bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Preparing Oligodeoxynucleotides Containing an Apurinic Site
Authors: Groebke Katrin , Leumann Christian 
Published: December 2004

AbstractIn three steps, 2‐deoxy‐D‐ribose has been converted into a phosphoramidite building block bearing a (t‐Bu)Me2Si protecting group at the OH function of the anomeric centre of the furanose ring. This building block was subsequently incorporated into DNA oligomers of various base sequences using the standard phosphoramidite protocol for automated DNA synthesis. The resulting silyl‐oligomers have been purified by HPLC and selectively desilylated to the corresponding free apurinic DNA sequences. The hexamer d (A‐A‐A‐A‐X‐A) (X representing the apurinic site) which was prepared in this way was characterized by 1H‐ and 31P‐NMR spectroscopy. The other sequences as well as their fragments, which formed upon treatment with alkali base, were analyzed by polyacrylamide gel electrophoresis.
Stereoselectivity of Dienamine [4 + 2] Cycloadditions Synthesis of Functionalised Decalins and Drimanes
Authors: Snowden Roger L. , Brauehli Robert , Wüst Manfred 
Published: December 2004

AbstractThe [4 + 2] cycloaddition stereoselectivity of dienamines 1–4 with dimethyl fumarate and fumaronitrile has been investigated, and functionalised decalins 21–40 have been prepared by elimination of Me2NH from cycloadducts 7–11 and 15–20; in the context of the synthesis of drimane sesquiterpenes, the reduction of dienediesters 29 and 30 is also described.
Enantio‐ and Diastereoselective Aldol‐Reaction of 2,6‐Dimethylphenyl Propionate Using Titanium‐Carbohydrate Complexes
Authors: Duthaler Rudolf O. , Herold Peter , Wyler‐Helfer Susanne , Riediker Martin 
Published: December 2004

AbstractChloro(cyclopentadienyl)bis(1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranos‐3‐O‐yl)titanium (1) is used for the transmetallation of Li‐enolates obtained from propionyl derivatives. While such Ti‐enolates of ketones and hydrazones appear to be unreactive, the (E)enolate13of 2,6‐dimethylphenyl propionate (11) adds to there‐side of aldehydes, affording varioussyn‐aldols14with high dia‐ and enantioselectivity (92–97% ds, 91–97% ee,cf.Scheme 2andTable 1). Racemicsyn‐aldols (±)‐14are obtained analogously from the achiral bis(2‐propyloxy)‐Ti‐enolate15(Scheme 2andTable 2). In contrast to the unstable Li‐enolate10, the Ti‐enolates13and15isomerize at −30°, presumably to the thermodynamically more stable (Z)‐enolates (Scheme 4), While the diastereoselectivity of the achiral enolate15is lost upon this equilibration, the chiral (Z)‐enolate27quite unexpectedly affordsanti‐aldols12of high optical purity (94–98% ec) and, in most cases, with acceptable‐to‐good diastereoselectivity (82–90% ds). Notable exceptions are branched unsaturated and aromatic aldehydes which form a greater proportion of synepimers of moderate optical purity (Scheme 5 and Table 3).Consistent with these findings, re‐facial‐and ami ‐selective aldol‐addition is also exhibited by the (Z)‐configurated Ti‐enolate22ofN‐propionyl‐oxazolidi‐none19(Scheme 3).
Cyclische Phenyl‐carbamate des Miotin‐Typs und ihre Wirkung auf die Acetylcholinesterase
Authors: Amstutz René , Enz Albert , Marzi Martin , Boelsterli Jakob , Walkinshaw Malcolm 
Published: December 2004

Cyclic Phenyl Carbamates and Their Action on AcetylcholinesteraseSeveral six‐, seven‐, and eight‐membered cyclic phenyl carbamates of the miotin type have been synthesised and their in vitro potency as inhibitors of acetylcholinesterase determined. The eight‐membered rings were found to be the most potent and are comparable with physostigrnin or miotin. It was concluded that, for maximum potency, the orientation of the carbamate group relative to the aromatic plane has to be close to orthogonal.
The Syntheses of Purine and Pyrimidine Secoribo‐nucleosides: Acyclo‐uridine Derivative of Cyclophosphamide
Authors: Zakerinia Maryam , Davary Hady , Hakimelahi Gholam H. 
Published: December 2004

