Configurational conditions and digraphs

Configurational conditions (Schließungsaussagen) of a noncommutative space will be developped from pairs (, ) of digraphs where is a partial digraph of . In this way we obtain an extensive generalization of Pfalzgraf 's q-simplex-conditions Sim_q.In Memoriam Hans Zassenhaus     

Some aspects of tailoring flame retardancy in HET-acid-based flame retardants

HET acid was condensed with either ethylene glycol or 1,4-butanediol to yield the respective oligoesters. These oligoesters were characterized by molecular weight, measured by vapor-pressure osmometry. The degradation mechanism of oligoesters of HET acid with either ethylene glycol or 1,4-butanediol was elucidated. The thermal properties of these polyesters were studied using differential thermal analysis and thermal volatilization analysis. The mechanism of degradation was proposed on the basis of pyrolysis–gas chromatography studies, the degradation products being subsequently identified by mass spectrometry. It turned out that in the course of decomposition, hexachlorocyclopentadiene was formed, which is believed to be the active substance for flame retardance in these systems. The aspect of tailoring flame retardancy by changing the chemical environment, i.e., by using different diols, is discussed.     

Stereochemistry of intramolecular Diels-Alder furan (IMDAF) reactions of furyl-substituted chiral ethanolamides

This paper describes the stereoselective outcome of the intramolecular Diels-Alder furan (IMDAF) reaction of substituted (2S,3S)-ethanolamides 9-13, which were synthesised from a furyl substituted cyanohydrin. The latter was obtained from 2-furaldehyde with high enantioselectivity by an oxynitrilase catalysed addition of hydrogen cyanide. The stereochemistry of the IMDAF products was shown to be dependent on the size of the ethanolamide substituents R. Small substituents (H, Me, CN) gave exclusively exo-cycloaddition, whereas more bulky ones (Ph, Et) gave both evo- and endo-addition, the larger phenyl substituent giving a high endo-exo-ratio.     

Natural product chemistry,part 137: Oxidation of acridone alkaloids: Synthesis of 5-methoxyacronycine

Summary Epoxidation of the acridone alkaloid acronycine (1) resulted in hydroxylation at the aromatic ring giving 5-hydroxyacronycine (3). The same reaction on 1,3-dimethoxy-10-methyl-9(10H)-acridinone (5) gave 1,3-dimethoxy-2-hydroxy-10-methyl-9(10H)-acridinone (6), 1,3-dimethoxy-2-hydroxy-4-peroxy-10-methyl-9(10H)-acridinone (8), and 1,3-dimethoxy-2,4-diperoxy-10-methyl-9(10H)-acridinone (9).

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Naturstoffchemie, 137. Mitt.: Oxidierung von Acridonalkaloiden: Synthese des 5-Methoxyacronycins (Kurze Mitt.)

Zusammenfassung Die Epoxidierung des Acridonalkaloids Acronycin führte zu einer Hydroxylierung des aromatischen Rings, wobei 5-Hydroxyacronycin (3) entstand. Die gleiche Reaktion mit 1,3-Dimethoxy-10-methyl-9(10H)acridinon (5) ergab 1,3-Dimethoxy-2-hydroxy-10-methyl-9(10H)acridinon (6), 1,3-Dimethoxy-2-hydroxy-4-peroxy-10-methyl-9(10H)acridinon (8) und 1,3-Dimethoxy-2,4-diperoxy-10-methyl-9(10H)acridinon (9).

     

Penicillamin-Komplexe des Nickels,Chroms und Molybdäns — Strukturelle Besonderheiten und biologische/medizinische Relevanz

Penicillamine Complexes of Nickel, Chromium, and Molybdenum — Structural Particularity and Biological/Medical Relevance The compounds Tl₂[Ni^II(H₂O)₆][Ni^II(D-pen)(L-pen)]₂[Ni^II(SCN)₂(H₂O)₄] 1 , Tl[Ni^II(D-pen)₂H] · H₂O 2 , Tl[Cr^III(D-pen)₂] 3 , and Na₂[MoO₄(pen)₂] · 3 CH₃OH · 3 H₂O 4 have been prepared by the reaction of nickel nitrate (for 1 ), nickel acetate (for 2 ), potassium chromate (for 3 ), and sodium molybdate (for 4 ) with D- and D, L-penicillamine, respectively. They were characterized by single-crystal X-ray structure analysis and other physical methods. Whereas penicillamine acts as a bidentate (N, S)-ligand in 1 and 2 , Cr^III (in 3 ), and Mo^V (in 4 ) are coordinated to the three ligand atoms N, O, and S. The presence of three different types of Ni^II-complexes a cationic, a neutral, and an anionic one in 1 is remarkable. For crystal data see Inhaltsübersicht.     

Carbocyclic galanthamin analogs: 4a,5,9,10,11,12‐hexahydro‐6H‐benzo[b]cyclohepta[cd]benzofurans

The synthesis of a novel unnatural carbocyclic analog of the acetylcholine esterase inhibitor galanthamine with a K₃[Fe(CN)₆] promoted oxidative tandem cyclization as the key step is reported.     

Aminoalkoholester von Hydroxyboranen,IX Salicylamid-Bor-Mannichbasen als potentielle Antitumorwirkstoffe

A synthesis of new boron containingMannich bases of salicylamide by reaction of salicylamide, formaldehyde and boron-heterocycles is reported.

VIII. Mitteilung:Stump, R. K., Zimmerman jr., H. K., Schleppnik, A. A., Gutsche, C. D., Liebigs Ann. Chem.667, 18 (1963).     

Stereochemical effects in supramolecular self-assembly at surfaces: 1-D versus 2-D enantiomorphic ordering for PVBA and PEBA on Ag(111)

We present investigations on noncovalent bonding and supramolecular self-assembly of two related molecular building blocks at a noble metal surface: 4-[trans-2-(pyrid-4-yl-vinyl)]benzoic acid (PVBA) and 4-[(pyrid-4-yl-ethynyl)]benzoic acid (PEBA). These rigid, rodlike molecules comprising the same complementary moieties for hydrogen bond formation are comparable in shape and size. For PVBA, the ethenylene moiety accounts for two-dimensional (2-D) chirality upon confinement to a surface; PEBA is linear and thus 2-D achiral. Molecular films were deposited on a Ag(111) surface by organic molecular beam epitaxy and characterized by scanning tunneling microscopy. At low temperatures (around 150 K), both species form irregular networks of flat lying molecules linked via their endgroups in a diffusion-limited aggregation process. In the absence of kinetic limitations (adsorption or annealing at room temperature), hydrogen-bonded supramolecular assemblies form which are markedly different. With PVBA, enantiomorphic twin chains in two mirror-symmetric species running along a high-symmetry direction of the substrate lattice form by diastereoselective self-assembly of one enantiomer. The chirality signature is strictly correlated between neighboring twin chains. Enantiopure one-dimensional (1-D) supramolecular nanogratings with tunable periodicity evolve at intermediate coverages, reflecting chiral resolution in micrometer domains. In contrast, PEBA assembles in 2-D hydrogen-bonded islands, which are enantiomorphic because of the orientation of the supramolecular arrangements along low-symmetry directions of the substrate. Thus, for PVBA, chiral molecules form 1-D enantiomorphic supramolecular structures because of mesoscopic resolution of a 2-D chiral species, whereas with PEBA, the packing of an achiral species causes 2-D enantiomorphic arrangements. Model simulations of supramolecular ordering provide a deeper understanding of the stability of these systems.