Showing papers by "University of Paderborn published in 1979"

Generalized liouville equation, entropy, and dynamic systems containing limit cycles

Abstract: The relation between the generalized Liouville equation, entropy production rates and autonomous systems of differential equations containing limit cycles is investigated. Moreover, the connection between the generalized Liouville equation and the Lie derivative of a differential form with respect to a vector field is discussed.

7‐(β‐D‐Arabinofuranosyl)pyrrolo[2,3‐d]pyrimidin‐4(3H)‐on ‐ das 7‐Desazaderivat des antiviralen Nucleosids Ara‐H

Abstract: 7-(β-D-Arabinofuranosyl)pyrrolo[2,3-d]pyrimidin-4(3H)-on (2a), das isostere 7-Desazaderivat des Virostatikums 9-(β-D-ArabinofuranosyI)hypoxanthin (Ara-H, 1b), wurde dargestellt. Glycosidierung von 4-Methoxy-2-methylthio-7H-pyrrolo[2,3-d]pyrimidin mit 2,3,5-Tri-O-benzyl-D-arabinofuranosylbromid fuhrt zum Gemisch der anomeren Nucleosidderivate 4a und 5a, die chromatographisch getrennt wurden. Entschwefelung mit Raney-Nickel liefert 4b und 5b, durch Saurehydrolyse entstehen 4c und 5c; die Benzylschutzgruppen werden hydrogenolytisch entfernt. Glycosidierungsposition und Anomerenkonfiguration wurden spektroskopisch und mittels CD bestimmt. 7-(β-D-Arabinofuranosyl)pyrrolo[2,3-d]pyrimidin-4(3H)-one -the 7-Deaza Derivative of the Antiviral Nucleoside Ara-H 7-(β-D-Arabinofuranosyl)pyrrolo[2,3-d]pyrimidin-4(3H)-one (2a), the isosteric 7-deaza derivative of the antiviral 9-(β-Darabinofuranosyl)hypoxanthine (ara-H, 1b), has been prepared. Glycosidation of 4-methoxy-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine with 2,3,5-tri-O-benzyl-D-arabino-furanosyl bromide results in a mixture of the anomeric nucleosides 4a and 5a, which are separated by chromatography. Desulfurisation with raney nickel leads to 4b and 5b and hydrolysis with hydrochloric acid yields 4c and 5c. The benzyl protecting groups are removed hydrogenolytically. The position of glycosidation and the configuration of the anomeric center has been determined spectroscopically and by CD measurements.

Circular Fluorescence Polarization of Achiral Molecules in Cholesteric Liquid Crystals

Abstract: In liquid crystalline matrices the molecular axes of solute molecules adopt an orientation which is given by the director of the liquid crystal. Consequently, the physical properties of the solute become anisotropic, governed by the director distribution within the matrix. An example of this general effect is the circularly polarized fluorescence emission of achiral molecules dissolved in cholesteric liquid crystals. The degree of circular polarization (CPF), given by a dissymmetry factor ge = (IL - IR)/1/2(IL + IR), is rather high (IL, IR intensity of left or right circularly polarized fluorescence, respectively). The sign of ge was found to depend (i) on the screw sense of the cholesteric helical structure, and (ii) on the direction of the electric transition moment within the emitting molecule. The absolute value of ge is a function of the helical pitch p. The CPF can be understood as an ensemble effect of helically orientated emitting chromophores (e.g. perylene, pyrene, azulene, diphenylhexatriene). Based on the theory of Mauguin and de Vries relations have been derived describing quantitatively the dependence of CPF on the structure of the emitting molecules as well as on the helix structure of the cholesteric solvent.

Ribosidierung von 7H‐Pyrrolo[2,3‐d]pyrimidin‐4(3H)‐on an N‐3

Abstract: Ribosidation of 7H-Pyrrolo[2,3-d] pyrimidin-4(3H)-one at N-3 The ribosidation of 7H-pyrrolo[2,3-d] pyrimidin-4(3H)-one (2a) With 2,3,5,-tri-O-acetyl-ribofuranosyl bormide (Wittenburg conditions) yields the N-3 nucleoside (3a). The glycosidic residue is directed towards N-7 or 4-O by spacious substituents at C-2.

