bluuebunny/crossref_metadata_2025 huggingface dataset:
Ringerweiterungen und Ringverengungen bei der Umsetzung von 1, 3‐Oxazolidin‐2, 4‐dionen und 1, 3‐Thiazoiidin‐2, 4‐dion mit 3‐Amino‐2H‐azirinen
Authors: Ametamey Simon M. , Heimgartner Heinz
Published: December 2004

Ring Enlargements and Ring Contractions in the Reaction of 1, 3‐Oxazolidine‐2, 4‐diones and l, 3‐Thiazolidine‐2, 4‐dione with 3‐Amino‐2H‐azirines

The reaction of 3‐amino‐2H‐azirines 1 and 1, 3‐oxazolidine‐2, 4‐diones 2 in MeCN at room temperature leads to 3, 4‐dihydro‐3‐(2‐hydroxyacetyl)‐2H‐imidazol‐2‐ones 3 in good yield (Scheme 2, Table 1). A reaction mechanism proceeding via ring enlargement of the bicyclic zwitterion A to give B, followed by transannular ring contraction to C, is proposed for the formation of 3. This mechanism is in accordance with the result of the reaction of 2a and the 15N‐labelled 1a*: in the isolated product 3a*, only N(3) is labelled (Scheme 1). The analogous reaction of 1 and 1, 3‐thiazolidine‐2, 4‐dione (5) is more complex (Schemes 4 and 5, Table 2). Besides the expected 3, 4‐dihydro‐3‐(2‐mercaptoacetyl)‐2H‐imidazol‐2‐ones 7, 5‐amino‐3, 4‐dihydro‐2H‐imidazol‐2‐ones of type 8 and/or N‐(1, 4‐thiazin‐2‐ylidene)ureas 9 are formed. In the case of 2‐(dimethylamino)‐1‐azaspiro[2. 3]hex‐1‐ene (1d), the postulated eight‐membered intermediate 6d could be isolated. Its structure as well as that of 9f has been determined by X‐ray structure analysis. A reaction mechanism for the formation of the 1, 4‐thiazine derivatives of type 9 is proposed in Scheme 6.
Chemie von α‐Aminonitrilen. Aziridin‐2‐carbonitril photochemische Bildung aus 2‐Aminopropennitril
Authors: Drenkard Susanne , Ferris James , Eschenmoser Albert
Published: December 2004

The English Footnotes (*) referring to Schemes 1‐6 are intended to provide an extension of this summary. In the Footnote (*) to Scheme 5, a definition of the term ‘chirogenic reaction step’ is given.

2‐Aminopropenenitrile in solvents such as MeCN, MeOH, or H2O is photoisomerized by UV light to racemic aziridine‐2‐carbonitrile (rac‐2); the larger part of the starting material, however, fragments to HCN and MeCN. The observed photocyclization constitutes a structural connection within an ensemble of C3H4N2 compounds considered to be potentially relevant to prebiotic chemistry.
Synthese von Pyrano[3,2‐b][1]benzopyranen aus 1‐Nitroglycalen
Authors: Brade Walter , Vasella Andrea
Published: December 2004

Synthesis of Pyranol [3,2‐b][1]benzopyrans from 1‐Nitroglycals

A synthesis of pyrano[3,2‐b][l]benzopyrans β‐addition of salicylic aldehyde to 1‐nitroglycals, followed by a Henry reaction, is described. This sequence gave the cis‐annelated pyranobenzopyranes 9 and 11 from 5 in 54 and 9% yield, respectively, demonstrating the pronounced diastereoselectivity of the β‐addition. Reductive denitration of the crude product mixture yielded 14(75%), 15(15%), and 16(7%), which were oxidized to the aryl ketones 20 and 21, respectively. Reduction of 20 (NaBH4) gave exclusively 15. The ketone 20 was deprotected to 22 and 23.
5‐Methylnaioxone and 5‐Methylnaltrexone: Synthesis and Pharmacological Evaluation
Authors: Schmidhammer Helmut , Mayer‐Valkanover Karin , Walla‐Kugler Michaela
Published: December 2004

Starting from 5‐methyl‐oxycodone (6), 5‐methylnaloxone (4), and 5‐methylnaltrexone (5) have been prepared in several steps. Both 4 and 5 behaved as partial agonists in the AcOH writhing agonism and antagonism test in mice.
Weitere Beiträge zur Synthese von (+)‐Aspicilin
Authors: Quinkert Gerhard , Döller Uwe , Eichhorn Mathias , Küber Frank , Nestler Hans Peter , Becker Heinrich , Bats Jan W. , Zimmermann Gottfried , Dürner Gerd
Published: December 2004

Further Contributions to the Synthesis of (+)‐Aspicilin

There are two reasons to try to find out. whether the initial and final parts of the ‘photochemical synthesis’ of the 18‐membered lichen macrolide (+)‐aspicilin (5a) can be improved (cf. Schemes 1 and 2). This synthesis acts as an indicator for the utility of the earlier introduced photolactonization and as a source of large‐ring‐sized lactones, objects for computer‐assisted conformational analysis.
Segregation of Charge in Ions of Dibenzo[a,c]naphthacene: Relation of Topology and Electronic Structure. An NMR, ESR, and ENDOR Study
Authors: Cohen Yoram , Fraenkel Yigal , Rabinovitz Mordecai , Felder Patrick , Gerson Fabian
Published: December 2004

1H‐ and 13C‐chemical shifts of the dianion of dibenzo[a,c]naphthacene (1) have unambiguously been assigned by 2D‐NMR spectroscopy. They indicate a remarkable charge distribution, as most of the negative charge is localized on the ‘anthracenic’ moiety, while the ‘phenanthrenic’ moiety is almost neutral. Association of 12− with alkali‐metal counterions has only a minor effect on the chemical shifts. The charge partitioning in 12−, which is reproduced by ωβ calculations in the frame of the Hückel model, must, thus, be considered as an intrinsic property of the 4nπ‐electron system of 12−. It is rationalized in terms of differing energy contents of the constituent anthracenic and phenanthrenic moieties. ESR and ENDOR studies of the radical anion 1\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} and the radical cation 1\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} show that the π‐charge distribution in 12− is reflected by the π‐spin distributions in the two radical ions of the alternant hydrocarbon 1.
Photo‐oxygenation of Styrenic Estrogens: Structural Analysis of 8,9‐Didehydro‐, 6,7‐Didehydro‐, and 9,11‐Didehydroestrone Derivatives and Their Reactivity towards Singlet Oxygen
Authors: Malet Carles , Planas Antoni , Brosa Carme , Piniella Juan F. , Rius Jordi
Published: December 2004

