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Keglevich P.,Budapest University of Technology and Economics | Abranyi-Balogh P.,Hungarian Academy of Sciences | Szigetvari A.,Spectroscopic Research Division | Szantay C.,Spectroscopic Research Division | And 2 more authors.
Tetrahedron Letters | Year: 2016

A quaternization reaction was observed at the tertiary nitrogen atom of the catharanthine part of vinblastine instead of the expected cyclopropanation in the Simmons-Smith reaction utilizing diiodomethane and diethylzinc. Investigating the energetic relations, thermodynamic stabilities and the interactions between the molecular orbitals by quantum chemical calculations elucidated the unexpected methylation and confirmed the reaction mechanism. Although the history of the Simmons-Smith reaction goes back more than half a century this represents the first time that the reaction and its possible side-reaction has been studied by DFT level calculations in a complex system. © 2016 Elsevier Ltd.


Herke K.,Budapest University of Technology and Economics | Hazai L.,Hungarian Academy of Sciences | Santa Z.,Spectroscopic Research Division | Dubrovay Z.,Spectroscopic Research Division | And 5 more authors.
Tetrahedron Letters | Year: 2010

Attempted cyclisation of N-methylated spiro benzazepine-cyclohexenone (5) into the corresponding Nmethyl tetracyclic unit of galanthamine-type alkaloids (6) instead gave an unexpected rearrangement to yield a cyclopentanoisoquinolinone derivative (7). Methylation of the tetrahydrobenzofurobenzazepine tetracycle resulted in the expected N-methyl derivative 6, and the anomalous product 8, with structure similar to that of 7. © 2010 Elsevier Ltd. All rights reserved.


Herke K.,Budapest University of Technology and Economics | Hazai L.,Hungarian Academy of Sciences | Dubrovay Z.,Spectroscopic Research Division | Hada V.,Spectroscopic Research Division | And 5 more authors.
Heterocycles | Year: 2011

Demethoxy-lycoraminone (8) was prepared in several steps starting from the appropriate benzo[c]azepine dione derivative (9). Ketone (9) was protected as a ketal group followed by methylation on the azepine nitrogen atom. After reduction of the imide carbonyl groups, deprotection, demethylation and ring closure were carried out as a one-pot reaction in methanesulfonic acid in the presence of racemic methionine. © The Japan Institute of Heterocyclic Chemistry.


Ilkei V.,Budapest University of Technology and Economics | Bana P.,Budapest University of Technology and Economics | Toth F.,XiMo Hungary Ltd. | Pallo A.,Hungarian Academy of Sciences | And 9 more authors.
Tetrahedron | Year: 2015

Bannucine is an Aspidosperma alkaloid isolated from the dried leaves of Catharanthus roseus. The molecule is a derivative of vindoline bearing a C10 substituent, a pattern common to the antineoplastic dimeric indole alkaloids of C. roseus. In bannucine, a 2-pyrrolidone moiety is attached at C5′ to the aromatic ring of the vindoline core at C10. In the present work we report the synthesis of bannucine and its 5′-epimer from natural (-)-vindoline using a cyclic N-acyliminium ion intermediate whose N-acylaminocarbinol precursor is synthesized by the partial reduction of succinimide. We also describe the separation and the structural analysis of the two epimers, using among others, single crystal X-ray diffraction methods, in order to clarify the orientation of the proton attached to the C5′ carbon. The in vitro antineoplastic activity of the pure epimers was also investigated, but none of the two substances showed significant activity on the examined tumour cell lines. © 2015 Published by Elsevier Ltd.


Keglevich P.,Budapest University of Technology and Economics | Kovacs P.,Hungarian Academy of Sciences | Hazai L.,Hungarian Academy of Sciences | Santa Z.,Spectroscopic Research Division | And 6 more authors.
Heterocycles | Year: 2012

In the course of the reaction between galanthamine and diazomethane in the presence of a catalyst, such as palladium(II) acetate or copper(I) bromide, methylene insertion into the aromatic ring was observed instead of the expected cyclopropanation of the carbon-carbon double bond. © 2012 The Japan Institute of Heterocyclic Chemistry.

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