bluuebunny/crossref_metadata_2025 huggingface dataset:
The Radical Cations of Bicyclo[2.2.1]hepta‐2,5‐diene (8,9,10‐Trinorborna‐2,5‐diene) and bicyclo[2.2.2]octa‐2,5‐diene (2,3‐Dihydrobarrelene). An ESR and ENDOR study
Authors: Gerson Fabian , Qin Xue‐Zhi
Published: December 2004

The radical cation of bicyclo[2‐2.1]hepta‐2,5‐diene (8,9,10‐trinorborna‐2,5‐diene; 1) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa‐2,5‐diene (2,3‐dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, methano‐bridge, and bridgehead protons are −0.780 ±0.005, +0.304±0.002, and −0.049±0.002 mT, respectively. The hyperfine tensor for the methano‐bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = −0.594 ± 0.005, Ay= −0.913 ± 0.005, and Az = −0.834 ± 0.005 mT (x parallel to CH‐ z parallel to 2pπ axis). For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, ethano‐bridge, and bridgehead protons are −0.68 ± 0.01, +0.162 ± 0.005, and −0.108 ± 0.005 mT, respectively. The hyperfine data for \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document} fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π‐MO's.
The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P‐450Cath., Proceeding with retention of configuration
Authors: Fretz Heinz , Woggon Wolf‐Dietrich , Voges Rolf
Published: December 2004

Incubation of the geraniols (R)‐(8‐2H1)[8‐3H1]‐1 and (S)‐(8‐2H1)[8‐3H1]‐1 with microsomal cytochrome P‐450Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8‐hydroxygeraniols (S)‐(8‐2H1)[8‐3H1]‐2 and (R)‐(8‐2H1)[8‐3H1]‐2. Their absolute configuration was assigned on the basis of the 1H‐decoupled 3H‐NMR Spectra of the corresponding dicamphanates (S)‐(8‐2H1)[8‐3H1]‐9 and (R)‐(8‐2H1)[8‐3H1]‐9, of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1.
Asymmetric Diels‐Alder Reaction of 1‐Methoxybuta‐1,3‐diene with (2R)‐N‐Glyoxyloylbornane‐10,2‐sultam
Authors: Bauer Tomasz , Chapuis Christian , Kozak Janusz , Jurczak Janusz
Published: December 2004

Starting from sultam 1, the chiral dienophile (2R)‐N‐glyoxyloylbornane‐10,2‐sultam (4) was readily prepared. Non‐catalyzed atmospheric‐ and high‐pressure as well as [Eu(fod)3]‐promoted [4 + 2] cycloadditions of 1‐methoxy‐buta‐1,3‐diene (5) to chiral dienophile 4, leading with high asymmetric induction to 6‐methoxy‐3,6‐dihydro‐2H‐pyran‐2‐yl derivatives 6–9, are described. The extent and direction of asymmetric induction in these reactions were established by 1H‐NMR analysis and chemical correlation, respectively. Stereochemical models for both non‐catalyzed and [Eu(fod)3]‐promoted reactions are proposed.
8‐Substituted Xanthines as Phosphodiesterase Inhibitors: Conformation‐Dependent Lipophilicity and Structure‐Activity Relationships
Authors: Walther Bernard , Carrupt Pierre‐Alain , El Tayar Nabil , Testa Bernard
Published: December 2004

The 8‐substituted xanthines 1–21 (including compound S 9795), caffeine (22), and the three isomeric dimethyl‐xanthines 23–25 (see Table 1), were examined for their lipophilic behaviour using a reversed‐phase HPLC technique. A number of flexible compounds showed a smaller‐than‐expected lipophilicity which based on conformational and tautomeric calculations were ascribed to the predominance of folded forms. A QSAR analysis of the phosphodiesterase‐inhibitory potency of several compounds showed favourable factors to be a low lipophilicity and the absence of a substituent on the N7 position.
Herstellung von substituierten 2‐Aminooxazol‐4‐carbonitrilen
Authors: Pascual Alfons
Published: December 2004

Preparation of Substituted 2‐Aminooxazole‐4‐carbonitriles

During our synthetic programme to convert 4‐isoxazolylthioureas 3 into the corresponding carbodiimides 5, a side reaction leading to the hitherto unknown 2‐aminooxazole‐4‐carbonitriles 6 was observed. By selecting appropriate reaction conditions, it was possible to improve the yields of the carbodiimides 5 as well as of the novel oxazole‐carbonitriles 6 at will, thus allowing the synthesis of 6 to be conducted in very good yields. To overcome the difficulty of isolating unstable carbodiimides, the synthesis of 6 is best carried out in a one‐pot procedure. A limited mechanistic study showed that the formation of 6 proceeds via 5 as the only intermediate. The stability of the NCN bonds against base attack (depending strongly on both sterical hindrance and electronic‐density factors) forms the only limitation of this new synthetic pathway to oxazole‐4‐carbonitriles.
5,10:8,9‐Disecosteroids (= Steroklastanes): A new type of modified steroids
Authors: Lorenc Ljubrinka , Bondarenko Lidija , Pavlović Vlada , Fuhrer Hermann , Rihs Grety , Kalvoda Jaroslav , Mihailović Mihailo Lj.
Published: December 2004

Thermolysis of steroidal 5α, 8α‐ peroxides of type 3a‐d generates as major products the corresponding diseco compounds containing a 14‐membered ring instead of the standard A‐B‐C‐ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β‐unsaturated ketones of type 4, formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer‐Villiger oxidation to give, as final products, the 15‐membered cyclic epoxyenol lactones of type 20 and 21. The structures of the various products were determined by 1H‐ and 13C‐NMR spectroscopy. The conformations of the 14‐ and 15‐membered rings were established by X‐ray structure analyses of 7 and 21a. A reaction mechanism for the above transformations is discussed.
Site‐Specific, Oxidative Addition of CC Bonds by ‘Anchored’ bare Fe(I) cations prior to CH bond activation. Preliminary communication
Authors: Karrass Sigurd , Schwarz Helmut
Published: December 2004

Evidence is presented for the first time that ‘naked’ Fe+ ions, complexed to the NH2 group of primary amines, are capable of intramolecularly activating CC bonds in a highly specific mode without preceding CH activation.
New Triterpenoid N‐Acetylglycosides with Molluscicidal Activity from Tetrapleura tetraptera TAUB
Authors: Maillard Marc , Hostettmann Kurt , Adewunmi Clement O.
Published: December 2004

