bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of bioactive 5α,8α-epidioxy sterols from the marine sponge Luffariella cf. variabilis
Authors: Gauvin Anne , Smadja Jacqueline , Aknin Maurice , Faure Robert , Gaydou Emile-Marcel
Published: April 2011

The lipid extract of the marine sponge Luffariella cf. variabilis from Mayotte (Indian Ocean) has proven to be an extraordinarily rich source of a wide variety of unusual steroids belonging to the 5α,8α-epidioxy sterol family. Ten epidioxy sterols have been identified: 5α,8α-epidioxycholesta-6,22-dien-3β-ol, 5α,8α-epidioxycholest-6-en-3β-ol, 5α,8α-epidioxy-24(ξ)-methylcholesta-6,22-dien-3β-ol, 5α,8α-epidioxy-24(S)-methylcholest-6-en-3β-ol and its epimer (24R), 5α,8α-epidioxy-24(S)-ethylcholesta-6,22-dien-3β-ol and its epimer (24R), 5α,8α-epidioxy-24(S)-ethylcholest-6-en-3β-ol and its epimer (24R), along with 5α,8α-epidioxy-24(ξ)-methylcholesta-6,9(11),22-trien-3β-ol. Their structures were determined by nuclear magnetic resonance (1H, 13C) and electron impact mass spectrometry. The mixture of the 10 steroids showed inhibitive activity against the human T-cell leukemia/lymphotropic virus type I (HTLV-I) and also displayed cytotoxic activity against the human breast cancer cell line (MCF7WT).Key words: Luffariella cf. variabilis, marine sponge, 5α,8α-epidioxy sterols, antitumor and antiviral activities.
Synthesis and characterization of two new "pincer" complexes of zinc(II). The X-ray crystal structures of the five coordinate complexes [ZnCl2{η3-NN'N-2,6-(R2NCH2)2C5H3N}] (R = n-Bu or Me)
Authors: Río Ignacio del , Gossage Robert A , Hannu Milja S , Lutz Martin , Spek Anthony L , Koten Gerard van
Published: April 2011

The potentially terdentate NN'N donor ligand 2,6-bis[di-(n-butyl)aminomethyl]pyridine (1) does not form a stable, isolable Ru complex using any standard Ru starting materials. This is in contrast to the dimethylamino derivative 2. In the presence of Zn metal as a reducing agent, the treatment of hydrated ruthenium trichloride with 2 leads instead to the isolation of a diamagnetic Zn(II) complex (3) of general formula [ZnCl2(1)]. Analysis of 3 (NMR, X-ray) reveals the complex to be a mononuclear Zn halide compound containing ligand 1 in an η3-NN'N bonding motif. The Zn atom is found to be five-coordinate and in a geometry best described as midway between trigonal bipyramidal and square pyramidal in structure. Similar experiments using 2 produce an analogous Zn species (4) which has likewise been fully characterized (NMR, X-ray) and found to be similar to 3 although the metal is in a distinctly square pyramidal environment. These compounds are viewed as relatives of the class of Zn "pybox" catalysts.Key words: pincer complexes, zinc(II) compounds, X-ray crystal structure.
Dew points of ternary methane + water + methanol. Measurement and correlation
Authors: Blanco Sofía T , Velasco Inmaculada , Rauzy Evelyne , Otín Santos
Published: April 2011

A water and methanol dew point generation device has been built up and tested. Experimental measurements of dew point for ternary methane + water + methanol were carried out between 1.01 × 105 Pa to 97.84 × 105 Pa and the temperature range from 248.71 to 282.93 K. A EOS-CR method (equation of state  chemical reticular) reproduces very accurately the experimental curves independently of the pressure and temperature ranges.Key words: dew point, experimental method, equation of state, excess function.
Classical analysis of intermolecular potentials for ArCO2 rotational collisions
Authors: Belchior J C , Braga J P , Lemes N HT
Published: April 2011

Classical trajectory calculations have been performed for four potential energy functions to describe ArCO2 collisions. A comparison is given between classical cross sections calculated using the two most recent potential surfaces and two older intermolecular potential surfaces based on the electron gas model. The two-dimensional atom ellipsoid model has also been applied for the study of multiple collisions. The model was able to predict such a phenomenon in agreement with quantum scattering results previously published for an ab initio potential surface in the region of very low collision energy. On the other hand, the two older potentials showed multiple collision effects at very high energies. The comparison of the cross sections showed some deviations from the experimental data. By introducing two parameters, a modified surface is proposed by changing the most recent intermolecular potential. In this case the agreement with experimental measurements and theoretical scattering cross sections was considerably improved. It is concluded that global potential surfaces for describing ArCO2 interaction are not well established. To achieve the requirement of reproducing all properties of this system, the present work suggests that one needs further experimental and theoretical investigations. Key words: classical trajectories, dynamics, cross sections, ArCO2 collisions, potentials.
Synthesis, characterization, and reactivity of manganese(II) and iron(II) trifluoroacetates. Crystal and molecular structure of two linkage isomers of polynuclear [Mn(CF3COO)2(THF)2]n
Authors: Calderazzo Fausto , Englert Ulli , Pampaloni Guido , Passarelli Vincenzo , Serni Giovanna , Wang Ruimin
Published: April 2011

The trifluoroacetates of manganese(II) and iron(II) have been prepared as THF or DMF adducts by reaction of metallic manganese or pentacarbonyliron(0) in THF or DMF, respectively, with CF3COOH(CF3CO)2O. Crystals of two linkage isomers of polynuclear [Mn(CF3COO)2(THF)2]nhave been obtained differing in the distribution of the bridging trifluoroacetato groups within the repeating units, namely [(THF)2Mn(µ-CF3COO)3Mn(THF)2(µ-CF3COO)] and [(THF)2Mn(µ-CF3COO)2Mn(µ-CF3COO)2(THF)2]. Photolysis of Fe(CO)5in CF3COOH(CF3CO)2O mixtures or in neat (CF3CO)2O gives the trifluoroacetato of iron(II) Fe(CF3COO)2, whose formation may occur through the intermediacy of Fe2(CO)9.Key words: linkage isomers, manganese, iron, carboxylates, X-ray structure.
Hydrogenation of carbon dioxide catalyzed by ruthenium trimethylphosphine complexes  Effect of gas pressure and additives on rate in the liquid phase
Authors: Thomas Colin A , Bonilla R Jason , Huang Yong , Jessop Philip G
Published: April 2011

