bluuebunny/crossref_metadata_2025 huggingface dataset:
A Neighboring Group Effect of Carbonyl as Shown in the Mass Fragmentation Patterns of 4-Oxochroman-5-acetic Acids and of Some Related Compounds
Authors: Duewell H , Haig TJ
Published: September 2010

Two examples of a neighbouring group effect of carbonyl first observed with 4-oxochroman-5-acetic acids are shown to occur quite generally during electron impact mass spectrometry of 2-acylbenzeneacetic acids, 2-acylbenzoic acids and their methyl esters. The free acids readily give the [parent - CO2] ion. 2-Acylbenzeneacetic acids and their methyl esters after loss of water or methanol, respectively, as a first step, lead to very stable isobenzofuran radical cations which form the base peaks in the mass spectra of the esters.
Solvent and Pressure Effects on the Tautomeric Equilibrium of 4-Phenylazo-1-naphthol
Authors: Nishimura N , Danjo K , Sueishi Y , Yamamoto S
Published: September 2010

The azo-hydrazone tautomerism of 4-phenylazo-1-naphthol has been studied in ethanol-water and acetone-water systems and at high pressures. The hydrazone form is favoured by adding water to organic cosolvents and by applying pressure. The effects of solvent polarity and pressure on the equilibrium constant (KT) between the tautomers were examined by using Kirkwood-type equations applied to chemical equilibrium. Remarkable deviations were observed in the Kirkwood plots for both types of mixtures. Solvent-induced polarization, especially of the hydrazone form in a high polarity region, was suggested. In ethanol-water mixtures, correlation is fair between ln KT and ET, while in acetone-water system the ln KT against ET plot was curved. The above findings, together with the difference in the volume data for the two systems, suggest an existence of special interactions between acetone molecules and hydrophobic parts of 4-phenylazo-1-naphthol.
Oxidative Coupling of Lignans. III. Non-Phenolic Oxidative Coupling of Deoxypodorhizon and Related Compounds
Authors: Cambie RC , Craw PA , Rutledge PS , Woodgate PD
Published: September 2010

Oxidative coupling of deoxypodorhizon (4) with thallium(III) oxide and trifluoroacetic acid may be controlled to give either deoxyisopodophyllotoxin (14) or isostegane (16). These results and those with related non- phenolic substances indicate that the aromatic substituents of the parent diarylbutane play an important role in determining the outcome of oxidative coupling.
Metathesis of Functionalized Alkenes. Synthesis of Insect Pheromones
Authors: Crisp GT , Collis MP
Published: September 2010

The ability of substituted phenoxy complexes of tungsten to effect metathesis of both functionalized and non-functionalized terminal alkenes has been investigated. This methodology has been applied to the synthesis of the insect pheromones tetradec-9-en-1-yl acetate, dodec-7- en-1-yl acetate and tricos-9-ene.
The Synthesis of Stypandrol, a Toxic Binaphthalenetetrol Isolated From Stypandra imbricata : New Syntheses of Dianellidin and Stypandrone
Authors: Rizzacasa MA , Sargent MV
Published: September 2010

New syntheses of the naphthalenoid natural products dianellidin [1- (1,8-dihydroxy-3-methylnaphthalen-2-yl) ethanone ] (2) and stypandrone [6-acetyl-5-hydroxy-7-methylnaphthalenel-1,4-dione] (20), which rely on the Fries rearrangement, are described. This methodology is then applied to the synthesis of stypandrol [1,1′-(1,1′,8,8′-tetrahydroxy- 6,6′-dimethyl-2,2′-binaphthalene-7,7′-diyl) bisethanone ] (1), a toxic naphthalenetetrol isolated from Stypandra imbricata R.Br. ('blind grass').
Preparation and Structure of Tetraphenylarsonium Tris(1,2-dicyanoethenedithiolato)technetate(IV)
Authors: Colmanet SF , Mackay MF
Published: September 2010

The reaction of sodium 1,2-dicyanoethenedithiolate [( mnt )Na2] with (NH4)2 [TcBr6] in ethanol yields crystals of (AsPh4)2 [ Tc ( mnt )3] (1) after precipitation with AsPh4Cl. The crystal structure of (1) has been determined by X-ray diffraction. Crystals are orthorhombic, space group Pbcn , a 20.256(1), b 15.513(1), c 18.274(1)Ǻ, Z 4. Refinement on 2910 diffractometer data measured with Cu Kα radiation converged at R 0.056. The structure consists of [ Tc ( mnt )3]2- anions and (AsPh4)+ cations . The technetium(IV) atom is coordinated to six sulfur atoms to give a distorted octahedron.
Spin Spin Interactions in Polynuclear Nickel(II) Complexes: A Low-Temperature Susceptibility and Magnetization Study of the Cubane Tetranuclear Complex Ni4II(chta)4(μ-OH)4(NO3)4.7H2O
Authors: Boyd PDW , Martin RL , Schwarzenbach G
Published: September 2010

The bulk magnetic susceptibility of the complex Ni4(chta)4(μ-OH)4(NO3)4.7H2O ( chta = cyclohexane-r-1,c-3,c-5-triamine) has been measured over the temperature range from 1.9 to 300 K at a field of 1 T. The observed data were fitted by a Heisenberg exchange model for the susceptibility of a cubane [Ni4II(μ-OH)4]4+ cluster with a single exchange interaction J between each pair of NiII ions for a single ion g value 2.20 and an antiferromagnetic spin-spin coupling parameter 2J = -1.14 cm-1. The bulk magnetization measured at fields of 1 to 5 T in the temperature range from 5 to 1.9 K differed from that calculated from the simple Heisenberg model above. Several possibilities were examined for this deviation including intercluster interactions, single ion zero-field splitting and differing exchange coupling constants between nickel(II) ions in the cluster. This last model was successful in describing the complete set of magnetic data. A comparison with other known oxygen-bridged nickel(II) cubane clusters shows a change from antiferromagnetic to ferromagnetic coupling as the Ni-O-Ni bond angle decreases. It appears that the cubane cluster studied here is in a region very close to the crossover from antiferromagnetic to ferromagnetic coupling between the nickel ions.
Nitrones and Oxaziridines. XXXVIII. Nitric Acid Oxidation of Some Pyrroline 1-Oxides
Authors: Black DS , Strauch RJ
Published: September 2010

2,4-Diaryl-5,5-dimethyl-1-pyrroline 1-oxides (5)-(7) undergo smooth oxidation by concentrated nitric acid in acetonitrile to give the hydroxy ketones (9)-(11). Reduction of compound (10) with sodium borohydride gives the diol (22), which can be dehydrated to the oxo nitrone (23). The stereochemical assignments of the alcohol (8) and the diol (22) are discussed.
Coordination of Pyridine-Substituted Pyrazoles and Their Influence on the Spin State of Iron(II)
Authors: Sugiyarto KH , Goodwin HA
Published: September 2010