Activity‐guided fractionation of the MeOH extract of the fruits of Tetrapleura tetraptera TAUB. (Mimosaceae) afforded 4 saponins 1–4, which exhibited strong molluscicidal properties against the schistosomiasis‐transmitting snails Biomphalaria glabrata. Chemical, enzymatic, and spectral methods (DCI‐MS, 1H‐NMR, 13C‐NMR) showed that they were N‐acetylglycosides of oleanolic acid and of echinocystic acid. Apart from saponin 1 (aridanin), previously isolated from this plant, glycosides 2–4 are new naturally occurring compounds.
Synthèse d'une sonde biotinylée à bras clivable allongé pour l'isolement des récepteurs de l'angiotensine II
Authors: Seyer René , Aumelas André , Marie Jacky , Claude Bonnafous Jean , Jard Serge
Published: December 2004

Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors Purification

We have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl‐NH(CH2)2SS(CH2)2CO‐Gly‐ϵ Ahx‐[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group. 1H‐NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd = 1 nM) and hence is a promising tool in their detection (autoradiography, gold‐, ferritin‐, enzyme‐, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe‐receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling 1 + 2 in presence of (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of the D‐Phe8 derivative that has antagonist properties.
Pteridines. Part XLII. Synthesis and properties of 8‐substituted 2,4‐dithiolumazines
Authors: Hübsch Walter , Jibril Ibrahim , Huttner Gottfried , Pfleiderer Wolfgang
Published: December 2004

Condensation reactions of the 5‐amino‐6‐(subst. amino)‐2,4‐dithiouracils 12 and 13 with diacetyl or benzil led to the 6,7,8‐trisubstituted 2,4‐dithiolumazines 14–16. Methylation of these compounds affected both thio functions forming various types of 2,4‐bis(methylthio)lumazine derivatives depending on the nature of the substituents at C(7) and N(8). The 6,7,8‐trimethyl‐2,4‐dithiolumazine (14) was converted into 7,8‐dihydro‐6,8‐dimethyl–7‐methylidene‐2,4‐bis(methylthio)pteridine (17), whereas the 8‐methyl‐6,7‐diphenyl‐(15) and the 8‐(2‐hydroxyethyl)‐6,7‐diphenyl‐2,4‐dithiolumazine (16) yielded the corresponding covalent inter‐ or intramolecular 7,8‐adducts 18–21. The unusual structures were proven by spectroscopic means and those of the alcohol adducts 20 and 21, furthermore, confirmed by X‐ray analysis.
Apparent Failure of the Wharton Rearrangement in a Tricyclo[7.1.1.02,7]undecane
Authors: Thomas Alan F. , Di Giorgio Roberto , Guntern Olivier
Published: December 2004

The Wharton rearrangement of 2,3‐epoxytricyclo[7.1.1.02,7]undecan‐3‐one, a sterically hindered system, which should have led to an allyl alcohol with the OH group at a bridgehead, gave instead the allylically rearranged alcohol. The desired hydroxy compound was prepared by the Barton modification of the Wharton rearrangement: borohydride reduction to the epoxy alcohols, reaction with N, N′‐thiocarbonylbisimidazole, and treatment with Bu3SnH. The bridgehead alcohol (and other 2‐oxygenated tricyclo[7.1.1.02,7]undecanes) readily rearranged under acidic or thermal conditions.
Synthesis and Biological Evaluation of 14‐Alkoxymorphinans Part 4 opioid agonists and partial opioid agonists in a series of N‐(cyclobutylmethyl)‐14‐methoxymorphinan‐6‐ones
Authors: Schmidhammer Helmut , Burkard Willy P. , Eggstein‐Aeppli Lislott
Published: December 2004

The N‐(cyclobutylmethyl)morphinans 12, 19, 20, 21, 27, and 29 and the N‐(2‐cyanoethyl) analogue 33 were prepared from different precursors. Pharmacological evaluation (e.g. opioid receptor binding assays, acetic‐acid writhing test, hot‐plate assay) points to a partial opioid agonism of compounds 12, 27, 29, and 33, and to full opioid agonism of compounds 19–21.
Synthèse énantiospécifique du (−)‐(1R, 3R, 5S)‐diméthyl‐1,3‐dioxa‐2,9‐bicyclo[3.3.1]nonane
Authors: Masoni Claudio , Deschenaux Pierre‐François , Kallimopoulos Thomas , Jacot‐Guillarmod André
Published: December 2004

Enantiospecific Synthesis of (−)‐(1R, 3R, 5S)‐1,3‐Dimethyl‐2,9‐dioxabicyclo[3.3.1]nonane

The isomer (−)‐(1R, 3R, 5S)‐endo‐1,3‐dimethyl‐2,9‐dioxabicyclo[3.3.1]nonane ((1R, 3R, 5S)‐8) has been synthesized from (−)‐(3R)‐methyl 3‐hydroxybutanoate. The key intermediate (3R, 5R)‐5 is proved to be a useful synthon for EPC syntheses.
Interaction between the buffer Tris and the eu(III) ion: Luminescence and potentiometric investigation
Authors: Pfefferlé Jean‐Marc , Bünzli Jean‐Claude G.
Published: December 2004

The interaction between the buffer 2‐amino‐2‐(hydroxymethyl)propane‐1,3‐diol (Tris) and the Eu(III) ion has been studied by luminescence spectroscopy in D2O. Emission and excitation spectra (5D0←7F0 transition) indicate an interaction with both [TrisH]+ and neutral Tris species. The former is weak and probably of the outer‐sphere type. The latter is of inner‐sphere type and corresponds to the formation of the [Eu(Tris)]3+ species (estimated logK1 = 2.3 ± 0.3). Buffer Tris is also demonstrated to prevent the formation of an Eu‐hydroxo species in the pD range of 7–8. Potentiometric measurements in H2O allowed a more precise calculation of the stability constant: logK1 = 2.44 ± 0.07. Comparison with the data for aliphatic amines and other metal ions lead to the conclusion that the Eu/Tris interaction is mainly achieved through the amino group. 1H‐NMR spectra in presence of Tb(III) ions confirmed both this assumption and the presence of a weak interaction with TrisH+. Quantitative determinations of association constants between lanthanide ions and macromolecules of biological interest performed in presence of Tris should, therefore, be corrected for the Eu/Tris interaction.
Synthesis of(+)‐(2S, 6S)‐trans‐α‐Irone and of(‐)‐(2S, 6S)‐trans‐γ‐Irone
Authors: Helmlinger Daniel , Fráter Georg
Published: December 2004