Kinetic and mechanistic studies of CO2 hydrogenation were performed in liquid triethylamine and at subcritical CO2 pressures to avoid complications from phase behaviour that are observed under supercritical conditions. Kinetic measurements of the hydrogenation of CO2 to formic acid, catalyzed by RuCl(O2CMe)(PMe3)4, support a CO2 insertion mechanism. The reaction is first-order in both H2 and CO2 under most conditions. The rate is strongly dependent on the choice of additive, with methanol giving the greatest rates. Because only trace amounts of methanol are needed, the effect of the additive is believed to involve direct interactions with the catalyst rather than changes in the physical properties of the reaction medium. The optimized rates exceed 3500 h1. Addition of an inert gas affects the rate of the reaction, probably via the phenomenon of gas expansion of the liquid phase.Key words: carbon dioxide, homogeneous catalysis, hydrogenation, formic acid, expanded liquids.
Synthesis and coordination studies of new aminoalcohol functionalized tertiary phosphines
Authors: Durran Sean E , Smith Martin B , Slawin Alexandra MZ , Gelbrich Thomas , Hursthouse Michael B , Light Mark E
Published: April 2011

The synthesis of two new aminoalcohol functionalized tertiary phosphines o-Ph2PCH2N(H)C6H4(OH) (I) and o-Ph2PCH2N(H)C6H4(CH2OH) (II) are reported. Oxidation with aqueous H2O2gave the corresponding phosphine oxides o-Ph2P(O)CH2N(H)C6H4(OH) (III) and o-Ph2P(O)CH2N(H)C6H4(CH2OH) (IV) (31P NMR evidence only). The ligating ability of I, II and, in several cases, the known ligand 2,3-Ph2PCH2N(H)C5H3N(OH) (V), was investigated with a range of late transition-metal precursors. Accordingly, reaction of 2 equiv of I (or II) with [MCl2(cod)] (M = Pd or Pt, cod = cycloocta-1,5-diene) gave the corresponding dichloro metal(II) complexes [MCl2(I)2] (M = Pd 1; M = Pt 2) and [MCl2(II)2] (M = Pd 3; M = Pt 4) in which I (and II) P-coordinate. Solution NMR studies reveal that 2 and 4 are exclusively cis whereas 1 and 3 are present as a mixture of cis and (or) trans isomers [4.7:1 (for 1); 2.2:1 (for 3)]. Reaction of 2 equiv of II with [Pt(CH3)2(cod)] gave the neutral complex [Pt(CH3)2(II)2] (5) whose X-ray structure confirmed a cis disposition of "hybrid" ligands. In contrast, reaction of I with [Pt(CH3)2(cod)] gave initially [Pt(CH3)2(I)2] (6) which, upon standing, afforded several products possibly reflecting an increased acidity of the phenolic groups of ligated I. Chloro bridge cleavage reactions of [{Ru(µ-Cl)Cl(p-cymene)}2] or [{Rh(µ-Cl)Cl{C5(CH3)5}}2] with I (or II) proceeds smoothly and gave the mononuclear complexes [RuCl2(p-cymene)I] (7), [RuCl2(p-cymene)II] (8), [RhCl2{C5(CH3)5}I] (9), and [RhCl2{C5(CH3)5}II] (10) in good yield. X-ray crystallography confirms both ruthenium complexes bear P-coordinated I (or II) ligands. Molecules of 7 are linked into linear chains via O-H···Clcoordintermolecular hydrogen bonding, a feature absent in the closely related compound 8. Reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with 1 equiv of I (or II) gave the corresponding gold(I) complexes [AuCl(I)] (11) and [AuCl(II)] (12). Bridge cleavage of the cyclometallated palladium(II) dimers [{Pd(µ-Cl)(C~N)}2] [C~N = C,N-C6H4CH2N(CH3)2, C,N-C10H6N(CH3)2, C,N-C6H4N=NC6H5] with V (or I) gave the neutral complexes [PdCl(C~N)V] (13-15) (or [PdCl(C9H12N)I] (16)), respectively. Chloride abstraction from 13 (or 15) with Ag[BF4] gave the cationic complexes [Pd(C~N)V][BF4] (17) (or 18) in which V P,Npyridyl-chelates to the palladium(II) metal centre. The X-ray structures of 13 and 18 have been determined and confirm the expected coordination environments. An array of intra- and intermolecular H-bonding contacts are also observed. All compounds have been characterized by a combination of spectroscopic and analytical studies.Key words: phosphines, crystal structures, alcohols, precious metals.
Transmetalation reactions with nitrogen-containing "pincer"-class ligands on platinum(II) centers
Authors: Albrecht Martin , James Stuart L , Veldman Nora , Spek Anthony L , Koten Gerard van
Published: April 2011

The transmetalation reaction of the aryllithium compound [Li(NCN)]2 (NCN is the monoanionic "pincer" ligand [C6H3(CH2NMe2)2-2,6]-) with the cyclometalated arylplatinum complex [PtCl(NCN)] afforded the bisaryl platinum(II) complex [Pt(NCN)2] (3) containing one η3-N,C,N-terdentate and the other η1-C-monodentate-bonded pincer ligand. Spectroscopic analyses on 3 suggest that η3 to η1 interconversion of the ligand binding mode (or vice versa) is inhibited. Two independent X-ray structure determinations on crystals of 3 revealed the existence of a rare polymorph containing one and three crystallographically independent molecules, respectively, in the unit cell. A similar transmetalation reaction with lithium and platinum complexes containing heteroleptic NCNRR' ligands (NCNRR' is [C6H3(CH2NRR')-2,6]- with R = R' = Me or R = Me, R' = Et) pointed to the formation of a heterodinuclear cationic bisaryl platinum lithium species as an intermediate of a preequilibrium to the final transmetalation products, involving, rapid transcyclometalation (TCM) reactions. These TCM reactions comprise the exchange of the monoanionic NCNRR' ligands between the platinum(II) and lithium centers. A consequence of the latter properties is that the strong PtN bonds in [PtX(NCN)] complexes are considerably weakened by the presence of Li+ cations.Key words: transmetalation, transcyclometalation (TCM), platinum, bisaryl complex, polymorphism.
Synthesis and antifungal properties of benzylamines containing boronate esters
Authors: Vogels Christopher M , Nikolcheva Liliya G , Norman David W , Spinney Heather A , Decken Andreas , Baerlocher Mark O , Baerlocher Felix J , Westcott Stephen A
Published: April 2011