Iron(II) and nickel(II) [MN6]X2 type complexes have been prepared from 2-(pyrazol-1-yl]pyridine (1pp), 2-(pyrazol-1-yl) imidazoline (pi), 2- (pyrazol-3-yl)pyridine (3pp) and 2,6-bis(pyrazol-3-yl)pyridine ( bpp ). Variable-temperature magnetic and Mossbauer spectral studies establish that [Fe(1pp)3]X2 is low spin and [Fe(pi)3]X2 is high spin over an extended temperature range, while both [Fe(3pp)3]X2 and [Fe( bpp )2]X2 undergo temperature-induced low-spin ↔ high-spin transitions. The nature of the transition depends on the extent of hydration and for salts of both cations the singlet state is generally stabilized as the extent of hydration increases. Hydrogen bonding effects are believed to be responsible for this. For anhydrous [Fe( bpp )2] [BF4]2 the transition is discontinuous and associated with hysteresis with Tc ↓ 173 K for decreasing temperature and Tc ↑ 183 K for increasing temperatures. The transition to the singlet state species is complete at low temperatures provided that the cooling rate is relatively slow. Rapid cooling to 77 K results in the trapping of a fraction of metastable quintet state species. For all other species containing either [Fe(3pp)3]2+ or [Fe( bpp )2]2+ the spin transition is continuous. Spectral data for [NiN6]X2 complexes establish an order of field strengths for the ligands pi < 3pp < 1pp < bpp , which, for the bidentate species only, is consistent with the observed electronic properties of the corresponding [FeN6]X2 complexes.
Imidazo[1,2-b]pyridazines. IV. Syntheses and Central Nervous System Activities of Some 3-Methoxy-6-phenoxy(Substituted Phenoxy and Naphthyloxy)-2-phenylimidazo[1,2-b]pyridazines
Authors: Barlin GB , Davies LP , Ngu MML
Published: September 2010

Syntheses are reported for some 3-methoxy-6-phenoxy(substituted phenoxy and naphthyloxy )-2-phenylimidazo[1,2-b] pyridazines; they were made in order to study their possible pharmacological activity in the mammalian central and peripheral nervous system. In initial biological screens to detect compounds with potential activity at receptors for the benzodiazepine class of drugs, the most active compounds were 3-methoxy-6-(2′-methylthiophenoxy)- and 6-(2′-dimethylaminophenoxy )-3-methoxy-2-phenylimidazo[1,2-b] pyridazine. Their respective IC50 values for displacement of 3H-diazepam (IC50 for unlabelled diazepam, 4.2 nM ) from rat brain plasma membranes (measured in the presence of 100 μM GABA) were 112 and 149 nM.
The Crystal and Molecular Structure of catena-{Aquabis[2-methyl-2-(phenylthio)-propanoato]cadmium(II) monohydrate}
Authors: Smith G , Oreilly EJ , Kennard CHL , Mak TCW , Yip WH , Chan WH
Published: September 2010

The crystal structure of
the cadmium complex of 2-methyl-2-(phenylthio) propanoic acid, [ Cd (C6H5SC(CH3)2CO2)2(H2O)]. H2O has been determined by X-ray diffration and refined to a residual R 0.051 for 2725 observed reflections. Crystals are orthorhombic, space group Pbca with a 10.819(2), b 9.030(1), c 47.24(2) A and Z 8. The stereochemistry about cadmium is distorted MO6S seven-coordinate with Cd -S 2.747(2)Ǻ and a Cd -O range 2.277-2.491(5)Ǻ. Bonds are from cadmium to a water, and to four oxygens from two bidentate carboxylate groups, one of which also forms a polymer link. The same carboxylate group is also involved in a five- membered (S,O) chelate ring.
Longitubine and Neolatifoline, New Pyrrolizidine Alkaloids From Hackelia longituba
Authors: Roitman JN
Published: September 2010

Methanolic extracts of freeze-dried Hackelia longituba I. M. Johnston (Boraginaceae) afforded two new pyrrolizidine alkaloids: longitubine (1), an analogue of latifoline (2) in which an acetoxy group has replaced the angeloxy group at C7 and neolatifoline (3a) or (3b), a diastereomer of latifoline esterified at C9 with a stereoisomer of latifolic acid. In addition, the known alkaloids latifoline (2), 9-angelylretronecine (4) and 7-angelylretronecine (5) were isolated and identified.
Addition of Aliphatic and Aromatic Amines to Catechol in Aqueous Solution Under Oxidizing Conditions
Authors: Manthey MK , Pyne SG , Truscott RJW
Published: September 2010

The oxidation of catechol in the presence of two aliphatic and aromatic amines has been investigated. In aqueous solutions of pH 7.0 and 11.7, the substitution pattern of the adduct was dependent on the type of amine used. Aromatic amines produced 4,5-disubstituted o-quinones, whereas aliphatic amines gave either 2,4,5-trisubstituted or 2,4-disubstituted o-quinone adducts. A rationale based upon the stability of vinylogous amides is presented to account for the observed substitution pattern.
The Stereochemistry of Organometallic Compounds. XXXIII. Preparation and Reactions of Some Substituted Buta-1,3-Dienes
Authors: Campi EM , Jackson WR
Published: September 2010

Hydroformylation and hydrocyanation of 2-methylhex-1-en-3-yne surprisingly both involve addition to the alkyne leading to the formation of formyl- and cyano-buta-1,3-dienes whose reactivity in Diels-Alder and ene-type reactions has been investigated.
The Chemistry of Pyrrolic Compounds. LXI. Petroporphyrins From the Julia Creek Oil Shale: Further Evidence for the Derivation of Etiotype Petroporphyrins From Chlorophyll
Authors: Clezy PS , Fookes CJR , Prashar JK
Published: September 2010

The synthesis of the porphyrins (2c-j) has been achieved by the oxidative cyclization of appropriately substituted biladienes-ac. The availability of authentic material has allowed the finalization of the structure of a series of aetiotype fossil porphyrins which vary in substitution pattern at positions 3 and 13. All
combinations of H, Me and Et at these positions have now been isolated from natural sources. This points to a common precursor, possibly a divinylporphyrin, and strengthens the belief that the chlorophylls are the prime source of the petroporphyrins. A vinyl group, or a close derivative, is found at position 3 of all chlorophylls while fragmentation of the ubiquitous isocyclic ring of the chlorophylls could yield the vinyl group at position 13.
Structural Studies of Technetium Complexes. XI. The Crystal Structure of Bis(tetraphenylarsonium) Bis(1,2-dicyanoethenedithiolato)nitridotechnetate(V)
Authors: Williams GA , Baldas J
Published: September 2010

