Die Chukrasine A,B, C,D und E,fünf neue Tetranortriterpene aus Chukrasia tabularisA. JUSS

The Chukrasines A, B, C, D and E, Five New Tetranortriterpenes From Chukrasia tabularis A . JUSS Five new tetranortriterpenes, chukrasins A, B, C, D and E, have been isolated from the wood of Chukrasia tabularis A . JUSS . On the basis of spectral and chemical evidence structures 1a - 1e were assigned to the new compounds.     

The structures of pukeleimides A,B, D,E, F,and G

Structures for pukeleimides A, B, D, E, F, and G, six novel pyrrolic compounds from a shallow-water variety of the marine blue-green alga bar|Lyngbya majuscula, are proposed from spectral data.     

Partialsynthese der Grandidone A, 7-Epi-A,B, 7-Epi-B,C, D und 7-Epi-D aus 14-Hydroxytaxodion

Partial Synthesis of Grandidones A, 7-Epi-A, B, 7-Epi-B, C, D and 7-Epi-D, from 14-Hydroxytaxodione Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved.     

Cyclopeptid-Antibiotika aus Aspergillus-Arten. Struktur der Echinocandine C und D

Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and D The echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B ( 1 ) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-α-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C ( 2 ), C₅₂H₈₁N₇O₁₅, contains 3-hydroxyhomotyrosine in the place of 3, 4-dihydroxyhomotyrosine present in 1 . Echinocandin D ( 3 ), C₅₂H₈₁N₇O₁₃, differs in two amino acids: 3, 4-dihyroxyhomotyrosine and 4, 5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine.     

Talaromycins C,D,E,and F

Four new spiroketal talaromycins have been isolated from T. stipitatus and, by equilibration with acid, have been structurally correlated with the previously identified talaromycins A and B.     

Simultaneous high-performance liquid chromatographic determination of altersolanol A, B, C, D, E and F

A high-performance liquid chromatographic model for the simultaneous determination of altersolanol A–F by using a reversed-phase column with an acetonitrile-water gradient elution system is described. The analysis can be completed within 13 min, the detection limits are 0.2–0.5 pmol per injection (5 μl) and the relative standard deviations are 0.90–1.34%. The method was applied satisfactorily to the determination of altersolanols in culture media of a strain of Alternaria solani without any prepurification.     

Darstellung und spektroskopische Charakterisierung der Monofluorohydro-closo-Borate [B6H5F]2− und [B12H11F]2−

Preparation and Spectroscopic Characterization of the Monofluorohydro-closo-borates [B₆H₅F]^2? and [B₁₂H₁₁F]^2? By treatment of [B₆H₆]^2? with 1-(chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane-bis(tetrafluoroborate)in acetonitrile monofluorohydro-closo-hexaborate [B₆H₅F]^2? ( 1 ) is formed in good yields. [B₁₂H₁₂]^2? reacts with unhydrous HF yielding the monofluorododecaborate [B₁₂H₁₁F]^2? ( 2 ). These compounds are separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from by-products. The ¹¹B nmr spectra exhibit the characteristic patterns (1 : 4 : 1) of a monosubstituted B₆ octahedron and (1 : 5 : 5 : 1) of a monosubstituted B₁₂ icosahedron with strong downfield shifts of the ipso-B nuclei at +9.3 ppm ( 1 ) and at +9.0 ppm ( 2 ). The ¹⁹F nmr spectra reveal quartets at ?212 ppm ( 1 ) and ?209 ppm ( 2 ) proving a B? F bonding. In the i.r. spectra, for ( 1 ) in the Raman spectrum too, cage vibrations depending on the F substituent at 1195 ( 1 ) and at 1182/1154 cm^?1 ( 2 ) are observed. The Raman spectra show the B₆F stretching mode at 535 cm^?1 and the B₁₂F stretching vibration at 445 cm^?1.     

Araguspongines B, C, D, E, F, G, H, and J, new vasodilative bis-1-oxaquinolizidine alkaloids from an okinawan marine sponge, Xestospongia sp

Nine new vasodilative alkaloids, araguspongines A, B (1), C (2), D (3), E (4), F (5), G (6), H (7), and J (8), were isolated from an Okinawan marine sponge, Xestospongia sp. On the basis of chemical and physicochemical evidence, the absolute stereostructures of araguspongines B, D, E, F, G, H, and J were determined respectively as 1, 3, 4, 5, 6, 7, 8, and the relative stereostructure of araguspongine C was determined as 2 having two 1-oxaquinolizidine moieties. Araguspongines B, D, and E each comprised a pair of the enantiomers, 1a and 1b, 3a and 3b, and 4a and 4b, respectively.     

Plectranthone A,B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae)

Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae) The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu₂, Rwanda, are proposed: plectranthon A ( 1 ; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B ( 2 ; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C ( 3 ; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D ( 4 ; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione ( 11 ), a compound very similar to 1–4 , was prepared by a Wagner-Meerwein, rearrangement of coleon E (⁵). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C₂₀-phenanthrenes of diterpenoid origin.     

Unimolekulare CH3-, CH4-, C2H4- und C3H4-Eliminierungen aus alkin- und arylsubstituierten Isopropylkationen in der Gasphase

Elimination of methyl, methane, ethylene, allene (or propyne) from two [C₃H₆Y]+ isomers (Y = p-(HC?C)? C₆H₄- and C₆H₅? C?C?) has been investigated using 13C and deuterium labelled compounds. It can be shown that the fragmentations are accompanied by extensive but not complete rearrangement of the carbon skeleton as well as by migration of the hydrogen atoms, the extent of which is determined by the reaction channel.     

Triterpene glycosides ofCaltha polypetala glycosides A,B, D,E, and F

Five individual triterpene glycosides — A, B, D, E, and F — which are hederagen-in mono- and biosides, have been isolated from the roots ofCaltha polypetala (Great Marsh Marigold), familyRanunculaceae. Glycosides E and F proved to be new compounds for which, on the basis of the results of acid and alkaline hydrolyses, methylation, methanolysis, and physicochemical methods of investigation, the following structures are proposed: E — hederagenin 3-0-D-glucopyranoside, 28-O-L-rhamnopyranoside; and F — heteragenin 28-O-[O-L-rhamnopyranosyl-(1→ 6)-D-glucopyranoside].     

Synthesis of xyloketal A, B, C, D, and G analogues

A series of demethyl analogues of the natural products xyloketal A, B, C, D, and G have been prepared in a notably direct manner from 3-hydroxymethyl-2-methyl-4,5-dihydrofuran and a series of corresponding phenols. These syntheses featured a boron trifluoride diethyl etherate-promoted electrophilic aromatic substitution reaction as a key step. In the case of the synthesis of analogues of xyloketal A, the process was found to be highly efficient (up to 93% yield). The optimized isolated yield of these reaction products is remarkable in view of the fact that this transformation involves, minimally, six individual reactions. Moreover, these synthetic studies provide significant insight into the possible biogenic origin of the xyloketal natural products.