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804 results on '"Dostal J"'

201. Structural studies of chelirubine and chelilutine free bases

Author

UCL, Dostal, J., Slavik, J., Potacek, M., Marek, R., Humpa, O, Sklenar, V, Tousek, J, de Hoffmann, Edmond, Rozenberg, Raoul, UCL, Dostal, J., Slavik, J., Potacek, M., Marek, R., Humpa, O, Sklenar, V, Tousek, J, de Hoffmann, Edmond, and Rozenberg, Raoul

Abstract

The structures of chelirubine and chelilutine free bases have been examined by 2D NMR spectroscopy and mass spectrometry. Chelirubine chloride (la) upon treatment with Na,CO, yielded free base which possessed the constitution of bis(5,6-dihydrochelirubin-6-yl) ether (2a). The free base of chelilutine (Ib) was determined to be bis(5,6-dihydrochelilutin-6-yl) ether (2b). The aqueous NH3 treatment of chelilutine (Ib) produced bis(5,6-dihydrochelilutin-6-yl)amine (3b). 6-Hydroxy-5,6-dihydrochelirubine (4a) and 6-hydroxy-5,6-dihydrochelilutine (4b) were detected only in CDCl3 solution by NMR spectroscopy. In CDCl3, the compound 2b underwent hydrolysis to 4b that was immediately followed by the reverse condensation to a diastereomer of 2b. Pseudokinetics of this reaction was followed by NMR spectroscopy and quantum chemical calculations were carried out to support the suggested type of molecular symmetry alteration. The known alkaloid dihydrochelirubine (5) was isolated for the first time from Sanguinaria canadensis.

Published
1998

202. Structure and transformations of the alkaloid sanguilutine

Author

UCL, Dostal, J., Declercq, Jean-Paul, Slavik, J., Potacek, M., Marek, R., Sklenar, V, de Hoffmann, Edmond, Rozenberg, Raoul, Tinant, Bernard, UCL, Dostal, J., Declercq, Jean-Paul, Slavik, J., Potacek, M., Marek, R., Sklenar, V, de Hoffmann, Edmond, Rozenberg, Raoul, and Tinant, Bernard

Abstract

Sodium carbonate treatment of sanguilutine chloride yielded 6-hydroxy-5,6-dihydrosanguilutine. In a non-polar environment, 6-hydroxy-5,6-dihydrosanguilutine spontaneously transforms to bis[6-(5,6-dihydrosanguilutinyl)] ether, whose structure was confirmed by X-ray analysis. Treatment of sanguilutine chloride with aqueous ammonia gave bis[6-(5,6-dihydrosanguilutinyl)]amine. Reaction of sanguilutine chloride with potassium cyanide yielded 6-cyanodihpdrosanguilutine; reaction of bis[6-(5,6-dihydrosanguilutinyl)]amine with ethanol gave 6-ethoxydihydrosanguilutine. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Published
1998

210. Structure of sanguinarine base

Author

UCL, Dostal, J., Bochorakova, H, Taborska, E., Slavik, J., Potacek, M., Budesinsky, M, de Hoffmann, Edmond, UCL, Dostal, J., Bochorakova, H, Taborska, E., Slavik, J., Potacek, M., Budesinsky, M, and de Hoffmann, Edmond

Abstract

The structure of sanguinarine free base was examined. The base is either bis[6-(5,6-dihydrosanguinarinyl)] ether (3) or bis[6-(5,6-dihydrosanguinarinyl)]amine (4) depending on whether Na2CO3 or NH3, respectively, is used as an alkalizing agent. Oxysanguinarine (5) was identified as a side product formed by disproportionation of the pseudobase intermediate 2a.

Published
1996

217. Structure of Chelerythrine Base

Author

UCL, Dostal, J., Taborska, E., Slavik, J., Potacek, M., de Hoffmann, Edmond, UCL, Dostal, J., Taborska, E., Slavik, J., Potacek, M., and de Hoffmann, Edmond

Abstract

The structure of chelerythrine free base was examined. When chelerythrine chloride [1b] was treated with aqueous K2CO3 solution, bis[6-(5,6-dihydrochelerythrinyl)] ether [3] was obtained. An excess of aqueous ammonia under the same conditions yielded bis[6-(5,6-dihydrochelerythrinyl)] amine [4]. The structures of both derivatives were determined by elemental analysis, ir, 1D and 2D nmr, eims, and cims. The formation of an unstable hydroxy adduce 2a (pseudobase) was observed in H-1-nmr experiments only.

Published
1995

247. Complex geometry of the Cenozoic magma plumbing system in the central Sahara, NW Africa.

Author

Keppie, J. Duncan, Dostal, J., and Murphy, J. B.

Subjects
*VOLCANIC ash, tuff, etc., *MAGMAS, *BASALT, *CENOZOIC stratigraphic geology, *GEOCHEMISTRY
Abstract

Topographic uplifts in the central Sahara occur in the Hoggar-Aïr and Tibesti-Gharyan swells that consist of Precambrian rocks overlain by Cenozoic volcanic rocks. The swells and associated Cenozoic volcanism have been related either to mantle plumes or to asthenospheric upwelling and to partial melting due to rift-related delamination along pre-existing Pan-African mega-shears during the collision between Africa and Europe. The Cenozoic volcanic rocks in the Hoggar generally range from Oligocene tholeiitic/transitional plateau basalts, which occur in the centre of the dome, to Neogene alkali basalts characterized by a decrease in their degree of silica undersaturation and an increase in their La/Yb ratios. The alkali basaltic rocks occur mainly along the margins of the dome and typically have less radiogenic Nd and Sr isotopic ratios than the tholeiitic/transitional basalts. The geochemistry of the most primitive basaltic rocks resembles oceanic island basalt (OIB) tholeiitic – in particular high-U/Pb mantle (HIMU)-type – and is also similar to those of the Circum-Mediterranean Anorogenic Cenozoic Igneous (CiMACI) province. These characteristics are consistent with, but do not require, a mantle plume origin. Geophysical data suggest a combination of the two mechanisms resulting in a complex plumbing system consisting of (a) at depths of 250–200 km, an upper mantle plume (presently under the Aïr massif); (b) between 200 and 150 km, approximately 700 km northeastward deflection of plume-derived magma by drag at the base of the African Plate and by mantle convection; (c) at approximately 150 km, the magma continues upwards to the surface in the Tibesti swell; (d) at approximately 100 km depth, part of the magma is diverted into a low S-wave velocity corridor under the Sahara Basin; and (e) at approximately 80 km depth, the corridor is tapped by Cenozoic volcanism in the Hoggar and Aïr massifs that flowed southwards along reactivated Precambrian faults. [ABSTRACT FROM PUBLISHER]

Published
2011
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