bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Preparative Route to 3-Unsubstituted Cephalosporins From Penicillin V
Authors: Davis M , Wu WY
Published: September 2010

p- Nitrobenzyl
(2R,3R)-2-(benzothiazol-2′-yldithio)-α-isopropylidene-4- oxo-3-phenoxyacetyl-aminoazetidine-1-acetate (7), readily prepared from penicillin V, can be converted into the corresponding 2-allylthio compound (2) by addition of allyl bromide and sodium borohydride at a low temperature. This compound (2) on treatment with ozone, followed by cyclization with trimethyl phosphite, produces a 3H-ceph-3-em ester (4). The ester can be easily de-esterified to the free acid (1b).
New Depsides From Dimelaena Lichens
Authors: Elix JA , Evans JE , Nash TH
Published: September 2010

The new depsides 3-chlorostenosporic acid (2), 3-chloroperlatolic acid (3) and subsphaeric acid (24) have been detected in Dimelaena lichens and the structures of the metabolites have been established by unambiguous synthesis. Wrightiin (methyl 3-chloroevernate) (21), a depside from Erioderma wrightii, has also been synthesized by using similar methodology.
The Use of a Phosphine Containing a Basic Group in the Mitsunobu Esterification Reaction
Authors: Camp D , Jenkins ID
Published: September 2010

Use of diphenyl (2-pyridyl) phosphine instead of triphenylphosphine in the Mitsunobu esterification reaction facilitates isolation of the desired ester. The resulting phosphine oxide is readily removed by a dilute acid wash. 31P n.m.r , investigations of the mechanism suggest that the pyridylphosphine behaves in an analogous manner to triphenylphosphine.
Lewis-Base Adducts of Group 11 Metal(I) Compounds .XLV. Conformational Systematics of [(N-base)1(AgX)1]N Complexes
Authors: Engelhardt LM , Gotsis S , Healy PC , Kildea JD , Skelton BW , White AH
Published: September 2010

A number of 1 : 1 silver(1) halide/nitrogen base adducts, [ LAgX ], have been synthesized by recrystallization of the parent silver(I) halide from the neat base, and their solid state structures determined by single-crystal X-ray diffraction and rationalized in terms of the hierarchy of structural types described in the preceding papers based on steric profile of the base. In consequence of increased metal atom size (cf. Cu), a more limited array of structural types is observed.[(pyridine) AgBr,I ] ∞, [(2,4,6-trimethylpyridine) AgCI,Br,I ] ∞ and [( quinaldine ) AgCI,Br ] are 'stair' polymers; [( piperidine ) AgBr,I ]4 and [(2,2,6,6-tetramethyIpiperidine) AgI ]4 are 'cube' tetramers, while [( diethylamine ) AgCI,Br,I ] provide the first complete metal halide series of the novel 'tube' polymer.
Lewis-Base Adducts of Group 11 Metal(I) Compounds. XLVII. Vinylpyridine Derivatives of Copper(I) Halides: Synthesis and Conformational Systematics
Authors: Engelhardt LM , Healy PC , Kildea JD , White AH
Published: September 2010

The syntheses and systematic single-crystal X-ray structural characterization of 1 : 1 copper halide ( CuX )/ligand (L) adducts, CuX.L [X= Cl, Br, I; L= 2-vinylpyridine (2-vpy) and 4- vinylpyridine (4-vpy)], are recorded. For X = Cl, Br; L = 2-vpy, the solid state structures are linear polymers, the basic unit of which is an NCuX2CuN dimer , with the fourth coordination site of each copper linked to adjacent units by coordination of the vinyl group. For X= C1, Br; L = 4-vpy, a linear polymeric NCuX/NCuX infinite spine in one dimension is cross-linked from successive copper/ligand groups alternately to either side through the vinyl groups to adjacent spines to give a puckered sheet structure. The iodides for both ligands are one-dimensional 'stair' polymers with non-coordinating vinyl groups.
Syntheses of the Benzylisoquinoline Alkaloids Isosevanine and Berbithine
Authors: Chantimakorn V , Nimgirawath S
Published: September 2010

The benzylisoquinoline alkaloids isosevanine (1) and berbithine (2) have been synthesized by alkylation of the Reissert compound (5), derived from 6,7-methylenedioxyisoquinoline, with the appropriate benzyl chlorides (6) and (7) respectively followed by hy drogenolysis of the protecting group.
Lewis-Base Adducts of Lead(II) Compounds. II. Nine-Coordinate Capped Square-Antiprism Stereochemistry, [M(bidentate)4(unidentate)], in Tetrakis(1,10-phenanthroline)(perchlorato-O)lead(II) Perchlorate
Authors: Engelhardt LM , Kepert DL , Patrick JM , White AH
Published: September 2010

Improved precision, consequent upon redetermination of the structure of the title compound [Pb( phen )4(OCIO3)] (CIO4) [5184 'observed', 1 > 2 σ(I), diffractometer reflections; R 0.05 11, enables improved characterization of the nine-coordinate lead(II) environment in terms of a capped square antiprism.
Conformational Studies of Some Piperazine-2,5-Diones: Crystal Structures of Three Isomeric Forms of Methylanhydropicroroccellin (Derivative of a Lichen Diketopiperazine) and a Derivative Bromohydrin
Authors: Sterns M , Patrick JM , Patrick VA , White AH
Published: September 2010

Single-crystal X-ray structure determinations have been carried out on three isomeric forms of the lichen diketopiperazine metabolite methylanhydropicroroccellin , C21H22N2O3, and a related bromohydrin , C20Hl9BrN2O3; all are based on a 6-benzyl-3-benzylidene-1,4- dimethylpiperazine-2,5-dione but differ in the substituents on the α and β carbons at position 6, enabling comparison of the resulting variation in conformation.
Formylation of Estrogens
Authors: Pert DJ , Ridley DD
Published: September 2010

Reimer-Tiemann formylations of oestradiol and oestrone were investigated and, whilst substitution was effected under certain conditions to give mixtures of 2- and 4-formyloestrogens, yields were very low and the method was unsuitable for preparative purposes. Regioselective methods were developed and 2-formyloestradiol was conveniently prepared from oestradiol by formylation of the lithio derivative of the bis(methoxymethyl) ether and removal of the rotecting groups with hydrochloric acid. 4-Formyloestradiol was prepared by a sequence of reactions starting with the methoxyethyl ether of 4-bromooestradiol, then metal-halogen interconversion, formylation with N-methylformanilide, and removal of the protecting group. A number of related
derivatives, including 2-formyloestriol, were prepared.
Ab initio Studies on Hydrazines: 2H-1,2,3-Triazol-2-amine With Special Reference to Its Equilibrium Structure and Vibrational Spectrum
Authors: Riggs NV
Published: September 2010