Bevorzugte O-Glycosidbildung bei der Ribosidierung von 5-Methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-on

Abstract: 6-Amino-5-(2,2-diethoxy-1-methylethyl)-2-mercaptopyrimidin-4-of (3 a) wurde durch Kondensation von racem. 2-Cyan-4,4-diethoxy-3-methylbuttersaure-ethylester (2) und Thioharnstoff gewonnen. Die Alkylierung von 3a mit Dimethylsulfat fuhrt zur Methylierung an 2-SH, wobei gleichzeitig Cyclisierung zu 5-Methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-on (4b) erfolgt. Verknupft man silyliertes 4 b mit 2,3,5-Tri-O-acetyl-l-brom-D-ribofuranose in Gegenwart von Quecksilber(II)-Salzen (Wittenburg-Bedingungen), so entsteht das O-Glycosid 6a und nicht wie bei der Reaktion von 2-Methylthio-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-on das N-7-Glycosid12). Durch milde Hydrolyse von 6a erhalt man 5-Methyl-2-methylthio-4-(D-ribofuranosyloxy)-7H-pyrrolo[2,3-d]pyrimidin (6b), dessen UV-Spektren bis pH 2 denen von 4-Methoxy-5-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidin (4c) gleichen, im starker Sauren jedoch Glycosid-Hydrolyse anzeigen. Favoured Formation of an O-Glycoside during Ribosidation of 5-Methyl-2-methylthio-7H-pyrrolo-[2,3-d]pyrimidin-4(3H)-one 6-Amino-5-(2,2-diethoxy-l-methylethyl)-2-mercaptopyrimidin-4-ol (3a) has been prepared via condensation of racem. ethyl 2-cyano-4,4-diethoxy-3-methylbutyrate (2) and thiourea. Alkylation of 3 a at 2-SH with dimethyl sulfate is accompanied by ring closure yielding 5-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-one (4b). Silylation of 4b followed by reaction with 2,3,5-tri-O-acetyl-1-bromo-D-ribofuranose in the presence of mercury(II) salts (Wittenburg conditions) gives the O-glycoside 6a and not the N-7-glycoside formerly obtained during ribosidation of 2-methylthio-7H-pyrrolo[2,3-b]pyrimidin-4(3H)-one12). Hydrolysis of 6a under mild conditions leads to deacetylation giving 5-methyl-2-methylthio-4-(D-ribofuranosyloxy)-7H-pyrrolo[2,3-d]pyrimidine (6b). The latter compound shows UV spectra similar to 4-methoxy-5-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine (4c) down to pH 2, but at lower pH values hydrolysis of the glycosidic bond occurs.

Synthese von (+)‐Discadenin und seinem Desamino‐ und Descarboxy Derivat

Abstract: Die Synthese von L(+)-Discadenin (1) sowie seinem Desamino- 2a und Descarboxy-Derivat (2 b) wird beschrieben. Alkylierung von N6-(3,3-Dimethylallylamino)purin mit der Bromverbindung 4 bzw. 4-Brombuttersaure-ethylester oder N-(3-Brompropyl)phthalimid fuhrt zu den geschutzten Purin-Derivaten 5a–c, deren Substitution an N-3 mit Hilfe der 1H- bzw. 13C-NMR-Spektroskopie und der pH-abhangigen UV-Spektren gesichert wurde. Hydrazinolyse entfernt die Phthaloylreste von 5a und c, alkalische Hydrolyse spaltet den Ethoxycarbonylrest in 5a und c. Die Reaktionsprodukte 1, 2a und b wurden durch UV, 1H/13C-NMR und Massenspektren charakterisiert. Die spektroskopischen Daten von L-Discadenin zeigten dabei volle Ubereinstimmung mit denen des Sporenkeimungsinhibitors aus Diciyostelium discouicum. Synthesis of i.(+)-Discadenine and its Deamino and Decarboxy Derivatives The synthesis of L.(+)-discadenine (1) and its deamino (2a) and decarboxy derivatives (2b) is described. Alkylation of N6-N(,3-dimethylallylamino)purine with the bromo compound 4. ethyl 4-bromobutyrate or N-(3-bromopropyl)phthalimide, respectively, leads to the protected purine derivatives 5a–c. The position of alkylation was confirmed by 1H/1.3C NMR spectroscopy and pH dependent UV spectra and was shown to be N-3. The phthaloyl residues of 5a and c are removed by hydrazinolysis and the cleavage of the ester group in 5a and b is accomplished by alkaline hydrolysis. The reaction products 1, 2a and b are characterised by UV, 1H/C NMR, and mass spectra. The spectroscopic data are in full agreement with those of the spore germination inhibitor from Dictyostelium discoideum.

