Mamanine and pohakuline,two unprecedented quinolizidine alkaloids from sophorachrysophylla

From the bark of the endemic Hawaiian tree Sophora chrysophylla Seem. we have isolated two unprecedented quainolizidine alkaloids, mamanine (4) and pohakuline (5). Both bases are 1-hydroxymethylenequinolizidines which are linked at C-3 to α-pyridone or α-piperidone moieties. The alkaloids may be intermediates in a heretofore unknown biogenetic pathway of Sophora alkaloids.     

Metallcarbonyl-Synthesen,XIV. Neuartige Vanadium-, Niob- und Tantal-Komplexe mit Wasserstoff-Brücken

Syntheses of Metal Carbonyls, XIV. Novel Vanadium, Niobium, and Tantalum Complexes Having Hydrido Bridges The novel homo- and heterodinuclear organometallic μ-hydrido compounds 3a – c of vanadium, niobium, and tantalum have been synthesized by light-induced reactions of the hydridoniobium complex (η⁵-C₅H₅)₂NbH₃ ( 1 ) with the half-sandwich complexes (η⁵-C₅H₅)M(CO)₄ ( 2a : M = V; 2b : M = Nb; 2c : M = Ta). These compounds have the general composition L_xM – H – Nb(CO)(η⁵-C₅H₅)₂. The formation of the M – H – Nb moieties is a dark-reaction preceded by two photoreactions that are independent from each other elimination of CO from 2a – c and elimination of H₂ from 1 , with the extruded carbon monoxide being transfered to the (η⁵-C₅H₅)₂NbH fragment; subsequent fixation of the species (η⁵-C₅H₅)₂Nb(CO)H thus generated to the photogragments (η⁵-C₅H₅)M(CO)₃ results in donor stabilization of these latter groups. The structural architecture of the derivatives 3a und b was established by X-Ray diffraction. The hydrogen bridges are to be considered as three-center two-electron functions that are responsible for a serious lengthening of the otherwise by at least 40 pm shorter metal-to-metal distances amounting to 371.3 pm in 3a and 373.3 pm in 3b (mean values).     

PHOTOBEHAVIOR OF EUGLENA GRACILIS: ACTION SPECTRUM FOR THE STEP-DOWN PHOTOPHOBIC RESPONSE OF INDIVIDUAL CELLS

Abstract—Light-induced behavioral responses of Euglena gracilis have been investigated in single cells by means of a video system coupled to an optical microscope. Light intensity-effect curves at different wavelengths in the near UV and visible range have been determined. From these curves the action spectrum for the step-down photophobic response of Euglena has been calculated. From a comparison with the results obtained using a population method by means of a phototaxigraph, it is concluded that a single photomotile reaction is responsible for cell accumulation, brought about by trapping in the light spot and possibly by phototaxis towards scattered light from organisms already in the light field.     

Determination of selenium in human tissues by atomic absorption spectrometry

A simple method is described for the determination of selenium in human tissues without the use of perchloric acid. Digestion with nitric and sulphuric acids is followed by hydride generation and atomic absorption spectrometry. Results for NBS bovine liver and IAEA horse kidney reference materials were in good agreement with assigned concentrations, as was also achieved with the perchloric acid digestion. Recovery of added selenium was >90%, and the relative standard deviation was 5.5% for within-batch and 6.9% for between-batch analyses. The values of selenium in heart tissue were 0.9–1.3 μg g^?1 dry weight.     

Synthetic thermally reversible gel systems. VII

Polymethacrylylglycinamides (PMG), like polyacrylylglycinamides (PAG), form thermally reversible aqueous gels, but higher molecular weights and/or concentrations are required and the melting points of the gels are lower. The heats of crosslinking for aqueous PMG gels fall in the range of ?5 to ?10 kcal/mole of crosslinks, the same as for aqueous PAG gels, implying that the crosslinks are chemically similar. PMG and PAG are incompatible with each other but both are individually compatible with some types of gelatin. The solubilities of PMG and PAG are similar. Various reagents, however, affect PMG and PAG gels in quite different manners. Aqueous PMG solutions, just outside conditions required for gelation, are rheopectic. Intrinsic viscosities [η] of PMG in 2M NaCNS are about 2.5 times those in water. The Huggins' k′ value for PMG in 2M NaCNS has a value of 0.39–0.40, and both it and [η] are essentially temperature-independent over the range 25–45°C. In water at 25°C for PMG, k′ has an average value of about 1.4. With increasing temperature, for H₂O, there is a considerable increase in [η] which is accompanied by a decrease in the value of k′. Osmotic molecular weight measurements on unfractionated PMG in H₂O at 40°C yield π/c versus c plots having essentially zero slope, implying a value of close to zero for the second virial coefficient, a value of about 0.5 for the polymer–solvent interaction parameter, and a condition close to a θ condition. An approximate viscosity–M _n relationship for polydisperse PMG is [η]_{2M NaCNS, 25deg;C} = 1.7 × 10^?8 M _n^1.5. The low value of K and high value of the exponent do not result from large differences in polydispersity but rather from a stiff, rodlike configuration in solution. This steric hindrance to rotation also manifests itself in the extreme brittleness of PMG films and in a ΔH_p for homopolymerization of only ?6 kcal/-mole. The infrared spectra of MG monomer and PMG are recorded as well as the density and refractive index for PMG. PMG has a glass transition at 226°C by DTA and by TGA, thermal decomposition sets in at about 300°C. From copolymerization with acrylic acid, values of 1.66 and +0.06, respectively, were obtained for the resonance factor Q and the electrical factor e for MG monomer.     

Distillation, on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS as a new combination for the determination of methylmercury in sediments and fish tissue

 Distillation as a way of sample digestion has been combined with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS (high performance liquid chromatography – ultra violet – post column oxidation – cold vapour atomic absorption spectrometry) for the determination of methylmercury at background levels in sediments, soils and fish tissue. To prove the accuracy of this method, it was applied to sediment and fish tissue reference materials. The results correspond with the reference values within their error ranges. Excellent recoveries (92–95%) were obtained for the sediment samples by means of the standard addition method. The standard deviations of the sediment samples were within an acceptable range (7.2–12.5%), those of the fish samples were substantially lower (3.4–5.0%). The detection limit is 0.04 ng/g for 1 g sample weight. Received: 23 November 1995/Revised: 16 April 1996/Accepted: 20 April 1996     

Oxydative Kupplung von Indolinen und 1,2,3,4-Tetrahydrochinolinen mit Kaliumpermanganat. 153. Mitteilung über Alkaloide

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.     

Preparation of 4-aryl-1,2,3,4-tetrahydro-3,3-dimethylisoquinolines and 1,2,3,4-tetrahydro-3,3-dimethyl-4-phenylbenz[h]isoquinolines

Synthetic procedures to prepare a number of 4-aryl-1,2,3,4-tetrahydro-3,3-dimethylisoquinolines and their benzo-homogues 3 through a series of intermediates are described. The condensation of α-(1-amino-1-methylethyl)arylmethanols 5 with arylaldehydes 6 gave imino derivatives 7 which on reduction with borohydride gave secondary amines 8 . The treatment of 8 with mineral acids gave the target compounds 3 . Biological activities of 3 are briefly discussed.     

Level-spacing distributions beyond the Wigner surmise

We introduce a dynamical system, for which it is possible to get such a large number of eigenvalues that deviations from Wigner's surmise are visible. The obtained level-spacing distribution agrees much better with the distribution derived from random matrix theory.