Addition of 3-H2NC6H4Bpin (pin = 1,2-O2C2Me4) to a series of aldehydes and 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)acetophenone afforded the corresponding benzylideneamines in moderate to high yields. Hydroboration of these imines with catecholborane (HBcat, cat = 1,2-O2C6H4) at room temperature gives, upon aqueous workup, the corresponding borylamines. An X-ray diffraction study was carried out on imine 1h derived from 9-anthraldehyde and 3-H2NC6H4Bpin. Crystals of1h were triclinic, a = 9.6793(4) Å, b = 10.7397(4) Å, c = 11.5353(4) Å, α = 105.1890(10)o, β = 97.3030(10)o, γ = 102.1480(10)o, Z = 2 with space group P[Formula: see text] and crystals of N-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-methoxybenzylamine 2c were orthorhombic, a = 8.6612(4) Å, b = 10.3794(4) Å, c = 20.6033(9) Å, Z = 4 with space group P212121. Amines have been tested for their antifungal properties against Aspergillus niger and Aspergillus flavus.Key words: benzylamines, boronate esters, aminoboron, hydroboration, antifungal.
An efficient route to 5-iodo-1-methylimidazole: synthesis of xestomanzamine A
Authors: Panosyan Francis B , Still Ian WJ
Published: April 2011

An efficient and practical route to C-5 functionalized N-methylated imidazoles is reported. 5-Iodo-1-methylimidazole was synthesized in four steps from imidazole, with complete regiospecificity, in 73% overall yield. The synthesis of xestomanzamine A, a marine natural product isolated in 1995 from an Okinawan sponge of Xestospongia sp., has been achieved using 5-iodo-1-methylimidazole in a modified Grignard reaction with a β-carboline ester moiety, in an overall yield of 59% based upon imidazole and 53% based upon tryptamine.Key words: xestomanzamine A, 5-iodo-1-methylimidazole, methyl β-carboline-1-carboxylate.
Dimeric and polymeric [Eu(tta)3L] complexes (tta = thenoyltrifluoroacetonato, L = 4,4'-bipyridine, trans-1,2-bis(4-pyridyl)ethylene, 4,4'-bipyridine- N,N'-dioxide)
Authors: Seward Corey , Wang Suning
Published: April 2011

The reaction of Eu(tta)3 (tta = thenoyltrifluoroacetonato) with 4,4'-bipyridine (bipy), trans-1,2-bis(4-pyridyl)ethylene (bipyete), and 4,4'-bipyridine-N,N'- dioxide (bipyo) yielded three distinct complexes [Eu(tta)3(bipy)(H2O)] (1), [Eu(tta)3(bipyete)(CH3OH)]·CH3OH·bipyete (2), and [Eu(tta)3(bipyo)]·CH3OH (3), respectively. Compounds 1 and 2 have a hydrogen-bond linked dimer structure, while 3 has a one-dimensional chain structure linked by coordination bonds, which further forms two-dimensional arrays, resulting in an intercalation lattice that hosts methanol guest molecules. In solution compounds 1 and 2 emit a red color, characteristic of Eu(III), when irradiated by UV light, while compound 3 has no emission either in solution or the solid state.Key words: europium complexes, luminescence, structure, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethylene, 4,4'-bipyridine-N,N'-dioxide.
2000 Macromolecular Science and Engineering Award LectureThe versatility of azobenzene polymers
Authors: Natansohn Almeria , Rochon Paul
Published: April 2011

The well-known transcistrans photoisomerization of azobenzenes produces at least three different kinds of motion in the polymer materials to which the azobenzenes are bound. The first is a photoinduced motion of the azobenzene groups only, and they can align in a selected position with respect to the light polarization. The second is a macroscopic motion of huge amounts of polymeric material, producing surface deformation, and the third is a reorganization of smectic domains in liquid crystalline polymers. These motions and their consequences are briefly discussed in relation to the polymer structure and some possible photonic applications are mentioned.Key words: photoinduced orientation, azobenzene polymers, surface gratings, photonics, thermochromism, photochromism, photorefractivity, photoinduced chirality and switching.
A topochemical rearrangement with multiple inversions of configuration
Authors: Wolfe Saul , Hsieh Yih-Huang , Batchelor Raymond J , Einstein Frederick WB , Gay Ian D
Published: April 2011

Crystalline 2-benzyloxypyridine-1-oxide rearranges slowly at room temperature to crystalline 1-benzyloxy-2-pyridone. No intermediates are detected when the process is followed by solid-state 13C NMR. The crystal structure of the pyridine-1-oxide strongly suggests that a topochemically controlled intramolecular process, in which the benzyl group migrates with retention of configuration, is not feasible. On the other hand, although somewhat disfavoured by initial solid-state O···C···O angles significantly less than the ideal 180°, intermolecular topochemically controlled processes can be envisaged that lead, with multiple inversions of configuration, either to net retention of configuration or to net inversion of configuration in the benzyl group. In contrast to the 5080% inversion observed in solution, in the solid state only inversion is observed experimentally when chirally labelled α-deuteriobenzyloxypyridine-1-oxide is allowed to rearrange.Key words: X-ray crystallography, solid-state 13C NMR, benzyl-α-D-alcohol, 2-benzyloxypyridine-1-oxide, 1-benzyloxy-2-pyridone.
Reanalysis of the biotransformation of 4(20),11(12)-taxadiene derivatives
Authors: Sun Di-An , Sauriol Françoise , Mamer Orval , Zamir Lolita O
Published: April 2011

Reanalysis of the biotransformation of 4(20),11(12)-taxadiene derivatives by Absidia coerulea ATCC 10738a unravelled additional unprecedented rearrangement reactions. 5α,7β,9α,10β,13α-pentaacetoxy-4(20),11(12)-taxadiene (1) was converted to 10 new minor taxane derivatives in addition to the previously reported C-1, C-14-hydroxylations and C-15-hydroxylated abeo-taxane. In addition, 2-deacetoxytaxinine J (2) was successfully metabolized with the same fungi.Key words: natural products, terpenes and terpenoids, microorganism, oxygenation, rearrangement.
Studies on the reduction and hydrolysis of nitroso acetals
Authors: Denmark Scott E , Guagnano Vito , Vaugeois Jean
Published: April 2011