AbstractThe synthesis of secoribo‐nucleoside analogues is described. Compounds 4 and 5 possess interesting antiviral effects in vitro. A procedure is also developed for the conversion of acyclo‐uridine nucleoside 7 to a novel derivative of cyclophosphamide 8.
Synthesis of rel‐(3RS,3aSR,7aSR)‐3‐(4‐Chlorophenyl)‐3a,4,5,6,7,7a‐hexahydro‐1‐methylindolin‐6‐one, the Main Metabolite of the Analgesic Ro 15‐8081: A Potent Amine‐Uptake Inhibitor
Authors: Bös Michael , Burkard Willy P. , Moreau Jean‐Luc , Schönholzer Peter 
Published: December 2004

AbstractThe synthesis of the title compound 2 and its diastereoisomer 3 was accomplished using tricarbonyl[1‐5‐n‐(4‐methoxycyclohexa‐2,4‐dien‐1‐yl)]iron tetrafluoroborate (4) as a precursor to the cyclohexanone ring. The assignments of the relative configurations of 2 and 3 are based on the X‐ray analysis of compound 3. Both compounds 2 and 3 are potent inhibitors of neuronal noradrenaline uptake in rats with similar potencies in vitro as compared to amitriptyline and desipramine. Compounds 2 and 3 are less potent as serotonin‐uptake inhibitors, very weak inhibitors of dopamine uptake, and virtually devoid of antinociceptive activity.
Reaction of 3‐Amino‐2H‐azirines with 2‐Amino‐4,6‐dinitrophenol (Picramic Acid): Synthesis of Quinazoline‐ and 1,3‐Benzoxazole Derivatives
Authors: Villalgordo José M. , Vincent Beverly R. , Heimgartner Heinz 
Published: December 2004

AbstractThe reaction of 3‐(dimethylamino)‐2H‐azirines 1a–c and 2‐amino‐4,6‐dinitrophenol (picramic acid, 2) in MeCN at 0° to room temperature leads to a mixture of the corresponding 1,2,3,4‐tetrahydroquinazoline‐2‐one 5, 3‐(dimethylamino)‐1,2‐dihydroquinazoline 6, 2‐(1‐aminoalkyl)‐1,3‐benzoxazole 7, and N‐[2‐(dimethylamino)phenyl]‐α‐aminocarboxamide 8 (Scheme 3). Under the same conditions, 3‐(N‐methyl‐N‐phenyl‐amino)‐2H‐azirines 1d and 1e react with 2 to give exclusively the 1,3‐benzoxazole derivative 7. The structure of the products has been established by X‐ray crystallography. Two different reaction mechanisms for the formation of 7 are discussed in Scheme 6. Treatment of 7 with phenyl isocyanate, 4‐nitrobenzoyl chloride, tosyl chloride, and HCl leads to a derivatization of the NH2‐group of 7 (Scheme 4). With NaOH or NaOMe as well as with morpholine, 7 is transformed into quinazoline derivatives 5, 14, and 15, respectively, via ring expansion (Scheme 5). In case of the reaction with morpholine, a second product 16, corresponding to structure 8, is isolated. With these results, the reaction of 1 and 2 is interpreted as the primary formation of 7, which, under the reaction conditions, reacts with Me2NH to yield the secondary products 5, 6, and 8 (Scheme 7).
Synthesis and Circular Dichroism of Optically Pure (±)‐(1S,2S,5S)‐5‐Methoxy‐3,4,6,7‐tetramethylidenebicyclo[3.2.1]oct‐2‐yl Derivatives. Baker's Yeast Reduction of 4‐Methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐one
Authors: Burnier Gérald , Vogel Pierre 
Published: December 2004