The crystal structure of [AsPh4]2 [ TcN(mnt)2] ( mnt = 1,2-dicyanoethenedithiolate) has been determined by single-crystal X-ray diffraction methods at 21 � 1 C. Crystals are monoclinic, space group Pn , with a 11 369(2), b 15.530(2), c 14.421(3) � , P 97.58(2)�, and Z 2. Full-matrix least-squares refinement gave a final R value of 0.057 for 4232 independent reflections. The technetium atom in the [TcN( mnt )2]2- anion has square-pyramidal coordination geometry with the nitrido ligand in the apical position, Tc =N 1.59(1) � , and four Tc -S bonds with distances varying between 2.367(4) and 2.419(4) �. The Tc =N core is disordered about a pseudo-inversion centre, but unequal occupancies of the disordered sites preclude a centrosymmetric structure.
Lewis-Base Adducts of Group 11 Metal(I) Compounds. LVI. Structural Characterization of μ,μ′-Dibromo-bis[(acetonitrile)(diphenyl-o-tolyl-phosphine)copper( I)] Bis(acetonitrile)
Authors: Engelhardt LM , Healy PC , Kildea JD , White AH
Published: September 2010

The title compound, [((2-MeC6H4)Ph2P)( MeCN )CuBr2Cu( MeCN )(PPh2-MeCH)]2MeCN has been isolated in the course of recrystallization of a 1 : 1 stoichiometric ratio of copper(]) bromide and the phosphine ligand from acetonitrile and characterized by a single-crystal X-ray structure determination. Crystals are triclinic, PI, a 13.148(2), b 10.673(2), c 8.101(1) � , α 84.24(4), β 89.42(4), γ 82.02(2)°, Z= 1 dimer ; R was 0.050 for 1772 independent 'observed' reflections. The dimer is centrosymmetric and is the first 1 : 1 : 1 mixed base copper(1) halide : phosphine : nitrile adduct to be so isolated and so characterized.
Cyclopentadienylideneethenone: Pyrolytic Generation and Argon Matrix Infrared Spectroscopic Study
Authors: Brown RFC , Browne NR , Coulston KJ , Eastwood FW , Irvine MJ , Pullin ADE , Wiersum UE
Published: September 2010

Two previously reported pyrolytic precursors for cyclopentadienylideneethenone (4) and benzyne produced two strong infrared bands attributable to ketene type compounds when their pyrolysates were examined by argon matrix isolation spectroscopy. To determine which band should be assigned to (4), four new precursors for (4) and benzyne and two analogues labelled with 13C at the carbonyl group have been synthesized. Precursors (8) and (14) are respectively a caged system and a bridged ,system bearing a mixed anhydride with trifluoroacetic acid. Flash vacuum pyrolysis of (8) and (14) at 600-700 with trapping at 77 K gave pyrolysates which contained biphenylene. Pyrolysis of (8) and (14) at 600-700�; in a stream of argon followed by deposition as an argon matrix at about 10 K showed that both produced a pyrolysate absorbing at 2089 cm-1 assigned to (4). Precursors (24) and (25) and the previously reported (18) and (27) are Meldrum's acid derivatives designed to yield the hypothetical cyclopentadienylidene Meldrum's acid (19) by cage fission or retro-Diels-Alder reaction. They all gave their biphenylene on flash vacuum pyrolysis at 600-700 � and their pyrolysates in argon matrices showed absorption both at 2089 cm-1 due to (4) and at 2225 cm-1 due to an unidentified ketene. The frequency shift resulting from substitution of 13C in the carbonyl group (52 cm-l) is in accordance with the assignment of the 2089 cm-1 band to (4). The pyrolysates from precursors 8a), (14), (18a), (25)and (27) were allowed to react with methanol and the resulting mixtures were hydrogenated. In all cases methyl cyclopentylacetate was obtained.
Kinetics of Acid-Hydrolysis of Nickel(II) and Copper(II) Compounds With the Cyclic Diamines 1,5-Diazocane and 4,4-Dimethyl-7-(5,5,7-trimethyl-1,4-diazepan-1-Yl)-5-azaheptan-2-ol
Authors: Collier W , Curtis LS , Curtis NF , Pomer IJ
Published: September 2010

The kinetics of acid-promoted hydrolysis reactions of nickel(II) and copper(ll) complexes of the cyclic diamines 1,5-diazocane ( daco ) and 4,4-dimethyl-7-(5,5,7-trimethyl-1,4-diazepan-1-yl)-5-azaheptan-2-ol (pyaz) in NaCl/HCl media ([Cl-] = 2 mol dm-3) are reported. For [Ni( daco )2]2+, beyond small [H+], an acid-limited rate constant of 2.0×10-5 S-l, involving dissociation of the first daco ligand, and for [Cu( daco )2]2+ a similarly acid-limited rate constant of 1.5×10-2 s-l, involving dissociation of the second daco ligand, were measured at 50°C. For [Ni( pyaz )]2+ and [Cu ( pyaz )2+ the rates of the hydrolysis reactions are again acid-limited, effectively independent of acid with rate constant of 1.0×10-2 s-1 for [Ni( pyaz )]2+ while for [Cu( pyaz )]2+ the rate follows the expression kobs , = 6.0×10-2[H+]/(l+4.6[H+]) S-l, both measured at 25°C.
Studies of Australian Soft Corals. XLVI. New Diterpenes From a Briareum Species (Anthozoa, Octocorallia, Gorgonacea)
Authors: Bowden BF , Coll JC , Vasilescu IM
Published: September 2010