A series of didehydro‐3‐O‐methyl‐estrones having a styrenic framework, with the ring‐A‐conjugated double bond in all three possible positions (8,9‐didehydro‐ (6),9,11‐didehydro‐ (1b), 6,7‐didehydro‐ (9), and the 12,18‐di‐nor‐8,9‐didehydroestrone analog 11), were compared for their reactivity towards singlet oxygen. Under dye‐sensitized photo‐oxygenation conditions, both, products derived from ene‐type reactions with the isolation of a stable hydroperoxide and a fragmentation product, were obtained from 6 (see Scheme 3), while only fragmentation took place for 1b (Scheme 1), Kinetic studies indicated that 6 is more reactive towards 1O2 than 1b (β = 9.2·10−3 mol·1−1 vs 3.3·10−2 mol·1−1, resp.). The observed reactivity, apparently, does not match with ene‐type reaction and [2 + 2]cycloaddition being in competition, since the most activated substrate 6 preferentially yields ene‐type products and their derivatives. Conformational analysis on the structure of 6 and 1b, both calculated by molecular‐mechanic techniques (MMPMI) and determined by X‐ray diffraction, show that the allylic H‐atoms satisfy the orthogonality rule for ene‐type reactions. The product distribution is best rationalized by applying Fukui's rule which takes into account a combination of electronic and geometric factors. Substrates 9 and 11 yielded photo‐products arising from ene‐type reaction with no stable primary products isolated (Scheme 4). Geometric considerations based on the calculated structures by molecular mechanics are consistent with the observed results.
Synthesis, structure, and reactivity of secosteroids containing a medium‐sized ring. Part 32. Conformations and photochemical reactivity of some unsaturated 5,10‐secosteroidal ketones
Authors: Lorenc Ljubinka , Pavlović Vladimir , Mihailović Mihailo Lj. , Kalvoda Jaroslav , Fuhrer Hermann
Published: December 2004

UV irradiation of the unsaturated (E)‐5,10‐secosteroidal ketones 1 and 6 results, in addition to (E/Z)‐isomeri‐zation, in an intramolecular Pateino‐Büchi reaction and, in the case of 1, in transannular cyclization (along with AcOH elimination). The stereochemistry of the observed intramolecular photoprocesses can be explained in terms of ground‐state conformations of the (E)‐seco‐ketones 1 and 6 in solution.
Fluxional Behaviour of Isocyanide Derivatives of Dodecacarbonyltetrairidium
Authors: Orlandi Alessandra , Ros Renzo , Roulet Raymond
Published: December 2004

The fluxional behaviour of [Ir4(CO)11(t‐BuNC)] (1) and [Ir4(CO)11(ArNC)] (Ar = 4‐methoxyphenyl, 4‐tolyl, phenyl, 4‐chlorophenyl, 4‐nitrophenyl; 2–5) has been investigated by 2D and variable‐temperature 13C‐NMR. These techniques give new evidence of the processes responsible for CO exchange, namely two successive merry‐go‐rounds causing Cotton‐like scrambling and a CO rotation about one metal center.
2D‐NMR ConformationaL Studies of ChiraL Functionalized Ferrocenylphosphine Ligands for the Gold(I)‐Catalyzed Aldol Reaction
Authors: Togni Antonio , Blumer Ruth K. , Pregosin Paul S.
Published: December 2004

The conformations in solution of six selected chiral 1,1′‐bis (diphenylphosphino)ferrocenyl ligands bearing functionalized side chains, the diastercoisomers 4 and 5 and 6–9, have been elucidated by 2D‐NMR methods (COSY, TOCSY, NOESY, and 1H,31P and 1H,13C correlations). The possible relationship between the preferred conformation and the stereoselectivity observed in the gold(I)‐catalyzed asymmetric aldol condensation in the presence of these ligands is discussed.
Über Pterinchemie. 90. Mitteilung. Synthese und Kristallstruktur des ersten chinoiden Dihydropterinmolybdän (IV)‐Komplexes
Authors: Fischer Berthold , Strähle Joachim , Viscoittinf Max
Published: December 2004

Synthesis and Crystal Structure of the First Quinoid Dihydropterinmolybdenum (IV) Complex

The first molybdenum(IV) complex with a quinoid dihydropterin, i.e. 2, was isolated and characterized by IR, UV and NMR data and single‐crystal X‐ray diffraction. The reaction of MoVIO2Cl2 with the biologically important 6β‐5,6,7,8‐tetrahydro‐L‐biopterin(2) (7) in MeOH gave almost quantitatively trichloro(1,5‐quinoid‐7,8‐dihydro‐6H‐L‐biopterin)oxomolybdenLim(IV) (2). The complex crystallizes with one molecule of MeOH in the noncentrosymmetric orthorhombic space group P212121 (No. 19) with unit cell dimensions a = 1009.3(3), b = 1104.7(3), and c = 1484.5(4) pm and Z = 4. The Mo‐atom has a distorted octahedral geometry (Fig.1). It is coordinated by N(5) and O(4) of the pterin ligand. The distance of the Mo–N(5) bond (202 pm) is unusually short compared to similar complexes. O(4) is located trans to a terminal oxo ligand. The octahedral coordination is completed by three Cl‐atoms in a meridional arrangement. Complex 2, with the Mo‐atom in the enzyme‐relevant oxidation state +IV and the pterin in the intermediate quinoid dihydro form, should lead to an extension of the proposed ‘common molybdenum cofactor’ model.
Deoxy‐nitrosugars. 17th communication. Synthesis of ketose‐derived nucleosides from 1‐deoxy‐1‐nitroribose
Authors: Mahmood Khalid , Vasella Andrea , Bernet Bruno
Published: December 2004