The geometries of four stationary structures of 2H-1,2,3-triazol-2-amine have been optimized with the 3-21G and 3-21G(N*) basis sets. The lowest-energy and only equilibrium structure predicted by these calculations is the 'perpendicular' Cs form (3), whereas infrared studies on benzo-annelated analogues had suggested it might be the 'parallel' Cs form (2) stabilized by 'double hydrogen-bonding' of the amino-hydrogen atoms to the flanking ring-nitrogen atoms. The latter form (2) is here characterized as the transition structure for rotation about the N-NH2 bond and, after zero-point vibrational-energy corrections, is calculated to lie 8.7 kJ mol-1 above the equilibrium structure (3) at HF/3-21G(N*) level or only 3.8 kJ mol-1 at MP4/6-31G** level. This very low barrier to internal rotation (cf. 26.5 kJ mol-1 for the analogous 1H-pyrrol-1-amine) may be due to double hydrogen-bonding of the kind suggested by the experimental study mentioned above. The transition structure for inversion at the NH2 centre is, as for 1H-pyrrol-1-amine, the perpendicular C2v structure (5), the barrier being 25.8 kJ mol-1 (cf. 24.5 kJ mol-1 for 1H-pyrrol-1-amine), and the planar C2v structure (4) is a second-order saddle point lying 41.7 kJ mol-1 above the equilibrium structure (3). Calculated NH-stretching frequencies, their separation, and relative intensities as compared with experimental values for benzo-annelated analogues offer broad support for the assignments above based on relative energies.
Graphite: The Ultimate Large Aromatic Molecule
Authors: Campbell SJ , Kelly DC , Peacock TE
Published: September 2010

A π-band theory calculation is reported on a single layer of graphite, the nomenclature and methods of molecular orbital theory being used. Interaction between non-nearest neighbours at increasing distances is included to determine the extent of significant electron interaction. A criterion to determine this limit is defined and used. A comparative study is made of the methods available for the evaluation of double integrals over triangular fields.
Synthesis and Stereochemistry of Tetramethyldecahydroanthracene Derivatives
Authors: Brecknell DJ , Carman RM , Schumann RC
Published: September 2010

A series of tetramethyldecahydroanthracene derivatives have been synthesized from the Diels -Alder product from 2,3-dimethylbuta-1,3-diene and p- benzoquinone . Their stereochemistry, conformational properties and n.m.r. spectra are discussed.
Studies of Australian Soft Corals. XLIII. The Structure Elucidation of a New Diterpene From Alcyonium molle
Authors: Bowden BF , Coll JC , Dai MC
Published: September 2010

The isolation of a new cladiellin based diterpene (6), (1S,2R,3S,4R,SR,6S,8E,11S,12R,13S,14S)-3-acetoxy-2,12-dibutanoyloxycladiell-8-ene-4,11-diol is reported from the soft coral Alcyonium molle (Octocorallia, Alcyonacea, Alcyoniidae). The structure was deduced by high-field n.m.r. spectroscopy including 13C-lH shift correlated 2D n.m.r. experiments and n.O.e. measurements. The absolute configuration was based on the kinetic resolution method of Horeau. This highly derivatized diterpene (6) is the first alcyonacean derived metabolite to possess hydroxy functionalities protected as butyrate esters, although this feature is relatively common among gorgonacean metabolites. Gorgosterol (7), which cooccurs with (6) in A. molle was identified and its 13C n.m.r. spectrum reported for the first time.
Nitrones and Oxaziridines. XL. Oxidation of 2H-Pyrroles and 3-Benzoyloxy-1-pyrrolines
Authors: Black DS , Strauch RJ
Published: September 2010

Peracid oxidation of 2H-pyrroles (1a-d) gave the related 2H-pyrrole 1-oxides (2a-d). Similar oxidation of the 3-benzoyloxy-1-pyrroline (7a) also gave a 2H-pyrrole 1-oxide (9), while other benzoyloxy pyrrolines (7b,c) yielded the related oxaziridines (8b,c). Some other oxygenated by-products were also identified.
X-Ray Crystal-Structure of 5-Acetoxymethyl-5-methyl-2-phenyl-1,3,2-dioxaphosphorinane 2-Oxide
Authors: Craig DC , Toia RF , Wacher VJ
Published: September 2010

The relative stereochemistries of the isomeric 5-acetoxymethyl-5-methyl-2-phenyl-1,3,2-dioxaphosphorinane 2-oxides have been assigned following single-crystal X-ray structural analysis of one of the isomers.
Synthesis of 2', 6'-Dihydroxychalcones by Using Tetrahydropyran-2-yl and Trialkylsilyl Protective Groups; the Crystal Structure Determination of 2',6'-Dihydroxy-2,4,6-trimethoxychalcone
Authors: Miles CO , Main L , Nicholson BK
Published: September 2010

Two improved general routes to 2′,6′-dihydroxychalcones are described in which the final step is protective-group removal from O 2′ under mild acid conditions. The first involves base-catalysed condensation of benzaldehydes with 2′-hydroxy-6′-tetrahydropyran-2-yloxyacetophenone, the second ring-opening of 5-hydroxyflavanones with 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a trialkylchlorosilane to trap out the chalcone as a bis silyl ether. Chalcones prepared by the first route are 2',6'-dihydroxychalcone (1), and its 4-methoxy (2), 3,4-dimethoxy (3), 3,4,5-trimethoxy (4), and 2,4,6-trimethoxy (5) derivatives. The 4-chloro derivative (6) and the chalcone from hesperetin are prepared by the second method. .The X-ray crystal structure of 2',6'-dihydroxy-2,4,6-trimethoxychalcone (5), the first for a 2',6′-dihydroxychalcone, is reported, the hydrogen involved in intramolecular hydrogen-bonding between the carbonyl and phenolic oxygens being located for the first time for any 2'-hydroxychalcone derivative. The O 6' involved in the intramolecular hydrogen-bonding is also hydrogen-bonded intermolecularly to the hydrogen of the other (2'-)hydroxy group of a neighbouring molecule in the lattice. 13C n.m.r. data are the first reported for a series of 2',6'-dihydroxychalcones.
Structural Investigations of Phosphoranes. A Single-Crystal X-Ray-Analysis of 1-Ethoxycarbonyl-2-oxopropylidene-triphenylphosphorane
Authors: Abell AD , Clark BM , Robinson WT
Published: September 2010