A 3:1 mixture of (+)‐(2S, 6S)‐trans‐α‐irone ((+)‐1) and (−)‐(2S, 6S)‐trans‐γ‐irone (−)‐2) has been synthesized with ca. 70% e. e. by the ene reaction of (−)‐(S)‐3 and but‐3‐yn‐2‐one.
Tricarbonyl‐chromium complexes of benzannelated cycloproparenes
Authors: Müller Paul , Bernardinelli Gérald , Jacquier Yvan , Ricca Alessandra
Published: December 2004

Reaction of 1H‐cyclopropa [b]naphthalene (1a) or 1H‐cyclopropa[b]anthracene (10a) with tris(acetonitrile)tricarbonylchromium affords cyclobutanaphthalenone and cyclobutaanthracenone 2 and 11, respectively. In contrast, the bis‐silylated Cycloproparenes 1b and 10b undergo complexation at the terminal benzene ring and lead to the arene‐tricarbonylchromium complexes 4b and 12, respectively. Desifylation of 4b to 4a is effected by t‐BuOK.
Deaminocolchinyl Methyl Ether: Synthesis from 2,3,4,4′‐Tetramethoxybiphenyl‐2‐carbaldehyde. Comparison of antitubulin effects of deaminocolchinyl methyl ether and dehydro analogs
Authors: Boyé Olivier , Itoh Yoshikuni , Brossi Arnold
Published: December 2004

Synthesis of deaminocolchinyl methyl ether 9 was achieved from tetramethoxy‐substituted biphenyl‐2‐carb‐aldehyde 12 via tricyclic ketone 20 and 5,6‐didehydro congener 11. Compound 9 was identical in every respect with material prepared from colchicine via 6,7‐didehydro congener 10. Measuring inhibition of tubulin polymerization in vitro showed compounds 4, 5, and 9–11 of the alloseries of colchicinoids to be particularly potent inhibitors.
Substituenteneffekte auf die NMR‐Spektren von Pentafulvenen. (13C, 13C)‐NMR‐Kopplungskonstanten (1J(C, C))
Authors: Bircher Hansruedi , Neuenschwander Markus
Published: December 2004

Substituent Effects on NMR Spectra of Pentafulvenes. 13C, 13C‐NMR Coupling Constants (1J(C, C))

1H‐ and 13C‐NMR spectra of 6‐monosubstituted pentafulvenes 1–8 have been analysed, and 1J(C, C) coupling constants have been determined from ID‐inadequate spectra of 13C satellites. It turns out that 13C,13C coupling constants of the ring C‐atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron‐donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ+ and 1J(C,C) values are obtained.
Synthese und NMR‐spektroskopische Charakterisierung neuer Adenin‐ und 6‐Thioxopurincarboxamidine
Authors: Ried Walter , Woithe Heinz
Published: December 2004

Synthesis and NMR‐Spectroscopic Characterization of New Adenine‐ and 6‐Thioxopurinecarboxamidines

Adenine (1) or 1H‐purine‐6(7H)‐thione (4) react with carboximidoyl chlorides 2 to yield the adenine‐9‐carboxamidines 3 or the 6,7‐dihydro‐6‐thioxo‐1H‐purine‐7‐carboxamidines 5 and 6,9‐dihydro‐6‐thioxo‐1H‐purine‐9‐carboxamidine 6 a, respectively. The structures of the compounds were determined by 1H‐ and 13C‐NMR spectroscopy.
Interaction between Oxygen Lone‐Pair Orbitals of Ether and α,β‐Unsaturated Ketone Functions in 3,5,6‐Trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one and 3,6‐Dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione: A PE‐Spectroscopic Investigation
Authors: Röser Karl , Carrupt Pierre‐Alain , Vogel Pierre , Honegger Evi , Heilbronner Edgar
Published: December 2004

Controlled ozonolysis of 2,3,5,6‐tetramethylidene‐7‐oxabicyclo[2.2.1]heptane (1) afforded 3,5,6‐trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one (2). Ozonolysis of 2 gave a 1:1 mixture of 3,5‐dimethylidene‐7‐oxa‐bicyclo[2.2.1]heptane‐2,6‐dione (3) and 3,6‐dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione (4). The He(Iα) photoelectron (PE) spectra of 2 and 4 have been recorded. Comparison with the PE data of related systems, and with the result of ab initio STO‐3G calculations, confirm the existence of significant through‐bond interactions between the oxygen lone‐pair orbitals n(CO) of the carbonyl functions and n(O) of the O(7) ether bridge.
Solution Structure of [Me‐L‐Leu7]Didemnin B Determined by NMR Spectroscopy and Refined by MD Calculation
Authors: Kessler Horst , Mronga Siggi , Will Martin , Schmidt Ulrich
Published: December 2004

Several homo‐ and heteronuclear two‐dimensional NMR techniques were used to assign all H‐ and C‐resonances of the two conformers A and B of [7‐(N‐methyl‐L‐leucine)]didemnin B. Didemnine is a biologically highly active cytostaticum and immunosuppressivum. The assignment of the aliphatic C‐atoms were done by the inverse H,C‐COSY with TOCSY transfer which connects complete proton spin systems and represents them on C‐atoms. The structure of both conformers (A and B) in (D6)DMSO solution was derived from homo‐ and heteronuclear couplings (J), temperature dependencies of NH protons, and NOE effects. Distances determined from the latter were used for refinements by restrained MD calculations using the GROMOS program. The solution structure of [Me‐L‐Leu7]didemnin B (A and B) was compared to that of didemnin B. The backbone structure of the macrocyclic ring and of the linear side‐chain moiety are very similar in conformer A and didemnin B, though the Ist1‐Hip2 region of the ring is slightly ex tended in conformer A. This may be caused by the influence of the Me‐L‐Leu7 residue in A and may be responsible for its reduced biological activity in comparison to didemnin B. The more weakly populated conformer B exhibits a βVI turn in the linear side‐chain moiety.
Synthesis and Properties of Acyclic and Cryptate Europium(III) Complexes Incorporating the 3,3′‐Biisoquinoline 2,2′‐Dioxide Unit
Authors: Lehn Jean‐Marie , Pietraszkiewicz Marek , Karpiuk Jerzy
Published: December 2004