Chemical transformation of nitroso acetals derived from tandem [4 + 2]/[3 + 2] cycloadditions of nitroalkenes have been investigated. New reduction methods were surveyed in an attempt to supplant the use of hydrogen and Raney nickel. Homogeneous catalytic hydrogenation was not successful, but samarium diiodide did effectively and selectively cleave one of the NO bonds in a number of nitroso acetals. Acid-promoted hydrolysis of the nitroso acetals produced both α-alkoxy nitrones and hydroxamic acids selectively via expected pathways.Key words: nitroso acetals, hydroxamic acids, α-alkoxy nitrones, reduction, hydrolysis.
Applications of crotyldiisopinocampheylboranes in synthesis: a formal total synthesis of (+)-calyculin A
Authors: Anderson Oren P , Barrett Anthony GM , Edmunds Jeremy J , Hachiya Shun-Ichiro , Hendrix James A , Horita Kiyoshi , Malecha James W , Parkinson Christopher J , VanSickle Andrew
Published: April 2011

The formal total synthesis of the marine metabolite (+)-calyculin A is reported. The key steps involve (i) the use of Brown allylboration chemistry to control the relative and absolute stereochemistry of homoallylic alcohol arrays, thus setting eight of the desired stereocenters; (ii) Stille coupling methodology in the construction of the cyano tetraene unit of the natural product; and (iii) a modified CornforthMeyers approach to the synthesis of the oxazole fragment.Key words: calyculin, marine natural product, phosphatase inhibitor, total synthesis, palladium catalyzed coupling reactions, allylboration reactions, aldol reactions, spiroketal, CornforthMeyers oxazole reaction.
Traceless solid-phase synthesis of 5-benzoylbenzimidazoles
Authors: Lee Kyung Joo , Janda Kim D
Published: April 2011

A traceless linker strategy for the solid-supported synthesis of 5-benzoylbenzimidazoles has been developed. A benzyl cyanide functional group was linked to 2% divinylbenzene cross-linked polystyrene through a dimethylsilyl linker. Coupling with 5-chloro-2-nitroaniline followed by oxidative decyanation gave benzophenone 11 as a key intermediate in an efficient one-pot reaction procedure. After reduction of the nitro group and oxidative cyclization with a variety of aldehydes in the presence of DDQ, a series of polymer-supported benzimidazoles was produced. Final traceless cleavage of the arylsilane linker with TBAF provided a small library of 5-benzoylbenzimidazoles.Key words: solid-support, traceless linker, arylsilane, 5-benzoylbenzimidazole.
Asymmetric synthesis of 3-aryl-substituted 2,3-dihydro-1H-isoindol-1-ones
Authors: Enders Dieter , Braig Volker , Raabe Gerhard
Published: April 2011

The first asymmetric synthesis of 3-aryl substituted 2,3-dihydro-1H-isoindol-1-ones via a tandem nucleophilic 1,2-addition ring closure procedure from SAMP and (or) RAMP hydrazones and subsequent oxidative cleavage of the auxiliary is reported.Key words: isoindolinones, asymmetric synthesis, hydrazones, 1,2-addition, NN bond cleavage.
Catalysis of transesterification reactions by lanthanides  Unprecedented acceleration of methanolysis of aryl and alkyl esters promoted by La(OTf)3 at neutral sspH and ambient temperatures
Authors: Neverov Alexei A , McDonald Todd , Gibson Graham , Brown R S
Published: April 2011

La3+ catalysis of the methanolysis of the esters p-nitrophenyl, 2,4-dinitrophenyl, and phenyl acetate (13), phenyl benzoate (4), and ethyl, i-propyl, cyclohexyl, and tert-butyl acetate (5, 6a, 6b, 7) was studied at 25°C as a function of sspH and [La(OTf)3]. The active form of the catalyst is attributed to a dimethoxy-bridged dimer of stoichiometry (La3+)2(OCH3)2, having maximum activity at sspH 8 to 9. For preparative reactions, the active catalyst can be made in situ simply by adding 0.01 equiv of La(OTf)3, and 0.01 equiv of NaOCH3 to a methanol solution containing the ester (1 M). Strong catalysis of methanolysis of both aryl and alkyl esters was observed, although tert-butyl acetate was inert. At sspH 8.5, where the catalyst is maximally active, the transesterification reactions are accelerated by 40 000-fold to 18 000 000-fold in the presence of as little as 5 mM catalyst relative to the background reaction depending on the ester structure. A mechanism for catalysis of transesterification is presented wherein the reactive species is generated by breaking a single LaOCH3 bond of the dimethoxy-bridged dimer to reveal a nucleophilic metal-bound methoxide  Lewis acid La3+ electrophilic pair.Key words: lanthanides, transesterification, methanolysis, catalysis, kinetics.
Cyclizationcycloaddition cascades for the construction of azapolycyclic ring systems
Authors: Padwa Albert , Kissell William S , Eidell Cheryl K
Published: April 2011

Cyclic 2-amidofuranones were obtained from the Rh(II)-catalyzed reaction of alpha-diazoketo substituted pyrrolidine derivatives. These compounds are derived by a [1,4]-hydrogen transfer from an initially formed carbonyl ylide dipole. Acylation of the amido-substituted furanone with pivalyl chloride provided a fused amidofuran, which underwent bimolecular Diels-Alder cycloaddition with N-phenylmaleimide. The Rh(II)-catalyzed decomposition of ethyl 2-diazo-3-oxo-(2-oxo-1-pent-4-enoyl-pyrrolidine-3-yl)propionate was also examined. In this case, the alkenyl group tethered to the amido carbonyl underwent smooth intramolecular [4+2]-cycloaddition with the amidofuran obtained from the acylation reaction. An alternate route for the synthesis of cyclic amidofurans was developed using a Pummerer induced cyclization of the thiophenyl substituted acetal derived from the aldol reaction of methoxyphenylsulfanyl acetaldehyde with α-valerolactam. Treatment of the amido-substituted acetal with dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF) generated an oxonium ion, which readily cyclized onto the adjacent carbonyl group. The amidofuran that was formed underwent an intramolecular Diels-Alder reaction when heated at 110°C in toluene. Subsequent ring opening of the transient [4+2]-cycloadduct followed by elimination of methanol and tautomerization of the resulting cyclohexadienone gave rise to the observed phenolic lactam in good overall yield.Key words: intramolecular, cyclization, Diels-Alder, diazo-ketoamide, rhodium(II).
Regioselective upper-rim functionalizations of calix[4]arene by diphenylphosphino groups
Authors: Gagnon Jonathan , Vézina Martin , Drouin Marc , Harvey Pierre D
Published: April 2011