A new approach to ketose‐derived nucteosides is described. It is based upon a chain elongation of 1‐deoxy‐1‐nitroaldoses, followed by activation of the nitro group as a leaving group, and introduction of a pyrimidine or purine base. Thus, the nitroaldose 7 was prepared from 3 by pivaloylation (→4), synthesis of the anomeric nitrones 5/6, and ozonolysis of 6 (Scheme 1). Partial hydrolysis of 4 yielded 8/9, which were characterized as the acetates 10/11 and transformed into the nitrones 12/13. Ozonolysis of 12/13 gave 14/15, which were acetylated to 16/17. Henry reaction of 7 lead to 19 and 20, which were acetylated to 21 and 22 (Scheme 2). Michael addition of 7 to acrylonitrile and to methyl propynoate yielded the anomers 23/24 and 25/26, respectively. Similar reactions of 16/17 were prevented by a facile β‐elimination. Therefore, the nitrodiol 15 was transformed into the orthoesters 27 and then, by Henry reaction, partial hydrolysis, and acetylation, into 28 and 29 (Scheme 2). The structure of 19 was established by X‐ray analysis. It was the major product of the kinetically controlled Henry reaction of 7. Similarly, the β‐D‐configurated nitroaldoses 23 and 25 were the major products of the Michael addition. This indicates a preferred ‘endo’‐attack on the nitronate anion derived from 7. AMI calculations for this anion indicate a strong pyramidalization at C(1), in agreement with an ‘endo’‐attack. Nucleosidation of 21 by 31 afforded 32 and 33. Yields depended strongly upon the nature and the amount of the promoter and reached 77% for 33, which was transformed into 34, 35, and the known ‘psicouridine’ (36; Scheme 3). To probe the mechanism, the trityl‐protected 30 was nucleosidated yielding 37, or 37 and 38, depending upon the amount of FeCl3. Nucleosidation of the nitroacetate 28 was more difficult, required SnCl2 as a promoter, and yielded 39 and 40. The β‐D‐anomer 40 was transformed into 36. Nucleosidation of 23 (SnCl4) yielded the anomers 41 and 42, which were transformed into 43 and 44, and hence into 45 and 46 (Scheme 4). Similarly, nucleosidation of 25 yielded 47 and 48, which were deprotected to 49 and 50, respectively. The nucleoside 49 was saponified to 51. Nucleosidation of 21 by 52 (SnCl2) afforded the adenine nucleosides 53 and 54 (Scheme 5). The adenine nucleoside 53 was deprotected (→55→56) to ‘psicofuranine’ (1), which was also obtained from 58, formed along with 57 by nucleosidation of 28. The structure and particularly the conformation of the nitroaldoses, nitroketoses, and nucleosides are examined.
Caro‐Cryptands: Tris‐carotenoid macrobicyclic ligands–synthesis, crystal structure, and dinuclear copper(I) complexes
Authors: Lehn Jean‐Marie , Vigneron Jean‐Pierre , Bkouche‐Waksman Itka , Guilhem Jean , Pascard Claudine
Published: December 2004

The tris‐carotenoid macrobicycles 1 and 2 were obtained in good yields in a one‐step macrobicyclisation condensation between the tripode N(CH2CH2NH2)3 and the polyolefinic dialdehydes 5 and 6. They form dinuclear cryptates by complexation of two CuI ions. The crystal structure of the tris‐carotenoid compound 2 confirms that it contains three parallel polyolefinic strands. These substances may formally be considered as prototypes of molecular ‘cables’ formed by three electron‐conducting molecular wires.
A New Synthesis of Coprine and O‐Ethylcoprine
Authors: Kienzler Thomas , Strazewski Peter , Tamm Christoph
Published: December 2004

Coprine (1), a toxine of the mushroom Coprinus atramentarius, was synthesized starting from the 2‐amino and 1‐carboxy‐protected L‐glutamic acids 4 and 12. Compound 4 was first decarboxylated by a radical chain reaction to bromide 5 which underwent ring closure to cyclopropanecarboxylate 6 on treatment with NaH (Scheme 1). Subsequent oxidative electrolysis of 7 to form tert‐butyl N‐(1‐ethoxycyclopropyl)carbamate (8) and acidic hydrolysis yielded the 1‐aminocyclopropanol hydrochloride (9). Selective cleavage of the amino‐protecting group of 8 (→ 10 or 11), coupling of the corresponding amine 13 with L‐glutamic acid 12, and acidic hydrolysis of the resulting L‐glutamine derivative 17 yielded O‐ethylcoprine (3) and coprine (1).
Studies on the Enzymatic Acylation of Quinic Acid, Shikimic Acid, Shikimic Acid, and Their Derivatives in Organic Solvents
Authors: Danieli Bruno , De Bellis Paolo , Barzaghi Laura , Carrea Giacomo , Ottolina Gianluca , Riva Sergio
Published: December 2004

Quinic acid (1a), shikimic acid (2), and their derivatives were acylated in organic solvents by several lipases and by the protease subtilisin Carlsberg. The most satisfactory results were obtained with methyl (or benzyl) quinate (7a (or 8a)) and lipase from Chromobacterium viscosum adsorbed on Celite, which showed an overshelming preference towards the acylation of OH–C(4). Under optimized conditions, the syntehtically useful 4‐O ‐acetylquinate 8d was isolated in ca. 90% yield. On the other hand, acylation of methyl shikimate (10a) showed no regioselectivity with any of the enzymes tested. A possible rationale for the different behavior of Chromobacterium viscosum lipase towards 7a and 10a is given, comparing the conformations of these two molecules, as deducted from 1H‐NMR and molecular‐mechanics calculation.
Complexes of Rhodium(III) with Two Chelating C⁁N Ligands and One Diimine Ligand
Authors: Maeder Urs , Von Zelewsky Alex , Stoeckli‐Evans Helen
Published: December 2004

The synthesis of two series of cyclometalated RhIIIcompounds is described, namely of 5 dinuclear chlorobridged species [{Rh(C⁁N)2} (μ‐Cl)2]Aand of 15 mononuclear complexes [Rh(C⁁N)2(N⁁N)]+B; C⁁N stands for five different cyclometalating ligands,i.e.deprotonated phenylpyridine, deprotonated 2‐(thienyl)pyridine, and three deprotonated 1‐aryl‐1H‐pyrazoles, and N⁁N for six diimine ligands such as 2,2‐bihyridine, 2,2′‐bi‐1H‐imidazole, and 2,2′‐bipyrimidine. For (2,2′‐bipyridine)bis[2‐(thien‐2‐yl)pyridinato‐N,C3′]rhodium(III) chloride, an X‐ray structure determination was carried out. In the other cases,1H‐NMR spectra established the configuration of the complexes. All mononuclear and dinuclear complexes show a C,Ccis‐configuration. The UV/VIS‐absorption bands at longest wavelength are most likely due to metal‐to‐ligand charge‐transfer (MLCT) transitions, depending on the nature of the cyclometalating ligand C⁁N and on the diimine ligand N⁁N. The receptor orbital is in some cases on the cyclometalating ligand, in others on the diimine. All monomer complexes exhibit at least one reversible reduction wave in the cyclovoltammogram in dimethylformamide solutions, attributable to a ligand‐centered reduction. It is, therefore, concluded that the LUMO in [Rh(C⁁N)2(N⁁N)]+is of L(π*) character, as opposed to [Rh(bpy)3]3+, where it is a metal d‐orbital. The crystal system of (2,2′‐bipyridine)bis[2‐(thien‐2‐yl)pyridinato‐N,C3′]rhodium(III) chloride—water (1/2.125) is tetragonal (space groupP4;R= 0.036,Rw= 0.040). The Rh‐atom has slightly distorted octahedral environment; the average distances are (RhN/thienylpyridine) = 2.060 (3), RhC = 1.9885 (3), and RhN(bipyridine) = 2.1415 (3) Å. Of the three ligands the 2,2′‐bipyridine is the most planar.
Fixation of 1,3,5‐Trithiane to a Trinuclear Ruthenium Framework: Synthesis, structure, and fluxionality of [Ru3(CO)6(μ2‐CO)3{μ3‐(η3‐C3S3H6)}]
Authors: Hoferkamp Lisa , Rheinwald Gerd , Stoeckli‐Evans Helen , Süss‐Fink Georg
Published: December 2004