The lithium and europium(III) cryptates of a macrobicyclic ligand 1 incorporating the 3,3′‐biisoquinoline 2,2′‐dioxide 2 have been prepared. The Eu(III) complex [Eu(2)2]Cl3 has also been obtained. These Eu(III) complexes present characteristic 1H‐NMR spectra containing markedly shifted resonances. They are strongly luminescent; the emission spectra, quantum yields, and lifetimes have been determined.
Approaches to the Synthesis of Cytochalasans Part9. A versatile concept leading to all structural types of cytochalasans
Authors: Ackermann Jean , Matthes Michael , Tamm Christoph
Published: December 2004

Starting from D‐glutamic acid (5), the bicyclic compounds 4a and 4b were synthesized via 17 (Schemes 1 and 2). The reaction leading to 4g and 4h with LiCuPh2 was not successful. But treatment of the N‐protected model lactams 19, 21, and 22 with Li2Cu(CN)Ph2 gave the amino ketones 24, 26, and 27, respectively (Scheme 3). The desired compound 23 was obtained from 20. Conversion of the unprotected lactams 28, 31, and 32 gave the phenyl derivative 34 in excellent yields. Ester 35 was transformed to the α ‐amino‐γ‐ oxo‐acid derivative 36. This conversion opens a novel access to this type of compounds.
Metal Complexes with Macrocyclic Ligands. Part XXXI. Protonation studies and complexation properties of tetraazamacrocyclic methylenephosphonates with earth‐alkali ions
Authors: Delgado Rita , Siegfried Liselotte C. , Kaden Thomas A.
Published: December 2004

The three ligands 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrakis(methylenephosphonic acid) (1), 1,4,7,11‐tetraazacyclotridecane‐1,4,7,11‐tetrakis(methylenephosphonic acid) (2), and 1,4,8,11‐tetraazacyclotetradecane‐1,4,8,1 1‐tetrakis(methylenephosphonic acid) (3) have been synthesized by condensation of the corresponding macrocycles with formaldehyde and phosphorous acid. The protonation and stability constants with the earth‐alkali ions have been determined at 25° and I = 0.1 M (Me4)N(NO3) by potentiometric titrations. Because of the high values of the first two protonation constants, 1H‐NMR measurements were necessary to determine them. Titrations in different supporting electrolytes (NaNO3, KNO3, RbNO3, CsNO3, and Me4N(NO3)) show that their choice is of paramount importance, as the above ligands can form complexes with alkali‐metal ions. The potentiometric results for the earth‐alkali ions show that beside mononuclear complexes of different degrees of protonation ([MLHn], n = 0–4), also binuclear species are formed ([M2LHm], m = 0–2). It is interesting that 1 with the smallest macrocyclic ring has the greatest tendency to form binuclear complexes, which are so stable that they partially prevent the formation of the corresponding mononuclear species. For [ML], [MLH], [M2L], and [M2LH], the stability sequence is Mg2+ < Ca2+ > Sr2+ > Ba2+, whereas for [MLH2], [MLH3], and [MLH4], the stability steadily decreases from Mg2+ to Ba2+.
Synthese cyclischer Depsipeptide durch direkte Amid‐Cyclisierung: 12gliedrige Depsipeptide mit alternierender Sequenz von α‐Hydroxy‐ und α‐Aminosäuren
Authors: Obrecht Daniel , Heimgartner Heinz
Published: December 2004

Synthesis of Cyclic Depsipeptides via Direct Amide Cyclization: Cyclic Depsipeptides with 12‐Ring Atoms and Alternating Sequence of α‐Hydroxy and α‐Amino Adds

The reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1; R1 = R2 = R3 = R4 = Me) with α‐hydroxy‐carboxylic acids, followed by selective hydrolysis of the terminal dimethylamide group yields the dipeptide analogues 15a and 18b (Schemes 3 and 4). After protection of the OH group (→ 16a and 19, resp.), coupling with the C‐terminus‐protected derivatives 14 and 18a, respectively, by a modified 1,1′‐carbonyldiimidazole procedure followed by hydrolysis gives the linear depsipeptides 17c and 20, respectively. Treatment with HCl gas in toluene at 100° leads to the cyclic depsipeptides 21 and 22 in very good yield. The two model reactions show that the ‘azirine/oxazolone‐method’, combined with the ‘direct amide cyclization’, is a versatile procedure for the synthesis of cyclic depsipeptides containing α,α‐disubstituted α‐amino acids.
Synthesis of Putative Intermediates on the Monensin Biosynthetic Pathway and Incorporation Experiments with the Monensin‐Producing Organism
Authors: Holmes Duncan S. , Sherringham John A. , Dyer Ulrich C. , Russell Simon T. , Robinson John A.
Published: December 2004

As a direct test of the Cane‐Westley hypothesis concerning the mode of assembly of ether rings in the polyether class of ionophore antibiotics, we describe experiments culminating in the synthesis of three putative intermediates on the monensin biosynthetic pathway and incorporation experiments with these materials and the monensin‐producing organism Streptomyces cinnamonensis. The putative intermediates synthesised include the trienes [21‐3H]‐7 and [13‐3H]‐10, and the diene [9‐3H]‐11. The results of the incorporation experiments conducted with whole cell cultures suggest that [13‐3H]‐10 and [21‐3H]‐7 are unable to cross the intact cell membrane of S. cinnamonensis, whereas diene [9‐3H]‐11 can gain entry to the cellular interior, but is then degraded efficiently, most likely by a pathway closely related to β‐oxidation, without being specifically incorporated into the antibiotic.
Design and Synthesis of Novel Opiate Antagonists with LH‐Stimulating Properties
Authors: Revesz Laszlo , Siegel Richard A. , Buescher Hans‐Heinz , Marko Magda , Maurer Richard , Meigel Harald
Published: December 2004

