D. Van Der Helm

Marine natural products. Xenicin: a diterpenoid possessing a nine-membered ring from the soft coral, Xenia elongata.

Der neue Naturstoff (I) fand sich erstaunlicherweise nur in Bestanden, die vor Heron Island (Australien) gesammelt wurden, nicht dagegen inExemplaren von der Picnic Bay, Magnetic Island (Australien) oder von den Fidschiinseln.

The crystal and molecular structure of trimethyltin(IV) chloride, a chlorine-bridged, linear polymer

Abstract The crystal and molecular structure of trimethyltin(IV) chloride has been determined by the heavy-atom technique, and refined to a final R value of 0.041 for 1375 independent reflections (2θ 2σ(I)) recorded at 138 ± 2 K on a Nonius CAD-4 counter diffractometer. The crystals are monoclinic with space group I2/c; a 12.541(8), b 9.618(11), c 11.015(11) A, β 92.62(7)°, Z = 8, Dcalcd 1.994 g cm−3. The needle crystals are composed of polymeric chains of chlorine atoms bridging non-planar trimethyltin(IV) units at unequal (2.430(2) and 3.269(2) A) distances. The zig-zag chains are bent at chlorine (angle SnCl Sn 150.30(9)°), but nearly linear at tin (angle ClSn Cl 176.85(6)°) to describe a distorted trigonal bipyramidal geometry at tin with the trimethyltin groups eclipsed. The interchain d(Sn Cl) distances are greater than 4.1 A. The angles carbon—tin—carbon (mean 117.1(3)°) are larger than tetrahedral, while the angles carbon—tin—chlorine (mean 99.9(2) A) are smaller, in accord with isovalent hybridization principles, but more severely distorted than in the gas-phase, monomeric structure. The tin—chlorine distance of 2.430(2) A is also longer than in the gas phase monomer, and the intermolecular contact of 3.269 A is shorter than in other organotin chloride bridged systems (sum of Van der Waals radii 3.85 A).

Purification and crystallization of ferric enterobactin receptor protein, FepA, from the outer membranes of Escherichia coli UT5600/pBB2

The ferric enterobactin receptor protein, FepA, was isolated and purified from the outer membranes of a genetically transformed strain of Escherichia coli (UT5600/pBB2) using anion‐exchange chromatography, chromatofocusing and gel filtration. The purified protein was found to crystallize from 25 mM sodium phosphate buffer in the presence of 0.8% β‐D‐octylglucoside under a range of conditions. The protein formed mostly small rods and needle‐shaped crystals in the hanging drop method.

The crystal structure of dimethylphenyltin(IV) acetate

Dimethylphenyltin(IV) acetate, (CH3)2(C6H5)SnOC(O)CH3, crystallizes in the orthorhombic space group Pbca with a 10.068(3), b 15.065(7), c 14.976(5) A; Z = 8; V 2271(2) A3. The structure was determined from 1793 observed out of 2348 unique reflections and refined on an R factor of 0.034. The geometry at tin is trigonal bipyramidal, with the oxygen atom of the acetate and the carbonyl oxygen of the adjacent symmetry-related (12 + x, 12 − y, 1 − z) acetate occupying the axial positions of the trans-C3SnO2 polyhedron to result in a polymer whose backbone, formed by the repetition of SnOC(O) fragment, adopts a conformation that is closer to the zig-zag configuration of trimethyltin acetate than to the helical form of triphenyltin acetate.

Oxy- and thio-phosphorus acid derivatives of tin(IV). The crystal and molecular structure of O-methylmethylphosphatotriphenyltin(IV)☆

Abstract O-Methylmethylphosphatotriphenyltin(IV) (II) is synthesized by treating stoichiometric amounts of O,O′-dimethylmonothiophosphatotriphenyltin(IV) (I) with mercury. The negative 119Sn chemical shift in solution relative to tetramethyltin for I corresponds to higher than four coordination (at tin) in solution. The values of the 119Sn Mossbauer isomer shift for I and II confirm the presence of tin as tin(IV). The magnitudes of the quadrupole splitting and the ratios of the QS to the IS of both compounds reveal that tin is higher than four coordinated. The solid state structure of II was determined by X-ray diffraction. The compound crystallized in the trigonal space group R 3 with a, b 31.433(15), c 10.259(3) A, V 8778.2 A3, Z = 18, Dx 1.56 g cm−3 at 138 K. In the solid state compound II exists as a highly symmetric cyclic hexamer in which planar trimethyltin(IV) groups are axially bridged by O-P-O linkages. The geometry about tin is trigonal bipyramidal with an axial O-Sn-O angle of 177.1(2)° and average C-Sn-C angle of 120.0(2)°. The structure of the hexameric ring is linear at tin but bent at phosphorus with an O-P-O angle of 117.1(2)°.