The reaction of dodecacarbonyltriruthenium with 1,3,5‐trithiacyclohexane (1,3,5‐trithiane) in refluxing THF yields [Ru3(CO)6(μ2‐CO)3{μ3‐(η3‐C3S3H6)}] (1) in which the three S‐atoms of the cyclic ligand coordinate to the three Ru‐atoms of the metal core. X‐Ray diffraction reveals a nearly perfect C3v symmetry for the molecule. The variable‐temperature 13C‐NMR spectra show the carbonyl ligands to be fluxional in solution.
Photoisomerization of 2H,6H‐Thiin‐3‐ones to 2‐(Alk‐1‐enyl)thietan‐3‐ones
Authors: Er Erhan , Margaretha Paul
Published: December 2004

Reaction of 3‐bromo‐3‐methylbutan‐2‐one (1) with mercapto‐esters 2 affords 5‐oxo‐3‐thiahexanoates 3 which cyclize to thiane‐3,5‐diones 4. Conversion of these dicarbonyl compounds to their ethyl enol ethers 5–7 followed by reduction with LiAlH4 gives 2H,6H‐thiin‐3‐ones 8–10. On irradiation (350 nm) in either MeCN, benzene, or i‐PrOH, these newly synthesized heterocycles isomerize efficiently to 2‐(alk‐l‐enyl)thietan‐3‐ones 11–13. The rearrangement seems to proceed from an excited singlet state, as it is not quenched by naphthalene, and also occurs with the same efficiency in the presence of added alkene. A (9‐S‐3) sulfuranyl‐alkyl biradical formed by bonding of C(α) of the enone CC bond on sulfur is discussed as possible intermediate.
Reactions of 2‐Monosubstituted 3‐Amino‐2H‐azirines with NH‐Acidic Heterocycles
Authors: Villalgordo José M. , Linden Anthony , Heimgartner Heinz
Published: December 2004

2‐Monosubstituted 3‐amino‐2H‐azirines 2 react with several heterocycles containing acidic NH groups via ring expansions, leading to benzo[g][1,2,5]thiadiazocin 1,1‐dioxide derivatives 6 and imidazoles 9, 10, and 13, respectively.
New Hydroxylated Spermidine Alkaloids from Pleurostylia opposita(WALL.) MERILL‐METCALF
Authors: Séguineau Corinne , Richomme Pascal , Bruneton Jean , Pusset Jacques
Published: December 2004

The leaves of a New Caledonian celastraceae, Pleurostylia opposita (WALL.) MERRILL‐METCALF, have yielded three new spermidine alkaloids, 7‐hydroxypleurostyline (1), 7‐hydroxycelacinnine (2), and 7′‐hydroxy‐7′,8′‐dihydropleurostyline (3), as minor basic constituents, together with three related alkaloids pleurostyline (4), celacinnine (5), and celallocinine (6).
Base‐Modified Nucleosides Related to 2‐Chloro‐2′‐deoxyadenosine
Authors: Kazimierczuk Zygmunt , Vilpo Juhani A. , Seela Frank
Published: December 2004

Derivatives of 2‐chloro‐2′‐deoxyadenosine (1a) containing secondary 6‐NH2 groups (5a‐c) or a 8‐Br substituent (9) were synthesized. They were tested together with ring‐modified congeners containing a pyrrolo[2,3‐b]pyridine, pyrrolo[3,2‐c]pyridine, or pyrazolo[3,4‐d]pyrimidine ring system as inhibitors of various leukemic cell lines. Only the 8‐Br derivatives 9 showed inhibitory activity, whereas the base‐modified congeners were not active. Compound 1a was protonated at a pKa = 1.4 (2′‐deoxyadenosine at pKa = 3.8). Protonation occurred at N(7) and not at N(1) as observed for dA.
Untersuchungen zur Stabilität und Reaktivität von (3‐Cyclopropylidenprop‐1‐enyl)‐ethyl‐ether
Authors: Stadlwieser Josef , Kienzle Frank , Arnold Wolf , Gubernator Klaus , Schönholzer Peter
Published: December 2004

Stability and Reactivity of 3‐Cyclopropylideneprop‐1‐enyl Ethyl Ether

3‐Cyclopropylideneprop‐1‐enyl ethyl ether (1) dimerizes to a cyclobutane derivative 2 which, upon prolonged heating, is converted to a cyclooctadiene (3). The reactivity of 1 is discussed. The structures of 2 and 3 as well as of their derivatives have been determined using 1H‐NMR spectroscopy and X‐ray crystal‐structure analysis.
Studies On Rare‐Earth Complexes with Crown Ethers. Part XXV. Synthesis, characterization, and structure of the complexes of lanthanide nitrates with 13‐crown‐4
Authors: Lu Tongbu , Wang Xin , Tan Minyu , Liu Yu , Inoue Yoshihisa , Hakushi Tadao
Published: December 2004

The lanthanide nitrate complexes with 13‐crown‐4(13‐C‐4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO3)3.(13‐c‐4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and 1H‐NMR spectra, conductivity measurements, and TG‐DTA techniques. The crystal and molecular structure of Nd(No3)3. (13‐c‐4) has been determined by single crystal X‐ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 Å3, Dc = 2.01 g cm−3, μ = 31.0 cm−1 (Mok2), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least‐squares to a final conventional R value of 0.032 for 5218 independent reflections with I ⩽ 3σ(I). There are two independent Nd(No3)3 · (13‐C‐4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers.
Nucleosides. Part LI The 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) and 2‐(2,4‐dinitrophenyl)ethoxycarbonyl (dnpeoc) groups for protection of hydroxy functions in ribonucleosides and 2′ ‐deoxyribonucleosides
Authors: Schirmesiter Helga , Himmelsbach Frank , Pfleiderer Wolfgang
Published: December 2004

