Synthesis of homochiral 2-C-perfluoroalkyl substituted d- and l-riboses

Homochiral 2-C-perfluoroalkyl substituted d- and l-riboses were synthesized via Barbier, Grignard and Ruppert type reactions. The influence of the size of the perfluoroalkyl groups, attached to C-2, on the furanose/pyranose as well as on the α-furanose/β-furanose and α-pyranose/β-pyranose ratio in solution was studied.     

Positron annihilation and1H NMR study of [Zn(1-propyltetrzole)6](BF4)2 and [Fe(Methyltetrazole)6](BF4)2 complexes

The complexes [Zn(1-propyltetraole)₆](BF₄)₂ (Zn-ptz) and [Fe(methyltetrazole)₆](BF₄)₂ (Fe-mtz) were investigated by positron annihilation and solid-state NMR spectroscopy. For Zn-ptz signs of structural rearrangements were found between 70 and 145 K. For the spin-crossover complex Fe-mtz a transition affecting the high-spin stat Fe²⁺ ions at lattice site B occurs below 15 K.     

1,3-Cycloaddition von alkinen an hetero-1,3-diene 1-aminopyrrole aus 1,2-diazabuta-1,3-dienen und 1-diethylaminopropin

1-Aminopyrroles (4) are obtained by reaction of 1,2-diazabuta-1,3-dienes (1) and ynamines (2). This reaction represents one of the very rare examples of 1,3-cycloaddition processes of alkynes and hetero-1,3-dienes.     

Die Verwendung von Bromchlor als Ma?l?sung in der Analyse

Zusammenfassung Die Verfasser haben ein einfaches Verfahren zur Herstellung einer in der Analyse brauchbaren Bromchlor-Maßlösung ausgearbeitet. Es wird festgestellt, daß die Bromchloradditionen infolge labiler Struktur des Bromchlors (heterolytische Dissoziation!) mit viel größerer Geschwindigkeit ablaufen als die Brom- oder Chloradditionen.Gut dissoziierende Quecksilber(II)-salze sichern eine weitere Steigerung der heterolytischen Dissoziation des Bromchlors, weil sie mit den Chloridionen der Lösung ein schlecht dissoziierendes Quecksilbersalz bilden, was zur Folge hat, daß die Geschwindigkeit der Additionsreaktion beschleunigt wird. Die Bromchloraddition der Maleinsäure und auch der Fumarsäure verläuft bei Anwesenheit von Quecksilber(II)-ionen binnen 15 min quantitativ.Auf Grund dieser Ergebnisse wird ein analytisches Verfahren zur Bestimmung von Maleinsäure und Fumarsäure ausgearbeitet.Es wird auch ein Verfahren zur Bestimmung von Maleinsäure allein neben Fumarsäure angegeben.     

Cyclization Studies with N-Mannich bases of 2-substituted indoles

The synthesis of the indoles 7 , 15 , 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH₂ units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22 , 23 , and 24 , respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26 . In the presence of SnCl₄, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27 , 28 ) and eight-membered rings (→ 29 ) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.     

Übergangsmetallkomplexe mit Anionen von 1-substituierten 1,2,3,4-Tetrazolin-5-onen und -thionen und von 1,3-Thiazolin-2-thion

Transition Metal Complexes with Anions of 1-substituted Tetrazolinones and -thiones and of 1,3-Thiazolin-2-thione The preparation of a series of anionic and phosphine containing complexes with the ambivalent anions of 1-R-tetrazolin-5-ones and -5-thiones, and of 1,3-thiazolin-2-thione is reported. According to the i.r. and ¹H n.m.r. spectra the S-heterocycles are bonded through the exocyclic sulfur atom to the metal; in the oxotetrazolinate compounds coordination occurs via the N² or N⁴ ring atoms. The copper and silver complexes [(Ph₃P)MX]₂ (X = anionic heterocycle) have been found to be dimeric.     

Synthesis of new thiazole analogues of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia. A new conversion of thiazolines into thiazoles

Three pyochelin analogues and their methyl esters all containing a thiazole ring have been synthesised from the same Weinreb amide key intermediate. One of these analogues called HPTT-COOH, a molecule released in the course of pyochelin and yersiniabactin biosynthesis, was efficiently synthesised using a new base induced conversion of the key compound 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide into 2′-(2-hydroxyphenyl)-2′-thiazole-4′-(N-methoxy,N-methyl) carboxamide.     

Isoprene functionalization : E/Z-isomerism of 1-sulfonyl substituted 2-methylbutadienes

The isomeric chlorosulfones 3, 4 and 5 are prepared by 1,4-addition of sulfonyl chlorides to isoprene, Dehydrohalogenation affords the corresponding 2- and 3-methylbutadienyl sulfones in a configuration which is dependent on the configuration of the chlorosulfone. Pure Z-2-methylbutadienyl sulfones 1 are obtained by displacement of primary halides by the Z-sulfinate anion 2. The Z-sulfones 1 are isomerized to E/Z-mixtures. The E/Z-mixtures are separated into their components and the configuration of the isomers is established by the NMR-NOE technique.     

Observation of the early stages of growth and the formation of growth spirals in epitaxial YBa2Cu3O7-δ thin films by AFM

Ultrathin epitaxial films of YBa₂Cu₃O_7– on SrTiO₃ prepared by Direct Current (DC) sputtering and pulsed laser deposition were imaged by Atomic Force Microscopy (AFM) to follow the different stages of growth of the thin films. Series of films with thicknesses between 1.2 nm and 12 nm (1–10 monolayers of YBa₂Cu₃O_7–) were prepared under identical conditions, optimized with respect to electrical and structural properties, to obtain information on the mechanisms responsible for the formation of growth spirals which are commonly observed in films having a thickness of several 10 nm or more. It could be shown that few layers are formed by a layered growth mode where material is attached laterally to 2D islands which are only one c-axis unit cell in height. In a later stage of growth when about 8–10 layers have been formed, the growth process changes to a mode which is mediated by growth spirals. This could be directly monitored in the AFM images where different defect structures like vertically sheared growth fronts and dendrite-like terraces of stacked islands as well as the resulting growth spirals could be identified.     

On Liouville decompositions in local fields

In 1962 Erd\H{o}s proved that every real number may be decomposed into a sum of Liouville numbers. Here we consider more general functions which decompose elements from an arbitrary local field into Liouville numbers. Several examples and applications are given. As an illustration, we prove that for any real numbers , not equal to 0 or 1, there exist uncountably many Liouville numbers such that are all Liouville numbers.