Opiate antagonists stimulate the release of LH and might, therefore, contribute to an innovative therapy for the treatment of numerous clinical syndromes characterized by hypofunction of the HHG axis. The purpose of this work was to design and synthesize pure opiate antagonists useful for this therapy. Me, Et, Pr, and PhCH2 groups were introduced at the crucial 14β‐position of morphines and morphinans via a hetero‐Diels‐Alder key step starting from thebaine derivative 1 and tested for opiate antagonism and LH‐stimulating activity. Me‐, Et‐, and Pr‐substituted compounds 11a–c were stronger antagonists than naltrexone, whereas Pr and PhCH2 substituents in 11c, 11d, 9d, 9d3, 9d4, and 9d5 led to orally active LH stimulators. Based on our finding that the μ‐antagonists 12 and 11b5 showed no LH stimulation, we conclude that a combination of both μ‐and χ‐antagonism is necessary for potent LH stimulation.
Stereoselectivity and Chiral Recognition in the Electron‐Transfer Reaction between Spinach Ferredoxin and Optically Active Cobalt(III) Complexes
Authors: Bernauer Klaus , Monzione Michel , Schürmann Peter , Viette Véronique
Published: December 2004

The kinetics of the electron transfer between reduced spinach [2Fe‐2S]‐ferredoxin and the optically active complexes [Co((R,R)‐ or (S,S)‐alamp)py]+ (I), [Co((R,R)‐ or (S,S)‐promp)H2O]+ (IIa), and [Co((R,R)‐ or (S,S)‐promp)py]+ (IIb) have been investigated. The reactions are stereoselective, and for I and IIa, the Stereoselectivity strongly depends on temperature due to large differences in the activation enthalpy between enantiomeric reagents. Isokinetic behaviour is observed between enantiomers, the ΔΔH values being largely compensated by the ΔΔS values. The compensation behaviour is explained by the combination of stereochemical interactions and desolvation processes on formation of the precursor complex or the transition state.
New 20(10→5)abeo‐Diterpenoids from Pygmaeopremna herbacea
Authors: Meng Qingchang , Hesse Manfred
Published: December 2004

Two new 20(10→5)abeo‐abietune diterpenoids, pygmaeooins B (1) and C (2), have been isolated from the roots of Pygmaeopremna herbacea (Verbenaceae). Their structures were elucidated on the basis of spectroscopic data, and chemically, both compounds were correlated with each other. The absolute configurations were assigned tentatively on the basis of biogenetic pathway.
Umsetzung von 3‐(Dimethylamino)‐2H‐azirinen mit 1,3‐Oxazolidin‐2‐thion zu 3‐(2‐Hydroxyethyl)‐2‐thiohydantoinen
Authors: Ametamey Simon M. , Heimgartner Heinz
Published: December 2004

Reaction of 3‐(Dimethylamino)‐2H‐azirines with 1,3‐Oxazolidine‐2‐thione to 3‐(2‐Hydroxyethyl)‐2‐ thiohydantoins

The reaction of 3‐(dimethylamino)‐2H‐azirines 1 and 1,3‐oxazolidine‐2‐thione (6), in MeCN at room temperature, yields, after hydrolytic workup, 3‐(2‐hydroxyethyl)‐2‐thiohydantoins 7 (Scheme 2). In the case of the spirocyclic 1c, crystallization of the crude reaction mixture leads to spiro [cyclopentane‐1, 7′(7′aH)‐imidazo [4, 3‐b] oxazole] ‐5′‐thione 8c. The mechanism is discussed.
On the Absolute Configuration of Penlanfuran and Related Sesquiterpenoids of the Sponge Dysidea fragilis from the North‐Brittany Sea
Authors: Mancini Ines , Guella Graziano , Cavazza Marino , Pietra Francesco
Published: December 2004

The 1,4‐addition of vinylmagnesium bromide/CuBr‐SMe2 to (+)‐(4s)‐cryptone ((+)‐6) in THF in the presence of Me3SiCI gives the silylenol ether 7 which partly undergoes hydrolysis to ketone 8 on aqueous workup; residual 7 is hydrolyzed with pyridinium p‐toluenesulfonate (PyTsOH) to give 8 which is protected in situ with ethylene glycol and then ozonolized to give aldehyde ()‐10. The latter, on addition of 3‐lithiofuran followed by dehydration and deprotection with Py TsOH, gives the unnatural (4S)‐enantiomer (+)‐2 of noroxopenlanfuran. All processes, except 11 → (+)‐2, are of good yield. On the basis of previous chemical transformations, this also establishes the (4R)‐configuration for penlanfuran ((−)‐1) and other sesquiterpenoids of the sponge Dysidea fragilis from the North‐Brittany sea. Non viable routes to (±)‐noroxoperlanfuran ((±)‐2) are also discussed.
Chiral [2H]‐Labelled Methylene Groups in Trienoic‐ and Dienoic Fatty Acids: A Facile Approach via Asymmetric Epoxidation of [2H] Allyl Alcohols
Authors: Neumann Christoph , Boland Wilhelm
Published: December 2004

Chiral [2H] ‐labelled methylene groups flanked by two double bonds within (poly)unsaturated fatty acids are readily available from trans‐2,3‐epoxy[2,3‐2H2] alk‐4‐yn‐l‐ols, obtained in their turn by asymmetric epoxidation of the corresponding (E)‐[2,3‐2H2] alk‐2‐en‐4‐yn‐l‐ols (see Scheme 3). The procedure is exemplified for (8S,3Z,6Z,9Z)‐[7,8‐2H2] trideca‐3,6,9‐trienoic acid ((8S)‐11) and (8R)‐11 (Scheme 4) as well as for (5S,3Z,6Z)‐[4,5−2H2]deca‐3,6‐dienoic acid ((5S)‐13) and (5R)‐13 (Scheme 5).
Tricyclic Pyridine Derivatives with High Affinity to the Central Benzodiazepine Receptor
Authors: Fischer Ulf , Möhler Hanns , Schneider Fernand , Widmer Ulrich
Published: December 2004

Novel tricyclic heterocycles were prepared and evaluated for their affinity to the central benzodiazepine receptor. The most potent compounds with IC50's in the nanomolar range were; found among thienoquinolizines and benzo[a]quinolizines (cf. Tables 2–5). The central ring of the tricyclic ring system may be partially unsaturated (cf. Tables 2 and 4) or fully unsaturated (cf. Tables 3 and 5) without loss of the high affinity to the receptor. The position of the ester group in the pyridinone ring is crucial for good binding (cf. Tables 1 and 2). It may be replaced by a broad variety of functional groups, e.g. amides, alkyl carbamates, alkyl groups, and hydroxyalkyl groups (cf. Tables 2–5). In the benzo[a]quinolizines, shifting the halogen atom from C(10) to C(9) leads to complete loss of affinity to the benzodiazepine receptor (cf. Table 4).
Chromatographische Trennung und quantitative Bestimmung aller acht Stereoisomeren von α‐Tocopherol
Authors: Vecchi Max , Walther Willy , Glinz Ernst , Netscher Thomas , Schmid Rudolf , Lalonde Michel , Vetter Walter
Published: December 2004