The Common 2′ ‐deoxypyrimidine and ‐purine nucleosides, thymidine (4), O4‐[2‐(4‐nitrophenyl)ethyl]‐thymidine (17), 2′‐deoxy‐N4‐[2‐(4‐nitrophenyl)ethoxycarbonyl]cytidine (26), 2′‐deoxy‐N6‐[2‐(4‐nitrophenyl)‐ethoxycarbonyl]adenosine‐39, and 2′‐deoxy‐N2‐[2‐(4‐nitrophenyl)(ethoxycarbonyl]‐O6‐[2–4‐nitrophenyl)ethyl]‐guanosine (52) were further protected by the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) and the 2‐(2,4‐dinitrophenyl)ethoxycarbonyl (dnpeoc) group at the OH functions of the sugar moiety to form new partially and fully blocked intermediates for nucleoside and nucleotide syntheses. The corresponding 5′‐O‐monomethoxytrityl derivatives 5, 18, 30, 40, and 56 were also used as starting material to synthesize some other intermediates which were not obtained by direct acylations. In the ribonucleoside series, the 5′ ‐O‐monomethoxytrityl derivatives 14, 36, 49, and 63 reacted with 2‐(4‐nitrophenyl) ethyl chloroformate (1) to the corresponding 2′,3′‐bis‐carbonates 15, 37, 50, and 64 which were either detriylated to 16, 38, 51, and 65, respectively, or converted by 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) treatment to the 2′,3′‐cyclic carbonates 66–69. The newly synthesized compounds were characterized by elemental analyses and UV and 1H‐NMR spectra.
Anatoliosides: Five Novel Acyclic Monoterpene Glylcosides from Viburnum orientale
Authors: Çaliş Ihsan , Yürüker Ayşen , Rüegger Heinz , Wright Anthony D. , Sticher Otto
Published: December 2004

Five new acyclic monoterpene glycosides 1–5 were isolated from the leaves of Viburnum orientale (Caprifoliaceae). Anatolioside (1) is a monoterpene diglycoside and its structure was elucidated as linalo‐6‐yl 2′‐O‐(α‐L‐rhamnopyranosyl)β‐D‐glucopyranoside (arbitrary numbering of linalool moiety). Compounds 2–5 are all derivatives of 1, containing additional monoterpene and sugar units, connected by ester and glycoside bonds. Their structures were established as linalo‐6‐yl O‐[(2E,6R)‐6‐hydroxy‐2, 6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″‴ → 2″″)‐β‐D‐glucopyranoside ( = anatolioside A; 2), linalo‐6‐yl O‐β‐D‐glucopyranosyl‐(1‴ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″ → 2′)–β‐D‐glucopyranoside ( = anatolioside B; 3), linalo‐6‐yl O‐β‐Dribo‐hexopyranos‐3‐ulosyl‐(1′‴ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl‐(1″ → 2′)‐β‐D‐glucopyranoside ( = anatolioside C; 4) and linalo‐6‐yl O‐[(2E, 6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1″‴ → 2″″)‐O‐β‐D‐glucopyranosly‐(1″″ → 6‴)‐O‐[(2E,6R)‐6‐hydroxy‐2,6‐dimethylocta‐2,7‐dienoyl]‐(1‴ → 4″)‐O‐α‐L‐rhamnopyranosyl(1″ → 2′)‐β‐D‐glucopyranoside ( = anatolioside D; 5). The structure determinations were based on spectroscopic and chemical methods (acid and alkaline hydrolysis, acetylation and methylation).
The Synthesis of Natural Acetylenic Compounds from Eutypa lata (Pers; F.) TUL
Authors: Defranq Eric , Zesiger Thierry , Tabacchi Rattaele
Published: December 2004

The synthesis of a series of novel acetylenic compounds 1–7, isolated recently from the fungus Eutypa lata, is described. The crucial step is the coupling reaction between a protected aryl halogenide and the acetylenic chain as a cuprous acetylide (Scheme 1). A more efficient method using bis(triphenylphosphine)palladium dichloride ([Pd(PPh3)2Cl2]) as catalyst was also carried out with success.
Enantiomeric Purities of (R)‐ and (S)‐Camphors from the Chiral Pool and High Enantiomeric Purities in General
Authors: Rautenstrauch Valentin , Lindström Mikael , Bourdin Bernadette , Curie Jane , Oliveros Esther
Published: December 2004

The commercially available camphor enantiomers are extensively used in several important areas of chemical research, and it seems that they are often considered to be enantiomerically pure (the meaning of the term is discussed); there are certainly no enantiomeric purities (e.p.) on record. By standard GLC on a modified cyclodextrin column, we have now found five commercial (R)‐camphors to have the same high but imperfect e.p., (99.62 ± 0.02)% (R), a sixth a slightly higher e.p., (99.76 ± 0.06) % (R), and three (S)‐camphors to have different and lower e.p. Nailing down these e.p. is useful by itself and puts into focus the sensitivity of present day GLC, and how little is know about high e.p. in general.
The Dynamic Behaviour and NMR Solution structures of complexes of the type (Bisphosphine)(cycloocta‐1,5‐diene)iridium(I) and the X‐ray crystal structure of (cycloocta‐1,5‐diene)((−)‐norphos)iridium(I) hexafluorophosphate
Authors: Hälg Werner J. , Öhrström Lars R. , Rüegger Heinz , Venanzi Luigi M. , Gerfin Tobias , Gramlich Volker
Published: December 2004

A square‐planar coordination geometry was found for the complex [Ir(cod){(−)‐norphos}][PF6] (1b[PF6]; cod = cylcoocta‐1,5‐diene and (−)‐norphos = [(2R,3R)‐8‐9‐10‐trinorborn‐5‐ene‐2,3‐diyl]bis(diphenylphosphine)) in the solid state by X‐ray diffraction. Crystal data: monoclinic, space group P21, a = 10.751 (6), b = 18.669(14), c = 12.037(8) Å, β = 114.82(5)°, Z = 2. A total structural assignment including the configurational and conformational aspects of this and the related compounds [Ir(bishosphine)(cod)]X (bisphosphine = (−)‐chiraphos = (2S,3S)‐2,3‐bis(diphenylphosphino)butane and (−)‐norphos, X = Cl, CF3SO3, or PF6) was carried out in solution by one‐ and two‐dimensional NMR spectroscopy. The complexes containing the CF3SO3− and PF6− anions are four‐coordinate cations with square‐planar geometry, whereas the chlorides are five‐coordinate neutral compounds showing solvent‐dependent dynamic behaviour. In toluene, two diastereoisomers of [IrCl(cod){(−)‐norphos}] (2b) exist and interconvert slowly at room temperature. This interchange is fast in CDCl3 solution, and it is likely to involve Cl dissociation and the formation of the cation [Ir(cod){(−)‐norphos}]+ as an intermediate.
Zum Mechanismus der sequentiellen Radikal‐Cyclisierung von (Bromomethyl)silyl‐ethern terpenoider Alkohole
Authors: Lakomy Ivo , Scheffold Rolf
Published: December 2004

On the Mechanism of Sequential Radical Cyclization of (Bromomethyl)silyl Ethers of Terpernoid Alcohols