The structures and relative stereochemistry of nine new briaran -based diterpenes from a Briareum species have been deduced from 2-D n.m.r. experiments at high field, and nuclear Overhauser effect experiments. The new compounds are (1R*2R*,3R*,5Z,7S*,8S*,9S*,10S*,11R*,-12S*,14S*,17R*)-2,3,14-triacetoxy-8,17:11,12-bisepoxy-9-hydroxybriar-5-en-18-one (5), (1R* ,2R* ,3R* ,5Z*,7S*,8S* ,9S*,10S*,11R*,12S*, 14S*, 17R*)-3,14-diacetoxy-2-butyryloxy-8,17:11,12-bisepoxy-9-hydroxybriar-5-en-18-one (6),(1R*,2R*,3R*,5Z,7S*,8S*,9S*,10S*,11R*,12S*,14S)-2,3,14-triacetoxy-11,12-epoxybriara-5,8(17)-dien-18-one(17),(1S*,2S*,4R*,5Z,7S*,8S*,9S*,10S*,2,4,9.12-tetraacetoxy-8,17-epoxy-11-hydroxybriara-5,13-dien-18-one (8),(1S*, 2S*,4R*, 5Z,7S*,8S*,9S*,10S*, 11S*, 12R*,13Z,17R*)-2,4,9-triacetoxy-8,17-epoxy-11,12-dihydroxybriara-5,13-dien-18-one (9), (1S *,2S*,4R*,5Z,7S*,8S*,9S*,10S*, 11S *,12R*,13Z,17R*)-2,4,9,12-tetraacetoxy-8,17-epoxy-11-hydroxybriara-5,13-dien-18-one(10),(1Si,2S*,5Z,7S',8S*,-9S*,10S*,11R*,12R*,13Z,17R*)-2,12-diacetoxy-8,17-epoxy-9-hydroxybriara-5,13-dien-18-one(ll), (1R*,2R*,3Si,5Z,7S* ,8S* ,9S* ,10S* ,11Z,14S*,17R*)-2,14-diacetoxy-3-butyryloxy-8,17-epoxy-9-hydroxybriara-5,11-dien-18-one (12) and (1R *,2R*,3S*,5Z,7S*,8S*,9S*,10S*,11Z,-14S',17R*)-2,3,14-triacetoxy-8,17-epoxy-9-hydroxybriara-5,11-dien-18-one (13). In addition to the nine new briaran derivatives, the same coral afforded two cladiellane derivatives (1R*,4R*,5S*,6R*,8R*,12R*,13R*,14R*)-cladiellane-4,8,12-triol (14) and its 4-acetoxy derivative (15). Aknowncembranoid diterpene (1R *,4R*,ZE,7E,l1E)-cembra-2,7,11-trien-4-ol(21) wasalso isolated together with an unprecedented perhydrophenanthrene-based diterpene (20): (1R *, 1aR*,4S*,4aR*,5aR*,8aR*)-4-isopropyl-l,8a-dimethyl-5-methylenetetradecahydrophenanthren-1-ol. The extraordinary biosynthetic ability of soft corals from the genus Briareum is once more revealed.
The Structure Factors for Silicon and Core Electron-Scattering in Charge Density Studies
Authors: Reynolds PA , Figgis BN
Published: September 2010

Extant extensive and accurate silicon structure factors have been fitted by multipolar models involving harmonic and anharmonic thermal parameters, anisotropic valence electron functions of variable radii, and a Is orbital with independent thermal parameters. The best model involves normal thermal and valence orbital population parameters together with variable 1s orbital population and cubic and quartic anharmonic thermal parameters. We conclude that, given their importance in this rather rigid material (B≈5000 pm2)it is probably necessary to introduce anharmonic parameters into the refinement process routinely for charge density studies in more complex systems. From the data at a single temperature we are unable to conclude whether the small change in 1s orbital population and the anharmonicity are real or are artefacts of an underlying breakdown of the assumption of rigid atoms. However, the thermal parameters derived agree with the results of other diffraction experiments involving variable temperature, including neutron studies.
Electrochemical Behavior of Bis[pentane-2,4-dithionato(1-)]iron(II), Fe(sacsac)2, and Dicarbonylbis[pentane-2,4-dithionato(1-)]iron(II), Fe(sacsac)2(CO)2
Authors: Brown SJ , Kok SKC , Lay PA , Masters AF
Published: September 2010

The redox behaviours of Fe(sacsac)2 and Fe( sacsac )2(CO)2 in chloroform are reported ( sacsac - = C5H7S2- = dithioacetylacetonate anion = pentane-2,4-dithionate anion). Fe( sacsac )2 is reversibly reduced to [Fe( sacsac )2]-, but no other redox processes are observed within the solvent limits. Fe( sacsac )2(CO)2 undergoes a reversible one-electron reduction followed by rapid loss of carbon monoxide to generate [Fe( sacsac )2]-. The oxidation of Fe( sacsac )2(CO)2 results in the oxidation of a dithioacetylacetonate ligand to the 3,5-dimethyl-1,2-dithiolium cation and the formation of a previously
uncharacterized complex believed to be [Fe( sacsac )(CO)2]+. The putative [Fe( sacsac )(CO)2]+ product of the oxidation also undergoes a reversible one-electron oxidation at a potential more positive than that of [Fe( sacsac )2]0/-1.
DNA-Binding Compounds. III. Synthesis of a Peptide-Linked Binuclear Platinum(II)-Terpyridine Complex
Authors: Bray AM , Kelly DP , Mack POL , Martin RF , Wakelin LPG
Published: September 2010

A procedure has been developed for linking two terpyridineplatinum(II), Pt(tpy), chromophores
by an oligopeptide chain. It relies on the use of a new reagent, succinimido 3-
(triphenylmethylthio)propanoate (2), to acylate the amino end groups of an α,ω-diaminoalkane
peptide. Subsequent deprotection of the sulfhydryl groups and coupling with [ (tpy )PtlICl ]CI
yields the binuclear complexes in good yields. This procedure allowed the synthesis of
[ ( tpy )PtS(CH2)2 CO-Gly-Gly-Gly-NH(CH2)3NHCO-(CH2)2SPt(tpy)Cl2 (5b).
Conformational Studies of Thyroid Hormones. I. The Diphenyl Ether Moiety
Authors: Craik DJ , Andrews PR , Border C , Munro SLA
Published: September 2010

Conformational flexibility round the diphenyl ether linkage in the thyroid hormones has been investigated by means of molecular orbital (AM1) and classical potential-energy calculations. The results obtained from these theoretical approaches are in qualitative agreement with those from n.m.r. spectroscopy, i.e., the barrier to rotation around this structural feature is sufficiently low to allow rapid interconversion between two stable conformers to occur at room temperature. Two pathways of rotation around the diphenyl ether bridge were explored and were both calculated to be approximately 14-15 kJ mol-1 by the AM1 method. This compares with the experimental barrier of 36 kJ mol-1. The potential-energy calculations gave barriers up to an order of magnitude larger which were inconsistent with experimental observations. A comparison of the AM1 data with results from previous studies with CNDO/2, which predicted a larger barrier, is also given. The detailed mode of interconversion around the two torsion angles involved in diphenyl ether rotation is investigated, as is the interplay of the bulky iodo substituents with the second aromatic ring during such conformational changes. The nature of torsion angle cooperation during rotations around this linkage is discussed.
Lewis-Base Adducts of Main Group 1 Metal-Compounds. XIII. Synthesis and Structures of Some Pyridine Base Lithium Bromide and Iodide Adducts
Authors: Raston CL , Robinson WT , Skelton BW , Whitaker CR , White AH
Published: September 2010