Separation and Quantitation of All Eight Stereoisomers of α‐Tocopherol by Chromatography

The results of the analysis of several derivatives of (all‐rac)‐α‐tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl‐ether derivative allows the separation and quantification of all eight possible stereoisomers of (all‐rac)‐α‐tocopherol.
Konstitutionsisomerie in Polykondensaten. Teil VI. Synthese und Eigenschaften von völlig geordneten und ungeordneten Bipolyamiden aus cis‐2,6‐Dimethylpiperazin und 1,2,5‐Thiadiazol‐3,4‐dicarbonyl‐dichlorid
Authors: Mühlebach Andreas , Pino Piero
Published: December 2004

Constitutional Isomerism in Polycondensates. Synthesis and Properties of Perfectly Regular and Random Bipolyamides from cis‐2,6‐Dimethylpiperazine and 1,2,5‐Thiadiazole‐3,4‐dicarbonyl Dichloride

The synthesis of constitutionally perfectly regular and random alternating copolyamides from the ‘symmetric’ monomer 1,2,5‐thiadiazol‐3,4‐dicarbonyl dichloride (4) and the ‘non‐symmetric’ monomer cis‐2,6‐dimethylpiper‐azine (7) by solution and interfacial polycondensation methods is described. Their constitutional regularities (s values) were determined by high‐resolution 13C‐NMR spectroscopy in CDCl3 solutions. Ordered and random copolyamides were amorphous with Tg values of ca. 200°. However, the regular head/tail and the random copolyamides with low molecular weights could be partially crystallized by annealing and showed large differences in their melting points (54°). Beside other physical properties, the membrane properties of the copolyamides were carefully investigated. In H2O desalination by reverse osmosis, no differences in salt rejections and permeabilities between constitutionally regular and random copolyamides were found (within experimental errors). In contrast, the regular head/head/tail/tail‐ and head/tail‐type copolyamides showed considerably larger separation factors in the gas separation (methane/hydrogen) than the random ones.
Photocycloaddition of Cyclohex‐2‐enones to Tetramethoxyethylene: Formation of 2,2,3,3‐Tetramethoxy‐1‐oxaspiro[3.5]non‐5‐enes
Authors: Cruciani Giuliano , Rathjen Hans‐Jürgen , Margaretha Paul
Published: December 2004

Cyclohex‐2‐enones 1a–1c undergo photocycloaddition to tetramethoxyethylene in benzene to afford 1‐oxa‐spiro[3.5]non‐5‐enes 3 in very good yields. In MeCN as solvent, higher relative amounts of bicyclo[4.2.0]octan‐2‐ones 4 are formed. Results from similar experiments with the same enones and 2,3‐dimethylbut‐2‐ene or 1,1‐dimethoxyethene indicate that the driving force for oxetane formation is a sufficiently large difference in redox potentials between Ered of the enone and Eox of the alkene. A mechanism is proposed for cycloalk‐2‐enone + alkene photocycloadditions wherein the cyclobutane adducts arise from an exciplex intermediate and the oxetanes from a subsequently formed contact ion‐pair.
2H‐benzimidazoles. Part 5. Convenient synthons for tricyclic heterocycles
Authors: Cada Armin , Kramer Walter , Neidlein Richard , Suschitzky Hans
Published: December 2004

The readily available 5‐nitrospiro[2H‐benzimidazole‐2,1′‐cyclohexane] (1) was converted into the carbonitrile 5 and the 4‐phenylthio derivative 4. The NO2 or the PhS substituents in 4 could be replaced regiospecifically by reaction with Me3SiN3 or NaN3, respectively. The 5‐azido derivative 8, resulting from NO2‐group replacement was made to cyclize photolytically to give the angular spiro[cyclohexane‐imidazophenothiazine] 18. The azide 9 obtained from the PhS replacement in 4 cyclized spontaneously to give the angular spiro[cyclohexane‐imidazobenzoxadiazole] 10 which, on reductive hydrolysis, furnished benzofurazan‐4,5‐diamine 14. The diamine 14 was converted by conventional methods into a imidazobenzoxadiazole 15, oxadiazoioquinoxaline 16, and selenadiazoloxadiazole 17. The carbonitrile 5 was converted, in simple steps, into the ‘stretched‐out’, angular pteridine and purine analogues, 25 and 28, respectively.
The synthesis of DL‐1‐(hexadecanoyloxy)methyl‐ and 1‐O‐hexadecanoyl‐inositols as potential inhibitors of phospholipase C
Authors: James D. , Massy R. , Wyss Pierre
Published: December 2004

The synthesis of racemic analogues of phosphatidylinositol (PI) and phosphatidylinositol 4,5‐bisphosphate (PIP2) starting from myo‐inositol is described. Inositol derivatives with and without homologalion at C(l) and with and without ionic groups (phosphate or sulfate) at C(4) and C(5) were prepared as well as homologated derivatives with deoxy composition at C(2) and/or C(6). In all these compounds, palmitate ester groups were introduced in place of the diacylglyceryl group of PI or PIP2.
Pterin chemistry. Part 89. Natural primapterin belongs to the L‐series of 7‐(polyhydroxypropyl)pterins
Authors: Viscontini Max
Published: December 2004

Natural primapterin (80 μg) was isolated from 200 ml of urine of a patient with mild hyperphenylalaninemia. The CD curve of the compound showed that it belongs to the L‐series of 7‐(polyhydroxypropyl)pterins.
Eine neue Methode zur stereochemischen Analyse offenkettiger terpenoider Carbonyl‐Verbindungen,
Authors: Knierzinger Andreas , Walther Willy , Weber Beat , Müller Robert Karl , Netscher Thomas
Published: December 2004

A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl Compounds

A new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)‐L‐diisopropyl‐tartrate acetals derived from dihydrocitronellal (6), hexahydropseudoionone (3), hexahydrofarnesal (7), and hexahydro far nesy lace tone (4), the C10, C13, C15, and C18 intermediates in various syntheses of naturally occurring tocopherols and vitamin K1, can be achieved by capillary GC on a cyanopropylsilicon‐coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present‐day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C‐atoms bearing two stereogenic centres is performed in a single operation for the first time.
Long‐Range Intramolecular Electron Transfer between two Naphthalene π‐Moieties Attached to a Rigid Norbornylogous Spacer of Variable Length: An ESR and ENDOR Study
Authors: Gerson Fabian , Wellauer Thomas , Oliver Anna M. , Paddon‐Row Michael N.
Published: December 2004

