bluuebunny/crossref_metadata_2025_split huggingface dataset:
From p‐Dimethoxybenzene to Crown‐benzenophanes, 4– Cation‐Complexing Properties of Bis(p‐phenylene‐34‐crown‐10) – A Structural and Spectrophotometric Study
Authors: Marquis Damien , Greiving Helmut , Desvergne Jean‐Pierre , Lahrahar Nacer , Marsau Pierre , Hopf Henning , Bouas‐Laurent Henri 
Published: July 2007

AbstractThe title compound 2, an electron‐rich macrocyclic paracyclophane of the coronand type, known to form a charge‐transfer complex with paraquat, was found to encapsulate strontium cations and to bind to magnesium cations. X‐ray analysis revealed that 2 forms a 2:1 (metal/substrate) complex with Sr(ClO4)2, in which the two benzene rings weakly overlap, whereas in the single crystals grown from Mg(ClO4)2, the metal cation prefers to lie outside the coronand (1:1 stoichiometry). In acetonitrile solution, cations were observed to trigger an hypsochromic shift of the UV absorption spectra, proportional to their size and charge density. The stoichiometries and binding constants were also determined by UV absorption titration in acetonitrile using the LETAGROP‐SPEFO program for several monovalent and divalent cations. For Na+, Ca2+, and Sr2+, 1:1 and 2:1 complexes were shown to be formed. In the free ligand, a weak interaction between the benzene rings was detected by fluorescence decay kinetic analysis, indicating the presence of two conformer populations within the nanosecond time scale. In solution, metal cations neither induce detectable excimer formation nor seem to have a strong influence on the fluorescence emission spectra, except a heavy atom quenching with Sr2+ and Ba2+, in contrast to the effect observed in absorption. However, Sr2+ and Mg2+induce a clear hypsochromic shift in the single crystal fluorescence spectra. Compound 2 was prepared by a new and efficient route which is compared to the previous procedures.
Synthetic Applications of Bis(iminophosphoranes) – Preparation of Some Derivatives of the 11H‐Quinazolino[2,3‐b]‐ and Quinazolino[4,3‐b]quinazoline Ring Systems
Authors: Molina Pedro , Conesa Carlota , de los Desamparados Velasco M. 
Published: July 2007

AbstractAza Wittig reaction of bis(iminophosphorane) 3 with two equivalents of aryl isocyanates directly provided the bicyclic guanidines 4. However, 3 undergoes intramolecular aza Wittig reaction on thermal treatment to give the iminophosphorane 6 derived from the 2‐(o‐azidophenyl)‐4(3H)‐quinazolinone. Compound 6 reacts with isocyanates, acyl chlorides and carbon disulfide to yield quinazolino[4,3‐b]quinazoline derivatives 8a–c, 9a–c, 10, and 11.
Secondary Fungal Metabolites and Their Biological Activity, VIII. – Partial Synthesis of Oosponol, an Antifungal Isocoumarin
Authors: Kovács Tibor , Sonnenbichler Johann 
Published: July 2007

AbstractThe partial synthesis of oosponol (4), which shows significant antibiotic activity, has been accomplished by enzyme catalyzed reactions including regioselective acetylation of (−)‐oospoglycol (1) followed by an oxidation step and hydrolysis by a lipase.
Solvolysis of Tricyclo[4.1.0.02,7]hept‐4‐en‐3‐yl and Tricyclo[4.1.0.02,7]hept‐3‐yl Methanesulfonates and p‐Nitrobenzoates – Remarkably Small Enthalpy Difference between the C7H7 Cations Tricyclo[4.1.0.02,7]hept‐4‐en‐3‐yl and 7‐Norbornadienyl
Authors: Bentley T. William , Llewellyn Gareth , Norman Simon J. , Kemmer Ralf , Kunz Ulrike , Christl Manfred 
Published: July 2007