The regioselective upper-rim functionalization of calix[4]arene have been performed to prepare all the multisubstituted diphenylphosphine derivatives. In addition, the X-ray structures of 5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetra-n-propoxycalix[4]arene and 5,11,17,23-tetrakis(diphenylphosphino)-25,26,27,28-tetra-i-propoxy-calix[4]arene have been determined. Regioselective functionalizations have been achieved using methods that involve appropriate choices of bases, alkyllithium-solvent systems, stoichiometry, and reaction times. A new and convenient method for selectively preparing derivitized calix[4]arenes at proximal positions in relative large scale quantity has been developed and involves a transesterification of the distal diester derivative into the proximal isomer.Key words: calix[4]arenes, phosphine, upper-rim, X-ray structure, transesterification.
An experimental and theoretical approach to phosphonodithioato complexes: molecular orbital analysis by hybrid-DFT and EHT calculations ontrans-bis[O-alkyl-phenylphosphonodithioato]NiII, and vibrational assignments
Authors: Aragoni M Carla , Arca Massimiliano , Devillanova Francesco A , Ferraro John R , Isaia Francesco , Lelj Francesco , Lippolis Vito , Verani Gaetano
Published: April 2011

The synthesis and the full spectroscopic characterization (FT-IR, FT-Raman,31P CP MAS NMR) of trans-bis[O-ethyl-phenylphosphonodithioato]NiII(3) are reported. On the basis of hybrid-Density Functional Theory (DFT) calculations and Extended Hückel Theory (EHT) calculations, performed on the simpler trans-bis[O-methyl-phenyl phos phono dithioato]NiII(2) model complex, the electronic structures of phosphonodithioato complexes in their ground states are fully described, and in particular the vibrational features are deeply analyzed, allowing an unprecedented insight into the vibrational features of trans-bis-O-methyl-phenylphosphono- and trans-bis(isopropylamidophosphono)-dithioato complexes of nickel(II), palladium(II), and platinum(II).Key words: phosphonodithioato complexes, IR, Raman, DFT calculation.
Organic and biological spectrochemical studies. XXIV. Electron spin resonance studies on the hydroquinone cation radical
Authors: Barabas A. B. , Forbes W. F. , Sullivan P. D.
Published: April 2011

The electron spin resonance spectrum of hydroquinone in aluminium chloride – nitromethane is interpreted in terms of cis–trans isomerism. Calculations based on the variation of the spectrum with temperature lead to a value for the potential barrier to rotation about the C—O bond of ca. 10 kcal/mole. The value of the constant QOH is discussed.
Optical rotatory dispersion studies. XLI. The absolute configuration of plicatic acid
Authors: Swan R. J. , Klyne W. , MacLean H.
Published: April 2011

The absolute configuration of the naturally occurring lignan plicatic acid (I, 2,3,6-trihydroxy-7-methoxy-2-hydroxymethyl-4-(3′,4′-dihydroxy-5′-methoxyphenyl)-tetralin-3-carboxylic acid) is shown, by optical rotatory dispersion data, to be 2R,3S,4R.
Transformations of steroidal neopentyl systems. II. Migration of acetate from the 3β- to the 19-hydroxyl in Δ5 and A/B-trans steroids
Authors: Wicha J. , Caspi E.
Published: April 2011

Acid-catalyzed hydrolysis of 19-triphenylmethyloxy-3β-acetoxy-Δ5 and -A/B-trans steroids gave the corresponding 19-acetoxy-3β-hydroxy products. In the absence of the 19-triphenylmethyloxy group, transesterification did not occur. Evidence supporting an intramolecular mechanism is presented. It is suggested that the reaction proceeds via an ortho ester VII resulting from the attack of the 19-ether oxygen on the "acetate cation" VI formed by the protonation of the acetate carbonyl.
Alkaloids of Aspidosperma excelsum Benth.
Authors: Benoin P. R. , Burnell R. H. , Medina J. D.
Published: April 2011

Three bases isolated from A. excelsum have been shown to be yohimbine, O-acetylyohimbine, and a previously unknown alkaloid C22H26N2O4 (excelsinine), which is ascribed the structure and stereochemistry shown in formula VI.
Franserin and confertin: new pseudoguaianolides isolated from franseria and ambrosia species
Authors: Romo J. , Vivar A. Romo de , Vélez A. , Urbina E.
Published: April 2011

Two pseudoguaianolides were isolated from Franseria ambrosioides Cav.: damsin of known structure and franserin whose constitution was established as a 10-hydroxytetrahydroambrosin (2). From Ambrosia confertiflora DC. were isolated the known desacetylconfertiflorin (12) and confertin, a new lactone found also as constituent of Ambrosia tenuifolia Harv et Gray. It was identified as the ketolactone 9 previously prepared from cumanin (11).
Odoratin: a new pseudoguaianolide isolated from Hymenoxis odorata DC.
Authors: Ortega A. , Vivar A. Romo de , Romo J.
Published: April 2011

The structure of odoratin, a constituent of Hymenoxis odorata DC. has been established as a pseudoguaianolide 1a with a stereochemistry related to the sesquiterpene lactones isolated in the genus Helenium.
Internal addition of acyl nitrenes to olefins
Authors: Brown Ivor , Edwards O. E. , McIntosh J. M. , Vocelle D.
Published: April 2011

Photolysis of cycloheptene-5-carbonyl azide, endo-norbornene-5-carbonyl azide and o-vinylbenzoyl azide gave very reactive acyl aziridines by internal addition of acyl nitrenes to the olefinic double bonds. Derivatives of 6-azabicyclo-[3,2,2]nonane and 1,2-dihydroisoindol-1-one were prepared. cis-2-Vinyl-cyclopropyl isocyanate, prepared photochemically at −78°, underwent Cope rearrangement at room temperature to 2,3-dihydro-1H-azepin-2-one. The mass spectra of a series of lactams are interpreted.
Carbon-13 Spin–Lattice Relaxation Times for Selected Steroids
Authors: ApSimon John W. , Beierbeck Helmut , Saunders John K.
Published: April 2011