The reaction of acetic anhydride with ethoxycarbonylmethylenetriphenylphosphorane has been shown by a single-crystal X-ray structure analysis to yield 1-ethoxycarbonyl-2-oxopropylidenetriphenylphosphorane rather than the previously reported phosphoniurn salt (3b). The geometry of resonance-stabilized phosphoranes is also discussed.
(+)-Iforrestine: a Novel Heterocyclic Nephrotoxin From Isotropis forrestii
Authors: Colegate SM , Dorling PR , Huxtable CR , Shaw TJ , Skelton BW , Vogel P , White AH
Published: September 2010

A compound that reproduces the acute renal proximal tubular necrosis associated with ingestion of Isotropis forrestii, by animals, has been isolated from the plant. The novel heterocyclic structure was determined by a single-crystal X-ray diffraction study. The spectroscopic data are presented and rationalized with respect to the assigned structure.
An N.M.R. Study of Electron Donor-Electron Acceptor Interaction Between Aromatic Hydrocarbons and Diazines
Authors: Hurst DT , Thakrar UB , Wells CHJ , Wyer J
Published: September 2010

Equilibrium constants have been measured by n.m.r , spectroscopy for the electron donor- electron acceptor interaction between a number of aromatic hydrocarbons and diazines . The values obtained have shown that the interaction is weak, and that the aromatic hydrocarbon acts as the electron donor and the diazine as the electron acceptor in the systems studied. Chemical-shift data have provided evidence for the relative positioning of the donor and acceptor components within the various complexes. The effect of temperature on the equilibrium constant for complex formation between (1H6)benzene and pyrazine has shown that the enthalpy of formation is close to zero.
The Crystal Structure of Bis(2-chlorophenyl) Disulfide
Authors: Mak TCW , Yip WH , Chan WH , Smith G , Kennard CHL
Published: September 2010

The crystal structure of bis(2-chlorophenyl) disulfide has been determined and refined to a residual of 0.035 for 1573 observed reflections. Crystals are monoclinic, space group P21/a with Z 4 in a cell of dimensions a 7.724(1), b 22.360(7), c 7.917(2) � , β 114. 75�. The two chlorophenyl rings are synclinally related with a torsion angle of -85.0 � down the disulfide bond vector.
2-O-Methylhiascic Acid, a New Tridepside in the Lichen Parmelinopsis neodamaziana
Authors: Elix JA , Jayanthi VK , Wardlaw JH
Published: September 2010

A new metabolite has been detected in Parmelinopsis lichens and its chromatographic behaviour shown to be identical to the tridepside 2-O-methylhiascic acid (6), prepared by unambiguous synthesis.
The Mechanism of Formation of Acenaphthylene on Pyrolysis of 8-Methylcyclobuta[a]naphthalene-1,2-dione
Authors: Brown RFC , Eastwood FW , Kissler BE
Published: September 2010

Flash vacuum pyrolysis of the l-13C labelled title dione (13) gives acenaphthylene labelled predominantly at C4 (65.9%) and C1 (27.6%). This is in accord with the intermediacy of the (labelled) acyloxycarbene (5), the lactone (6) and the carbene (7). The minor leakage of label to C3 (5.8%) and C5 (0.7%) is discussed. Irradiation of labelled dione (13) in methanol with ultraviolet light gives 3-methoxy-9-methyl[1-13C] naphtho [1,2-c]furan-1(3H)-one (19).
Tropical Marine Algae. III. New Sesquiterpenes From Laurencia majuscula (Rhodophyta, Rhodophyceae, Ceramiales, Rhodomelaceae)
Authors: Coll JC , Wright AD
Published: September 2010

The isolation and structural elucidation of new sesquiterpenes from Laurencia majuscula, collected from Zoe Bay, Hinchinbrook Island, North Queensland, are reported. One collection contained the novel triquinane derivative: (1S*,2S*,3S*,5S*,8S*,9S*)- tricyclo [6.3.0.01.5] undecan-2-ol (3), and four halogenated chamigrene derivatives: the known 1(15)Z compound (4) and the new (1(15)E,2Z,4S,8R,9S)-8,15-dibromochamigra-1(15,2,1112-trien-9-ol (5), the known isoobtusadiene (6) and the new metabolite (1S,2S,4R,8R,9S)-1-chloro-2,8-dibromochamigr-11(12)-en-9-ol (7). A second collection afforded the same range of sesquiterpenes (3)-(7)and an additional tricyclic sesquiterpene related to ( Δ10)- rhodolaureol (16), namely ( Δ 11(12))-isorhodolaureol (8). The relationship was confirmed by oxidation of (8) to give the expected non-conjugated enone (15) which rearranged in slightly acidic chloroform to the conjugated enone (17), identical with the oxidation product from rhodolaureol (16).
Stereoselection in the Aprotic Conjugate Addition Reactions of Lithiated 1-Isobutylbut-2-enyl Sulfoxide, Sulfone and Phosphine Oxide With Cyclopent-2-enone and Methylcyclopent-2-enone
Authors: Haynes RK , Vonwiller SC , Hambley TW
Published: September 2010

Lithiated 4-(t- butylsulfinyl)- and 4-(t-butylsulfonyl )-6-methylhept-2-ene, and [(E)-1-isobutylbut-2-enylldiphenylphosphine oxide, undergo conjugate addition with cyclopent-2-enone and 2-methylcyclopent-2-enone to deliver mixtures of diastereomers arising from reaction through C3 of the allyl system. The relative configuration of the major product obtained from the lithiated phosphine oxide and 2-methylcyclopent-2-enone has been determined by an X-ray crystallographic study. The proportions of diastereomers formed are rationalized in terms of carbanions which have a low barrier to rotation about the C1-C2 bond of the allyl system, and steric interactions prevailing in the trans-decalyl and related transition states experienced by the reactions. The reaction of the lithiated phosphine oxide with 2-methylcyclopent-2-enone has a diastereoselection useful for synthetic approaches towards vitamin D derivatives.
Tropical Marine Algae. V. The Structure Determination of Two Novel Sesquiterpenes From the Red Alga Laurencia tenera (Rhodophyceae, Ceramiales, Rhodomelaceae)
Authors: Coll JC , Skelton BW , White AH , Wright AD
Published: September 2010

