Mössbauer Spectroscopic Studies of Ferrocenylaldimines and their TCNQ Complexes

A series of ferrocenylaldimines (Fc-CH=N-R) has been prepared by Schiff base condensation of formylferrocene with polyacenylamines RNH₂ where R = naphthyl, 5,6,7,8-tetrahydronaphthyl, anthracenyl, and pyrenyl groups. This step was followed by oxidation with TCNQ to give [Fc-CH = N-R][TCNQ]² salts. The electronic state of iron in these compounds was investigated by means of⁵⁷Fe Mössbauer spectroscopy.     

Asymmetric induction in mixed [2 + 2] photoadditions employing a chiral auxiliary in the alkene component

Asymmetric induction was achieved in the photoaddition of 3-methyl-2-cyclohexenone to optically active enoates 1a–c and the absolute configuration of the major adduct was determined.     

Cumulative subject index volumes 41–45

Orbital correlation diagrams for the black phosphorus to A7 (arsenic) phase transformation for various points in the Brillouin zone are presented and analyzed in symmetry terms. The level doublings observed at the black phosphorus geometry for several points are directly attributable to the nonsymmorphic nature of the space group (Herring's theorem). Doublings observed at the A7 structure derive from the choice of a four-atom, rather than two-atom, unit cell to view the geometrical transformation. The space group requirements at the beginning and end points of the transformation process simply control the form of orbital correlation diagrams. In general, $\text{HOMO}\text{LUMO}$ crossings are found at $\text{k = (}\text{1}\text{2}\text{,α,β)}$ where bonds are made and broken along the x direction, a result with simple analogies to more easily visualized one-dimensional problems.     

Mass spectral study of ring E of taraxasterol and compounds with similar ring substitution

The origin of the [M–69]⁺ and [M–111]⁺ signals in the mass spectrum of taraxasterol was studied through the use of C(18), (19), (21), (22) and/or (30) deuteriated derivatives. The generality of these signals for ring systems with an exocyclic methylene group and a methyl moiety on an adjacent carbon was verified with 2-methylmethylenecyclohexane, 1-methyl-2-methylene-trans-decalin, 1,10-dimethyl-2-methylene-trans-decalin and some of their deuteriated derivatives. The most plausible mechanism for the formation of the [M–69]⁺ ion appears to involve cleavage of both bonds allylic to the exocyclic methylene group with a 1,3-hydrogen transfer from the adjacent ring. Genesis of the [M–111]⁺ ion is more complicated but a five-membered allylic ion generated from ring D is proposed.     

Über einige neue Bispirane

We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).

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Mit 3 Abbildungen     

A modification of the heteropoly blue method for the microgram determination of arsenic in biological materials

Summary A sensitive method has been developed for analysis of trace amounts of arsenic in biological materials using the heteropoly blue method. The method employs a closed apparatus and a nitrogen atmosphere, and allows the detection of arsenic in ppm concentration using samples of 100 mg.

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Zusammenfassung Eine empfindliche Methode zur Bestimmung von Arsenspuren in biologischem Material im Wege der Molybdänblaumethode wurde ausgearbeitet. Man arbeitet dabei in einer geschlossenen Apparatur in Stickstoffatmosphäre und kann so in 100-mg-Proben Arsenkonzentrationen in der Größenordnung von ppm bestimmen.

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Presented at the 6th Annual Northeast Regional Meeting of the American Chemical Society, Burlington, Vermont, August 19, 1974.     

Lanthanide triflate-catalyzed three component synthesis of alpha-amino phosphonates in ionic liquids. A catalyst reactivity and reusability study

The catalyst reactivity and reusability for the lanthanide triflate-catalyzed three component synthesis of alpha-amino phosphonates have been examined in room temperature ionic liquids, [bmim][X], in which the catalytic activities were very dependent on the counter anion, X, as well as on the phosphorus nucleophile, and moreover, the catalyst immobilized in an ionic liquid was reused several times without any loss of activity.     

Beitrag zum Stabilisierungsmechanismus des Wollkeratins durch einige Metalle

Zusammenfassung Das Verhalten des Wollkeratins ist im kochenden Wasser nach Behandlung mit Kupfer-, Kadmium-, Silber- und Quecksilbersalzen unnormal, nicht nur verglichen mit dem Verhalten des metallfreien Proteins, sondern auch gegenüber des unter gleichen Bedingungen mit anderen Metallen behandelten Keratins. Die beobachteten Phänomene werden in einigen Fällen entweder mit der Annahme der Bildung von Vernetzungen zwischen benachbarten Polypeptidketten durch Komplexbildung des Metalls mit einigen Gruppen des Keratins oder durch Blockieren des Cysteins und der Verhinderung des Disulfidaustausches erklärt. In anderen Fällen jedoch, besonders bei Silber, ist die Erklärung der eintretenden Veränderung mit Hilfe dieser zwei Mechanismen nicht möglich, und es wird die direkte Reaktion des Metalls mit dem Schwefel des Cystins vorgeschlagen. Hierbei wird das Cystin und damit die Disulfidbindung gespalten. Die Spaltung dieser Bindung und die Verhinderung ihrer Rückbildung, entweder in derselben oder in anderer Lage, senkt die Zahl der Quervernetzungen im Keratin herab und damit die Fixierung der Polypeptidketten in ihrer ursprünglichen Lage. Hieraus resultiert eine Schrumpfung der Ketten und die Kontraktion der Faser.

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Summary Wool fibres containing cadmium, copper, mercury or silver set in a different way than the untreated ones or the fibres which contain other metals. This behaviour is explained in some cases by assuming the formation of complexes between the metal and the protein or by the disulphide exchange mechanism. In other cases, however, and particularly with silver this is not possible, and therefore the direct reaction between the metal and the sulphur of cystine is proposed. According to this mechanism the contraction of the fibre is due to the breakdown of the disulphide bond and the inability of its reformation.

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Mit 10 Abbildungen und 2 Tabellen     

Total synthesis of kendomycin: a macro-C-glycosidation approach

Kendomycin, also known as (-)-TAN 2162, is a novel polyketide-derived ansamycin isolated from Streptomyces sp., which exhibits potent antagonist and agonist activities at the endothelin and calcitonin receptors, respectively. This bacterial metabolite also possesses a strong antibiotic activity against a range of gram-positive and -negative bacteria and cytostatic effects on the growth of human cancer cell lines. When a novel macroglycosidation reaction is employed as the key step, the first enantioselective total synthesis of kendomycin has been accomplished. A Friedel-Crafts-type ring closure of the acyclic precursor containing tetrahydropyran and benzofuran moieties produces the macrocycle as a single stereoisomer in good yield, thus establishing the aryl C-glycosidic linkage of the ansa core. This reaction requires a phenolic glycosyl acceptor and appears to proceed through a rapid O-glycosidation followed by a slow rearrangement to an aryl C-glycoside. The requisite secomacrocycle is prepared by the Pd(0)-catalyzed B-alkyl Suzuki-Miyaura cross-coupling of two subunits, which in turn can be expeditiously assembled from readily available building blocks in a modular fashion.