The spin–lattice relaxation time (T1) data for a number of androstane and cholestane derivatives is presented. The NT1 value of carbon-3 in several of the compounds is found to be shorter than the average NT1 value for the other ring carbons which is interpreted in terms of anisotropic motion with the long steroid axis being the preferred axis of rotation. As this effect is only observed for carbon-3, an effective molecular correlation time can be calculated from the average NT1 value for all other CH and CH2 carbons. The correlation time (τi) for internal rotation of a methyl group is shown to depend on the number of 1,3 diaxial methyl group – hydrogen interactions. Thus τi(C-19) is shorter than τi(C-18) for androstane, τi(C-19) is shorter for trans-cholestanol than for either cis-cholestanol or cholesterol. The effects of substituents and conformational changes on τi as well as the effect of solvent on T1 are discussed.
Fluorinated alkoxides. Part XI. Studies on highly fluorinated amino-alcohols and their metal derivatives
Authors: Chang In-Soon , Willis Christopher J.
Published: April 2011

We describe the synthesis of a number of difunctional molecules in which the fluorinated tertiary alcohol grouping, -C(CF3)20H, is combined with a nitrogen donor site such as an amino-group or a pyridine ring. In all cases, zwitterionic behaviour in solution is found resulting from intramolecular proton transfer from the acidic fluorinated alcohol to the nitrogen, and this sometimes persists in the solid state, e.g. NH2CH2CH2C(CF3)20H exists as the dipolar ion +NH3CH2CH2C(CF3),0-. Measurements of pK values suggest that the behaviour of the fluorinated amino-alcohols may be compared with that of the amino-acids, subject to changes to be expected from the lower acidity of the -C(CF3)20H group. Metal complexes of the fluorinated amino-alcohols form readily; specifically, neutral complexes of Co2+, Ni2+, and Cu2+ of formula M(L),, where L is an ionized amino-alcohol chelating through the ionized hydroxy group and the nitrogen atom. Measurements of formation constants show that the six-membered chelate rings are the most stable, while a comparison of the stabilities of fluorinated amino-alkoxy complexes with those of analogous aminoacids shows that the former are less stable: this is attributed to the steric influence of the trifluoromethyl groups.
Observations on nitroxyl free radicals in arylamine carcinogenesis and on spin-trapping hydroxyl free radicals
Authors: Floyd Robert A
Published: April 2011

The work presented illustrates the valuable ways that spin-trapping and nitoxyl free radical chemistry has helped us in gaining a better view of the nature of certain biological processes and thus, hopefully, will help to disentangle the principles governing the causes of certain diseases.
Synthesis of taxodione
Authors: Burnell Robert H. , Jean Michel , Poirier Donald
Published: April 2011

Two syntheses of taxodione are described, as well as some of the model experiments that preceded them. The yields are low but comparable to most other syntheses of this extended quinone.
Coordination compounds of indium. Part 43. Indium(III) derivatives of benzenethiol, and the crystal structure of tetraphenylphosphonium bromotris(benzenethiolato)- indate(III), Ph4P[BrIn(SPh)3]
Authors: Chadha Raj K. , Hayes Peter C. , Mabrouk Hassan E. , Tuck Dennis G.
Published: April 2011

In(SPh)3 is readily prepared by the reaction of InCl3 and NaSPh in methanol. The compound is a Lewis acid, forming 1:1 adducts with 2,2′-bipyridine, 1,10-phenanthroline, N,N,N′,N′-tetramethylethanediamine, bis(diphenylphosphino)ethane, and dimethylsulphoxide, and 1:2 adducts with pyridine, trimethylamine, and triphenylphosphine. Reaction with R4NX (X = Cl, Br, I) or similar salts gives R4N[XIn(SPh)3] salts, which are 1:1 electrolytes. The structure of Ph4P[BrIn(SPh)3] has been determined by X-ray methods. The crystals are monoclinic, space group P21/c, with cell dimensions a = 9.964(3) Å, b = 13.477(3) Å, c = 30.359(7) Å, α = 98.30(2)°, Z = 4, R = 0.0622 for 2924 unique observed reflections. The anion has distorted tetrahedral symmetry in the InBrS3 kernel, with In—Br = 2.527(2) Å, and In—S(av) = 2.450 Å. The vibrational spectra of In(SPh)3 and its derivatives in the region 500–200 cm−1 are discussed.
Complexes of W(VI) and Mo(VI) with glycolic, lactic, chloro- and phenyl-lactic, mandelic, and glyceric acids studied by 1H and 13C nuclear magnetic resonance spectroscopy
Authors: Caldeira M. Madalena , Ramos M. Luisa , Gil Victor M. S.
Published: April 2011

A proton and carbon-13 nuclear magnetic resonance study is reported on the number, stoichiometry, geometry, and stability of the complexes that form when sodium tungstate or sodium molybdate is mixed with each one of the following α-hydroxyacids in aqueous solution at pH values in the range 3–8: glycolic, lactic, chloro-3- andphenyl-3-lactic, mandelic, and glyceric acids. The predominant complexes have 1:2 composition and pK of formation of the order of −5 to −16.
Chimie des radioprotecteurs: synthèse d'alkylamino-2 éthanethiols encombrés sur l'atome d'azote
Authors: Laduranty Joelle , Barbot Francis , Miginiac Léone
Published: April 2011

Synthesis of 2-alkylaminoethanethiols with a tertiary group fixed to the nitrogen atom has been achieved. A very convenient method of access to such 2-alkylaminoethanethiols with one, two, and three allyl substituents is the reaction between allylic organomagnesium compounds and thiazolidines, 2-alkylthiazolines, and 2-methylthiothiazolines respectively.
1H nuclear magnetic resonance and molecular orbital studies of the structure and internal rotations in ethylbenzene
Authors: Schaefer Ted , Penner Glenn H. , Sebastian Rudy
Published: April 2011

Rather extensive geometry-optimized computations at the STO-3G, 4-21G, 4-31G, and 6-31G levels of abinitio molecular orbital theory suggest that the fourfold component of the barrier to internal rotation about the Csp2—Csp3 bond in ethylbenzene amounts to about 20% of the twofold component. The 1H nuclear magnetic resonance spectral parameters, extracted by complete analyses of the spectra arising from the ten protons, are reported for ethylbenzene in acetone-d6, CCl4, CS2, and perfluoromethylcyclohexane solutions. The long-range proton–proton spin–spin coupling constants demonstrate that the internal barrier is insensitive to the polarity of the solvent, in contrast to polar solute molecules such as benzyl fluoride. The coupling constants do not support a dependence of the internal barrier on the internal pressure of the solvent.
Extraction and transport of alkali metal salts by crown ethers and cryptands: estimation of extraction constants and their relationship to transport flux
Authors: Fyles Thomas Murray
Published: April 2011

