bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel glyceryl ester (glyceryl dendryphiellate A), a trinor‐eremophilane (dendryphiellin A1), and eremophilanes (dendryphiellin E1 and E2) from the marine deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT
Authors: Guerriero Antonio , Cuomo Vincenzo , Vanzanella Fortunato , Pietra Francesco 
Published: December 2004

AbstractContinuing studies of the global extracts from cultures of the marine deuteromycete Dendryphiella salina have led to the isolation of novel compounds that add to the scarce list of marine fungal metabolites. Besides (22E)‐ergosta‐4.6,8(14),22‐tetraen‐3‐one which, though known from basidiomycetes, was unknown in the sea, they are an unusual glyceryl ester, i.e. glycer‐1‐yl dendryphiellale A (= (+)‐(2R)‐2,3‐dihydroxyprop‐l‐yl (6S,2E,4E)6‐methylocta‐2,4‐dienoate; (+)‐1), a trinor‐eremophilane, i.e. dendryphiellin A1 ( = (+)‐(3R*,4E,6E)‐7‐{[(1R*,2S*,7R*,8aR*)‐1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2yl]oxycarbonyl}‐3‐methylhepta‐4,6‐dienoic acid; (+)‐11), and two eremophilanes, i.e. dendryphiellin El ( = (+)‐(1R*, 2S*, 7S*,8aR*)‐1,2,6,7,8,8a‐hexahydro‐1,8a‐dimethyl‐7‐(1‐methylethenyl)‐6‐oxonaphthalen‐2‐yl(6S,2E,4E)‐6‐methyl‐octa‐2,4‐dienoate; (+)‐13) and dendryphiellin E2 ( = (+)‐(1R*, 2S*, 8aR*)‐1,2,6,7,8,8a‐hexahydro‐7‐isopropyl‐idene‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6S,2E,4E)‐6‐Methylocta‐2,4‐dienoate; (+)‐14). Absolute configurations have been established for (+)‐1 via total synthesis and for the acid portion of (+)‐13 and (+)‐14 via transesterification in NaOMe/MeOH which gave in both cases melhyl dendryphiellate A ((+)‐16) of known configuration and the free alcoholic moiety of (+)‐14, i.e. (+)‐17.
Synthesis of 24‐Methylidene[24‐14C]‐ and 24‐Methylidene[7‐3H]cholesterol
Authors: Monteagudo Edith S. , Burton Gerardo , Gros Eduardo G. 
Published: December 2004

AbstractThe syntheses of 24‐methylidene[24‐14C]cholesterol (7a) and of 24‐methylidene[7‐3H]cholesterol (7b) from commercially available (20S)‐3‐oxopregn‐4‐ene‐20‐carbaldehyde (1) are described. The method also provides simple preparations of 3β‐acetoxy[24‐14C]chol‐5‐en‐24‐oic acid (4) and 24‐oxocholest‐5‐en‐3β‐yl acetate (6b).
Stereoselektive Synthesen von substituierten Tricarbonyl[tris(methylen)methan]eisen(0)‐Komplexen
Authors: Kappes Dag , Gerlach Hans , Zbinden Peter , Dobler Max 
Published: December 2004

Stereoselective Syntheses of Substituted Tricarbonyl[tris(methylen)methan]iron(0) ComplexesThe complexes 3, 9, 10, 22, and 23 with one, two, and three Me substituents at the tris(methylen)methane moiety have been synthesized from the (acyloxy‐1,3‐diene)(tricarbonyl)iron(0) complexes 1, 4, 5, 20, and 21, respectively, by ionic hydrogenation with BF3 and Et3SiH at −78° in CH2C12. These reductions are completely stereoselective, and their course can be predicted by assuming a dominant stereoelectronic control of the reaction. Formation of the carbocationic intermediates 11 from 4 and 12 from 5, e.g., takes place only if the dissociating OC bond is antiperiplanar to the donor C(β)Fe bond. Fast H‐transfer then converts the intermediate 11 to 9 and 12 to 10. The configurations of 17 and 20 can be deduced from the structure of 22 and those of 18 and 21 from that of 23. An X‐ray structure determination of (1R,4S)camphanoate (−)‐13 derived from alcohol (−)‐7 confirms the configuration of 5 deduced above, The structures of the complexes 9 and 10, 22 and 23 were determined by their unique NMR spectra. The diastereoisomeric complexes 6 and 7 have been synthesized from aldehyde 8 with MeMgI, the diastereoisomers 17 and 18 analogously from 16 or from methyl ketone 19 by reduction with LiAlH4. Optically active starting materials (+)‐1, (−)‐13, (+)‐20, and (+)‐21 gave, by ionic hydrogenation, the complexes (−)‐(3R)‐3, (+)‐(2S,4S)‐10, (−)‐(R,R, S)‐22, and (−)‐(R,R,R)‐23 respectively, with known absolute configurations.
1‐Methoxycarbonyl‐substituiertes 2,3‐Dihydropyridin‐4(1H)‐on (= Methyl‐1,2,3,4‐tetrahydro‐4‐oxopyridin‐1‐carboxylat) als Chromophor für die photochemische [2 + 2]‐Cycloaddition
Authors: Guerry Philippe , Blanco Philippe , Brodbeck Heinz , Pasteris Olivier , Neier Reinhard 
Published: December 2004