The cyclic products of the Bu3SnH‐promoted radical reaction of (E)‐1‐[(bromomethyl)dimethylsilyloxy]‐2‐methylhept‐2‐ene (6) consists to 98% of a 1:2 mixture of (±)‐(4RS,5RS)‐ and (±)‐(4‐RS,5SR)‐4‐butyl‐2,2,5‐trimethyl‐1‐oxa‐2‐silacyclohexane (8a and 8b, respectively). It is, therefore, concluded that the 6‐‘endo’→5‐‘exo’ tandem cyclization of the 5‐mehtyl‐3‐oxa‐2‐siladeca‐5,9‐dien‐l‐yl radical (reaction 1 → 2) is not necessarily a concerted process, but may be explained as a sequence of individual steps via free‐radical intermediates.
Luminescence of Europium(III) Chelates with 4‐(Arylethynyl)pyridines as Ligands
Authors: Takalo Harri , Hänninen Elina , Kankare Jouko
Published: December 2004

Some Spectral properties and luminescence intensities of EuIII chelates with 4‐(arylethynyl)pyridine‐2,6‐dicarboxylic acids 1–15 and 2,2′,2″,2′″‐{[4‐(arylethynyl)pyrridine‐2,6‐diyl]bis(methylenenitrilo)} tetrakis(acetic acids) 16–26 were measured both in H2O and EtOH solutions for the purpose of developing suitable labels to be used in time‐resolved luminescence‐based bioaffinity assays (Tables 1 and 2). The substitution at the Ar group has a significant effect upon the observed luminescence intensities, excitation wavelengths, and decay constants of the complexes, Moreover, the changes in the environment cause great variation in those properties of certain EuIII chelates.
Molecular Geometries by the Extended‐Hückel Molecular Orbital method II: Hydrocarbons and organic molecules containing O, N, and S
Authors: Brändle Martin , Calzaferri Gion
Published: December 2004

Bond lengths and bond angles of hydrocarbons and of organic molecules containing oxygen, nitrogen, and sulfur have been investigated by the extended‐Hückel method in its improved ASED (atom superposition and electron delocalization) form. We have examined in detail bond lengths and bond angles of hydrocarbon ‐aliphatic, conjugated, rings, and aromatic – and we have also studied reaction enthalpies. Both properties can be calculated resonably well, if a small adjustment of the parameter k in the distance dependent Wolfsberg‐Helmholz formula is accepted. We have also found that moderate contraction of the usually applied 2s‐oxygen, the 2s‐nitrogen, and the 3s‐sulfur Slater exponents is sufficient to obtain astonishingly good geometries for important classes of organic molecules containing these elements. The three‐membered rings (CH2)2X(X  CH2, NH, O, and S) which have attracted much interest and stimulated theoretical studies have been investigated, and we have found that their geometries can be reproduced nicely. It is important that geometry calculation of the investigated molecules can be carried out without losing transparency and well established prediction capabilities of the original EHMO procedure. The extended‐Hückel method in its improved ASED form is, therefore, a useful tool for combining the information of EHMO results with good geometry calculation.
Triplet‐State Energy of the Photostabilizer Tinuvin P
Authors: Allan Michael , Asmis Knut , Bulliard Christophe , Haselbach Edwin , Suppan Paul
Published: December 2004

Electron‐energy‐loss spectroscopy shows that the lowest triplet level of the photostabilizer molecule Tinuvin P (= 2‐(2′‐hydroxy‐5′‐methylphenyl)benzotriazole) is at ca. 3.0 eV. Tinuvin P acts as a photostable inner filter rather than as a quencher of excited impurity sites.
Synthese eines 1,2‐trans‐konfigurierten, äquatorialen Glycosyl‐phosphonat‐Analogen von D‐myo‐Inositol‐1,4,5‐trisphosphat
Authors: Czollner LáSzló , Baudin Gisèle , Bernet Bruno , Vasella Andrea
Published: December 2004

Synthesis of a 1,2‐trans‐Configurated, Equatorial Glycosylphosphonate Analogue of D‐myo‐Inositol 1,4,5‐Trisphosphate

The diphosphonate analogue 3 of D‐myo‐inositol 1,4,5‐trisphosphate (1), a 1,2‐trans‐configurated, equatorial glycosylphosphonate, was synthesized and characterized as its hexasodium salt 3a. In a first approach, the silylated galactal 4 (Scheme 1) was transformed into the oxirane 5 and hence, by treatment with Me3SiP(OMe)2, into a mixture of the glycosylphosphonate 6 and its silyl ether 7. This mixture was desilylated and then treated with acetone and FeCl3 to yield 8 and 9 (64 and 22%, resp., from 4). In a second approach, the acetates 11/12(Scheme 2) were treated with P(OMe)3/Me3SiOTf in MeCN to afford the anomeric glycosylphosphonates 16/17 (1:1, 60%), while the trichloroacetimidate 10 gave mostly the αD‐anomer 16. The αD‐anomer 20 was obtained from 12 and P(OPh)3. The highest yield of a β‐Dphosphonate was realized by treating 12 with the cyclic phosphite 15 (→ 18/19, 40% each). The β‐D‐phosphonate 17 was debenzylated (→21) and protected to give 8. Transformation of 8 into the bromide 22 (43%) proved difficult due to the facile demethylation of thephosphonate, and was best followed by treatment of the crude product with CH2N2 and 2,2‐dimethoxyporpane. Phosphorylation of 22 yielded 41% of the (dimethoxyphosphoryl)phosphate 23. The conditions of the Arbuzov reaction slowly converted the bromide 23 into the bis(phosphoryl)phosphate 24 (69%), which was then deprotected. The resulting 3 was purified via the ammonium salt and transformed into 3a (72%).
Homoconjugated ketones with extended unsaturation: Wavelength‐selective, regioselective, diastereoselective, and enantiospecific photochemical transformations of methyl 7‐oxospiro[5.5]undeca‐1,3‐and ‐2,4,‐diene‐2‐carboxylate
Authors: Oren Jakob , Vardi Michaela , Viskin Rossana , Abramson Sarah , Fuchs Benzion
Published: December 2004

The title molecules were shown to photorearrange with remarkable selectivity. Wavelength variation steers the rearrangement modes, of which the [1,2]‐acyl shift was found to be largely regioselective, diastereoselective, and enantiospecific. Chemical intercorrelation of products and mechanistic studies were carried out all along. The potential significance of these photochemical processes in selective synthetic schemes is discussed.
Development of Luminescent Europium(III) and Terbium(III) chelates of 2,2′:6′,2″‐ terpyridine derivatives for protein labelling
Authors: Mukkala Veli‐Matti , Helenius Matti , Hemmilä Ilka , Kankare Jouko , Takalo Harri
Published: December 2004

The synthesis and luminescence properties are reported for 20 different chelates composed of 2,2′:6′,2″‐terpyridine as the energy‐absorbing and donating group, EuIIIand TbIII as the emitting ions, methylenenitrilo(acetic acids) as the stabel chelate‐forming moieties, and isothiocyanato or(4,6‐dichloro‐1,3,5‐triazin‐2‐yl)amino groups as the activated moieties for coupling to biomolecules.
Stabilizing Effect by Geminal Dioxy Substitution and Anomeric Effect in 3,6‐Dihydro‐6‐methoxy‐1,2‐oxathiin 2‐Oxides
Authors: Deguin Brigitte , Vogel Pierre
Published: December 2004