AbstractBaker's yeast reduction of 4‐methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐one (11) under fermenting conditions afforded (−)‐(1S,2S,4R)‐4‐methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐ol ((−)‐13) in 60% yield with an e.e. > 99.5%. Its methanesulfonate (−)‐14 was hydrolyzed and rearranged with high stereo‐selectivity into (+)‐(1S,2S,5S)‐5‐methoxy‐3,4,6,7‐tetramethylidenebicyclo[3.2.1]octan‐2‐ol ((+)‐15). The absolute configuration of (−)‐13 was deduced from the CD spectrum of its 4‐(dimethylamino)benzoate ((+)‐22) applying the chiral exciton‐coupling method. The CD spectrum of (+)‐15 and of its (tert‐butyl)dimethylsilyl ether ((+)‐23) showed exciton‐split type of Cotton effects attributed to through‐space interactions between the s‐gauche‐buta‐diene and s‐cis‐butadiene chromophores of these systems.
Pterin chemistry. Part 88. A simple synthesis of 5‐Deoxy‐L‐[5‐2H1]arabinose and L‐[3′‐2H1] biopterin
Authors: Adier Carmen , Curtius Hans‐Christoph , Datta Subir , Viscontini Max 
Published: December 2004

AbstractA simple synthesis of 5‐deoxy‐L‐[5‐2H1]arabinose was performed to obtain L‐[3′‐2H1]biopterin. The reduced form of this model substance is needed to investigate the pathway of 7‐substituted pterins in patients with primapterinuria.
A New Combined Purification/Phosphorylation Procedure for Oligodeoxynucleotides
Authors: Banmvarth Willi , Wippier Jürgen 
Published: December 2004

AbstractWe describe a new principle for the purification of oligodeoxynucleotides using a purification handle which leads to a covalent linkage of the desired DNA sequence to a solid matrix. Truncated sequences are removed by washing steps. The release of the pure target sequence is performed in such a way that it is obtained directly in its 5′‐phosphorylated form which represents a further advantage. In addition, the system can be used for 5′‐thiol modifications of synthetic DNA.
Synthesis of 3‐Deaza‐2′‐deoxyadenosine and 3‐Deaza‐2′,3′‐dideoxyadenosine: Glycosylation of the 4‐Chloroimidazo[4,5‐c]pyridinyl Anion
Authors: Seela Frank , Rosemeyer Helmut , Fischer Sabine 
Published: December 2004

AbstractThe convergent syntheses of 3‐deazapurine 2′‐deoxy‐β‐D‐ribonucleosides and 2′,3′‐dideoxy‐D‐ribonucleosides, including 3‐deaza‐2′‐deoxyadenosine (1a) and 3‐deaza‐2′,3′‐dideoxyadenosine (1b) is described. The 4‐chloro‐lH‐imidazo[4,5‐c]pyridinyl anion derived from 5 was reacted with either 2′‐deoxyhalogenose 6 or 2′,3′‐dideoxyhalogenose 10 yielding two regioisomeric (N1 and N3) glycosylation products. They were deprotected and converted into 4‐substituted imidazo[4,5‐c]pyridine 2′‐deoxy‐β‐D‐ribonucleosides and 2′,3′‐dideoxy‐D‐ribonucleosides. Compounds 1a and 1b proved to be more stable against proton‐catalyzed N‐glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase.
Stereochemistry of the Robinson Anellation: Studies on the Mode of Formation of the Intermediate Hydroxy Ketones
Authors: Nussbaumer Cornelius 
Published: December 2004