1‐Methoxycarbonyl‐Substituted 2,3‐Dihydropyridin‐4(1H)‐one(= Methyl 1,2,3,4‐Tetrahydro‐4‐oxopyridine‐1‐carboxylate) as Chromophore for Photochemical [2 + 2]‐CycloadditionsWith olefins having an electron‐acceptor as well as with olefins having an electron‐donor substituent, 1‐methoxycarbonyl‐substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis‐junction. Only the ‘endo’/‘exo’ selectivity at the C‐atom bearing the olefin substituent cannot be controlled. The photodimerization of 12 is the only side reaction. Using a slight excess of the olefin, the photodimerization can be suppressed. The protecting group at the N‐atom of the dihydropyridinone can be varied in order to introduce an internal sensitizer, as shown with 1‐acyl‐substituted compound 29, which underwent the cycloaddition process even with sunlight.
Structure cristalline d'une thiazolorifamycine: rifamycine P
Authors: Léger Jean‐Michel , Carpy Alain 
Published: December 2004

Crystal Structure of a Thiazolorifamycine: Rifamycine PThe crystal structure of a natural thiazolorifamycin, rifamycin P, as an adduct with EtOH and H2O, has been determined by X‐ray crystallography by a combination of direct methods and Patterson techniques. Block‐diagonal least‐squares refinement using 5996 independent reflections and 1475 parameters led to an R factor of 0.092 (two independent molecules of rifamycin P). The middle part of the ansa chain, essential for activity against the bacterial DNA‐dependent RNA polymerase (DDRP) resembles that of active rifamycins. The four OH groups lie on the same side of the molecule and are almost in the same plane. Interatomic distances between the O‐atoms agree well with a spatial model derived from X‐ray studies, performed on semisynthetic active rifamycins.
Preparation of a Key Intermediate for the Synthesis of the (±)‐Pentalenolactone E Methyl Ester by Catalytic ‘Palladium‐Ene Cyclization’/Methoxycarbonylation
Authors: Oppolzer Wolfgang , Xu Jin‐Zhu , Stone Charles 
Published: December 2004

AbstractBicyclic alcohol (±)‐2, an advanced intermediate for the synthesis of the methyl ester 1 of pentalenolactone E, has been synthesized in nine operations starting from aldehyde 7. The key step 6 → 9 is a Pd‐catalyzed, tandem intramolecular alkyne allylation/carbonylation reaction.
Synthese von enantiomerenreinem Mimulaxanthin und seiner (9Z,9′Z)‐ und (15Z)‐Isomeren
Authors: Baumeler Andreas , Eugster Conrad Hans 
Published: December 2004