The hetero‐Diels‐Alder addition of SO2 to (E)‐hexa‐1,3‐diene (4) gives first 6‐ethyl‐3,6‐dihydro‐1,2‐oxathiin 2‐oxide (= 6‐ethylsultine) with the Et group occupying a pseudoaxial position, and then the more stable stereoisomer 6 with the Et substituent in a pseudoequatorial position. The SO2 additions to 1‐methoxybuta‐1,3‐diene (7) and to 1‐methoxy‐3‐[(trimethylsilyl)oxy]buta‐1,3‐diene (8) give the 6‐methoxysultines 9 and 10, respectively, with the MeO groups in pseudoaxial positions and which do not equilibrate with sultines having pseudoequatorial MeO substituents (anomeric effect). A lower limit of ΔΔG = 3.9 kcal/mol was evaluated at −60° for the stabilizing effect arising from the geminal vicinity of a MeO and sulfinate moiety in 3,6‐dihydro‐6‐methoxy‐4‐[(trimethylsilyl)oxy]‐1,2‐oxathiin 2‐oxide.
Structural Investigations of 13‐O‐Demethyl‐FK506 and Its Isomers Generated by in vitro Metabolism of FK506 Using Human‐Liver Microsomes
Authors: Schüler Wolfgang , Schmieder P. , Kessler Horst , Christians Uwe , Holze Ines , Sewing Karl‐Friedrich , Schiebel Hans‐Martin
Published: December 2004

FK506 is currently under investigation as immunosuppressant after organ transplantation and in immune diseases. The structure of a demethylated metabolite 1 of FK506 isolated after in vitro metabolism by human‐liver microsomes was established using two‐dimensional homo‐ and heteronuclear NMR experiments. The demethylation position was found to be at OC(13) using HMBC spectra. In contrast to FK506, 7 different isomers could be differentiated in COSY, HMBC, and HMQC spectra. The intensity of their signals was 50:18:11:9:6:6 (one isomer could not be quantified). This isomerization may be explained by epimerization at C(10) or alternative formations of the hemiketal ring between C(10) and C(13) or C(9) and C(13), in addition to cis/trans‐isomerism about the amide bond (see Scheme). The structural variation is possible by participation of the OH group at C(13) formed after demethylation and could be derived from HMBC spectra. Chemical exchange evidenced by ROESY spectra proved the rotational isomerism. NMR investigation of the structure of 13‐O‐demethyl‐FK 506 (1) revealed at least seven isomers.
Lacton‐Bildung durch Ringerweiterung unter Alkalimetall‐halogenid‐Katalyse
Authors: Stojanova Diana S. , Milenkov Branimir , Hesse Manfred
Published: December 2004

Lactone Formation by Ring Enlargement Catalyzed by Alkali‐Metal Halogenides

In the presence of alkali‐metal or tetraalkylammonium halogenides, 1‐(3′‐hydroxypropyl)‐2‐oxocyclododecane‐1‐carbonitrile (1) underwent ring enlargement to give 12‐cyanopentadecan‐15‐olide (2). In DMF solution, the halogenides catalyzed this reaction, the influence of more basic anions being more pronounced. The rearrangement was strongly influenced by H2O: in the presence of, e.g., 10 equiv. of H2O, it was nearly blocked. On boiling in pure solvent, 1 was rearranged thermally to 2.
Ring‐Transformationen bei der Umsetzung von 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin mit 1‐substituierten Imidazolidin‐2,4,5‐trionen
Authors: Schläpfer‐Dähler Marlise , Heimgartner Heinz
Published: December 2004

Ring‐Transformations in the Reaction of 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirines with 1‐Substituted Imidazolidine‐2,4,5‐triones

Reaction of 1‐substituted imidazolidine‐2,4,5‐triones ( = N‐substituted parabanic acids; 2) and 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) in i‐PrOH or MeCN at room temperature yields 5,6,7,7a‐tetrahydro‐3H‐imidazo[3,4‐a]imidazole‐5,7‐diones 3 (Scheme 1). By 15N‐NMR studies, using (3‐15N)‐2a, it has been shown that only N(1) in (15N)‐3a is labelled and, hence, N(4) stems from 1, e.g. the azirine reacts via cleavage of the N(1)=C(3) bond. In MeCN at room temperature, the azacyclols 3 rearrange slowly to give monocyclic 2H, 5H‐imidazol‐2‐ones 4 (Scheme 3); the 15N‐label in (15N)‐4a is in position 1. Both reactions proceed via deep‐seated skeletal rearrangements, most probably via ring‐expansion/ring‐contraction processes.
8‐Aza‐2′‐deoxyguanosine and Related 1,2,3‐Triazolo[4,5‐d]pyrimidine 2′‐Deoxyribofuranosides
Authors: Seela Frank , Lampe Sigrid
Published: December 2004

The synthesis of 8‐azaguanine N9‐, N8‐, and N7‐(2′‐deoxyribonucleosides) 1–3, related to 2′‐deoxyguanosine (4), is described. Glycosylation of the anion of 5‐amino‐7‐methoxy‐3H‐1,2,3‐triazolo[4,5‐d]pyrimidine (5) with 2‐deoxy‐3,5‐di‐O‐(4‐toluoyl)‐α‐D‐erythro‐pentofuranosyl chloride (6) afforded the regioisomeric glycosylation products 7a/7b, 8a/8b, and 9 (Scheme 1) which were detoluoylated to give 10a, 10b, 11a, 11b, and 12a. The anomeric configuration as well as the position of glycosylation were determined by combination of UV, 13C‐NMR, and 1H‐NMR NOE‐difference spectroscopy. The 2‐amino‐8‐aza‐2′‐deoxyadenosine (13), obtained from 7a, was deaminated by adenosine deaminase to yield 8‐aza‐2′‐deoxyguanosine (1), whereas the N7‐ and N8‐regioisomers were no substrates of the enzyme. The N‐glycosylic bond of compound 1 (0.1 N HCl) is ca. 10 times more stable than that of 2′‐deoxyguanosine (4).
1‐(2′‐Deoxy‐β‐D‐xylofuranosyl)cytosine: Base pairing of oligonucleotides with a configurationally altered sugar‐phosphate backbone
Authors: Seela Frank , Wörner Karlheinz , Rosemeyer Helmut
Published: December 2004

