M. Bilayet Hossain

Metallorganische verbindungen der lanthanoide: XXXI. Synthese und molekülstruktur einiger cyclopentadienyllutetiumhydride☆

Abstract The reaction of alkyl- and aryl-(dicyclopentadienyl)lutetium complexes ( 1 ) with H 2 or D 2 gives dimeric dicyclopentadienyllutetiumhydride ( 2 ) or -deuteride ( 3 ). Dicyclopentadienyllutetiumchloride ( 4 ) reacts with sodium in tetrahydrofuran (THF) with formation of [Na(THF) 6 ][(Cp 2 LuH) 3 H] ( 5 ). Tricyclopentadienyllutetium ( 6 ) reacts with NaH or NaD to give the complexes [Na(THF) 6 ][(Cp 3 Lu) 2 H]·2(THF) ( 7 ) or [Na(THF) 6 ][(Cp 3 Lu) 2 D]·2(THF) ( 8 ), respectively. The molecular structures of 2 and 7 were determined by single crystal X-ray diffraction.

Marine natural products: Deodactol, antineoplastic sesquiterpenoid from the sea hare aplysia dactylomela

Abstract Deodactol, a halogenated bisabolene-type sesquiterpene alcohol, has been isolated from the sea hare Aplysia dactylomela , and its structure and absolute configuration have been determined by X-ray diffraction. The compound crystallizes in the monoclinic system with the following crystal data: a=6.723(2), b = 11.838(1), c= 10.962(2) A, β=99.41(2)°, V= 860.7; ϱx= 1.669 g cm −3 at −135±2°C; space group P2 1 . The structure was solved by the heavy-atom method from 3-dimensional diffractometer data collected at −135±2°C using CuK α radiation. The final R factor for 1854 reflections is 0.029. The absolute configuration of the molecule was determined by the “R Method” of Hamilton. Deodactol has a strong intramolecular OHO hydrogen bond bridging its tetrahydropyranyl and cyclohexanol rings. The alcohol shows moderate cytotoxic activity. The absolute configuration of deodactol corresponds to that of several halogenated chamigrenes and supports the proposed biogenetic hypothesis linking halogenated bisabolenes and chamigrenes.

Crystal structure of retro-isomer of the siderophore ferrioxamine E

AbstractThe structure of the retro-isomer of ferrioxamine E sesqui-hydrate, a ferrioxamine E analog in which the N-hydroxy and carbonyl functions are transposed, was found to be isomorphous with that of ferrioxamine E. The interchange of N and C atoms in the three hydroxamate groups seemed to have caused some noticeable differences in the iron-coordination octahedron. The difference in the average Fe–O(N) and Fe–O(C) distances in the retro-isomer, 0.061Å, is about one-half of that observed in case of ferrioxamine E, 0.102Å. The ligand bite of the two complexes is similar (1.27), the retro-isomer has a smaller (42°) twist angle than that (45°) of ferrioxamine E. Crystal data: C27H45N6O9Fe·1.5H2O, triclinic,

The crystal and molecular structure of trimethyltin chloride at 135 K. A highly volatile organotin polymer

{P\bar 1}

Novel Oxidation Products of Two Sponge-Derived Sesquiterpenes, 4α-Formamedo- and 4α-Isocyanogorgon-11-Ene

, a = 19.816(8), b = 10.567(8), c = 7.973(5)Å, α = 106.54(6), β = 94.99(7), γ = 97.92(6)°, V = 1571.1(12)Å3, Z = 2, Dcalc = 1.439g/cm3·λ = 0.71073Å.

Crystal structure and absolute configuration of the indole alkaloid arborescidine C

The crystal structure determination of the Ga(III) complex of racemized anguibactin (C15H16N4O4S) confirms the previously predicted chemical structure of this novel siderophore isolated from the fish pathogenic bacterium, Vibrio anguillarum 775. The structure of the complex consists of a dimeric binuclear unit, (C15H14N4O4S·CH3O)2Ga2 which possesses a crystallographic center of symmetry. Each Ga ion forms a distorted octahedral coordination using one of the dihydroxy catechol O atoms, the thiazoline nitrogen, the hydroxamate (N–O) group and the nonprotonated nitrogen atom of the imidazole ring. The coordination sphere is completed by two bridging methoxide oxygen atoms. The dimer is further stabilized by a pair of hydrogen bonds between the second benzohydroxy group and the nitroso oxygen of the hydroxamate group. Crystal data: C15H14N4O4SGa·(CH3O)·(1.5) (CH3OH), monoclinic, P21/n, a = 16.890(4), b = 11.680(3), c = 11.227(3)Å, β = 110.29(4)°, V = 2077.4(9)Å3, Z = 4, Dcalc = 1.583 g cm−3, λ = 1.54178Å.

X-ray structure of sesterterpene, 16β-acetoxy-24-methyl-12,24-dioxoscalaran-25-al

Abstract : Trimethyltin chloride is the key starting material in the laboratory synthesis of the trimethyltin derivatives most subject to study. It is an article of commerce, and has itself been extensively studied by a great variety of spectroscopic and physical methods. There in the literature starting in 1970 a trail of oft referenced private communications which describe a yet unpublished X-ray structure which is incorrect. In addition, the structure of the analogous triphenyltin chloride, which is monomeric at ambient temperature, is said to undergo a change on cooling to a chlorine bridged polymer, but this suggestion is based upon NQR data a 77K which cannot be reproduced. The structure of the homologous trimethyltin fluoride cannot be solved because of disorder, and thus the widely-quoted bridging halide structures for R3SnX compounds are being confirmed here in there case of the title compound for the first time. Solid trimethyltin chloride at 135K is associated through bent chlorine bridges into a one-dimensional polymer containing non-planer C3Sn moieties in a distorted, axially-most electronegative, trigonal bipyramid at tin. (Author)

Cyclic peptides from the ascidian Lissoclinum patella: conformational analysis of patellamide D by x-ray analysis and molecular modeling

Abstract The synthesis of several 1-oxa-6-heteraspiro[2.5]octanes is reported herein for the first time. Stereochemical analysis via NMR studies and a single crystal X-ray diffraction analysis of 6-phenyl-1-oxa-6-phosphaspiro[2.5]octane 6-sulfide have been completed and provide the basis for correlations of structures for other members of the families yet unknown. Epoxidation of cis-2,6-diphenyl-4-thianone with dimethyl-oxosulfonium methylide in DMSO led, surprisingly, to a tertiary alcohol, presumably via ring opening of the expected intermediate epoxide. This is the first example of this type of ring opening in the presence of this base but the reaction time was longer than that normally employed in this process. Since the family members of the parent spiro[2.5]octanes are rare, an X-ray diffraction analysis was performed on 6-phenyl-1-oxa-6-phosphaspiro[2.5]octane 6-sulfide. This analysis revealed a space group of Pna21 with cell dimensions of: a=13.056(3) A, b=14.268(3) A, and c=6.1522(11) A. The phos...