Laurencia tenera has been shown to contain two novel sesquiterpenes. The structure of the less abundant metabolite (3) was determined by single-crystal X-ray diffraction as (1S,2R,4S,5R,6R,8S,9R)-4,8-dibromo-2,5,6,9-tetramethyltricyclo[7.2.0.01.6] undecane-3-one.‡ The more abundant, but less stable metabolite (4) was investigated by extensive high-field N.M.R. spectroscopy. Its structure is proposed as (1S*,2R*,4R*,5R*,6R*,8R*)-4-bromo-2,5,6-trimethyl-11-methylenetricyclo[6.2.1.01.6]undecan-3-one.§ The sesquiterpene (3) is isomeric with the known metabolite perforatone (5).
Coriamyrtin and Tutin. A Crystallographic and Conformational Study
Authors: Gulbis JM , Mackay MF , Wong MG
Published: September 2010

X-ray analyses have defined the conformational detail of two closely related convulsants, coriamyrtin and tutin. Their structural and pharmacological similarity to picrotoxinin suggest that the three sesquiterpenes act at the same inhibitory synapses and utilize the same binding site. Their geometries, optimized by using AM1 and MacroModel , were found to be consistent with the crystallographic results.
Synthesis of the Lichen Depsides Glomelliferic Acid, Loxodellic Acid, Glomellic Acid, Their 4-Ortho-Demethyl Analogs and Oxostenosporic Acid
Authors: Elix JA , Whitton AA
Published: September 2010

Total syntheses of the lichen depsides glomelliferic acid (1), loxodellic acid (2), glomellic acid (3), 4-O-demethylglomelliferic acid (4), 4-O-demethylloxodellic acid (5), 4-O-demethylglomellic acid (6) and oxostenosporic acid (7) are reported.
Potential Antimalarials. VIII. Mono- and Di-mannich Bases of 2-(7′-Trifluoro-methylquinolin-4′-ylamino)phenol Via 2-Nitrophenols
Authors: Barlin GB , Yan JH
Published: September 2010

Di-Mannich bases have been prepared by the reaction of 2-nitrophenol and formaldehyde with dimethylamine, diethylamine, dipropylamine, pyrrolidine, piperidine, 2-, 3- and 4-methylpiperidine, 3,5-dimethylpiperidine and morpholine. The nitro compounds were reduced catalytically to the corresponding 2-aminophenols which with 4-chloro-7-trifluoromethylquinoline gave the di-Mannich bases of 2-(7′-trifluoromethylquinolin-4′-ylamino)phenol. Analogous compounds were synthesized from 3-and 5-methyl-2-nitrophenols, and pyrrolidine. The mono-Mannich compounds, 6-(3′-methylpiperidin-1′-ylmethyl)- and 6-(pyrrolidin-1′- ylmethyl)-2-(7″-trifluoromethylquinolin-4″-ylamino)pheno, were also prepared. The results for tests against a chloroquine-sensitive isolate (FCQ-27) and chloroquine-resistant isolate (K-1) of Plasmodium falciparum are reported.
Synthesis of Novel Cross-Linked Amino Acid Derivatives
Authors: Easton CJ , Peters SC
Published: September 2010

Reactions of the derivatives of cysteine (6), serine (7) and lysine (8a), with the bromide (1), afforded the corresponding cross-linked amino acid derivatives (11), (12) and (13). Of the linked species (11)-(13), the cysteine derivative (11) was found to be the most stable under a variety of conditions. A mixture of the cross-linked serine derivative (12) and the cysteine derivative (6) in chloroform containing triethylamine reacted to give the cross-linked cysteine derivative (11) and the serine derivative (7). Similarly, a mixture of (13) and (6) in chloroform reacted to give (11).
The Formation of Ketones by a Reaction Equivalent to R-+R′COCH2+→R′COCH2R
Authors: Katritzky AR , Wrobel L , Savage GP , Deyrupdrewniak M
Published: September 2010

A general method has been developed for the overall transformation of α- bromo ketones to α-alkyl or α-aryl ketones , with benzotriazole being used as a synthetic auxiliary. α- Benzotriazolyl ketones , when converted into their phenylhydrazones, reacted smoothly with alkyl and aryl Grignard reagents, which displaced benzotriazolate, to give the corresponding α-alkyl or α-aryl hydrazones. In some cases, these hydrolysed directly to the α-alkyl or α-aryl ketones. In each case, the product was treated with 2,4-dinitrophenylhydrazine to isolate the target ketones as the corresponding 2,4-dinitrophenylhydrazones.
Thermal-Degradation of Polymers and Polymer Models. V. A Model for Copoly(styrene-methyl methacrylate)
Authors: Fallon GD , Holland KA , Rae ID
Published: September 2010

The synthesis of (�)- and meso-dimethyl 2,3-dimethyl-2,3-bis(2′-methyl-2′-phenylpropyl)butane-dioate from methyl 2,4-dimethyl-4-phenylpentanoate , via a silyl enol acetal, is described. The X-ray structure of the meso isomer shows serious distortions from normal bond lengths and angles, most notably a length of 162.7(4) pm for the crowded central C-C bond. The compounds were synthesized as models for head-to-head units which might form by chain termination through dimerization of macroradicals during copolymerization of styrene and methyl methacrylate . Thermal degradation of the diphenyl -substituted diesters at 210° gave products which may have formed by plausible routes from radicals resulting from homolytic cleavage of the crowded C-C bond. Inclusion of the phenyl groups makes the molecules more crowded than the corresponding tetraesters which were reported earlier, and a comparative rate study shows that the aromatic compounds are less stable to heat as a result of the penultimate effects of greater crowding at carbons which are β to the thermally vulnerable bond.
Pyrolysis of Aryl Azides.X. Effects of Azide Concentration on Rate Constants and Product Yields
Authors: Dyall LK , Smith PAS
Published: September 2010