The syntheses and single-crystal X-ray structure determinations of adducts of the lithium(I)
halides with the following stoichiometries are reported: 1 : 3 lithium(I) bromide, iodide/ pyridine, monomers; 1 : 2 lithium(I) bromide/ quinoline and lithium(I) iodide/ quinaldine , both as [L2LiX2LiL2] dimers ; and 1 : 1� lithium(I) iodide/2,4,6-trimethylpyridine, 'step' tetramer.
Phenolic Analogs of Amino Carboxylic Acid Ligands for 99mTc. 4. N-(2-Hydroxybenzyl)glycines (hbg)
Authors: Wilson JG
Published: September 2010

Ten tridentate ligands , N-(2-hydroxybenzyl) glycines ( hbg ) (5), were prepared by the Mannich reaction of a phenol with formaldehyde and glycine and/or by the reduction of the Schiff base of a substituted salicylaldehyde and glycine. In three instances the bis compounds (6b,c,i) were also formed by the first method.
Reactions of 3,4,5-Trimethylbiphenyl and 2,3,4-Trimethylbiphenyl With Nitrogen Dioxide
Authors: Hartshorn MP , Judd MC , Martyn RJ , Robinson WT , Wright GJ , Vannoort RW
Published: September 2010

Reaction of 3,4,5-trimethylbiphenyl (1) with nitrogen dioxide gives four mononitro compounds (3)-(6) and three dinitro compounds (7)-(9). Similar reaction of 2,3,4-trimethylbiphenyl (2) gives three nitroaromatic compounds (11)-(13), three nitrate esters (14)-(16), and two nitro dienones (17) and (18). Dinitro dienone (17) rearranges in solution to give the corresponding hydroxy nitro dienone (19). The differences between the two sets of products are discussed, and an addition-elimination mechanism is proposed for the mode of formation of the nitro dienones (17) and (18). X-Ray crystal structures are reported for compounds (4) and (19).
Bifloratoxin, a Toxic Aminoglycoside of Carboxyatractyligenin, From Melanthera biflora
Authors: Macleod JK , Gaul KL , Oelrichs PB
Published: September 2010

The structure of the toxic kaurene aminoglycoside bifloratoxin (3) from Melanthera biflora (L.) Willd ( syn. Wedelia biflora DC.) has been determined, and complete 1H and 13C n.m.r. spectral assignments achieved. The aglycon unit of bifloratoxin (3) is identical to carboxyatractyligenin (11), the aglycon of carboxyatractyloside (8).
An N.M.R. Investigation of the Mills-Nixon Effect
Authors: Collins MJ , Gready JE , Sternhell S , Tansey CW
Published: September 2010

The 4J(H-C-C-Me) coupling constant, previously established1-3 as a probe of bond order, was used to examine the bond orders in a series of ortho -bridged compounds: benzocyclopropene , 1,2- dihydrobenzocyclobutene , indan and tetralin . No evidence for sterically induced bond fixation (i.e. the Mills-Nixon4 effect) was found, but some evidence for electronic distortion In the corresponding benzylic ketones was observed. The experimental results are in accord with SCF/MO calculations.
Purpurins Bearing Functionality at the 6,16-meso-Positions: Synthesis From 5,15-Disubstituted meso-[β-(Methoxycarbonyl)vinyl]porphyrins
Authors: Gunter MJ , Robinson BC
Published: September 2010

Porphyrins bearing p-X-phenyl substituents (X=Me, OH, OTs , NMe2, NO2) at the 5,15-meso-positions have been synthesized. meso-Formylation of the nickel derivatives produced the derivatives (4), (12), (17) and (23) which show atypical broadened Soret and Q-band absorptions, the latter at 570-750 nm. The optical and n.m.r. spectra of the corresponding free base monoformyl derivatives also indicate electronic perturbations of the porphyrin rr -system. Wittig reactions with ( methoxycarbonylmethylene ) triphenylphosphorane, followed by demetallation, resulted in the meso-acrylate porphyrins (8), (14), (19) and (25), which also exhibit unusual electronic spectra consistent with a distortion of the macrocyclic ring current. The p-dimethylaminophenyl derivative (14) also shows protonation-dependent spectra indicating a quinomethene structure. The meso-acrylate porphyrins were efficiently converted into type A purpurins under basic conditions. Type B purpurins were also formed, and the relative yields of types A and B are temperature and solvent dependent, but independent of the presence of oxygen. These results are in contrast to those for the formation of octaethylpurpurin derivatives; likewise, no evidence of a purpurin - porphyrin equilibrium was observed for these compounds. In the presence of oxygen and strong visible light the meso-formyl-2- ( methoxyoxalyl ) chlorins are formed. The electronic spectra of the purpurins are typified by strong absorptions in the red region of the spectrum; the p- dimethylaminophenyl derivative (27) also exhibits a solvent-dependent spectrum, which is explained in terms of a dimethylaminoquinomethene tautomerism. The purpurins and porphyrin derivatives have potential application in photodynamic cancer therapy.
The Constituents of the Bark of Litsea elliptica (Lauraceae)
Authors: Arbain D , Dasma N , Ibrahim S , Sargent MV
Published: September 2010

Extraction of the fresh bark of Litsea elliptica Bl ., yielded (+)-reticuline (4) and a steam-volatile oil containing undec-10-en-2-one (1) and
tridec-12-en-2-one (2).
Structural Study of (-)-8-Epi-11-nordriman-9-one
Authors: Dastlik KA , Ghisalberti EL , Skelton BW , White AH
Published: September 2010

The structure of the title compound (1) has been determined by X-ray crystallographic methods. This compound, not previously described as a natural compound, has been isolated from two varieties of the mulga Acacia aneura. Some points of confusion in the literature regarding spectral parameters assigned to (1) are clarified.
Synthesis of the 3-Aza[9]metacyclophane System by Oxidative Cleavage of a 3-Aza[6](1,7)naphthalenophane Derivative
Authors: Bremner JB , Jaturonrusmee W
Published: September 2010