ESR, ENDOR, and TRIPLE‐resonance studies are reported on the radical anions of 7(1,0), 7(2,0), and 7(1,1) in which a completely rigid spacer separates two naphthalene π‐moieties by 2, 4, and 6 CC single bonds, respectively. Whereas 7(1,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} has to be considered as a ‘truly’ charge‐ and spin‐delocalized radical anion of a homobinaphthylene‐like system, the frequency of intramolecular electron transfer in 7(2,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} and 7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} is governed by the migration rate of the counterfort (K+) between two equivalent sites at the π‐moieties. Under conditions of tight ion pairing (solvent 2‐methyltetrahydrofuran), the unpaired electron in 7(2,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} and 7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} is localized on one π‐moiety and the pertinent spectra resemble that of the radical anion produced from an analogous mononaphthalene derivative 8. On the other hand, with solvents of higher cation‐solvating power (1,2‐dimethoxyethane or its mixtures with N,N,N′,N′,N″,N′‐hexamethylphosphoric triamide), delocalization of the electron spin over both π‐moieties becomes evident, thus indicating that the electron‐transfer rate exceeds the hyperfine time‐scale (ca. 107s−1). Simultaneous occurrence of ‘localized’ and ‘delocalized’ radical anions is also observed, in particular for 7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}. Previous findings for the radical anion of 6(1) which, like 7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, contains two naphthalene π‐moieties separated by 6 CC single bonds are reinterpreted in the light of the results obtained in the present work. Exhaustive reduction of 7(2,0) and 7(1,1) leads to the formation of triplet dianions in which each of the two π‐moieties houses one unpaired electron.
Novel C9 and C11 Hydrocarbons from the Brown Alga Cutleria multifida; Sigmatropic and Electrocyclic Reactions in Nature. Part VI
Authors: Keitel Jürgen , Fischer‐Lui Iris , Boland Wilhelm , Müller Dieter G.
Published: December 2004

In addition to the known C11H16 hydrocarbons multifidene (4), aucantene (2), and ectocarpene (5), the marine brown alga Cutleria multifida produces trace amounts of the C9H12 hydrocarbon 7‐melhylcycloocta‐1,3,5‐triene (8) and its valence tautomer 7‐methylbicyclo[4.2.0]octa‐2,4‐diene, A second novel C9H12 hydrocarbon is 6‐vinyicyclo‐hepta‐1,4‐diene (9), a lower homologue of ectocarpene (5). Among the C11H16 hydrocarbons, 7‐((1E/Z)‐prop‐l‐enyl)cycloocta‐1,4‐diene (10/11) is found for the first time. The structure of all new products is confirmed by synthesis and spectroscopic data. The biosynthesis of the new hydrocarbons 8–11 is obviously linked to the pathways which lead to the major products giffordene (7), (6S)‐ectocarpene ((6S)‐5), and (4R,5R)‐aucantene ((4R,5R)‐2). Consecutive reactions of certain thermolabile primary products proceed via electrocyclic ring closure, 3,3‐sigmatropic rearrangement, or a 1,7‐sigmatropic H‐shift.
Stoffwechselprodukte von Mikroorganismen. 257. Mitteilung. (3S,5R,6E,8E)‐Deca‐6,8‐dien‐1,3,5‐triol, ein neues Stoffwechselprodukt von Streptomyces fimbriatus (MILLARDet BURR 1926)
Authors: Niederer Daniel , Séquin Urs , Drautz Hannelore , Zähner Hans
Published: December 2004

(3S,5R,6E,8E)‐Deca‐6,8‐diene‐1,3,5‐triol, a New Metabolite from Streptomyces fimbriatus (MILLARD et BURR 1926)

The title compound 2, a new C10‐metabolite related to the previously found (3S‐8E)‐1,3‐dihydroxydec‐8‐en‐5‐one (1), was isolated from the culture filtrate of Streptomyces fimbriatus, strain Tü 2335 by solvent extraction and chromatography. The constitution and the absolute configuration were determined by spectroscopic methods and chemical derivatization. The relative configurations were determined by NOE measurements with the silyl‐protected 3,5‐isopropylidene derivative of 2.
Reaktionsverhalten tricyclischer 4H,8H‐Benzo[1,2‐c:4,5‐c′]‐diisoxazol‐4,8‐dione gegenüber Reduktionsmitteln
Authors: Neidlein Richard , Bischer Alfred , Kramer Walter
Published: December 2004

Reaction Behavior of 4H,8H‐Benzo[1,2‐c:4,5‐c′]diisoxazole‐4,8‐dionos towards Reducing Agents

By reduction of the 3,7‐diamino‐substituted heterocycles 1c–d and 6a–d, the quinoid 2,5‐diamino‐3,6‐dioxo‐cyclohexa‐ 1,4‐diene‐ 1,4‐dicarboxamides 2c–h and 7a–d are synthesized. The diaminodicarboxamides 2 can be recyclised by use of Pb(AcO)4. The dialkylamino‐substituted derivatives 1c–h react with NaBH4 under conservation of the heterocyclic system to the tetrahydro‐benzo[1,2‐c:4,5‐c′] diisoxazoldiones of type 5. The NMR‐spectroscopic behavior of 2 and 7 is discussed.
Bilden sich aus Pentafulven und Cyclopentadien [6+4]‐Cycloaddukte??
Authors: Niggli Urs , Neuenschwander Markus
Published: December 2004

Does [6+4] Cycloaddition between Pentafulvene and Cyclopentadiene Take Place?

