Fullerenes and diamondoids are at the core of nanoscience. Comparable monodisperse silicon analogues are scarce. Herein, we report the synthesis of the parent siladodecahedrane, which represents the largest Platonic solid. It shares its pattern of pentagonal faces with the smallest fullerene, C 20 , and its saturated, H-terminated skeleton with diamondoids. Similar to endofullerenes, the silicon cage encapsulates a chloride ion ([Cl@Si 20 H 20 ] − ); similar to diamondoids, its Si−H termini offer a wealth of opportunities for further functionalization. Mere treatment with chloromethanes leads to the perchlorinated cluster [Cl@ Si 20 Cl 20 ] − . Both compounds were characterized by mass spectrometry, X-ray crystallography, NMR spectroscopy, and quantumchemical calculations. The experimentally determined 35 Cl resonances of the endohedral chloride ions are particularly diagnostic to probe the Cl − → Si 20 interaction strength as a function of the different surface substituents, as we have proven by high-level computational analyses.
Froma strain of Streptomycesantibioticus seven yellow phenazines were isolated. The antibacterially most active antibiotic was identified as (-)-saphenamycin, a second one with compoundDC-86-Y(saphenic acid). Three compoundswere new: Saphenic acid methyl ether, 6-acetylphenazine-l-carboxylic acid and an inseparable mixture of fatty acid esters of saphenic acid. Twosimple phenazines were phenazine-1-carboxylic acid (tubermycin B) and unsubstituted phenazine, which was isolated for the first time from a microorganism.The most striking property of the actinomycete strain Tii 2706 was the dark green color of its extracts. The chemistry of the green pigments, the esmeraldines, will be described in a forthcoming paper. In addition to the esmeraldines a series of yellow pigments were present in the cultures. Since the chemical and spectroscopic properties of these compoundsare the basis of the structural elucidation of the esmeraldines, we describe them in this paper.The strain Tii 2706 could be identified by the classification of Hutter2) and Nonomura3) as Strep tomyces an tibio ticus.Most of the yellow pigments discernible by TLC in the crude extracts could be isolated in pure state by repeated chromatographic procedures under various conditions (see Experimental part).The following compounds were isolated and characterized :Saphenamycin (1) The only compoundpossessing high antibacterial activity was identical in its analytical and spectroscopic properties with saphenamycin (1), an antibiotic described by Umezawa'sgroup. Its structure follows from an X-ray study4). AnX-ray structural elucidation carried out independently in our laboratory50 gave identical results. We have further characterized saphenamycin by the preparation of the methyl ester (2) and the methyl ether methyl ester (3) which were formed from 1 by reaction with diazomethane. The dimethylated product (3) showed the same chromatographic and spectroscopic properties as a racemic synthetic sample6).From Umezawa'spaper one could have the impression that natural saphenamycin is a racemic compound ([a]D 0°in chloroform). Indeed our compound also did not show optical activity when measured in chloroform. However, in DMSO it is optically active, M2D4-3°. The esters 2 and 3Preceding communication see ref 1.
From a strain of Strepfomyees antibioticus, Tii 2706, two dark green substances, the esmeraldines A and B, 4 and 3, respectively, were isolated. The structural elucidation was carried out by spectroscopic comparison with some simpler phenazines obtained from the same organism, saphenamycin (1) and related compounds, and by a series of chemical transformations. Esmeraldin 6 (3) is the 6-methylsalicylic acid ester, and esmeraldin A (4) a mixture of higher saturated and unsaturated fatty acid esters of esmeraldic acid. The latter is a heterocyclic compound with seven rings and four N-afoms, formally derived by condensation of two phenazine residues of the saphenic acid family. The esmerdldins are mixtures of diastereoisomers.Einleitung. -Kurzlich haben wir uber die Isolierung einer Reihe von Phenazinen aus Kulturen von Streptomyces antibioticus, Stamm Tu 2706, berichtet [2]. Die einzige antibakteriell hochwirksame Verbindung der Reihe war das Saphenamycin (l), ein Antibioticum, das schon fruher von Umezawa und Mitarbeitern [3] beschrieben worden war. Eine zweite Verbindung, Saphensaure (2), war identisch mit einem Abbauprodukt des Enzymhemmers DC-86-M [4]. Die auffidlligste Eigenschaft des Stammes war die tief grune Farbe seiner Kulturen und der daraus bereiteten Extrakte. Aus den Rohextrakten konnten die gelben Phenazine durch Chromatographie abgetrennt werden, wahrend die grunen Pigmente aus der Saule erst nach dem Zufugen von HCOOH zum Losungsmittel eluiert wurden. Die grunen Fraktionen liessen sich durch Craig-Verteilung in zwei Hauptkomponenten, die Esmeraldine B (3) und A (4) auftrennen. Fur kleinere Mengen eignete sich auch die Tropfchen-Gegenstrom-Chromatographie. Chromatographisch einheitliche Produkte (DC) wurden durch eine Kombination der beiden Methoden erhalten.
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