Metabolism and metabolite pharmacokinetics of BRB-I-28, a class Ib antiarrhythmic agent

SummaryThe metabolism of BRB-I-28 (7-benzyl-3-thia-7-azabicyclo[3.3.1]nonane), a novel class Ib antiarrhythmic agent, was characterized in vivo in dogs and rats and in vitro with rat liver microsomal preparations containing a NADPH-generating system. In dogs, rats and the in vitro hepatic microsomal oxidation system, BRB-I-28 was extensively metabolized to form 7-benzyl-3-thia-7-azabicyclo [3.3.1]nonane-3-oxide (I), a major metabolite. The metabolite I was produced via S-oxidation, presumably by the hepatic P-450 system. Formation of a minor metabolite, 7-benzoyl-3-thia-7-azabicyclo[3.3.1]nonane (II) via the oxidation of the benzylic site was also identified in rats. Following intravenous and oral administration of BRB-I-28 to dogs, the plasma concentration of major metabolite I could be best described by a 1-compartmental model. The plasma AUC of metabolite I was 20% (i.v.) and 179.4% (oral) of that of the parent BRB-1-28, respectively, suggesting that BRB-I-28 was metabolized significantly by the first pass effect following oral administration. Extensive metabolism of BRB-I-28 to form metabolites I and II, which have demonstrated much lower antiarrhythmic activities, further supports previously observed pharmacodynamic and pharmacokinetic findings.

Structure of ferrichrome-type siderophores with dissimilarNδ-acyl groups: Asperchrome B1,B2,3,D1, D2 and D3

SummaryAsperchromes are a series of iron-chelating compounds which contain a cyclic hexapeptide backbone as in ferrichrome siderophores and differ from the latter in having heterogenous acyl groups in the ornithine side chains. The molecular structures of the asperchrome B and D series have been determined by1H- and13C-NMR spectroscopy; single-crystal X-ray diffraction was used to determine the detailed structural features of asperchrome B1 and asperchrome D1. Asperchrome B1 crystallizes in the triclinic space group P1 witha= 1.3143(5) nm,b=1.2200(5) nm,c=0.8949(3) nm,α=105.17(4)°,β=94.03(3)°, γ=109.65(3)°,V=1.2843 nm3,Z=1, ρx =1.446 g cm−3. FinalR=0.054 for 4625 reflections measured at 138 K using MoKα. Asperchrome D1 crystallizes in the monoclinic space group P21 witha=1.2248(11) nm,b=1.3795(9) nm,c=1.3644(6) nm,β=93.24(6)°,V=2.3016 nm3,Z=2, ρx=1.418 g cm−3. FinalR=0.110 for 3180 reflections measured at 138 K using MoKα radiation. The conformation of the molecular backbone and iron coordination geometry in both asperchrome B1 and D1 compare well with those observed in other known ferrichrome siderophores. The differences in the acyl groups are illustrated and the structural results are correlated with their iron transport properties.

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

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)

Two polymorphic forms of 3-hydroxy-2-methyl-4H-pyran-4-one (maltol)

The crystal structures of two polymorphic forms of maltol, C 6 H 6 O 3 , have been determined. The polymorphs exhibit different crystal-packing arrangements through intermolecular hydrogen bonding involving the hydroxyl H atoms. Form (1) has a near-planar chain of molecules linked by hydrogen bonds while form (2) has mutually hydrogen-bonded dimers. In both polymorphic forms there are also weaker C-H...O bonds which give greater stability to the chains of form (1) and link the dimers in form (2).

CARBON-13 NMR STUDIES OF 1-PHENYL-4-PHOSPHORINANONE AND DERIVATIVES. SINGLE CRYSTAL X-RAY DIFFRACTION ANALYSIS OF 1-PHENYL-4-PHOSPHORINANONE 1-OXIDE AND 1-SULFIDE

Abstract The 13C nmr spectral analysis has been recorded for the title compounds in DCC13, and all data appear to be in a accord with chair forms. Single crystal x-ray diffraction analysis of 1-phenyl-4-phosphorinanone 1-oxide and the corresponding sulfide revealed flattened chair forms in the solid state. Neither the solution data nor the x-ray data provided any evidence for a twist form for either compound as has been suggested for the carbon counterpart, namely, cyclohexane-1,4-dione.