AbstractIn an extension of previous work, tricyclo[4.1.0.02,7]heptan‐3‐ol (5) was synthesised in four steps from benzvalene. Methanesulfonates 12 and 6b, c, prepared from 5 and 4‐halotricyclo[4.1.0.02,7]hept‐4‐en‐3‐ols 4b, c, were too unstable to be isolated, but were unambiguously characterised by their NMR spectra. On treatment of the unsubstituted tricycloheptenol 4a with methanesulfonyl chloride, the expected mesylate 6a could not be observed. Even at −40°C, only its consecutive products 3‐chlorotricyclo[4.1.0.02,7]hept‐4‐en (7a) and 7‐chloronorbornadiene (8a) were discernible. The analogous reaction of 6b occurred only at room temperature, with formation of the dichlorotricycloheptene 7b and the dichloronorbornadiene 8b. Rearrangement products of 6b and 12 were the chloronorbornadiene mesylate 10b and anti‐7‐norbornenyl mesylate (13), respectively. – The solvolysis of 6b, c in aqueous ethanol and of 6b in 2,2,2‐trifluoroethanol (TFE) gave nonrearranged products exclusively, i.e. the alcohols 4b, c, the ethyl ethers 17b, c, and the trifluoroethyl ether 18b. In contrast, from 12 only rearranged products arose, namely anti‐7‐norbornenol (30) and its ethyl ether 31. The solvolysis of the unsubstituted tricycloheptenyl p‐nitrobenzoate 11a in 80% aqueous ethanol proceeded about equally fast in parallel reactions with cycloalkyl‐oxygen and acyl‐oxygen cleavage. In addition to the tricycloheptenol 4a, the tricycloheptenyl ethyl ether 17a, ethyl 7‐norbornadienyl ether (19), 7‐norbornadienyl p‐nitrobenzoate (20), and ethyl p‐nitrobenzoate were formed. No acyl‐oxygen cleavage took place in TFE as solvent, where the tricycloheptenyl trifluoroethyl ether 18a, 20, 7‐norbornadienyl trifluoroethyl ether (21), and the cyclopentadienylvinyl trifluoroethyl ethers 22/23 were produced. A new mechanism is proposed for the route to the major products 22/23 via the intermediate 7‐norbornadienyl cation (9a), which was attacked by TFE at the two‐membered bridge stabilising the positive charge. Thus formed, tricyclo‐[3.2.0.02,7]hept‐3‐en‐endo‐6‐yl trifluoroethyl ether (24) underwent a Diels‐Alder cycloreversion generating the cyclopentadienylvinyl trifluoroethyl ether 25, the immediate precursor of 22/23. – From kinetic data for these processes and thermochemical data for appropriate hydrocarbons, the enthalpy difference between the C7H7 cations, tricyclo‐[4.1.0.02,7]hept‐4‐en‐3‐yl (3a) and 7‐norbornadienyl (9a), was calculated to be only 8 kcal mol−1.
Preparation and Characterization of Oligo‐(2,2′‐Bipyridyl)pyrazines
Authors: Heirtzler Fenton R. , Neuburger Markus , Zehnder Margareta , Constable Edwin C. 
Published: July 2007

AbstractAn improved preparation of 2,2′‐bipyridine‐6‐carboxaldehyde 1 provides this compound in good yield for the further syntheses of oligo‐(2,2′‐bipyridyl)pyrazines 6–8, new ligands for supramolecular metallorganic complexes. According to 1H‐NMR spectroscopic and X‐ray crystallographic studies, the bis(2,2′‐bipyridyl) compound 6 exists in a helical conformation in solution and in the solid state. The structure of the tetrakis(2,2′‐bipyridyl) compound 8 is also confirmed through its crystal structure.
Synthesis and In Vitro Antitumor Activity of 2′‐Deoxy‐5‐fluorouridylyl‐(3′→5′)‐2′‐deoxy‐5‐fluoro‐N4‐octadecylcytidine: A New Amphiphilic Dinucleoside Phosphate
Authors: Schott Herbert , Ludwig Peter S. , Gansauge Frank , Gansauge Susanne , Schwendener Reto A. 
Published: July 2007