AbstractThe stereochemical outcome of the base‐catalyzed cyclization of diketones 5–8 has been investigated under protic conditions (Scheme 3). The more stable trans‐fused ketols are preferentially formed in kinetically controlled aldol reactions, when the incipient angular substituent R = H (6 → 10a) or CN (7 → 11a, 8a → 12a). For R = Me (as in 5), axial attack of the side‐chain enolate double bond on the ring CO group results in the rather selective formation of cis‐9b. It is assumed that these cyclizations are controlled by relative product stabilities (product‐like transition state) and steric effects. The competition between fused (e.g. 9) and bridged ketol (e.g. 13) formation in these cyclizations is discussed. The cis‐fused (‘steroid’) ketols were readily equilibrated with their trans‐counterparts (9b ⇄ 9a, 10b ⇄ 10a, 11b ⇄ 11a) under aprotic conditions (5 mol‐% of LDA, THF, 0°), thus, allowing assessments of relative stabilities.
The Photoreversible Addition of Sulfur Dioxide to Benzobenzvalene: A new Approach to the Benzoprefulvene Biradical
Authors: Burger Ulrich , Gmünder Christian , Schmidlin Serge , Bernardinelli Gérald 
Published: December 2004

AbstractBenzobenzvalene (naphthvalene; 1) is shown to add SO2 to a lateral bicyclobutane bond with formation of a sulfone 2 and a ‘γ‐sultine’ 3. The structure of the latter is unambiguously established by X‐ray diffraction. Both adducts extrude SO2 upon direct photolysis at 254 nm and regenerate 1 accompanied by naphthalene in a 1:3 ratio. This result is interpreted in terms of a reversible homolytic cleavage leading, for both, 2 and 3, to the same sulfinyloxy biradical 5, which by loss of SO2 gives the benzoprefulvene biradical 6. The latter in its singlet state undergoes ring closure to 1, or it opens to give naphthalene.
A Study on the Odour/Structure Relationship of Patchoulol and Norpatchoulenol
Authors: Spreitzer Helmut 
Published: December 2004

AbstractIn continuation of studying structure/activity relationships of odorous compounds, the influence of the bridgehead‐bonded Me group of (+)‐norpatchoulenol (1) and (−)‐patchoulol (2) and the olfactory properties of the corresponding unsaturated and saturated derivatives (±)−3, (±)−4 and (±)−5, (±)−6, respectively, are studied. The key odour descriptors‐wood, earth, and camphor‐are used for classification.
Synthesis of the 6‐C‐Methyl and 6‐C‐(Hydroxymethyl) Analogues of N‐Acetylneuraminic Acid and of N‐Acetyl‐2,3‐didehydro‐2‐deoxyneuraminic Acid
Authors: Vasella Andrea , Wyler René 
Published: December 2004

AbstractThe synthesis of 6‐C‐methyl‐Neu2en5Ac (4), 6‐C‐(hydroxymethyl)‐Neu2en5Ac (5), and 6‐C‐methyl‐Neu5Ac (6) is described. The 4‐methylumbellyferyl glycosides 8 and 9 were also prepared but proved unstable. Protection of the previously reported nitro ether 10 (→11) followed by a Kornblum reaction gave the branched‐chain derivative 13 which was transformed into aldehyde 14 and hence via 16 into the‐protected 6‐C‐hydroxymethylated 20 and into the 6‐C‐methyl‐substituted 18 (Scheme 1). Debenzylidenation of 20 and 18 afforded the diols 21 and 19, respectively. Selective oxydation of 19 followed by esterification (→ 22), acetylation (→ 23), and elimination led to the protected 6‐C‐methyl‐Neu2en5Ac derivative 24 (Scheme 2). Bromomethoxylation yielded mainly 25 and some 26, which were reductively debrominated to 27 and 28, respectively. Attempted deprotection of 27 did not lead to the corresponding acid, but to the 2,7‐ and 2,8‐anhydro compounds 29 and 30 which were characterised as their peracetylated esters 31 and 32 (Scheme 3). The structure of 32 was established by X‐ray analysis. Oxydation of 19 and 21, followed by deprotection, esterification, and acetylation gave 37 and 38, respectively (Scheme 4). The branched‐chain Neu2en5Ac derivatives 4 and 5 were obtained by β‐elimination (→ 39 and 40) and deprotection. Omission of the esterification after oxydation of 33 and 34 gave the lactones 35 and 36 which were transformed into 37 and 38, respectively. Bromoacetoxylation of 39 gave 41‐43 which were reductively debrominated to 44 (from 41 and 42) and 45 (Scheme 5). Bromoacetoxylation of 40 yielded 46 which was debrominated to 47. Glycosidation of the glycosyl chlorides obtained from 44 and 47 led to the α ‐D‐glycosides 48 and 49 and to the elimination products 39 and 40, respectively (Scheme 6). Transesterification of 48, followed by saponification gave the unstable glycoside 8 and hence 6‐C‐methyl‐Neu5Ac (6). The unstable glycoside 9 was obtained by similar treatment of 49 but yielded 50 under acidic conditions. The branched‐chain 4 and 5 were weak inhibitors of Vibrio cholera sialidase, and 8 and 9 were very poor substrates.
Microbial Metabolism of the Diterpene Sclareol: Oxidation of the A Ring by Septomyxa affinis
Authors: Kouzi Samir A. , McChesney James D. 
Published: December 2004