Reaction of 10,11-dimethoxy-1,4,5,6-tetrahydro-7,9-ethano-3-benzazecine-3(2H)- carbonitrile (3) with ozone at -78°, followed by destruction of the ozonide with dimethyl sulfide, gave, in 82% yield, 15-formyl-12,13-dimethoxy-8-oxo-4-azabicyclo[9.3.1]pentadeca-1(15), 11,13-triene-4-carbonitrile (4), a representative of the new 3-aza[9] metacyclophane system. The precursor (3) was obtained by cyanogen bromide-induced eliminative ring destruction of 8,9-dimethoxy-2,3,5,6,10,11,11a,11b-octahydro-1H-benzo[de] pyrido [3,2,1-ij] quinoline (2) in 96% yield. An attempt to make the analogous precursor for the 3-aza[8] metacyclophane system was unsuccessful due to a preferred nucleophilic attack by bromide ion. Reduction of (4) with sodium tetrahydroborate gave 8-hydroxy-15-( hydroxymethyl )-12,13-dimethoxy-4- azabicyclo [9.3.1]pentadeca-1(15),11,13-triene-4-carbonitrile (5) in 79% yield.
Olefin Isomerization Catalysts Based on Dithio Palladium(II) Complexes
Authors: Cavell KJ , Chan KY , Peacock EJ , Ridd MJ , Davies NW
Published: September 2010

The catalytic double-bond shift isomerization of α-olefins by dithio-β-diketonate palladium complexes Pd{CH3C(S)CHC(S)CH3}(PL1L2L3)X(1) and [Pd{CH3C(S)CHC(S)CH3}{Ph2PCH2CH2PPh2}]Y(2)(X = 1, Br; Y = halide, PF6, BPh4) is described. Catalysts are formed on activation of the complexes by a variety of alkylaluminium cocatalysts . Several of the catalysts are highly active for isomerization of oct-1-ene and but-1-ene, activities being higher than normally obtained for palladium systems. In contrast to the majority of palladium-based catalysts product distributions rapidly approached thermodynamic equilibrium, with a strong preference for trans products at each stage of the reaction. Products from the isomerization of oct-1-ene were analysed by g.l.c.-F.t.i.r . in conjunction with Kovats retention indices.
The C-Arylation of α-Cyano Esters and Malononitriles by Aryllead(IV) Triacetates
Authors: Kozyrod RP , Morgan J , Pinhey JT
Published: September 2010

The arylation of soft carbon nucleophiles by aryllead (IV) triacetates has been extended to α- cyano esters and malononitriles. Arylation did not occur with the parent compounds, ethyl cyanoacetate and malononitrile, but in both series monosubstituted compounds reacted to give α-aryl derivatives in synthetically useful yields. A study of the effect of some tertiary aromatic amines and dimethyl sulfoxide, substances which complex with lead(IV), has been carried out, and in two cases the influence of bulky α- substituents has been examined.
A Molecular Dynamics Simulation of the Structure of Sodium Ion in Liquid Ammonia
Authors: Hannongbua S
Published: September 2010

The structural properties of Na1/ammonia solution have been studied by means of a molecular dynamics simulation, the experimental density of pure liquid ammonia being used. In contrast to the previous study for the lithium ion in liquid ammonia, a free orientation of the ammonia molecules in the first solvation shell of the sodium ion has been found. The effects of elevated temperature on the structure function of the cationic solvation shell could be observed clearly i.e., an increase in temperature leads to significant changes in molecular orientation and an increase in the average dipole moment of solvated ammonia. The intramolecular geometry changes of an ammonia molecule relative to the pure liquid were similar to those reported for Li1/ammonia solution.
Mechanisms of Nucleophilic Attack at Carbon-Nitrogen Double Bonds. The Solvolysis of Substituted Benzohydrazonoyl Halides in Aqueous Binary Mixtures
Authors: Rowe JE
Published: September 2010

Rate data for the solvolysis of a series of substituted benzohydrazonoyl halides in aqueous dioxan at 329 K and in aqueous ethanol and methanol at 303 K are presented. The products in the aqueous alcohols were measured by h.p.l.c ., and the selectivities determined. The data are used to support proposals about the mechanism of the reaction.
Multinuclear (13C, 31P, 77Se) Magnetic Resonance Studies on Organophosphorus Selenides and Sulfides. II. Tri- and Tetra-Tertiary Phosphines
Authors: Colton R , Whyte T
Published: September 2010

Selenium and sulfur have been reacted in various stoichiometries with two tritertiary phosphines Ph2P(CH2)2P(Ph)(CH2)2PPh2(P2P′) and MeC (CH2PPh2)3 (P3), and two tetratertiary phosphines Ph2P(CH2)2P(Ph)(CH2)2P(Ph)(CH2)2PPh2 (P2P′2) and P({CH2}2PPh2)3 (P3P′). The products have been fully characterized in solution by multinuclear (13C, 31P, 77Se) magnetic resonance spectroscopic studies. Reaction of P2P′ with one mole of selenium gives almost exclusively the product with the central phosphorus selenated (P2P′Se′) and reaction with greater quantities leads to the identification of P2P′SeSe′ and P2P′Se3 by their phosphorus-31 and selenium-77 n.m.r. spectra. The reactions between P2P′2 and various mole equivalents of selenium are similar to those of P2P′, leading to the identification of P2P′2Se′, P2P2.′Se′2, P2P′2SeSe′2 and P2P′2Se4 by both phosphorus-31 and selenium-77 n.m.r. spectroscopies although carbon-13 n.m.r. spectroscopy is required to unambiguously determine their structures. P3 reacts with three moles of selenium to give P3Se3. When P3 is reacted with less than 3 mole equiv. of selenium, phosphorus-31 and selenium-77 n.m.r. spectra cannot distinguish between pure selenides and mixtures of selenides. However, carbon-13 n.m.r. spectra show that reaction of P3 with less than 3 mole equiv. of selenium leads to almost tatistical distributions of P3, P3Se, P3Se2 and P3Se3. The reactions between P3P′ and selenium give a combination of the above behaviours. The central phosphorus is selenated first, but subsequent additions of selenium lead to a distribution of selenium among the terminal phosphorus atoms to give mixtures of P3P′SeSe′, P3P′Se2Se′ and P3P′Se3Se′ which cannot be distinguished by phosphorus-31 n.m.r. spectroscopy, but can be by selenium-77 n.m.r. spectroscopy. Reaction of P2P′ (and P2P′2) with sulfur in any proportion is quite different to that with selenium, and gives only P2P′S3 (and unreacted P2P′). The reactions between P3 or P3P′ and sulfur are similar to those between these compounds and selenium. Reactions between selenium or sulfur and a series of ditertiary phosphines have been investigated in an attempt to clarify the different reactions of the elements with P2P′ and P2P′2.
An Infrared Study of Formic Acid Adsorption on Co/SiO2 and SiO2 Surfaces
Authors: Li GX , Ridd MJ , Larkins FP
Published: September 2010

