Stoffwechselprodukte von Mikroorganismen. 177. Mitteilung. Avilamycin C

From cultures of the Avilamycin (Avilamycin A) producing organism, Streptomyces viridochromogenes, strain ETH 23575, a second antibiotic, Avilamycin C, C₆₁H₉₀Cl₂O₃₂ could be isolated in crystalline form. Both Avilamycins belong to the group of the Orthosomycins. By IR., ¹H- and ¹³C-NMR. spectroscopy and by transformation to a common derivative it could be proven that Avilamycin A is a methyl ketone, Avilamycin C the corresponding methyl carbinol.     

Ueber die Titration der Schwefels?ure mit Benzidinchlorhydrat

Zusammenfassung In Vorstehendem wurde zunächst die Ausführung der von einem von uns ausgearbeiteten Schwefelsäuretitration mittelst Benzidinchlorhydrats nochmals genau beschrieben, sodann wurden die Bedingungen festgestellt, unter denen verschiedene Schwefelsäuremengen am genauesten zu bestimmen waren. Es hat sich dabei herausgestellt, dass die Schwefelsäure bis zu 0,01g H₂SO₄ herunter nach der beshriebenen Methode auf 1–2 genau bestimmt werden kann. Die Anwendung der Methode auf verschiedene Fälle (Ammoniumsulfat, Alaun, Zinksulfat-heptahydrat, Mohr'sches Salz, Mangansulfat-tetrahydrat), wobei die Metalle in einigen Fällen vorher ausgefällt wurden, bestätigten die zuvor festgestellten Regeln; ausserdem wurde gezeigt, dass beim Ausfällen von Zink, Eisen und Mangan nach dem angegebenen Verfahren Schwefelsäure nicht mitgerissen wird. Die Zeit, welche eine derartige Bestimmung, auch wenn die beschriebenen Ausfällungen vorgenommen werden müssen, bei einiger Uebung erfordert, ist sehr kurz, weil alles Auswaschen und so weiter in Fortfall kommt, so dass auch hier ein Vortheil gegenüber dem gewichtsanalytischen Verfahren vorhanden ist.     

Synthesen von Xyluron- und Riburonsäurederivaten

Zusammenfassung Durch acylierende Dehydratisierung von 1,2-Isopropyliden-d-xylo-und-d-ribo-pentodialdo-furanoseoxim bzw. aus Furanuronsäureestern und-amiden werden über eine Reihe von Zwischenstufen verschiedene 3-O-Acyl-pentofuranuronsäurenitrile synthetisiert und deren Reaktionen untersucht.

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Synthesis of xyluronic and riburonic acid derivatives

Various 3-O-acyl-pentofuranurononitrils were synthesized by acylating dehydration of 1,2-isopropylidene-d-xylo- andd-ribo-pentodialdo-furanose oximes, or pentofuranuronic acids via intermediates. Their reactions were investigated.

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Mit 1 Abbildung

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Aus den DissertationenH. W. Oberwalder (1970) undE. Wildschek (1967), Technische Hochschule in Graz.     

Über die Herstellung von Äther der enantio-14, 15-Dinorlabdan-Reihe aus Eperusäure

The Conversion of Eperuic Acid into Ethers of the enantio-14, 15-Dinorlabdane Series 5 and 6 are strongly odiferous substances of the ambra-type. Their enantiomers 7 and 8 , hitherto unknown, have been synthesized from eperuic acid (4) and their olfactory properties compared with those of 5 and 6 . 4 was esterified by CH₂N₂ and dehydrogenated with (C₆H₅Se)₂/H₂O₂ to the α,β-unsaturated ester 9 (61%). Oxidation by KMnO₄ in acetone yielded the ketone 3 (60%). Epoxidation followed by treatment with acid converted 3 into the acetals 7 (61%) and 8 (14%). 7 and 8 differ from 5 and 6 in odor intensity, and 6 and 8 show slightly different odor quality.     

Photochemische Reaktionen. 107. Mitteilung. Zur Photochemie offenkettiger 2,6-bzw. 2,7-Dien-Carbonylverbindungen

The Photochemistry of Open-Chained 2,6- or 2,7-Dien-Carbonyl Compounds On ¹n, π*-excitation (λ > 347 nm) citral (5) and the methyl ketone 10 isomerize to compounds A (7, 19) and B (6, 20) , whereas the phenyl ketone 11 changes into the isomer 24 of type E. Evidence is given that the conversions to A and B may arise from the ³n, π*-state of the 2,6-diene-carbonyl compounds. On ¹n, π*-excitation (λ = 254 nm) 5 and 10 yield the isomers A (7, 19) and D (18, 22) , but no products of type B. Furthermore, conversion of 10 to the isomer 21 of type C is observed. Selective ¹n, π*-excitation (λ = 254 nm) as well as selective ¹n, π*-excitation (λ > 347 nm) of the 2,7-diene-carbonyl compounds 12 and 13 give rise to isomerization to the compounds F (25, 28) , exclusively. The intramolecular [2 + 2]-photocycloadditions are shown to be triplet processes. UV.-irradiation (λ > 280 nm) of compounds F (25, 28) furnishes the isomeric products G (26, 29) which photoisomerize to oxetanes of type H (27, 30).     