First-order rate constants (k1) have been measured for pyrolysis of azidobenzenes in decalin solution, in the presence of a free-radical chain inhibitor to prevent any induced decomposition. The new values of k1 for the spontaneous unimolecular thermolysis are lower than previously reported ones, and require revision of published neighbouring group effects. Product yields ( azo compound and primary amine) vary with initial concentration of azide in ways which suggest the species responsible for induced decomposition is not triplet arylnitrene , but a solvent-derived free radical. There is no evidence for induced decomposition when nitrobenzene is the solvent. For aryl azides with no neighbouring group effects operating in their pyrolysis, the Arrhenius parameters Eact and ΔSactobey a precise linear relationship.
Structure and Synthesis of the Lichen Xanthone Isoarthothelin (2,5,7-Trichloronorlichexanthone)
Authors: Elix JA , Jiang H , Portelli VJ
Published: September 2010

The structure of isoarthothelin (2,5,7-trichloro-1,3,6-trihydroxy-8-methyl-9H-xanthen-9-one or 2,5,7-trichloronorlichexanthone)(2), a metabolite of an Australian Buellia species and Lecanora broccha, was confirmed by total synthesis. Previous reports of the natural occurrence of (2) refer for the most part to an isomeric compound.
Potential Antimalarials. XI. 4'-Chloro-3-(substituted amino)-methyl-5-(7-trifluoromethylquinolin-4-ylamino)biphenyl-2-ols
Authors: Barlin GB , Jiravinyu C
Published: September 2010

Syntheses are reported for 3-(t-butylamino)methyl-4′-chloro-5-(7′-trifluoromethylquinolin-4′-(ylamino)biphenyl-2-ol (5b) and analogous Mannich bases from diethylamine, pyrrolidine, piperidine, 3- and 4-methylpiperidine, 4-benzylpiperidine and 4-benzylpiperazine via N- substituted 3-aminomethyl-4′-chloro-5-nitrobiphenyl-2-ols (9). These compounds have been prepared for evaluation as antimalarials.
Carbanion Rearrangements in the Gas Phase: The Unusual Claisen Rearrangement of Deprotonated Allyl Vinyl Ether
Authors: Eichinger PCH , Bowie JH
Published: September 2010

Allyl vinyl ether is reported to undergo a facile Wittig rearrangement to yield penta-1,4-dien-3-ol under base- catalysed conditions in the condensed phase. In marked contrast, the Wittig rearrangement is not a major reaction in the gas phase. Instead, initial rearrangement occurs by a Claisen process and subsequent fragmentations involve some of the most complex interconversions yet proposed for negative ions.
Dysidamide, a Novel Metabolite From a Red Sea Sponge Dysidea herbacea
Authors: Carmely S , Gebreyesus T , Kashman Y , Skelton BW , White AH , Yosief T
Published: September 2010

A hexachloro metabolite, dysidamide (2) has been isolated from a Red Sea sponge Dysidea herbacea. The structure of (2) has been established from spectroscopic and chemical evidence, and confirmed by an X-ray crystal structure determination. Crystals of (2) are orthorhombic P212121, a 20.509(13), b 18.411(11), c 11.356(9)Ǻ, Z 8. The structure was refined by least-squares methods to a residual of 0.049 for 2277 'observed' reflections. Two different conformations of the molecule are present in the crystal.
Halogenated Terpenoids. XXVI. The Carvone Tetrabromides and Carvone Pentabromides
Authors: Carman RM , Venzke BN
Published: September 2010

Two novel carvone tetrabromides and two novel carvone pentabromides are reported. n.m.r. data for a number of carvone tetrabromides and pentabromides are compared. A structure is assigned to Wallach's1 'α-carvone pentabromide', m.p. 142-143°.
The Pyrolysis of 4,7-Dimethylcyclobuta-[b]naphthalene-1,2-dione; Failure to Detect Hydrogen Migration in 5,8-Dimethyl-2,3-didehydronaphthalene
Authors: Brown RFC , Browne NR , Coulston KJ , Eastwood FW
Published: September 2010

5,8-Dimethylnaphthalene-2,3-dicarboxylic anhydride (8) is not significantly decomposed on pyrolysis at 950°/0.05 mm. The corresponding cyclobutanaphthalene-1,2-dione (9) on pyrolysis at 670°/0.06mm gave 1,4-dimethylnaphthalene (17%), 1,4,7,10- tetramethyldibenzo [ b,h ] biphenylene (15) (3%), unidentified products, and much carbon. There was no evidence for hydrogen migration leading to the rearrangement of the 2,3-didehydronaphthalene (10) to the 1,2-didehydronaphthalene (11).
The Synthesis of Some Thiazolo- and Oxazolo[5,4-d]pyrimidines and Pyrimidinylureas. II.
Authors: Hurst DT , Atcha S , Marshall KL
Published: September 2010

The reaction of some 5-acylaminopyrimidines, having 4-oxo groups, with phosphorus oxychloride or phosphorus pentasulfide leads to the oxazolo- or thiazolo -[5,4-d] pyrimidines respectively. The condensation of amidinothiourea with pentane-2,4-dione leads to 1-(4,6-dimethylpyrimidin-2-yl)urea directly, and subsequent reaction with diethyl acetylene- dicarboxylate gives a thiazolylaminopyrimidine . The synthesis of some other pyrimidinylureas and thioureas has also been carried out.
Potential Antimalarials. XIII. Mono-Mannich Bases of 4-[7-Chloro (and 7-trifluoromethyl)quinolin-4-ylamino] and 4-(7-Bromo-1,5-naphthyridin-4-ylamino)-3-methylphenol
Authors: Barlin GB , Jiravinyu C
Published: September 2010

The preparation of di-Mannich bases derived from 4-[7-chloro(and 7-trifluoromethyl)quinolin-4-ylamino] and 4-(7-bromo-1,5-naphthyridin-4-ylamino)-3-methylphenol are reported. In tests for antimalarial activity against the FCQ-27 ( chloroquine -sensitive) and K-1 ( chloroquine -resistant) isolates of Plasmodium falciparum in vitro, the 3-methylphenols were shown to be less active than their demethyl analogues reported previously.
4-O-Methylhiascic Acid and 5-O-Acetyl-4-O-methylhiascic Acid, Two New Lichen Tridepsides
Authors: Elix JA , Yu J , Tonsberg T
Published: September 2010