Reaction of a 1:1 mixture of cyclopentadiene (CPD) and pentafulvene (1a) at 20° gives a complex mixture. The low‐molecular‐weight part mainly consists of pure and mixed dimers (ca. 73 %) besides corresponding trimers (ca. 20%) and some corresponding oligomers according to GC/MS investigations (Fig. 1). The 3 predominant ‘mixed dimers’ between CPD and 1a have been separated, and structures 4–6 (Scheme 3) are assigned according to 400‐ and 600‐MHz 1H‐NMR investigations. These results show that HOMO(CPD)‐LUMO(fulvene) interactions are important in pentafulvene cycloadditions. Dimer 6 results from [6+4] cycloaddition followed by [1,5]‐H shifts.
Synthesis and Structure of the Copper(II) Complex of a Chiral Bis(dihydrooxazole) Ligand
Authors: Hall Jonathan , Lehn Jean‐Marie , DeCian André , Fischer Jean
Published: December 2004

The bridged bis(dihydrooxazole) compound (−)‐2 and its silylated derivative (−)‐3 have been synthesised as building blocks for chiral ligands. The complex of (−)‐3 with CuII has been obtained, and its crystal structure has been determined. The CuII ion is bound to two deprotonated ligands in a twisted tetracoordinated geometry.
Le (−)‐(2S)‐2‐Hydroxyhexanedioate de diéthyle, nouveau bloc chiral pour la synthèse énantiospécifique
Authors: Blaser Florian , Deschenaux Pierre‐François , Kallimopoulos Thomas , Jacot‐Guillarmod André
Published: December 2004

The (−)‐(2S)‐Diethyl 2‐Hydroxyhexanedioate, a New Chiral Building Block for Enantioselective Synthesis

(−)‐(2S)‐Diethyl 2‐hydroxyhexanedioate ((2S)‐3) has been obtained by enantioselective reduction of diethyl 2‐oxohexanedioate (1) with baker's yeast. The key intermediate (−)‐(5S)‐ethyl 5,6‐dihydroxyhexanoate ((5S)‐5) is proved to be a useful synthon for the synthesis of chiral δ‐lactones and a precursor of leukotriene LTB4 ((5S)‐13).
Photochemical Reactions of Tetrahydroquinoxalin‐2(1H)‐ones and Related Compound
Authors: Nishio Takehiko , Kondo Masaji , Omote Yoshimori
Published: December 2004

Photochemical behaviors of the pyrazinone derivatives 5,6,7,8‐tetrahydroquinoxalin‐2(1H)‐ones 1a–c and 1,5,6,7,8,9‐hexahydro‐2H‐cyclohepta[b]pyrazin‐2‐one 1d were investigated. Dye‐sensitized photo‐oxygenation of 1a‐c gave the 1:1 adducts 5a–c of the corresponding 3,8a‐epidioxy‐3,5,6,7,8,8a‐hexahydroquinoxalin‐2(1H)‐one 4 and H2O, whereas 1d gave 3,9a‐epidioxy‐1,3,5,6,7,8,9,9a‐octahydro‐2H‐cyclohepta[b]pyrazin‐2‐one 4d (Scheme 2). The different kind of products was interpreted as being the result of the ring strain and steric hindrance of endoperoxides produced from 1a–d with singlet oxygen. Irradiation of 1a–b in the presence of alkenes gave tricyclic azetidine derivatives 9 by [2 + 2] cycloaddition of the CN bond of 1 to the alkene.
The Synthesis of 3‐Acyl‐2,3‐dihydro‐2,2‐dimethyl‐1,3‐thiazoles
Authors: Vorbrüggen Helmut
Published: December 2004

Acylation of 2,5‐dihydro‐2,2‐dimethyl‐1,3‐thiazoles leads to 3‐acyl‐2,3‐dihydro‐2,2‐dimethyl‐1,3‐thiazoles as potential starting materials for the total synthesis of racemic cephalosporins.
Synthese von Monomorin I, einem Spurpheromon der Pharao‐Ameise (Monomorium pharaonis)
Authors: Vavrecka Mojmir , Hesse Manfred
Published: December 2004

Synthesis of Monomorin I, a Trail Pheromone of the Pharao Ant (Monomorium pharaonis)

Katalytic hydrogenation of the 4‐nitroalkanone 5 yielded the cis‐pyrrolidine ester 6 (Scheme). The preparation of 5 was accomplished by ethanolysis of the nitrocyclohexanone derivative 4. Iodination at C(α) of 6, followed by cyclization, gave a nearly 5:6 mixture of the two C(5)‐epimers 10/9 of octahydroindolizine. Epimerisation of the undesired 10 to 9 and subsequent transformation of the latter gave racemic monomorine I (1; 34% yield from 5).
A New Total Synthesis of D‐threo‐L‐talo‐Octose
Authors: Neff Denis‐Pierre , Chen Yuanwei , Vogel Pierre
Published: December 2004

A new approach to the total, asymmetric synthesis of D‐threo‐L‐talo‐octose ((−)‐1) and its derivatives is presented. It is based on the chemoselective Wittig‐Horner monoolefination of a 5‐deoxy‐D‐ribo‐hexodialdose derivative 4 obtained by selective reduction of (−)‐5‐deoxy‐2.3‐O‐isopropylidene‐/β‐D‐ribo‐hexofuranurono‐6,1‐lactone ((−)‐3). Allylic bromination of the resulting methyl (E)‐oct‐6‐enofuranuronate (+)‐5 followed by intramolecular nucleophilic displacement of the so‐obtained bromides gave a 13.3:1 mixture of (−)‐methyl (E)‐l,4‐anhydro‐6,7‐dideoxy‐2,3‐O‐isopropylidene‐β‐L‐talo‐oct‐6‐enopyranuronate ((−)‐8) and methyl (E)‐l,4‐anhydro‐6,7‐dideoxy‐2,3‐O‐isopropylidene‐α‐D‐allo‐oct‐6‐enopyranuronate (9). The double hydroxylation of the enoate (−)‐8 followed Kishi's rule and gave the corresponding D‐threo‐β‐L‐talo‐octopyranuronate derivative (−)‐11 with a good diastereoselectivity. Reduction of ester (−)‐11 and deprotection led to pure (−)‐1.
Synthesis of Unsubstituted and 4,4′‐Substituted Oligobipyridines as Ligand Strands for Helicate Self‐Assembly
Authors: Harding Margaret M. , Koert Ulrich , Lehn Jean‐Marie , Marquis‐Rigault Annie , Piguet Claude , Siegel Jay
Published: December 2004

A general strategy for the synthesis of oligobipyridine ligands 2–5 containing from two to five 2,2′‐bipyridine subunits, for helical metal complexes is described (sec Scheme). Both the unsubstituted parent strands (a series) as well as their derivatives bearing fester or amide functions in the 4,4′‐positions of the bipyridine moieties (b–d series) have been obtained.