Marek L. Główka

Stacking of six-membered aromatic rings in crystals

Geometrical preferences of stacking and the possibilities and limitations of using stacking in designing crystal structures have been analyzed, based on the crystal structures of benzenes, pyridines and s-triazines. It is shown that crystallographic symmetry imposes severe restrictions on stacking parameters and that alteration of the p -electron distribution in the aromatic ring by incorporation of heteroatom(s) significantly increases the possibility of stacking. q 1998 Elsevier Science B.V. All rights reserved.

The imbalanced kekule structure contributions in the ring in 1,3,5-trisubstituted benzene derivatives: Low temperature X-ray study on 1,3,5-trimethoxybenzene, and ab initio calculations on 1,3,5-triformylo - benzene and trimethoxy-benzene and the related di-substituted systems

Abstract A low temperature X-ray structural determination for 1,3,5-trimethoxybenzene reveals π-electron localisation in the ring. ab initio calculations for 1,3,5-trimethoxybenzene and 1,3,5-triformylobenzene show that these nonsymmetrical substituents induce opposite imbalance of Kekule structures in the ring. An empirical rule is proposed - that cis CC-bonds in the ring show increased double bond character (compared to the trans bond) when the substituent is of X-Y kind (with a single XY bond), and less double bond character if the substituent is of the X=Y type (with a double XY bond). Additional calculations for cis and trans conformers of 1,4-dimethoxybenzene differ dramatically in the degree of π-electron localisation, supporting the idea that the dominating factor of these distortion is a through-space effect.

Synthesis, structure, and tuberculostatic activity of dimethyl benzoylcarbonohydrazonodithioates

New dimethyl benzoylcarbonohydrazonodithioates were obtained by CS2 addition to arylcarboxylic acid hydrazides and methylation of the formed adduct. The new derivatives were tested for their activity against Mycobacterium tuberculosis. Some compounds exhibited high activity toward sensitive and resistant strains.Graphical abstract

Intramolecular hydrogen bond between 4-oxo and 3-carboxylic groups in quinolones and their analogs. Crystal structures of 7-methyl- and 6-fluoro-1,4-dihydro-4-oxocinnoline-3-carboxylic acids

Abstract Crystal structures of two cinnoline analogs of quinolones and statistics on quinolones molecular forms observed in the crystal state have been determined. It has been shown that common quinolones may be divided into two main types, depending on presence of proton acceptor, usually aliphatic amine group, capable of protonation under mild conditions. Quinolones lacking amine group or having one(s) bound to an aromatic system exist at physiological pH mainly in a free acid form, in which acidic hydrogen atom is locked into an intramolecular hydrogen bond. The phenomenon enhances permeability of quinolones through lipophilic cell membranes but decreases the concentration of carboxylate form capable of specific binding with bacterial DNA. Molecular (neutral) form was observed exclusively in the crystalline state for these quinolones. The dominant forms seem different for quinolones having amine substituents with unconjugated lone pair electrons at N atom. Even in the crystalline state, they may exist also in a zwitterionic form, which was found to dominate in secondary amines crystallised at neutral pH. Our limited data suggest that position and order of amine group may play important role in controlling quinolones absorption, transport and concentration and thus their biological profile.

Synthesis of Chiral 2,4-Chiral 2,4-Dichloro-6-menthoxy-1,3,5-triazines and 2-Chloro-4, 6-Dimenthoxy-1,3,5-triazines as Enantiodifferentiating Coupling Reagents. An X-ray Study on 2,4,6-Trimenthoxy-1,3,5-triazine

Abstract Chiral mono-di-and trimenthoxy-1,3,5-triazines ware obtained from natural menthol and cyanuric chloride and applied as enantioselective coupling reagents in the synthesis of dipeptides.

Synthesis, characterization, and tuberculostatic activity of novel 2-(4-nitrobenzoyl)hydrazinecarbodithioic acid derivatives

A series of novel S-esters of 2-(4-nitrobenzoyl)hydrazinecarbodithioic acid and S,S′-diesters of (4-nitrobenzoyl)carbonohydrazonodithioic acid were synthesized by reaction of 4-nitrobenzohydrazide and N-methyl-4-nitrobenzohydrazide with carbon disulfide and alkyl halides in the presence of triethylamine. Novel 5-(4-nitrophenyl)-1,3,4-oxadiazoles were also obtained. The structures were confirmed by IR, NMR, and mass spectroscopy, and by elemental analysis. All the compounds obtained were screened in vitro for their tuberculostatic activity. Promising preliminary results were obtained for some of the compounds. The crystal structure of the most active compound was determined.Graphical abstract

Crystal structures of 3-(4-pyridinyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrimidine and its 6-hydroxy derivative

Abstract(1): C10H11N5,Mr=201.23, from water, P

Crystal structure of enantiomeric 3-amino-6,7-dihydro-6-hydroxy-5H-1,2,4-triazolo [3,4-b] 1,3-thiazine

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