AbstractMicrobial metabolism of the diterpene sclareol (1) was studied. Screening studies have shown a number of microorganisms capable of metabolizing 1. Preparative‐scale fermentation with Septomyxa affinis ATCC 6737 has resulted in the production of three fungal metabolites that have been characterized by 2D‐NMR techniques and chemical reactions. These metabolites have been identified as 8α,13β‐dihydroxylabd‐14‐en‐3‐one (2), labd‐14‐ene‐3β.8α,13β‐triol (4), and labd‐14‐ene‐2α,8α,13β‐triol (6).
The Solid‐State and Solution Conformations of (+)‐Chelidonine
Authors: Kamigauchi Miyoko , Miyamoto Yuko , Iwasa Kinuko , Sugiura Makiko , Nishijo Zjujiro , Takao Narao , Ishida Toshimasa , In Yasuko , Inoue Masatoshi 
Published: December 2004

AbstractThe solid‐state and solution conformations of (+)‐chelidonine (1), a biologically active alkaloid, were determined by X‐ray diffraction and 1H‐NMR spectroscopy, X‐Ray diffraction analysis revealed a conformer with B/C ‘anti‐type’ cis conjunction, a half‐chair of ring B, and a twist half‐chair of ring C. One H2O molecule per one alkaloid molecule was cocrystallized and stabilized by H‐bonding with OHC(11). Analysis of the thermal behavior of the crystal showed more thermal stability in the monohydrate than the anhydrate. The NMR measurement of concentration and temperature dependences in CDCl3 and in (CD3)2SO suggested that the OH group of 1 was intramolecularly H‐bonded to N(5) in (CD3)2SO and intermolecularly H‐bonded to the solvent in CDCl3. Conformational‐energy calculations by the MNDO method showed that the intramolecular H‐bond was little affected by the conformational stabilization of 1.
Influence of the Axial Alkyl Ligand on the Reduction Potential of Alkylcob(III)alamins and Alkylcob(III)yrinates
Authors: Zhou De‐Ling , Tinembart Olivier , Scheffold Rolf , Walder Lorenz 
Published: December 2004