A method is described for the estimation of two phase extraction constants from stability constants for complexation of alkali metal cations by crown ethers and cryptands. The total free energy change for extraction of alkali metal salts from water to a non-polar organic solvent is evaluated as a sum of free energy terms for complexation, transfers of cation, anion, and complex between solvents, and ion pairing in the non-polar solvent. The method gives satisfactory agreement with a variety of published extraction constants and can be used predictively. As an example, the influence of extraction constant on transport flux was examined using calculated extraction constants and the rate data of Lamb etal. (J. Am. Chem. Soc. 102, 6820 (1980)); rates are adequately modelled by a simple analysis of diffusion.
Glycosides from Muscaricomosum. 7. Structure of three novel muscarosides
Authors: Adinolfi Matteo , Barone Gaspare , Corsaro Maria Michela , Lanzetta Rosa , Mangoni Lorenzo , Parrilli Michelangelo
Published: April 2011

Muscarosides D, E, and F, three new 27-norlanostane tetra-, penta-, and hexasaccharides, respectively, isolated from the bulbs of Muscaricomosum, were respectively shown to be (23S,24S)-3-O-{α-L-arabinopyranosyl(1→3)[β-D-apio-D-furanosyl(1→2)]-β-D-glucopyranosyl(1→2)-α-L-arabinopyranosyl(1→6)-β-D-glucopyranosyl}-17,23-epoxy-3β,24,30,31-tetrahydroxy-27-nor-5α-lanost-8-ene 4, (23R)-3-O-{α-L-arabinofuranosyl(1→2)-α-L-arabinopyranosyl(1→3)[α-L-rhamnopyranosy(1→2)]-β-D-glucopyranosyl(1→2)-α-L-arabinopyranosyl(1→6)-β-D-glucopyranosyl}-17,23-epoxy-3β,31-dihydroxy-27-nor-5α-lanost-8-en-15,24-dione 5, and (23S)-3-O-[β-D-apio-D-furanosyl(1→2)-β-D-glucopyranosyl(1→2)-α-L-arabinopyranosyl(1→6)-β-D-glucopyranosyl]-17,23-epoxy-3β,31-dihydroxy-27-nor-5α-lanost-8-en-15,24-dione 6. The structural details were elucidated by a combination of fast-atom-bombardment mass spectroscopy, one- and two-dimensional nuclear magnatic resonance spectroscopy, and comparison to model compounds expressly synthesized.
Enantioselective synthesis of isoquinoline alkaloids: phenylethylisoquinoline and aporphine alkaloids
Authors: Czarnocki Zbigniew , MacLean David B. , Szarek Walter A.
Published: April 2011

A new and improved procedure for the preparation of (R)-2-alkoxycarbonyl-1-formyl-1,2,3,4-tetrahydro-6,7-dimethoxyisoquinolines has been developed beginning from D-(−)-tartaric acid. The utility of these aldehydes in the asymmetric synthesis of isoquinoline alkaloids of high enantiomeric purity has been extended to the synthesis of phenylethylisoquinolines, which have been further transformed in straightforward steps into the homoprotoberberine and homoaporphine ring systems. In this manner, (S)-homolaudanosine, (S)-5′-methoxyhomolaudanosine, (S)-2,3,9,10,11-pentamethoxyhomoprotoberberine, and (S)-O-methylkreysigine have been synthesized. The conversion of (S)-laudanosine to (S)-glaucine, an aporphine alkaloid, has also been realized.
Interaction of diiodine with some tetra-substituted dithiooxamides. Crystal and molecular structure of bis(morpholinothiocarbonyl)bis(diiodine)
Authors: Atzei Davide , Deplano Paola , Trogu Emanuele F. , Bigoli Francesco , Pellinghelli Maria Angela , Vacca Alberto
Published: April 2011

The reaction of some tetra-substituted dithiooxamides R2NC(S)C(S)NR2 (R = CH3:Me4dto; R = C2H5:Et4dto; R2N = OC4H8N:Mo2dto) with diiodine has been investigated by spectrophotometric methods in CHCl3. The formation in solution of 1:1 and 1:2 charge-transfer (c.t.) complexes between the reagents has been observed. A new computer program, derived from "SUPERQUAD" (P. Gans, A. Sabatini, and A. Vacca. J. Chem. Soc. Dalton Trans. 1195 (1985)), has been applied to evaluate the formation constants. The 1:2 c.t. complexes have been isolated in the solid state, and an X-ray structure analysis of the [OC4H8NC(S)C(S)NC4H8O]•2I2 compound indicated that the crystals are triclinic, space groups [Formula: see text], with a = 14.659(6), b = 15.111(6), c = 9.317(5) Å, α = 92.29(2), β = 99.71(2), γ = 99.48(2)° and Z = 4. In particular the torsion angle S—C—C—S (≈90°) shows that the conformation of the dithiooxamide is not trans.
Preparation, chemical and electrochemical reduction of pyrido[2,3-b]quinoxalines and pyrido[3,4-b]quinoxalines
Authors: Armand Joseph , Boulares Line , Bellec Christian , Pinson Jean
Published: April 2011

The reaction of 2,3-diaminopyridine with the dimeric 4,5-dimethylcyclohexa-3,5-dien-1,2-dione gives 7,8-dimethylpyrido[2,3-b]quinoxaline, 1, in good yields; in the same way 3,4-diaminopyridine gives the 7,8-dimethylpyrido[3,4-b]quinoxaline 2. The electrochemical reduction of 1 and 2 in hydroorganic medium gives the 5,10-dihydro compounds 6 and 7; 1 and 2 present a single 2e− polarographic wave, in contrast to phenazine which shows two monoelectronic waves. The catalytic hydrogenation of 1 and 2 gives 6 and 7 and does not involve the pyridinic ring as in the case of pyridopyrazines. AlLiH4 does not react with 2 but 1 is reduced into the 1,2-dihydro derivative 8. The behavior of 1 and 2 is thus different from that of pyridopyrazines (which give the 1,2,3,4-tetrahydro compounds) and from that of phenazine (which gives the 5,10-dihydro derivative). NaBH4 reacts with pyridopyrazines to give, according to the substituents, 1,2- or 5,6-dihydro or 1,2,3,4-tetrahydro derivatives. Methylmagnesium chloride reacts with 1 to give a mixture of 2-methyl-1,2-dihydro, 2,6,7-trimethyl, and 4,6,7-trimethylpyrido[2,3-b]quinoxaline. In the case of 2, 4,6,7-trimethylpyrido[3,4-b]quinoxaline is obtained.
Synthesis and substitution chemistry of some bis(dithiolate) complexes of molybdenum, Mo(S2C6H3R)2(PMePh2)2, R = H, Me
Authors: Lazarowych Natalie J. , Morris Robert H.
Published: April 2011