A new metabolite has been
detected in the lichen Parmelinopsis schindleri and its chromatographic behaviour shown to be
identical to the synthetic tridepside 4-O-methylhiascic acid (6). The isolation, characterization and total synthesis of 5-O-acetyl-4-O-methylhiascic acid (7), a new tridepside from the lichen Koerberiella wimmeriana is described.
Molecular Topology of Di(9-Anthryl)Ethanedione (9,9'-Anthril) and Some Generically Related Cyclic 1,2-Diketones
Authors: Becker HD , Skelton BW , White AH
Published: September 2010

The molecular structures of di (9-anthryl) ethanedione (9,9′-anthril) and those of four 1,2-diketones derived from 9,9′-anthril by way of intramolecular cycloadditions were investigated by single-crystal X-ray diffraction studies. Two crystal modifications of 9,9′-anthril were available and found to differ in the dihedral angles (43.9 and 178.3°) about the 1,2-dicarbonyl moiety. The 1,2-dicarbonyl group of the cyclobutanedione moiety in the anthril 4π+4π cyclomer is associated with a dihedral angle of 2.6°. In the anthril isomer derived by 4π+2π cycloaddition, an exceptionally long single bond is indicative of molecular strain. The molecular structures of a keto enol and of a novel 1,2-diketo substituted triptycene, both obtained from the 4π+2π cyclomer by acid-catalysed rearrangement and dehydrogenation, respectively, were established. The topological and spectroscopic differences between the keto en01 and its 1,2-diketo precursor are discussed.
Approaches to a Key Lactone Intermediate Required for the Synthesis of Pyranonaphthoquinone Antibiotics
Authors: Brimble MA , Spicer JA
Published: September 2010

Addition of 2-trimethylsilyloxyfuran (19) to naphthoquinone (20) gave in 91% yield the furo [3,2-b] naphtho [2,1-d]furan (18) which upon treatment with ceric ammonium nitrate gave the hydroxy ester (24) in 70% yield. Attempts to induce an intramolecular transesterification of hydroxy ester (24) to bislactone (6), a key intermediate required for the synthesis of several pyranonaphthoquinone antibiotics, were unsuccessful. Hydroxy ester (24), however, is closely related to the antibiotic juglomycin (32).
Topological Resonance Energies: a Caveat
Authors: Langler RF
Published: September 2010

Even hydrocarbon Lewis structures which must have two non-bonding electrons are examined. Such structures are shown to have surprisingly large topological resonance energies. Three theorems are presented which permit the general conclusion that the propensity
for topological resonance energies to lead to 'obviously false chemical conclusions' originates with the 'π-energies' produced from the matching polynomials for even hydrocarbons with non-bonding electrons.
Synthesis of Casein-Related Peptides and Phosphopeptides. XII. The Synthesis of O-Phosphoseryl-Containing Peptides With Site-Specific Serine Residues
Authors: Perich JW , Johns RB
Published: September 2010

The synthesis of the two Ser/Ser(P)-containing peptides H-Ser-Ser(P)-Ser(P)-NHMe.CF3CO2H and H-Ser(P)-Ser-Ser(P)-NHMe.CF3CO2H is described. The selective use of Boc-Ser(PO3Ph2)-OH and Boc -Ser( Bzl )-OH in the Boc mode of peptide synthesis for the preparation of the protected Ser( Bzl )/Ser(PO3Ph2)-containing peptides is followed by platinum-mediated hydrogenolytic cleavage of the benzyl ether and phenyl phosphate groups.
Vinylindenes and Some Heteroanalogues in the Diels-Alder Reaction. IX. 3-Vinylbenzofuran and 1,4-Naphthoquinone
Authors: Pearson JR , Porter QN
Published: September 2010

3-Vinylbenzofuran and 1,4-naphthoquinone react to give r-5a,6,c-12a,c-12b-tetrahydroanthra-[1,2-b]benzofuran-5,13-quinone. This adduct undergoes ring opening to 2-(2-hydroxyphenyl)-anthraquinone with base and oxygen, but shows no rearrangement to anthra[2,3-b]benzofuran- 5,13-quinone.
Methyl 12-Hydroxyakuammilan-17-oate: a New Indolenine Alkaloid From Rauwolfia sumatrana
Authors: Arbain D , Adnan AZ , Birkbeck AA , Byrne LT , Harahap AK , Sargent MV
Published: September 2010

Extraction of the leaves of Rauwolfia sumatrana Jack ( Apocynaceae ) has yielded the new akuammicine-type alkaloid methyl 12-hydroxyakuammilan-17-oate (2) the structure of which followed from its spectral properties. v
A Facile Synthesis of a 2,2,3,3-Tetrasubstituted Tetrahydropyran
Authors: Brecknell DJ , Carman RM , Robinson WT , Schumann RC
Published: September 2010

An unusually facile acid- catalysed condensation has been observed between acetone and the unsaturated diol (3), producing a mixture of isomeric bicyclic tetrahydropyrans (6) and (8), with the formation of a new fully substituted carbon-carbon single bond. The structures were determined by n.m.r. and that of the major product (6) was confirmed by X-ray crystallography.
Towards the Synthesis of a Dewar Furan Stabilized by a Pinching Group: the Role of Dewar o-Xylylenes as Dienes and Dienophiles
Authors: Warrener RN , Pitt IG , Russell RA
Published: September 2010

The synthesis of a photosubstrate (42) suitable for the production of a Dewar furan (46) containing a four-carbon bridge at the 1,4-position is described. The route to this product illustrates an example of transfer technology in synthesis, by using the oxanorbornadiene (29). Other active species such as Dewar benzene (32) and Dewar o-xylylene (50) play key roles as intermediates. Diels-Alder cycloadditions are also central to the overall strategy, and some observations are made regarding the facial specificities operating, especially in regard to Dewar o-xylylene (50) and its dimerization. Attempts to isolate the photoproducts, presumably involving the Dewar furan (46) as intermediate, were unsuccessful.
Intramolecular Oxidative Coupling of Aromatic Compounds. I. Oxidation of Diphenolic Substrates
Authors: Krauss AS , Taylor WC
Published: September 2010