Chemischer Transport von Eisensulfid. II. Experimentelle Ergebnisse beim Transport von FeSx mit Jod

Chemical Transport of Iron Sulphide. II. Experimental Results on the Transport of FeS_x with Iodine It is possible to deposite monocrystals of iron sulphide FeS_x by means of CTR method using iodine as transport agent. The presence of sufficient, high sulfur partial pressures is the most important condition for the FeS_x being transported, in other words: x must be equal or greater than approximately 1.04. The transport velocity and the shape of the deposited crystals depend on temperature, amount of iodine, and composition of the original material. The expected differences between the composition of the deposited solid and that of the residue can be verified experimentally.     

Oxydation von Allylalkoholen mit Blei(IV)-acetat

Lead tetraacetate (LTA) oxidation of the allylic alcohols 1, 10, 14 and 19 leads to the formation of the epoxides 2, 11, 15 and 20 , products of a novel internal addition reaction of the electron deficient alcohol oxygen to the allylic double bond. In some cases ( 10, 14 ) the formation of a new type of acetoxylated enolethers ( 12, 16 ) is observed. The LTA oxidation of the allylic dienols 21 and 29 gives rise to the formation of the epoxyacetates 25 and 33 , products of a similar internal addition reaction. Furthermore, a variety of cyclization products ( 22, 23, 24, 26, 30, 31, 32 and 34 ) has been isolated whose formation requires an isomerisation of the allylic trans double bond to a cis one.     

X‐ray investigations of bicyclic α‐methylene‐δ‐valerolactones. V. (4aS,7R,8aR)‐7‐Isopropenyl‐4a‐methyl‐3‐methyleneperhydrochromen‐2‐one

The title compound, C₁₄H₂₀O₂, adopts a conformation in which the δ‐valerolactone and cyclohexane rings are almost coplanar with one another. The γ‐methyl substituent occupies an axial position with respect to the cyclohexane ring. The δ‐valerolactone moiety adopts an envelope arrangement, while the cyclohexane ring exists in a chair conformation.     

Hierarchical dynamics in allostery following ATP hydrolysis monitored by single molecule FRET measurements and MD simulations

We report on a study that combines advanced fluorescence methods with molecular dynamics (MD) simulations to cover timescales from nanoseconds to milliseconds for a large protein. This allows us to delineate how ATP hydrolysis in a protein causes allosteric changes at a distant protein binding site, using the chaperone Hsp90 as test system. The allosteric process occurs via hierarchical dynamics involving timescales from nano- to milliseconds and length scales from Ångstroms to several nanometers. We find that hydrolysis of one ATP is coupled to a conformational change of Arg380, which in turn passes structural information via the large M-domain α-helix to the whole protein. The resulting structural asymmetry in Hsp90 leads to the collapse of a central folding substrate binding site, causing the formation of a novel collapsed state (closed state B) that we characterise structurally. We presume that similar hierarchical mechanisms are fundamental for information transfer induced by ATP hydrolysis through many other proteins.

We report on a study that combines advanced fluorescence methods with molecular dynamics simulations to cover timescales from nanoseconds to milliseconds for a large protein, the chaperone Hsp90.     

Synthesis and properties of a novel family of fluorous triphenylphosphine derivatives

A novel approach to the preparation of perfluorotail-functionalized triarylphosphines using a p-silyl substituent as the branching point has been developed. This approach enabled the attachment of between three and nine perfluorotails per phosphorus atom, resulting in the production of highly fluorous tris[p-(1H,1H,2H, 2H-perfluoroalkylsilyl)aryl]phosphines, P[C(6)H(4)-p-SiMe(3)(-)(n)()(CH(2)CH(2)C(x)()F(2)(x)()(+1))(n)()](3) (n = 1, 2, 3; x = 6, 8), containing between 50 and 67 wt % fluorine. (31)P NMR studies indicate that the phosphorus atoms, and consequently the sigma-donor and pi-acceptor properties of these phosphines, are not influenced by the electron-withdrawing perfluoroalkyltails. The fluorous triarylphosphines are readily soluble in fluorous solvents and display fluorous phase preference in several fluorous biphasic systems. The phase partitioning of these fluorous ligands, as well as their donor properties, is discussed in relation to their potential for fluorous biphasic catalyst separation.