It is demonstrated from an i.r. study of the adsorption of formic acid on a Co/SiO2 catalyst that the adsorbates on the SiO2 surface and on the cobalt metal clusters are respectively a physically bonded HCOOH molecule and a formate species. The former species is easily desorbed but the latter remains stable at least up to 523 K. The ratio of formate species to physically bonded HCOOH is approximately 2:1 for a catalyst with a cobalt loading of 5 wt %.
The Determination of Chirality of N-Methyl- and N,N-Dimethyl-phenylalanine by G.L.C.
Authors: Arbain D , Langley J , Picker K , Taylor WC
Published: September 2010

The chirality of N- methylphenylalanine enantiomers can be determined on a micro scale by g.l.c . of N-pentafluoropropionyl amino acid isopropyl esters on a Chirasil -L-Val capillary column. N,N- Dimethylphenylalanine enantiomers cannot be similarly derivatized and cannot be separated. However, prior treatment with ethyl chloroformate followed by acid hydrolysis effects demethylation to the N-methyl analogues which can then be derivatized for g.l.c . Contrary to literature reports N-methylphenylalanine can be prepared by reductive alkylation of phenylalanine.
Assignment of Local Conformation in Medium-Ring Unsaturated Lactones Derived From Labda-8(17),14-dien-13-Ol (Manool)
Authors: Grant PK , Hanton LR , Lynch GP , Simpson J , Slim GC
Published: September 2010

The unsaturated lactone (2) derived from manool (1) has a particularly rigid 10-membered ring which gives rise to high asymmetric induction in epoxidation with m-chloroperoxybenzoic acid. The corresponding 11-membered lactone (14) shows greater flexibility. The conformations of lactone (2) and epoxy lactones (12) and (13) have been determined by X-ray diffraction studies.
The Chemistry of Pyrrolic Compounds. LXVI. The Synthesis of Two Petroporphyrins Substituted With a Fused 5-Membered Ring-System - Examples of Possible Chlorophyll c Involvement in Petroporphyrin Formation
Authors: Clezy PS , Vanphuc L , Prashar JK
Published: September 2010

The synthesis of the petroporphyrins (3e) and (4e) has been completed, and their presence as the nickel complexes (3a) and (4a) in the Julia Creek shale oil deposits has been confirmed. While the derivation of (4e) from a chlorophyll c is generally accepted, it is proposed that (3e) may also originate from this group of pigments, thus highlighting the importance of these photosynthetic pigments as a source for fossil porphyrins.
Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXIII. Stereochemistries and Structures of the 1 : 1 Adducts of Cu1X (X = Cl, Br, I) With 2,2'-Bipyridine
Authors: Skelton BW , Waters AF , White AH
Published: September 2010

Syntheses and single-crystal X-ray structural characterizations (at c. 295 K) are recorded for the 1 : 1 adducts of copper(I) chloride, bromide and iodide with L = 2,2′-bipyridine. The chloride is triclinic, Pī , a 14.069(5), b 10.520(3), c 7.872(2)Ǻ, α 69.00(2), β 88.62(3), γ 70.70(2)°, Z = 4 formula units; R was 0.041 for No 1805 'observed' [I > 3σ(I)] reflections. The bromide is monoclinic, P21/c, a 8.788(3), b 13.206(6), c 9.895(3)Ǻ, β 117.90(2)°, Z = 4 formula units; R 0.036 for No 1007. The iodide is monoclinic, C2/c, a 17.571(3), b 8.587(7), c 16.796(3)Ǻ, β 120.17(2)°, Z = 8 formula units; R 0.041 for No 1038. The chloride is ionic, [CuL2]+ [ ClCuCl ]-; in the cation, Cu-N are 2.005(6)-2.039(6)Ǻ with interligand N-Cu-N 114.4(3)-132.4(2)°, while, in the anion, Cl-Cu-Cl is 177.3(1)°, with Cu-Cl 2.086(2) and 2.091(2)Ǻ. The bromide (unlike its 1,10-phenanthroline counterpart, which is ionic) is a centrosymmetric dimer , as also is the iodide. In the bromide, Cu-N are 2.083(6), 2.099(5), and Cu-Br 2.428(2), 2.463(1)Ǻ, Cu…Cu and Br…Br being 2.850(1) and 3.975(2)Ǻ respectively. In the iodide, Cu-N are 2.070(8), 2.08(1), and Cu-I, 2.583(3)Ǻ (×2), and Cu…Cu and I…I are 2.610(2) and 4.420(1)Ǻ.
New Thermal and Photochemical Routes to Dewar Furan and Other Isomers on the C4H4O Energy Surface: the Role of Isobenzofuran as a Trapping Agent
Authors: Warrener RN , Pitt IG , Russell RA
Published: September 2010

Photolysis of the specially synthesized substrate (39) leads to quantitative fragmentation into the phthalimide (56) and Dewar furan (4a). Dewar furan has only transient existence even at -65°, yet can be trapped effectively with isobenzofuran but not furan. Rapid isomerization to cycloprop-2-enecarbaldehyde (57) occurs at the photolysis temperatures and this product is also trapped by the isobenzofuran . In the absence of trapping agent, photolysis of (39) produces some furan but no 1H n.m.r . evidence can be obtained for (4a) or (57), even at low temperatures (-85°). Separate irradiation of (57) causes extensive polymerization, without yielding other recognizable products. Furan is concluded, therefore, to arise from photoisomerization of (4a) rather than photochemical or thermal isomerization of (57). Separate thermal study of (57) shows that isomerization to furan only occurs above 420°. Flash vacuum pyrolysis of the polycyclic epoxide (72) provides a new retro- Diels-Alder route to (57) which likely proceeds via (4a) as an intermediate. At high temperatures (57) is isomerized to furan. A new Dewar benzene oxide (41) and Dewar benzene (45) are reported en route to the photosubstrates (39) and (50) respectively. Photolysis of (50) provides a high-yielding source of cyclobutadiene , which in the absence of trapping agent yields the syn-dimer (59).
Pigments of Fungi. XXII. Synthesis of (±)-Austrocortirubin and Related Tetrahydroanthraquinones
Authors: Burns CJ , Gill M
Published: September 2010

The fungal tetrahydroanthraquinones austrocortirubin (1) and austrocortilutein (3) and their deoxy derivatives (2) and (4), respectively, are synthesized in racemic form from naphthopurpurin (6).
Constituents of Eupomatia Species. XIII. The Structures of New Lignans From the Tubers and Aerial Parts of Eupomatia bennettii
Authors: Carroll AR , Taylor WC
Published: September 2010