The synthesis of (2RS,3SR)-1-(3,5-dihydroxy-4-methoxyphenyl)-(4-hydroxy-3,5-dimethoxy-phenyl)-2,3-dimethylbutan-1-one (26) is described. Diphenolic oxidative coupling of (26) did not produce a eupodienone -type product. An aryltetralin derivative was formed instead by aryl-benzyl coupling and was further oxidized to the novel oxa spiro dienone (63). The acetoxy compound (71) derived by reduction of the carbonyl group in (26) gave a similar product (72).
The Preparation of Dimethyl (1-α,2-β,5-β,6-α)-9-Oxatricyclo[4.2.1.02,5]nona-3,7-diene -3,4-dicarboxylate: a New Transfer Reagent for Dimethyl Cyclobutadiene-1,2-dicarboxylate
Authors: Russell RA , Longmore RW , Weerasuria KDV , Warrener RN
Published: September 2010

A synthesis, based on transfer technology, of the title compound is reported and its advantages over previously described reagents are discussed.
Reaction of t-Butoxy Radicals With Cyclic Alkenes Studied by the Nitroxide Radical-Trapping Technique
Authors: Busfield WK , Grice DI , Jenkins ID , Thang SH
Published: September 2010

The pattern of reactions occurring between t- butoxy radicals and a number of cyclic alkenes has been investigated by the nitroxide radical-trapping technique. The major reaction pathway is allylic abstraction unless this position is at a bridgehead as in norbornene where the major pathway is radical addition. The technique is sufficiently sensitive to identify minor reaction pathways of non-allylic substitution and radical addition when in the presence of extensive allylic substitution. Some stereoselective effects are also detected.
Activation Parameters for Ring Opening of (Bicyclo[n.1.1]alk-1-yl)methyl Radicals
Authors: Pigou PE , Taylor DK
Published: September 2010

Ring opening of the (bicyclo[1.1.1]pent-1-yl)methyl (4), (bicyclo[2.1.1]hex-1-yl)methyl (5) and (bicyclo[3.1.1]hept-1-yl)methyl (6) radicals has been investigated by semiempirical molecular orbital theory MINDO/3 and AM1) and by experiment. Our results indicate that (4) ring-opens extremely rapidly, with an estimated energy barrier of less than 22 kJ mol-1. The higher homologues (5) and (6) rearrange more slowly with barriers of about 42.2 and 46.0 kJ mol-1 respectively. This trend is also observed in the MINDO/3 and AM1 results, with the latter giving the better agreement with experiment.
Studies on the Stereochemical Characterization of N-Methylated Amino Acids
Authors: Ang SG , Low SH
Published: September 2010

Various methods that could be used to determine the absolute configuration of N,N- dimethylated amino acids were investigated. Two methods utilizing 1H nuclear magnetic resonance (N.M.R.) spectroscopy were successful. The first involved the conversion of the N,N- dimethylated amino acids into diastereoisomers by reaction with methyl (S)-(+)- mandelate . In the second method, the N,N- dimethylated amino acids were amidated with 3,5-dinitroaniline, and 1H n.m.r. analysis was carried out with the addition of a chiral solvating agent, (R)-(-)-1-(9-anthryl)-2,2,2-trifluoroethanol [(R)-(-)-atfe ]. Another method involving the use of high-performance liquid chromatography ( h.p.l.c .), with bis (L-aspartic cyclohexylamide )copper(II) complex CuII (L- Aspchex )2, as the chiral mobile phase was also examined but was found to be unsuccessful in resolving the D- and L-isomers of N,N- dimethylated amino acids.
Crystal Structure of N,N'-Diphenyl-guanidinium m-Chlorobenzeneseleninate
Authors: Antolini L , Marchetti A , Preti C , Tagliazucchi M , Tassi L , Tosi G
Published: September 2010

The synthesis, and crystal and molecular structure of N,N′- diphenylguanidinium m- chlorobenzeneseleninate (C19H18CIN3O2Se), Mr 434.78, are reported. The crystal lattice of the compound belongs to the monoclinic space group P21/c with a 7.277(1), b 12.793(2), c 20.013(4) Ǻ, β 94.733(12)°, V 1859.8 Ǻ3, Z 4, Dobs 1.53 (by flotation), Dcalc 1.555 g cm-3, λ(Mo Kα ) 0.71069 Ǻ, μ 21.0 cm-1, F(000) 880, T 293 K, R 0.057 and Rw 0.059 for 1745 unique observed reflections with I>2.0σ(I). The crystal packing consists of parallel layers of anions intercalated with cations interacting through electrostatic contacts. Vibrational spectra have been also recorded, and are discussed.
An Approach to the Total Synthesis of Diterpenoid Plant Growth Substances Isolated From Gametophytes of the Fern Genus Anemia
Authors: Chiu CKF , Mander LN , Stuart AD , Willis AC
Published: September 2010

Reduction of the oxoindan acid (9) by potassium in liquid ammonia followed by in situ alkylation with 3-methylbut-2-enyl bromide furnished enol ether (14) which was transformed into the acetal (17) and thence aldehydes (18; R = COCH3 and COCHCl2). Acid- catalysed aldol reactions then afforded the ethanoindene derivatives (19; R=COCH3 and COCHCl2). Further elaboration gave carbinol (28) which is envisaged as an intermediate for the total synthesis of the diterpenoid antheridiogens obtained from gametophytes of the fern genus Anemia, including acid (2). The relative stereochemistry of acetal (17) was established by X-ray crystallographic analysis.
Ritter Reactions. VII. Diverse Reactivity of the 3-Azatricyclo[5.3.1.04,9]-undec-2-ene System With Dimethyl Acetylenedicarboxylate
Authors: Ung AT , Bishop R , Craig DC , Scudder ML , Yunus J
Published: September 2010

The imine functionality of the 3-azatricyclo[5.3.1.04,9]undec-2-ene derivatives (3a-c) reacts with dimethyl acetylenedicarboxylate to yield the lactam (5), the amino ester (6), and the oxopyrroline (7) respectively. Crystal structures of (6) [C31H34N2O5, Pca21, a 17.736(1), b 9.8412(4), c 15.584(1) � , Z 4, R 0.032] and (7) [C33H36N2O6, Pca21, a 14.0610(8), b 9.6602(6), c 20.818(1) � , Z 4, R 0.038] were determined. These widely differing modes of reaction result from the nature of the imine C2 substituent present in the starting material(3). Tentative mechanistic explanations are presented.
Candida cylindracea Lipase-Catalyzed Synthesis of Retinyl and Oleyl Palmitates; Carbon Chain Length Dependence of Esterase Activity
Authors: Oconnor J , Petricevic SF , Stanley RA
Published: September 2010