AbstractThe new amphiphilic dinucleoside phosphate, 2′‐deoxy‐5‐fluorouridylyl‐(3′→5′)‐2′‐deoxy‐5‐fluoro‐N4‐octadecylcytidine (4) was synthesized on a gram scale, using the phosphotriester method, starting from the cytostatic drug 2′‐deoxy‐5‐fluorouridine (5FdU) and 2′‐deoxy‐5‐fluoro‐N4‐octadecylcytidine (1d). In in vitro clonogenic growth assays using the human pancreatic adenocarcinoma cell line MIA PaCa 2, the amphiphilic dimer was significantly more effective than the parent monomeric 5FdU. The IC50 of the dimer was 10 μg/ml when applied as an aqueous solution and 12 μg/ml when given as a liposome dispersion, whereas with 5FdU the IC50 concentration was not reached within the concentration range used.
Michael Addition versus 1,3‐Cycloaddition Reactions of Pyridinium Ylides with (Arylmethylene)isoxazol‐5‐ones: Diastereoselective Formation of 4‐[1‐Aryl‐2‐(1‐pyridinio)ethyl]isoxazolium‐5‐olates
Authors: Risitano Francesco , Grassi Giovanni , Bruno Giuseppe , Nicolò Francesco 
Published: July 2007

AbstractThe reactions of (arylmethylene)isoxazol‐5‐ones 1 with pyridinium ylides 2 lead to the diastereoselective formation of olates 4. The reasons for the favored Michael addition and the unsuccessful subsequent cyclization to fused O‐heterocycles are discussed on the basis of X‐ray analysis as well as 1H‐NMR and chemical evidences.
Asymmetric Synthesis of (R,S)‐Dehydroiridodial, (R,S)‐Dehydroiridodiol and Analogues
Authors: Enders Dieter , Kaiser Anja 
Published: July 2007

AbstractThe synthesis of (R,S)‐(–)‐dehydroiridodiol(dial) [(R,S)‐6b], isolated from the plant Actinidia polygama Miq., and its analogues, in high diastereo‐ and enantiomeric purity (ee ⩾ 96%) is described. Key steps of the synthesis are the Michael addition of metallated SAMP hydrazones [(S)‐1] to the 2‐cyclopentenecarboxylate 2 and subsequent conversion to the 5‐substituted 2‐methylcyclopentenecarboxylates 5.
Cycloadditions, 55. – Substituent Effects in Tandem Intramolecular Silyl Nitronate Olefin Cycloadditions (ISOC) Leading to Functionalized Tetrahydrofurans
Authors: Hassner Alfred , Friedman Oded , Dehaen Wim 
Published: July 2007

AbstractThe intramolecular silyl nitronate olefin cycloaddition (ISOC) leading to substituted, fused‐ring tetrahydrofurans 6 was examined with regard to optimum conditions and substituent effects. The required unsaturated nitro ethers 3 resulted from low‐temperature, base‐mediated Michael addition of allyl alcohols 2 to nitroolefins 1, followed by conversion to unsaturated silyl nitronates 4. Cycloaddition of the latter and elimination of silanol provided 6. One‐pot tandem reactions, starting with nitroolefins 1 and allyl alcohols 2 and involving four steps, sometimes proceeded in better yields but often gave unexpected side products. Terminal olefinic electron‐donating substituents (Me, MeO) increased the rate of cycloaddition, while an internal olefinic methyl substituent slowed down the reaction. In the case of nitronates possessing ester or nitrile moieties as terminal olefin substituents, tandem Michael addition to produce substituted furans 14, 15 occurred faster than trapping of the nitronate anion by TMSCI.
Synthesis of Carbon‐Backbone‐Elongated GDP‐L‐Fucose Derivatives as Substrates for Fucosyltransferase‐Catalysed Reactions
Authors: Vogel Christian , Bergemann Claudia , Ott Andrej‐Jakob , Lindhorst Thisbe K. , Thiem Joachim , Dahlhoff Wilhelm V. , Hällgren Christer , Palcic Monica M. , Hindsgaul Ole 
Published: July 2007