AbstractThe irreversible‐reduction potentials of 26 alkylcob(III)alamins (RCblIII 1a–z) and 26 alkylcob(III)yrinates (R‘Cby’III; 2a–z) (Ep 1a–z and Ep 2a–z, resp.) have been measured in situ by single‐scan voltammetry of hydroxocob(III)alamin hydrochloride (vitamin B12b‐ HCl; 1) or heptamethyl cob(II)yrinate perchlorate (ClO4‘Cby’II; 2) in presence of the corresponding alkyl halides (RX;3a–z) in DMF. The reduction potentials of alkylcobalt complexes exhibiting half‐life times as short as a few seconds become measurable by this technique. Thermodynamic cycles prove that the observed reduction potentials are closely related to the standard reduction potentials E°(RCoIII + e−⇆R⋅ + CoI). Electron‐withdrawing groups and/or an increased degree of substitution at the Co‐bound C‐atom in RCblIII and, R‘Cby’III shift Ep(1a–z) and Ep (2a–z) towards positive potentials. Linear correlations have been found between Ep(1a–z) (Ep(2a–z)) of RCblIII (R‘Cby’III) and the pKa of RH (or the Taft σ*‐ or the Hammett σ‐values of R) within each class of R, i. e. MeCblIII (Me‘Cby’III), primary RCblIII (R‘Cby’III) and secondary RCblIII (R‘Cby’III). The correlations allow to distinguish between electronic effects of the Co‐bound alkyl residues and their steric interactions with the corrin side chains. The correlations have further been used to visualize the light‐induced formal insertion of an olefin into the Co, C‐bond of an alkylcobalamin (Scheme 2, 1a→1u), a key step in the vitamin‐B12‐catalized C, C‐bond formation.
The Coordination Chemistry of 1,2‐Bis[(diphenylphosphino)methyl]benzene with Nickel(II), Palladium(II), Platinum(II), and Platinum(0) and the X‐Ray Crystals Structure of [Pt{1,2‐bis[(diphenylphospino)methyl]benzene}(C2H4)]
Authors: Camalli Mercedes , Caruso Francesco , Chaloupka Stanislav , Leber Ernest M. , Rimml Heinrich , Venanzi Luigi M. 
Published: December 2004

AbstractThe preparation of complexes [MX2(1)] (M = Ni, Pd, and Pi; X ‐ Cl, Br, and I; 1 = 1,2‐bis[(diphenylphosphino)methyl]benzene). [Pt(OSO2CH3)Et(1)], [Pt(alkene)(1)] (alkene ‐ C2H2, and CH2 = CHCN), and [(1)Pt‐(μ‐H)2PtH(1)][BPh4] is reported. Their 1H‐ and 31P‐NMR spectra were recorded and used lor structural assignments. The X‐ray crystal structure of [Pt(C2H4)(1)] was determined. It is shown that the PPtP bond angle in this complex differs significantly from those found in related compounds with monodentate phosphines, and that this difference is likely to be due to intramolecular contacts.
Umsetzungen von 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin mit Barbitursäure‐Derivaten
Authors: Schläpfer‐Dähler Marlise , Heimgartner Heinz 
Published: December 2004

Reactions of 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirines with Barbituric‐Acid DerivativesThe reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) and 5,5‐disubstituted barbituric acids 5 in i‐PrOH at ca. 70° gives 2‐[5‐(dimethylamino)‐4,4‐dimethyl‐4H‐imidazol‐2‐yl]alkanamides of type 6 in good yields (Scheme 1). The formation of 6 proceeds with loss of CO2; various reaction mechanisms with a zwitterionic 1:1 adduct B as common intermediate are discussed (Schemes 2 and 5). Thermolysis of product 6 leads to 2‐alkyl‐5‐(dimethylamino)‐4,4‐dimethyl‐4H‐imidazoles 8 or the tautomeric 2‐alkylidene derivatives 8′ via elimination of HNCO (Scheme 3). The latter undergoes trimerization to give 1,3,5‐triazine‐2,4,6‐trione. No reaction is observed with 1,5,5‐trisubstituted barbiturates and 1 in refluxing i‐PrOH, but an N‐alkylation of the barbiturate occurs in the presence of morpholine (Scheme 4). This astonishing reaction is explained by a mechanism via formation of the 2‐alkoxy‐2‐(dimethylamino )aziridinium ion H which undergoes ring opening to give the O‐alkylated 2‐amino‐N1,N1‐dimethylisobutyramide I as alkylating reagent (Scheme 4).
Eine neue 1,3‐Oxathiolan‐Synthese: Spirocyclische 1,3‐Oxathiolane aus der Lewis‐Säure katalysierten Umsetzung von 1,3‐Thiazol‐5(4H)‐thionen mil Oxiranen
Authors: Tromm Peter‐Claus , Heimgartner Heinz 
Published: December 2004