Mathematical, clinical, and laboratory study of hemodynamic changes in the placental circulation.

Abstract: Various rheological properties of blood were investigated in pregnant and non-pregnant women of similar age. The results from 27 women with abnormal pregnancies were compared to those obtained from 17 non-pregnant women. In abnormal pregnancies we found a reduction of the erythrocyte filtration and a pathological use in red cell aggregation and in the shear resistance of the aggregates. Fractional light transmission (T7/T0) was higher than 1.0, suggesting that pressure gradients in the capillary circulation are not sufficient to disperse red cell aggregates. Thus, rheological factors may be partly responsible for the clinical consequences of pre-eclampsia. Pathological red blood cell aggregation and stagnation are consequences of the changed flow properties in the microcirculation. Even a small decrease of the local pressure gradients in the microcirculation of patients with pre-eclampsia would impair the dispersal of red blood cells and lead to their increased aggregation. Complete occlusion of the placental circulation by these aggregates would impair oxygen transfer at a speed that has been calculated from a diffusion equation based on the concept of the placenta as a hollow cylinder.

Immobilisierung von Adenosinacetalen mit variablem Alkylidenrest — die Funktion des Spacers bei enzymatischer Desaminierung / Immobilization of Adenosine-Acetals with Variable Alkylidene Residues — the Function of the Spacer during Enzymatic Deamination —

Abstract: Acetalation of the cis-diol moiety of adenosine or inosine with aliphatic ketoesters of different chain lengths leads to alkylidene derivatives of the nucleosides, which differ in the number of methylene groups in the hydrocarbon chain. By alkaline hydrolysis of the ester group in 1a - c or 3a - c the corresponding acids 2a - c and 4a - c have been prepared. The configuration of the new chiral centres has been determined as R.Enzymatic deamination of the alkylidene derivatives of adenosine leads to the inosine compounds. The rate of deamination reaction is raised by an increasing number of methylene groups in the alkylidene residues or by use of the esters instead of the acids.The alkylidene derivatives of adenosine were coupled with 6-aminohexylagarose yielding polymers with adenosine as ligands. No enzymatic deamination of the polymer with the shortest spacer was observed. The polymers with the longer spacers were converted to the corresponding inosine derivatives. The velocity of the deamination reaction was raised by an increasing spacer length.

3‐Desamino‐ und 3‐Descarboxyderivate des Nucleosids „X”︁

Abstract: Da Biosyntheseuntersuchungen gezeigt haben, das der Aminocarboxypropylrest des Nucleosids „X” (la) von S-Adenosyl-L-methionin (2) stammt, 2 aber auch als Donor von Methyl-, Aminopropyl- und Carboxypropylresten fungieren kann, haben wir die beiden noch unbekannten Uridinderivate 1 b und 1 c uber N-3-Alkylierung von 2′,3′-O-Isopropylidenuridin und anschliesende Abspaltung der Schutzgruppen dargestellt. l a – c wurden durch 13C-NMR-Spektroskopie charakterisiert. Im Gegensatz zu den UV-Spektren zeigen die 1 H-NMR-Spektren dieser Verbindungen eine starke Abhangigkeit vom pH-Wert. 3-Deamino- and 3-Decarboxy-Derivatives of the Nucleoside „X” Since biosynthetic investigations have shown that the aminocarboxypropyl side chain of the nucleoside „X” (la) comes from S-adenosyl-L-methionine (2) and that compound 2 can also function as a donor of methyl-, aminopropyl- and carboxypropyl-groups, we have synthesized the two unknown uridine derivatives l b and l c. The latter compounds were obtained via N -3-alkylation of 2′,3′-O-isopropylideneuridine followed by removal of the protecting groups and characterized by 13C NMR spectroscopy. In contrast to the UV spectra the 1 H NMR spectra of 1a – c show a strong dependence on pH.

2′(3′),5′-Diphosphate des Nucleosids X und N3-alkylierter Uridin–Derivate

Abstract: 2′(3′), 5′-Diphosphates of the Nucleoside X and N3 - Alkylated Uridine Derivatives The synthesis of 2′(3′),5′-diphosphates of the rare nucleoside X (1a) and the N3 - alkylated uridine derivatives 1b, c, and 2b has been accomplished by treatement of the nucleosides with 15 fold excess pyrophosphoryl chloride.