Solid‐phase synthesis of the oligo(2′‐deoxynucleotides) 19 and 20 containing 2′‐deoxy‐β‐D‐xylocytidine (4) is described. For this purpose, 1‐(2‐deoxy‐β‐D‐threo‐pentofuranosyl)cytosine ( = 1‐(2‐deoxy‐β‐D‐xylofuranosyl)‐cytosine; 4) was protected at its 4‐NH2 group with a benzoyl (→ 5) or an isobutyryl (→8) residue, and a dimethoxytrityl group was introduced at 5′‐OH (→ 7, 10; Scheme 2). Compounds 7 and 10 were converted into the 3′‐phosphonates 11a,b. While 19 could be hybridized with 21 and 22 under formation of duplexes with a two‐nucleotide overhang on both termini (19 · 21: Tm 29°; 19 · 22: Tm 22°), the decamer 20 bearing four xCd residues could no longer be hybridized with one of the opposite strands. Moreover, the oligonucleotides d[(xC)8C] (13), d[(xC)4C] (14), d[C(xC)4C] (15), and d[C(xC)3C] (16) were synthesized. While 13 exhibits an almost inverted CD spectrum compared to d(C9) (17), the other oligonucleotides show CD spectra typical for regular right‐handed single helices. At pH 5, d[(xC)8C] forms a stable hemi‐protonated duplex which exhibits a Tm of 60° (d[(CH+)9] · d(C9): Tm 36°). The thermodynamic parameters of duplex formation of (13H+ · 13) and (17H+ · 17) were calculated from their melting profiles and were found to be identical in ΔH but differ in ΔS (13H+ · 13: ΔS = −287 cal/K mol; 17H+ · 17: ΔS = −172 cal/K mol).
Nucleotides. Part XLIII. Solid‐phase synthesis of oligoribonucleotides using the 2‐dansylethoxycarbonyl (  2‐{[5‐(dimethylamino)naphthalen‐1‐yl]sulfonyl}ethoxycarbonyl; dnseoc) group for 5′‐hydroxy protection
Authors: Bergmann Frank , Pfleiderer Wolfgang
Published: December 2004

A new efficient method for solid‐phase synthesis of oligoribonucleotides via the phosphoramidite approach is described. The combination of the base‐labile 2‐dansylethoxycarbonyl (Dnseoc) group for 5′‐OH protection with the acid‐labile tetrahydro‐4‐methoxy‐2H‐pyran‐4‐yl (Thmp) group as 2′‐OH blocking group is orthogonal regarding cleavage reactions and fulfills the requirements of an automated synthesis in an excellent manner if the phosphoramidite function carries the N,N‐diethyl‐O‐[2‐(4‐nitrophenyl)ethyl] substitution.
Mixed Azines of Naloxone with Dihydromorphinone Derivatives
Authors: Schmidhammer Helmut , Kaspar Felizia , Marki Arpad , Borsodi Anna
Published: December 2004

The mixed azines 4 and 5 were prepared by reaction of naloxazone (2) with either oxymorphone (6) or 14‐O‐methyloxymorphone (7) and tested in vitro using opioid receptor binding assays and in vivo using the AcOH‐writhing test in mice. Compound 4 was found to be a partial agonist, while compound 5 was a potent opioid agonist with higher potency than morphine.
Synthesen mit Übergangsmetall‐Komplexen. Teil 2. Neue Fluoranthen‐Derivate mit (1,6‐Methano[10]annulen‐2‐yl)‐ und/oder (Naphthalin‐1‐yl)‐Substituenten
Authors: Neidlein Richard , Kux Ulrich
Published: December 2004

Syntheses with Transition‐Metal Complexes. New Fluoranthene Derivatives with 1,6‐Methano[10]annulen‐2‐yl and/or Naphthalen‐1‐yl Substituents

In the course of investigations of molecules bearing ‘parallel triple bonds’, the fluoranthene derivatives 6–10 were synthesized by reaction of the ‘rhodacycle’ 4 with selected alkynes. The spectroscopic data of 6–10 are discussed.
Synthesis and Biological Activity of Tetrahydropyrido[2′,3′:4,5]imidazo[1,2‐c]pyrimidine‐6,8‐diones
Authors: Sraga Jan , Guerry Philippe , Kompis Ivan
Published: December 2004

Substituted 4‐oxoquinoline‐3‐ (1a) and 4‐oxo‐1,8‐naphthyridine‐3‐ (1b) carboxylic acids are clinically useful antibacterial agents exerting their activity by inhibiting the subunit A of DNA gyrase. Recently, pyrimido‐[1,6‐a]benzimidazoles 2 were found to be a new class of inhibitors of this enzyme. As, in 1, replacement of C(8) by the N‐atom was shown beneficial for the biological properties, a synthesis of the corresponding aza analogues of 2 has been carried out. The synthesis, DNA gyrase inhibitory activity, and in vitro antibacterial activity of the target compounds 16–19 are reported.
Stereoselective Syntheses of Tetrahydroesterastin‐β ‐Lactam Analogues
Authors: Huber Isabelle , Schneider Fernand
Published: December 2004

A total synthesis of the optically active tetrahydroesterastin β ‐lactam analogue 2 using Miller's hydroxamate approach is described (Scheme 2). Significant modification of published procedures has resulted in a short and facile stereospecific preparation of the N‐[(benzyloxycarbonyl)methyl]‐β ‐lactam 17 starting from the readily available D‐serine. This material served as intermediate for the preparation of a variety of N‐[(benzyloxycarbonyl)methyl]tetrahydroesterastin β‐lactam analogues (Scheme 5).
Reaktion von Phenyldiazomethan mit 1,3‐Thiazol‐5(4H)‐thionen: Basenkatalysierte Ring‐Öffnung des Primäradduktes
Authors: Petit Mireille , Linden Anthony , Heimgartner Heinz , Mlostoń Grzegorz
Published: December 2004

Reaction of Phenyldiazomethane with 1,3‐Thiazole‐5(4H)‐thiones: Base‐Catalyzed Ring Opening of the Primary Adduct

Reaction of 1,3‐thiazole‐5(4H)‐thiones 1 and phenyldiazomethane (2a) in toluene at room temperature yields the thiiranes trans‐ and cis‐1,4‐dithia‐6‐azaspiro[2.4]hept‐5‐enes (trans‐ and cis‐4; Scheme 2). With Ph3P in THF at 70°, these thiiranes are transformed stereospecifically into (E)‐ and (Z)‐5‐benzylidene‐4,5‐dihydro‐1,3‐thiazoles 5, respectively. In the presence of DBU, 1 and 2a react to give 1,3,4‐thiadiazole derivatives 6 or 7 via base‐catalyzed ring opening of the primary cycloadduct (Scheme 3). In the case of 2‐(alkylthio)‐substituted 1,3‐thiazole‐5(4H)‐thiones 1c and 1d, this ring opening proceeds by elimination of the corresponding alkylthiolate, yielding isothiocyanate 7. The structures of (Z)‐5c and 6b have been established by X‐ray crystallography.