The new bis(dithiolate) complexes Mo(1,2-S2-4-R-C6H3)2(PMePh2)2, R = H, Me, are readily synthesized from three different types of starting materials: trans-Mo(N2)2(PMePh2)4, MoCl4(PMePh2)2, and MoOCl2(PMePh2)3. The 31P NMR spectra of the dithiolate complexes at low temperature are consistent with a cis stereochemistry of the PMePh2 ligands and isomerism with respect to inversion at sulfur and relative positioning of the methyl groups on the chelating 1,2-S2-4-Me-C6H3 ligands. The singlet in the 31P NMR spectrum at room temperature arises from rapid interconversion of these isomers. Substitution of one or two of the PMePh2 ligands in the dithiolate complexes proceeds under mild conditions to give the complexes Mo(S2C6H4)2(CO)(PMePh2), Mo(S2C6H4)2(CN-t-Bu)(PMePh2), Mo(S2C6H3Me)2(dppe), Mo(S2C6H4)2(depe), Mo(S2C6H4)2(PMePh2)(PMe3), Mo(S2C6H4)2(PMePh2)(P(OMe)3), and Mo(S2C6H4)2(P(OMe)3)2. The 31P and 13C NMR spectroscopy of these bis(dithiolate) complexes suggest that they have monodentate ligands cis disposed.A reversible equilibrium exists between Mo(S2C6H4)2(PMePh2)2 and Mo(S2C6H4)2(CO)(PMePh2) in the presence of carbon monoxide in solution. Isolation of Mo(S2C6H4)2(CO)(PMePh2) is facilitated by use of CH3I as a "phosphine sponge" reagent. If the sulfur ligands are viewed as dianions, then this is the first thermally stable carbonyl complex of molybdenum(IV). Keywords: molybdenum, dithiolate, diphenylmethylphosphine, carbonyl, NMR.
Conformational analysis of 1-oxaspiro[5.5]undecanes. A powerful probe for the endo and the exo anomeric effects in acetals
Authors: Deslongchamps Pierre , Pothier Normand
Published: April 2011

A 13C nuclear magnetic resonance spectroscopy study of 1-oxaspiro[5.5]undecanes 1, 4, and 5 as a function of temperature is reported. Compound 1 exists as a rapidly equilibrating mixture of a major and a minor conformer (1a and 1b) at room temperature that can be observed at low temperature. By comparison, 1,7-dioxaspiro[5.5]undecane 2 is conformationally rigid in a single conformation (2a) at room temperature. This completely different behavior demonstrates the importance of the endo and the exo anomeric effects in the acetal function. Keywords: spiro ethers, conformational analysis, 13C NMR.
Phase transitions in solid cycloheptene
Authors: Haines Julian , Gilson D. F. R.
Published: April 2011

The phase transition behaviour of cycloheptene has been investigated by differential scanning calorimetry, proton spin-lattice relaxation, and vibrational spectroscopy (infrared and Raman). Two solid–solid phase transitions were observed, at 154 and 210 K, with transition enthalpies and entropies of 5.28 and 0.71 kJ mol−1 and 34.3 and 3.4 JK−1, respectively. Cycloheptene melted at 217 K with an entropy of melting of 4.5 JK−1 mol−1. The bands in the vibrational spectra of the two high temperature phases were broad and featureless, characteristic of highly disordered phases. The presence of other conformers, in addition to the chair form, was indicated from bands in the spectra. The ring inversion mode was highly phase dependent and exhibited soft mode type behaviour prior to the transition from the low temperature phase. The low frequency Raman spectra (external modes) of these phases indicated that the molecules are undergoing isotropic reorientation. In the low temperature phase, the vibrational bands were narrow; the splitting of the fundamentals into two components and the presence of nine external modes are consistent with unit cell symmetry of either C2 or Cs with two molecules per primitive unit cell. A glassy state can be produced from the intermediate phase and the vibrational spectra were very similar to those of the high temperature phases, indicating that static disorder was present. The barriers to reorientation, as obtained from proton spin-lattice relaxation measurements, are 9.0 kJ mol−1 in both the high temperature phases, and 15.4 kJ mol−1 in the low temperature, ordered phase. Keywords: cycloheptene, phase transition, differential scanning calorimetry, NMR, vibrational spectroscopy.
Cyclization of farnesyl diphosphate to pentalenene. Orthogonal stereochemistry in an enzyme-catalyzed SE′ reaction
Authors: Cane David E. , Weiner Steven W.
Published: April 2011

Pentalenene synthase catalyzes the cyclization of farnesyl diphosphate (1) to the sesquiterpene hydrocarbon pentalenene (4). Separate incubations of (4S,8S)-[4,8-3H2, 4,8-14C2]farnesyl diphosphate (1a) and (4R,8R)-[4,8-3H2, 4,814C2]farnesyl diphosphate (1b) with pentalenene synthase isolated from Streptomyces UC5319 and analysis of the derived labeled pentalenenes, 4a and 4b, respectively, by chemical degradation established that H-8si of FPP was lost upon cyclization to pentalenene. Consideration of the plausible conformations of the enzymatic cyclization intermediates indicates that the electrophilic allylic addition-elimination (SE′) reaction in which the C-4,5 bond of pentalenene is formed involves an orthogonal relationship between the C—C bond being formed and the C—H bond that is ultimately broken.
Macleanine, a unique type of dinitrogenous Lycopodium alkaloid
Authors: Ayer William A. , Ma Yu-Ting , Liu Jia-Sen , Huang Mei-Fen , Schultz L. Wayne , Clardy Jon
Published: April 2011

The structure of macleanine, a unique type of Lycopodium alkaloid, was deduced from its spectroscopic (especially 1H and 13C nuclear magnetic resonance) properties and from biogenetic considerations. The structure was verified by an X-ray crystallographic study of the hydroperchlorate.