AbstractStarting from the 6‐O‐tert‐butyldimethysilyl‐2,3;4,5‐di‐O‐isopropylidene‐D‐galactose diethyl dithioacetal (4) and proceeding through a Wittig reaction and Swern oxidation, a series of L‐fucose analogues, which unlike the normal L‐fucose possess an extended alkyl‐chain at C‐5, can be produced. The elongated carbon backbone in the L‐fucitols (22–25) as well as in the L‐fucose derivatives (30–33) increases the hydrophobic nature of the sugar molecule, promoting liquid‐crystalline properties in both series. The further derivatization of the L‐fucose analogues 30, 31 leads to the corresponding β‐L‐galacto‐deco‐ and dodeco‐pyranosyl phosphates 46, 47 and, in turn, to the respective pyranosyl guanosine 5‐diphosphates 48, 49. The reaction of the β‐L‐galactopyranosyl guanosine 5‐diphosphate 48 with 8‐methoxycarbonyloctyl 2‐acetamido‐2‐deoxy‐4‐O‐(β‐D‐galactopyranosyl)‐β‐D‐glucopyranoside (50) in the presence of a 3/4‐α‐fucosyltransferase furnished an O‐glycosidic linkage of the α‐L‐galactopdecopyranose 30 at the 3‐O‐position of the N‐acetyllactosamine glycoside 50. The chemo‐enzymatic coupling reaction proves that the synthesized carbon‐backbone‐elongated L‐galactopyranosyl guanosine 5‐diphosphates are suitable substrates for the α‐fucosyltransferases.
Allenyl Enolates – A New Class of Chiral Ambident Nucleophiles, 5. Ireland–Claisen Rearrangements of Allenic Silyl Ketene Acetals
Authors: Becker Markus , Krause Norbert 
Published: July 2007

AbstractAllenic silyl ketene acetals 3 formed by conjugate 1,6‐addition of organocuprates to 2‐propen‐1‐yl and 2‐buten‐1‐yl 2‐en‐4‐ynoates 1 and regioselective enolate capture with silyl electrophiles readily undergo [3,3]‐Ireland‐Claisen rearrangements to the 2‐substituted methyl 3,4‐dienoates 4. The simple diastereoselection of the formation of 4b could be improved by variation of the silylating agent as well as the addition of bases. in the case of product 4c, the sigmatropic rearrangement also takes place with good diastereofacial selectivity, i.e., with axis‐to‐center chirality transfer.
Chemistry of Aziridine Carboxylic Acids, 7. Synthesis of Ethyl (2R,3S)‐N‐Boc‐ and ‐N‐Benzyl‐3‐vinylaziridine‐2‐carboxylates: New Potential Building Blocks for Enantiomerically Pure Unsaturated Amino Acids
Authors: Jähnisch Klaus 
Published: July 2007

AbstractEnantiomerically pure cis‐ and trans‐1H‐aziridine‐carboxylic acid derivatives 2a, b and 3a, b have been prepared by asymmetric Michael‐type addition of ammonia to chiral acrylates 1a, b with high syn selectivity. The title compounds were obtained from the diols 8a, b by Corey‐Winter olefination.
Recent Advances in N‐Protection for Amino Sugar Synthesis
Authors: Debenham John , Rodebaugh Robert , Fraser‐Reid Bertram 
Published: July 2007

AbstractRecent synthetic efforts in the construction of oligosaccharides, glycoproteins, glycolipids and other glycoconjugates containing a variety of 2‐amino‐2‐deoxy sugars have led to the development of new methods for nitrogen protection. These new nitrogen‐protecting groups have been removed from substrates using mild and often chemoselective conditions. In this microreview, the preparation, present uses, and deprotection of amino sugar derivatives employing these new agents are described. Applications of phthalimides with electron‐withdrawing groups including the tetrachlorophthaloyl (TCP), dichlorophthaloyl (DCPhth), dithiasuccinoyl (Dts), N‐pent‐4‐enoyl and N,N‐diacetyl functionalities are discussed.
Pheromone Synthesis, CLXXIX. Synthesis of Lurlenic Acid and Lurlenol, the Sex Pheromones of the Green Flagellate Chlamydomonas
Authors: Takanashi Shin‐Ichi , Mori Kenji 
Published: July 2007