The structures of new extractives from the tubers and aerial parts of Eupomatia bennettii F. Muell. have been assigned as follows: eupomatenoid-15, 2-(4′-methoxyphenyl)-3-methyl-5-(E)-propenylbenzofuran (1); eupomatenoid-16, 7-methoxy-2-(4′-methoxyphenyl)-3-methyl-5-(E)- propenylbenzofuran (3); eupomatenoid-17, 5-allyl-7-methoxy-2-(4′- methoxyphenyl)-3-methylbenzofuran (5); eupomatenoid-18, 5-allyl-2- (3′,4′-dimethoxyphenyl)-7-methoxy-3-methylbenzofuran (6). Eupobennettin was shown to be (2′α,3′α,4̸β,5′α)-5-[3′,4′-dimethyl-5′-(3′,4′,5′-trimethoxyphenyl)tetrahydrofuran-2′-yl]-2,3-dimethoxyphenol (7). Spectroscopic studies and a biomimetic synthesis proved that bennettinone was 2-(4′-allyl-2′-methoxyphenoxy)-1-(3′,4′-dimethoxyphenyl)propan-1-one (10).
The Stereochemistry of Organometallic Compounds. XXXV. Hydroformylation of ortho-Propenylanilines and ortho-Propenylphenols: a New Route to 4,5-Dihydro-3H-1-benzazepines
Authors: Anastasiou D , Jackson WR
Published: September 2010

Rhodium- catalysed hydroformylation of readily available ortho-propenylanilines gives 4,5- dihydro-3H-1-benzazepines together with small amounts of substituted 3-methylquinolines (≤15%). The regioselectivity of these reactions and the hydroformylation of related ortho-propenylphenols are discussed.
Stereocontrolled Functionalization of Cycloheptadiene by Nucleophile Addition to Cycloheptadienyliron Complexes - Preparation and Reactions of 6-Methylcyclohepta-2,4-dienol Derivatives
Authors: Pearson AJ , Lai YS , Srinivasan K
Published: September 2010

Addition of alkoxide nucleophiles to methyl-substituted cycloheptadienyliron complex (6) proceeds with complete stereo-and regio-selectivity. The product cycloheptadiene complexes are readily demetallated to give cycloheptadienes that can be further functionalized to give potential building blocks for the synthesis of macrolide antibiotics. Stereocontrolled reduction of the keto derivative (26) allows access to a stereochemically complementary cycloheptadiene. Functionalization of the diene moiety of these compounds is described.
Cyclohexyneplatinum(0) Complexes Containing Di-t-butylphenylphosphine, t-butyldiphenylphosphine or Trimethylphosphine
Authors: Bennett MA , Fick HG , Warnock GF
Published: September 2010

Cyclohexyneplatinum (0) complexes Pt(C6H8)L2 [L = PBut2Ph(4), PbutPh2(5)] analogous to the known complex (3) (L=PPh3) have been prepared by reaction of the two-coordinate complexes PtL2 with 1,2-dibromocyclohexene and 1% sodium amalgam. The corresponding tricyclohexylphosphine complex is formed by a similar reaction but it could not be isolated in a pure state. Attempts to prepare analogues of (4) and (5) containing cycloheptyne or cyclooctyne were unsuccessful, possibly because the bulky t-butyl groups of the tertiary phosphines hinder coordination of the larger rings. Bulky tertiary phosphines do not displace PPh3 from (3) but trimethylphosphine reacts with (3) to give successively Pt(C6H8)(PMe3)2(PPh3) (10) and Pt(C6H8)(PMe3)2 (11), as shown by 31P{1H) n.m.r. spectroscopy. The tertiary phosphines in these complexes equilibrate rapidly at room temperature in benzene and only (10) can be isolated as a solid from the reaction. Complexes (4) and (5) react with HCl (1 molar proportion) to give n1-cyclohexen-l-yl complexes trans- PtCl (C6H9)L2 [L= PBut2Ph(6), PButPh2 (7)]. In the absence of air, (4) reacts with methanol at 65°C to give the hydrido complex trans- PtH (C6H9)(PBut2Ph)2 (8). In the presence of oxygen from the air, however, the main product is the dioxygen complex Pt(O2)(Pbut2Ph)2 (9). This represents an unusual example of complete displacement of cyclohexyne from a platinum(0) complex by a π-acceptor ligand.
Biosynthetic-Studies on Tajixanthone and Shamixanthone, Polyketide Hemiterpenoid Metabolites of Aspergillus variecolor
Authors: Ahmed SA , Bardshiri E , Mcintyre CR , Simpson TJ
Published: September 2010

The biosynthesis of tajixanthone and related metabolites of Aspergillus variecolor has been studied by incorporation experiments with simple and advanced precursors labelled with the stable isotopes 13C, 2H and 18O. Tajixanthone is shown to be derived through ring cleavage of an octaketide -derived anthraquinone with introduction of two dimethylallyl moieties. From the results of isotopic labelling experiments and chemical studies on model compounds, an overall biosynthetic pathway is proposed and information on the mechanisms of interconversion of proposed intermediates is obtained.
New and Revised Spectral Assignments of Nitrocelluloses: the 1H and 13C N.M.R. Spectra of Cellulose 2,3,6-Trinitrate and Cellulose 3,6-Dinitrate
Authors: Curtis NJ , Vanaltena IA , Hounslow AM
Published: September 2010

Authoritative assignments have been made for the 13C and 1H nuclear magnetic resonance spectra of both essentially pure cellulose 2,3,6-trinitrate (la) and cellulose 3,6-dinitrate (1b), by using correlation spectroscopy. This study clarifies previous conflicting assignments for (1a); the revised assignment is ( ppm ): C1, 98.1; C2, 77.5; C3, 78.6; C4, 75.3; C5/C6, 70.0 in (D6) dimethyl sulfoxide . The same relative positions are retained in (D6)acetone. The study has confirmed that the product of hydroxylamine-mediated denitration is cellulose 3,6-dinitrate. Attempts to evaluate α, β γshift factors, for the change in substitution from C-ON02 to C-OH, were largely unsuccessful.
Partially Racemic Compounds as Brushtail Possum Urinary Metabolites
Authors: Carman RM , Klika KD
Published: September 2010

The hydroxycineole (2) and cineolic acid (3) obtained as urinary metabolites from the brushtail possum (Trichosurus vulpecula) after the ingestion of l,8-cineole (1), are partial racemates. The compounds have been examined by gas chromatographic analysis over chiral stationary phases, and by the synthesis of optically pure enantiomers. Female possums show different enantiomeric ratios from males. Possible advantages to the animal in the use of a partial racemate as a pheromone are discussed.