure at each iteration a maximal expected reduction of the region of indeterminacy, which contains all globally optimal points. It is shown that such an algorithm does not necessarily converge to a global optimum. 相似文献
117.
Hansen KT 《Chaos (Woodbury, N.Y.)》1992,2(1):71-75
It is shown that for the four-disk system and the hyperbola billiard it is possible to construct a new symbolic plane preserving the orientation existing in the dynamical space. Physical orbits are mapped into the topological well-ordered plane and it is shown that the forbidden and allowed orbits are separated by a monotone pruning front. 相似文献
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