AbstractLurlenic acid {(4E,8E,12E)‐14‐[2′‐hydroxy‐3′,4′‐dimethyl‐5′(1″‐β‐D‐xylopyranosyloxy)phenyl]‐4,8,12‐trimethyltetradeca‐4,8,12‐trienoic acid (1)} and lurlenol (2), the sex pheromones produced by the female gametes of the green flagellate Chlamydomonas, were synthesized by starting from D‐xylose, 2,3‐dimethyl‐p‐hydroquinone and geranylgeraniol or farnesol. Synthetic 1 and 2 were biologically active, while the possible biogenetic precursor 3 was inactive.
Positional and Facial Selectivity in Diels‐Alder Reactions of (−)‐(aS,7S)‐Colchicine: Synthesis of Novel Analogues of the Alkaloid
Authors: Brecht René , Haenel Frank , Seitz Gunther , Frenzen Gerlinde , Pilz Astrid , Massa Werner , Wocadlo Sigrid 
Published: July 2007

AbstractPositional and facial selectivity in Diels‐Alder reactions of several hetero‐ and carbodienophiles with (−)‐(aS,7S)‐colchicine (1) has been examined. In all cases, cycloaddition occurred with high positional selectivity at the 8,12‐positions of the alkaloid and preferentially from the diene facesynto the allylic substituent at the stereogenic center C‐7. The observed high π‐facial diastereoselectivity is independent of the polarity of the solvent used and is therefore probably a consequence of steric factors. The structures of the Diels Alder‐adducts of1with singlet oxygen,N‐phenyl‐1,2,4‐triazolinedione (PTAD) andtrans‐cyclooctene,4,5, and15, respectively, were assigned on the basis of spectral data and verified by X‐ray crystallography.
Photoreactions of trans‐10b,10c‐Dimethyl‐10b,10c‐dihydropyrenes
Authors: Cerfontain Hans , Koeberg‐Telder Ankie , Bakker Bert H. , Mitchell Reginald H. , Tashiro Masashi 
Published: July 2007

AbstractThe photoisomerization of trans‐10b,10c‐dimethyl‐10b,10c‐dihydropyrene (1), its 2,7‐di‐tert‐butyl derivative 5 and a series of potassium sulfonate derivatives of 1, in both [D8]1,4‐dioxane and [D2]dichloromethane as solvent, has been studied using λ = 420–570 nm irradiation. Irradiation of a deoxygenated solution of 1 in dioxane leads to the exclusive formation of anti‐8,16‐dimethyl[2.2]metacyclophane‐1,9‐diene (2), whereas the photoconversion of 1 in a non‐degassed solution leads to the successive formation of 2 and 5,8‐epidioxy‐anti‐8,16‐dimethyl[2.2]metacyclophane‐1,9‐diene (7). Similarly, irradiation of the 2,7‐di‐tert‐butyl derivative 5 in oxygen containing [D8]dioxane as solvent leads to the consecutive formation of the corresponding 5,13‐di‐tert‐butyl derivatives 6 and 8. Irradiation of mixtures of potassium sulfonate derivatives of 1 (1‐Sn) in D2O as solvent leads to photoisomerization with formation of the correspondingly substituted sulfonate derivatives of 2. Only with the dipotassium 2,4‐ and 2,5‐disulfonates of 1 eventually small amounts of the corresponding epidioxy‐bridged products 7 were formed. The photoisomerization 1‐Sn → 2‐Sn appeared to be most effective for 1‐2‐S and 1‐2,5‐S2 and least effective for 1‐2,4,7‐S3 and 1‐2,4,7,10‐S4. In the dark, the epidioxy products 7 and 8 reverted to give initially the corresponding metacyclophanes 2 and 6, and subsequently the respective dihydropyrenes 1 and 5, and the dark reactions of the potassium sulfonate derivatives 2‐Sn yielded the correspondingly substituted 1‐Sn. A quantitative study showed that the dark reactions steps 7 → 2, 8 → 6, and 2‐Sn → 1‐Sn (n = 1–4) exhibit first‐order kinetics. For the deoxygenation of 5,8‐epidioxy‐anti‐8,16‐di‐methyl[2.2]metacyclophane‐1,9‐diene (7) the rate coefficient is ca. 2.7 times that of its 5,13‐di‐tert‐butyl derivative (8), and the rate coefficient for the isomerization 2‐Sn → 1‐Sn follows the order 2‐5‐S → 2‐5,13‐S2 > 2‐1,5,10‐S3.
An Efficient Procedure for the Preparation of 3‐Acetyl‐2,3‐dihydrobenzo‐thiazoles by Ring Contraction of 2,4‐Diaryl‐2,3‐dihydro‐1,5‐benzothiazepines under Acetylating Conditions
Authors: Tóth Gábor , Lévai Albert , Balázs Barbara , Simon András 
Published: July 2007