A New 1,3‐Oxathiolane Synthesis: Spirocyclic 1,3‐Oxathiolanes from the Lewis‐Acid‐Catalyzed Reaction of 1,3‐Thiazole‐5(4H)‐thiones and OxiranesThe BF3·Et2O‐catalyzed reaction of 2,4,4‐trisubstituted 1,3‐thiazole‐5(4H)‐thiones 13 with alkyl‐ and phenyl‐substituted oxiranes 7 in CH2Cl2 at room temperature leads, in very good yields, to 1‐oxa‐4,6‐dithia‐8‐azaspiro[4.4]non‐7‐enes 14 and 15.
Nucleotides. Part XXXIVSynthesis of Modified Oligomeric 2′–5′A Analogues: Potential Antiviral Agents
Authors: Herdewijn Piet , Ruf Klaus , Pfleiderer Wolfgang 
Published: December 2004

AbstractA series of new 2′–5′‐oligonucleotide trimers carrying a 9‐(2′,3′‐anhydro‐β‐D‐ribofuranosyl)‐(59), 9‐(3′‐deoxy‐β‐D‐glycero‐pent‐3‐enofuranosyl)‐(63), 9‐(3′‐azido‐3′‐deoxy‐β‐D‐xylofuranosyl)‐(62), and 9‐(3′‐halo‐3′‐deoxy‐β‐D‐xylofuranosyl)adenine (60 and 61) moiety at the 2′‐terminal end have been synthesized via the phosphotriester method. The properly protected, modified monomeric building blocks (6, 9, 16, 19, 27, 33, 36, 37, and 43) were obtained, in general, by a sequence of reactions, introducing the protecting groups into the right positions. Their condensations with the intermediary dimeric 2′‐terminal phosphodiesters 48 and 49 led to the fully protected 2′–5′‐trimers 50–58 which were deblocked to form the free 2′–5′‐trimers 59–63. Easy elimination of HBr on deprotection did not allow to form the trimeric (3′‐bromo‐3′‐deoxy‐β‐D‐xylofuranosyl)adenine analogue but only 63 carrying an unsaturated sugar moiety instead. The newly synthesized compounds have been characterized by UV and NMR spectra as well as by elemental analysis.
Neurotoxic Sesquiterpenoids from the Yellow Star Thistle Centaurea solstitialis L. (Asteraceae)
Authors: Wang Ying , Hamburger Matthias , Cheng Celine H. K. , Costall Brenda , Naylor Robert J. , Jenner Peter , Hostettmann Kurt 
Published: December 2004

AbstractIngestion of yellow star thistle (Centaurea solstitialis L.) by horses produces parkinsonism due to nigro‐pallidal degeneration. The toxin responsible has not been identified so far. A CH2Cl2 extract from the aerial parts of C. solstitialis exhibited significant neurotoxicity against primary neuronal cultures of foetal rat brain. Activity‐guided fractionation yielded the known sesquiterpene lactones solstitialin A (1), 13‐0‐acetylsolstitialin A (3), cynaropicrin (4), and the hitherto unknown 3‐O‐acetylsolstitialin A (2). In the bioassay with rat foetal full cell culture, 3 and 4 were toxic in a concentration‐dependent manner and may be responsible for the ability of the plant to cause neurodegenerative changes in the brain of horses.
Magnetic‐Field Effect in Aromatic Dediazoniation
Authors: Laali Kenneth K. , Gao Hong 
Published: December 2004

AbstractHomolytic dediazoniation of tribromo‐ and trichloro‐benzenediazonium tetrafluoroborates in highly ionizing, low‐nucleophilicity solvents (trifluoroethanol and trifluoromethanesulfonic acid (TfOH)) exhibits a strong magnetic‐field dependency of dediazoniation products; a more facile singlet‐to‐triplet intersystem crossing results in increased radical‐escape products at higher magnetic fields.