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Notes: Abstract The in vitro binding of the naturally occurring β-carbolines harman and norharman in their tritium-labelled forms to cell membranes from the rat brain and liver and from bovine adrenal medulla was investigated. Displacement of the specific [3H]harman binding in bovine adrenal medulla and rat liver by several β-carbolines and monoamine oxidase (MAO) inhibitors revealed the pharmacological profile of a single, high-affinity binding site (K D 4.92±0.43 nmol/l, Bmax 8.47±0.17 pmol/mg protein; adrenal medulla) which corresponded to the active site of MAO type A (MAO-A). Similar characteristics have previously been found for brain tissue from rat, marmoset and pig. In order to determine the temperature dependence of the [3H]harman binding, the K D and Bmax values for rat cerebral cortex were calculated from the results of saturation experiments at 5 temperatures (range: 0°C–37°C). Whereas the Bmax values under all conditions were − 4 pmol/mg protein, the K D values, with increasing temperature, ranged from ≈ 3 nmol/l to 30 nmol/l. The calculated linear van't Hoff plot (-In K D against 1/T) suggested an enthalpy-driven binding of [3H]harman to MAO-A. At least three different [3H]norharman-binding sites were detected. In the rat forebrain, ≈85% of the specific binding (at about 2 nmol/l of [3H]norharman) can be attributed to a MAO binding site of type B: the binding is displaceable, in nmol/l concentrations by the potent and selective MAO-B inhibitors MDL 72,974A, R(−)-deprenyl and pargyline and, in μmol/l concentrations, by S(+)-deprenyl and the potent and selective MAO-A inhibitors clorgyline, harmine, harman, harmaline, brofaromine 5-F-α-methyltryptamine. After suppression of the MAO binding sites with 1 μmol/l clorgyline and μmol/l R(−)-deprenyl, a second binding site was found. However, the binding at this site was biphasically displaceable by harman and norharman (Hill-slopes about 0.5 and 0.6, curvilinear Rosenthal plots) suggesting the presence of negative co-operativity or of two binding sites (states). A similar clorgyline/R(−)-deprenyl resistent single (Hill-slopes of displacement by norharman, harman and 6-hydroxy-β-carboline about unity; linear Rosenthal plots) high affinity binding site (K D 7.5±2 nmol/l, Bmax 130±30 fmol/mg protein) was found in bovine adrenal medullary cell membranes. A third quite different clorgyline/R(−)-deprenyl resistent high-affinity (K D≈14 nmol/l) and high-density (Bmax 10–30 pmol/mg protein) binding site was detected in the liver. The specific binding at this site was not displaceable by harman or most other substituted β-carbolines or by tetrahydro-β-carbolines, but was displaced by norharman and several newly synthesized 6-substituted aromatic β-carbolines (e.g. F-, CH3-, CH3O-, HO-). The [3H]norharman binding site in the liver is certainly not identical with any of the binding sites for MAO-inhibitors, benzodiazepines or sigma receptor ligands and is slightly enriched in the microsomal (P3) fraction whereas most of the specific [3H]harman binding was detected in the crude mitochondrial (P2) fraction.