AbstractReaction of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines 1 with a mixture of acetic anhydride and pyridine afforded 3‐acetyl‐2,3‐dihydrobenzothiazoles 2 as sole products in good yields. Stereochemistry and the hindered rotation of the amide group were studied by means of NMR spectroscopy and the results were corroborated by AM1 calculations. A reaction mechanism for the ring contraction is proposed.
Demethyl(trifluoromethyl)actinomycins, II. Bis(trifluoromethylated) 4‐(2′‐Benzoxazolyl)actinocin Derivatives
Authors: Bahner Isabel , Lackner Helmut 
Published: July 2007

AbstractIn a previous study, performed in connection with the total synthesis of trifluoromethylated actinocinyl peptides 2a, the oxidative condensation of the corresponding o‐aminophenol precursor 1 furnished a novel trimerisation product, which had been tentatively assigned to the triphenedioxazine structure 3[1]. Now, an improved synthesis of the trimer and extensive 1‐ and 2D‐NMR studies have resulted in a new, quite unexpected structure: the 4‐(2′‐benzoxazolyl)actinocin derivative 8a, which replaces 3. Apparently, the quinone‐sided CF3 group of an actinocin intermediate is unusually activated and reacts with a third o‐aminophenol unit. The modifications to the synthesis increase the overall yield of demethyl‐(trifluoromethyl)actinomycins by a factor of five.
New Synthesis of 28‐Homobrassinolide from Stigmasterol
Authors: Hazra Braja G. , Kumar Tirunahari Pavan , Joshi Padmakar L. 
Published: July 2007

AbstractAn efficient and short synthesis of 28‐homobrassinolide (6) has been achieved in 12 steps with 15.6% overall yield from stigmasterol (8). Salient features of this synthesis are: (a) use of tetradecyltrimethylammonium permanganate for chemoselective cis‐dihydroxylation of the 2,22E‐dien‐6‐one 9, avoiding the use of OsO4; (b) one‐step epoxidation of the (22E)‐olefin and Baeyer‐Villiger oxidation of the B‐ring ketone 11 with trifluoroperoxyacetic acid; and (c) regioselective ring‐opening of the 22,23‐epoxide 12 to the bromohydrin 13 with LiBr and Amberlyst‐15 resin under mild conditions and in excellent yield.
Asymmetric Synthesis of Primary Amines by Nucleophilic Addition of Alkyllithium Compounds to Aldehyde SAMP/RAMP Hydrazones
Authors: Enders Dieter , Nübling Christoph , Schubert Heinrich 
Published: July 2007