The ester activity of lipase from Candida cylindracea has been investigated in paraffin/water biphasic mixtures and in an aqueous ethanol solution. In the biphasic mixture with paraffin as an inert solvent, the equilibrium was found to be at approximately 75% esterification of palmitic acid and oleyl alcohol. Analysis was by a titrimetric assay. In a monophasic solvent of aqueous ethanol, more than 50% of retinol was converted into retinyl palmitate in 1 h. Analysis was by spectrofluorophotometry. Thus the Candida lipase can synthesize esters in the presence of a bulk water phase. The formation of the esters over the hydrolysis products is thought to be due to the partitioning of the hydrophobic reactants between the surface and interior of the organic phase. The esterase
activity of the lipase has been determined against a range of 4 nitrophenyl alkanoates (carbon chain length 2-18) at pH 7 and 37�C in Tris buffer. Maximum activity occurred with the butanoate ester. The Michaelis-Menten parameters were determined for this substrate in the presence and absence of butan-1-ol which inhibited the reaction. The range of these data illustrates the potential for using this enzyme for biocatalytic purposes.
Isolation, X-Ray Crystal Structure and 59Co Nuclear Magnetic Resonance Spectral Investigation of the Partially Nitrated Cobalt(III) Acetylacetonato Complex [Co(acac)2(NO2acac)]
Authors: Appleton TG , Gahan LR , Oliver PJ
Published: September 2010

The complex [Co( acac )2(NO2acac)] has been isolated after fractional crystallization from a reaction mixture of [Co( acac )3] and nitrating agent. The complex crystallizes in the triclinic space group P1, with c 14.557(2) � , α 78.98(1), β 83.71(2), γ75.32(1)° and Z 2. The structure refined to a final R value of 0.074 for 2287 'observed' [I > 3 σ(I)] reflections. The structure consists of discrete complex molecules with the cobalt atom surrounded by six oxygen atoms at the corners of a distorted octahedron. The NO2 group is twisted at 50.7� to the chelate ring on which it is situated and has little influence on the geometry, with intrachelate and interchelate oxygen-oxygen separations essentially the same as those found in [Co( acac )3]. The 59Co n.m.r. spectra of the [Co( acac )2(NO2acac)] complex, as well as [Co( acac )3], [Co(NO2acac)3] and [Co( acac )(NO2acac)2], have been recorded, this resonance being particularly sensitive to substitution on they γcarbon atom of the acetylacetonato chelate ring. The 59CO relaxation rates for the [Co( acac )2(NO2acac)] and [Co( acac )(NO2acac)2] complexes are faster than that displayed by the symmetric [Co(NO2acac)3] complex, (1948 � 20, 2765 � 30 and 1696 � 20 s-1, respectively). The results obtained for the relaxation rates for these complexes are compared with those obtained for similar halide-substituted complexes [Co( acac )3-n( Xacac )n] � (X = Cl , Br, I; n = 0-3).
Chiral Sulfur Compounds. XV. Diastereoselective Additions of Lithiated S-Benzyl-N-t-butyldiphenylsilyl-S-methyl-sulfoximine to Imines and Aldehydes
Authors: Pyne SG , Dikic B , Skelton BW , White AH
Published: September 2010

The lithium salt of racemic S-benzyl-N-t- butyldiphenylsilyl-S-methylsulfoximine (2) undergoes 1,2-addition to imines that have been activated by precomplexation with boron trifluoride diethyl etherate (BF3.Et2O), and aldehydes , with high diastereoselectivity. The relative lS*,2S.*,S*s stereochemistry of the major diastereomeric adducts of (2) and EtCH = NPh and PriCH = NPh , and the relative lS *,2S*,S*s stereochemistry of the major diastereomeric adduct of (2) and propanal were unequivocally determined by single-crystal X-ray structure analysis. An open transition state has been proposed to account for the stereochemical outcome of these reactions.
Synthesis of New Lichen Xanthones
Authors: Elix JA , Crook CE , Hui J , Zhu ZN
Published: September 2010

The unambiguous total synthesis of seventeen chlorine-containing derivatives of norlichexanthone (1,3,6-trihydroxy-8-methyl-9H-xanthen-9-one) has been achieved by using the condensation of an appropriately substituted methyl or ethyl orsellinate and phloroglucinol or 2-chlorophloroglucinol in the key step.
An N.M.R. Investigation of Ground-State Polarization of Some Substituted Aromatic Systems
Authors: Collins MJ , Hatton PM , Sternhell S
Published: September 2010

The previously established n.m.r. method for estimating mobile bond orders was applied to the investigation of ground-state polarization of benzene derivatives with ortho or para pairs of +R/-R substituents, naphthalene and five heteroaromatic systems (furan, thiophen, pyrrole, quinoline and pyrazole). Evidence for significant ground-state polarization which is solvent-independent was found in a number of these systems, especially benzene, pyrrole and pyrazole.
On the Structure of Silica Glass and Water
Authors: Lidin S , Andersson S , Fogden A , Jacob M , Blum Z
Published: September 2010

A simple mechanism for alteration of the local structure of SiO2 or H2O polymorphs by flipping of Si-O-Si or O-H---O groups is given. This operation provides a natural basis for the interpretation of structural transformations. When applied in an ordered manner the flipping motivates the transition between crystalline polymorphs. Similarly the disorder produced by random flipping models the corresponding melting transition, yielding simple descriptions of the structure of silica glass and water.
Syntheses of Karwinaphthol B, 7-Methoxyeleutherin and Ventiloquinone E
Authors: Cameron DW , Crosby IT , Feutrill GI , Pietersz GA
Published: September 2010

Acylation of the aryl nitromethane (35) with (9) gave the enone (45), which underwent cyclization to the tricyclic system (50). Thermally induced aromatization to the naphthopyran (51) and oxidation gave ventiloquinone E (3). On selective demethylation this gave ventiloquinone G methyl ether (54). Analogous chemistry based on the aryl nitromethane (57) gave tricyclic nitro compound (60). On thermally induced aromatization this gave karwinaphthol B (5), while application of the Nef reaction and concomitant oxidation gave 7-methoxyeleutherin (2).