Notes: Abstract. The in vitro binding of the naturally occurring β-carbolines harman and norharman in their tritium-labelled forms to cell membranes from the rat brain and liver and from bovine adrenal medulla was investigated. Displacement of the specific [3H]harman binding in bovine adrenal medulla and rat liver by several β-carbolines and monoamine oxidase (MAO) inhibitors revealed the pharmacological profile of a single, high-affinity binding site (K D 4.92±0.43 nmol/l, Bmax 8.47±0.17 pmol/mg protein; adrenal medulla) which corresponded to the active site of MAO type A (MAO-A). Similar characteristics have previously been found for brain tissue from rat, marmoset and pig. In order to determine the temperature dependence of the [3H]harman binding, the K D and Bmax values for rat cerebral cortex were calculated from the results of saturation experiments at 5 temperatures (range: 0°C–37°C). Whereas the Bmax values under all conditions were ∼4 pmol/mg protein, the K D values, with increasing temperature, ranged from ∼3 nmol/l to 30 nmol/l. The calculated linear van‘t Hoff plot (-ln K D against 1/T) suggested an enthalpy-driven binding of [3H]harman to MAO-A.   At least three different [3H]norharman-binding sites were detected. In the rat forebrain, ∼85% of the specific binding (at about 2 nmol/l of [3H]norharman) can be attributed to a MAO binding site of type B: the binding is displaceable, in nmol/l concentrations by the potent and selective MAO-B inhibitors MDL 72,974 A, R(–)-deprenyl and pargyline and, in μmol/l concentrations, by S(+)-deprenyl and the potent and selective MAO-A inhibitors clorgyline, harmine, harman, harmaline, brofaromine 5-F-α-methyltryptamine. After suppression of the MAO binding sites with 1 μmol/l clorgyline and 1 μmol/l R(–)-deprenyl, a second binding site was found. However, the binding at this site was biphasically displaceable by harman and norharman (Hill-slopes about 0.5 and 0.6, curvilinear Rosenthal plots) suggesting the presence of negative co-operativity or of two binding sites (states). A similar clorgyline/R(–)-deprenyl resistent single (Hill-slopes of displacement by norharman, harman and 6-hydroxy-β-carboline about unity; linear Rosenthal plots) high affinity binding site (K D 7.5±2 nmol/l, Bmax 130±30 fmol/mg protein) was found in bovine adrenal medullary cell membranes. A third quite different clorgyline/R(–)-deprenyl resistent high-affinity (K D ∼14 nmol/l) and high-density (Bmax 10–30 pmol/mg protein) binding site was detected in the liver. The specific binding at this site was not displaceable by harman or most other substituted β-carbolines or by tetrahydro-β-carbolines, but was displaced by norharman and several newly synthesized 6-substituted aromatic β-carbolines (e.g. F-, CH3-, CH3O-, HO-). The [3H]norharman binding site in the liver is certainly not identical with any of the binding sites for MAO-inhibitors, benzodiazepines or sigma receptor ligands and is slightly enriched in the microsomal (P3) fraction whereas most of the specific [3H]harman binding was detected in the crude mitochondrial (P2) fraction.

Notes: Durch säurekatalysierte Addition von Methanol an Methyl-6-desoxy-α-D-Δ5-xylo-hexenopyranosid (1) wurden die Bisglykopyranoside Methyl-5-C-methoxy-6-desoxy-α-D-glucopyranosid (2) und Methyl-5-C-methoxy-6-desoxy-β-L-idopyranosid (3) erhalten. Die Geschwindigkeit der Addition sowie die gegenseitige Umwandlung von 2 und 3 wurden gaschromatographisch verfolgt. Da keine Epimerisierung an C-1 erfolgt, wird abgeleitet, daß die saure Glykosidspaltung hier über ein cyclisches Carbonium-Oxonium-Ion verläuft.

Notes: Eine Reihe von Zucker-Siliciumverbindungen wurde durch Addition von Methyldiäthoxysilan an ungesättigte Monosaccharidderivate dargestellt. Als Ausgangsprodukte dienten unter anderen die bisher unbekannten Verbindungen 6.7-Didesoxy-1.2;3.4-di-O-isopropyliden-α-D-galakto-hept-6-enopyranose (2) mit unverzweigtem sowie 3-O-Acetyl-3-C-äthinyl-1.2;5.6-di-O-isopropyliden-α-D-allofuranose (8b) und Äthindiyl-3-C-.3′-C-bis-[3-O-acetyl-1.2;5.6-di-O-isopropyliden-α-D-allofuranose] (9b) mit verzweigtem Kohlenstoffgerüst. An die Verbindung 9b ließ sich, offenbar aus sterischen Gründen, kein Silan addieren.

Notes: 6-Methyl-2,3-bis(methoxycarbonyl)-5,6-dihydro-4H-pyran (2a) setzt sich mit Hydrazinhydrat zum Dihydrazid 3 um, welches unter Hydrazinabspaltung in das 2-Methyl-3,4,5,6,7,8-hexahydro-2H-pyrano[2,3-d]pyridazin-5,8-dion (4) übergeht. Durch Behandlung von 4 mit POCl3/Pyridin erhält man das 5,8-Dichlorpyranopyridazin 5, dessen Reaktivität gegenüber nucleophilen Agentien untersucht und diskutiert wird. Die IR- und NMR-Daten der erhaltenen Verbindungen werden aufgeführt.