AbstractThe aldehydes 1 or 5 are converted to the SAMP hydrazones 2 or the α‐alkylated SAMP hydrazones 7 and treated with organolithium compounds at low temperature. Cleavage of the NN bond of the resulting hydrazines 3 and 8 with Raney‐Ni/H2, or of the N‐methoxycarbonylhydrazines 9 with Li/NH3, yield the amines 4 with 61–90% ee, the amines 11 with 45–96% de and 93 → 99% ee. The absolute configuration of the amines 11 was established by X‐ray analysis of an appropriate MTPA derivative.
High Regioselectivity in Polar Additions to 1,6‐Diazacyclodeca‐3,8‐diynes
Authors: Ritter Joachim , Gleiter Rolf 
Published: July 2007

AbstractThe reactions of 1,6‐dialkyl‐1,6‐diazacyclodeca‐3,8‐diynes (9, a = CH3, b = C2H5, c = i‐C3H7) with HCl, H2O and CH3OH have been investigated. The reaction of 9c with HCl selectively gives N,N′‐diisopropyl‐4‐chloro‐1,2,3,5,6,7‐hexahydro‐2,6‐naphthyridine (13c) in quantitative yield. Investigation of this reaction at different temperatures allows the activation parameters for the process to be derived (ΔH≠ = 24 ± 1 kcal · mol−1, ΔS≠ = – 9 ± 2 cal · mol−1 · K−1). The regioselective reaction of 9c with methanol affords a quantitative yield of N,N′‐diisopropyl‐4‐methoxy‐1,2,3,4,5,6,7‐hexahydro‐2,6‐naphthyridine (29c). Addition of water to 9a in the presence of H2SO4 gives N,N‐dimethyl‐7‐oxo‐1,2,3,4,5,6,7,8‐octahydro‐2,6‐naphthyridine (28a) in low yields (15%). If the addition of water is carried out in the presence of Hg2+, the yield of 28a is increased considerably. The mechanisms of all three reactions are discussed and those involving electrophilic addition (AdE2) are favored.
Reactions of α,β‐Enones with Diazo Compounds, 2. Synthesis of Dihydrofuran Derivatives
Authors: Anac Olcay , Daut Ayse 
Published: July 2007

AbstractSeveral α,β‐unsaturated ketones were treated with dimethyl diazomalonate and ethyl acetodiazoacetate under bis(acetyl‐acetonato)copper(II) catalysis. Dihydrofuran derivatives, obviously arising from carbonyl ylides, were isolated in high yields. Structural identifications were carried out using 2D‐NMR‐spectroscopic data.
Properties and Reactions of Substituted 1,2‐Thiazetidine 1,1‐Dioxides: 3‐Acetoxy‐1,2‐thiazetidine 1,1‐Dioxide, Synthesis and Reactions with C‐Nucleophiles
Authors: Schwenkkraus Peter , Merkle Stefan , Otto Hans‐Hartwig 
Published: July 2007

AbstractN‐Silylated 3‐acetoxy‐1,2‐thiazetidine 1,1‐dioxide (5) is prepared from L‐cystine. Reactions of 5 with silyl enol ethers yield C‐3‐substituted β‐sultams 6, 12 and 15. Desilylation of 6 affords 7, which undergoes photochemical cyclization to give the bicyclic β‐sultam 10. In the course of such reactions, a portion of the C‐3‐substituted β‐sultam is consumed in a retro‐Michael‐type reaction, leading to the open‐chained sulfonamides 8 and 13 as side products. In the case of reactions between 5 and silyl enol ethers of cyclic ketones 16, only such open‐chained products, 17, are isolated. Reactions of 5 with substituted malonates yield the β‐sultams 19 and 20. Structures and stereochemistry are elucidated by spectroscopic methods.
Enantiospecific Synthesis of 2,5‐Disubstituted Piperidine Derivatives: Synthesis of (+)‐Pseudoconhydrine
Authors: Dockner Michael , Sasaki N. André , Riche Claude , Potier Pierre 
Published: July 2007

AbstractA novel methodology for the synthesis of any one of the four stereoisomers of a 2,5‐disubstituted piperidine in optically pure form is described, starting from readily available chiral building blocks 10 and 11 (or their antipodes). The utility of this approach is demonstrated in the total synthesis of (+)‐pseudoconhydrine hydrochloride, the structure of which was confirmed by X‐ray analysis.