Synthesis of Enantiomerically Pure Mimulaxanthin and of Its (9Z,9′Z)‐ and (15Z)IsomersWe present the details of a synthesis of optically active, enantiomerically pure stereoisomers of mimulaxanthin (=(3s,5R,6R,3′S,5′R,6′R)‐6,7,6′,7′‐tetradehydro‐5,6,5′,6′‐tetrahydro‐β,β‐carotin‐3,5,3′,5′‐tetrol) either as free alcohols 1a and 24a or as their crystalline (t‐Bu)Me2Si ethers 1b and 24b. Grasshopper ketone 2a, a presumed synthon, unexpectedly showed a very sluggish reaction with Wittig‐Horner reagents. Upon heating with the ylide of ester phosphonates, an addition across the allenic bond occurred. On the contrary, a slow but normal 1,2‐addition took place with the ylide from (cyanomethyl)phosphonate but, unexpectedly, with concomitant inversion at the chiral axis. So a mixture of(6R,6S,9E,9Z)‐isomers 6–9 was produced {(Scheme 1). However, a fast and very clean 1,2‐addition occurred with the ethynyl ketone 12 to yield the esters 13 and 14 (Scheme 2). DIBAH reduction of the separated stereoisomers gave the allenic alcohols 15 and 16 in high yield. Mild oxidation to the aldehydes 17 and 18 followed by their condensation with the acetylenic C10‐bis‐ylide 19 led to the stereoisomeric 15,15′‐didehydromimulaxanthins 20 and 22, respectively (Schemes 3 and 4). Mimulaxanthins 1 and 24 were prepared by partial hydrogenation of 20 and 22 followed by a thermal (Z/E)‐isomerization. As expected, the mimulaxanthins exhibit very weak CD curves, obviously caused by the allenic bond that insulates the chiral centers in the end group from the chromophor. On the contrary, some of the C15‐allenic synthons showed not only fairly strong CD effects but also a split CD curve which, in our interpretation, results from an exciton coupling between the allene and the C(9)C(10) bond. We postulate a rotation around the C(8)C(9) bond, presumably caused by an intramolecular H‐bond in 16 or by a dipol interaction between the polarized double bonds in 6, 7, 8, and 17.
Palladium‐Catalyzed Ene‐Type Cyclizations of Terpenoid 1,6‐Enynes
Authors: Knierzinger Andreas , Grieder Alfred , Schönholzer Peter 
Published: December 2004

AbstractPalladium‐catalyzed ene‐type cyclizations of 1,6‐enynes 2 yield methylidene‐cyclopentane derivatives 3. Removal of protecting groups from 3 furnishes the diols 4 and 5, whose configurations were established by a combination of X‐ray and 1H‐NMR techniques. The predominant formation of isomers 4 is discussed in the context of two alternative hypothetical mechanisms previously proposed for this type of cyclization.
Syntheses of Pyrrolo[2,3‐d]pyrimidine 2′,3′‐Dideoxyribonucleosides Related to 2′,3′‐Dideoxyadenosine and 2′,3′‐Dideoxyguanosine and Inhibitory Activity of 5′‐Triphosphates on HIV‐1 Reverse Transcriptase
Authors: Seela Frank , Muth Heinz‐Peter , Röling Angelika 
Published: December 2004

AbstractThe synthesis of 4‐chloropyrroIo[2,3‐d]pyrimidine and 2‐amino‐4‐chloropyrrolo[2,3‐d]pyrimidine α‐D‐ and β‐D‐2′,3′‐dideoxyribonucleosides6a,band7a,bis described (Scheme 1). Glycosylation of the pyrrolo[2,3‐d]‐pyrimidinyl anions of1a,bwithin situprepared 2,3‐dideoxy‐α/β‐D‐glycero‐pentofuranosyl chloride (2) was regioselective but afforded anomeric mixtures of the 2′,3′‐dideoxyribonucleosides3a/4aand3b/4b, respectively. The glycosylation products were deprotected and subjected to nucleophilic displacement yielding various pyrrolo[2,3‐d]pyrimidine 2′,3′‐deoxyribonucleosides related to 2′,3′‐dideoxyadenosine and 2′,3′‐dideoxyguanosine. One‐pot phosphorylation gave the corresponding triphosphates. Some of them are strong inhibitors of HIV‐1 reverse transcriptase, similar to corresponding purine 2′,3′‐dideoxynucleotides, but exhibit a better selectivity index in comparison to DNA polymerases. According to that, the N(7) of the purine moiety is not an essential binding position of ddATP or ddGTP at the active centre of HIV‐1 reverse transcriptase.
1,7‐Dideaza‐2′,3′‐dideoxyadenosine: Syntheses of Pyrrolo[2,3‐b]pyndine 2′,3′‐Dideoxyribofuranosides and Participation of Purine N(1) during HIV‐1 Reverse Transcriptase Inhibition
Authors: Seela Frank , Gumbiowski Rainer 
Published: December 2004

AbstractThe syntheses of 1,7‐dideaza‐2′,3′‐dideoxyadenosine (1) and related pyrrolo[2,3‐b]pyridine 2′,3′‐dideoxyribi and 2′,3′‐didehydro‐2′,3′‐dideoxyribonucleosides (see 2–5) are described. As starting materials, 2′‐deoxyribo‐nucleosides 6 or 7 were used. The 3′‐OH group was removed by Barton deoxygenation or via mesylation follow by elimination and catalytic hydrogenation. Compound 1 was also obtained from the direct glycosylation of 4‐nitro‐1H‐pyrrolo[2,3‐b]pyridine (17) with the 2,3‐dideoxyribofuranosyl chloride 18. The triphosphate 25 of 1 showed only marginal activity against HIV‐1 reverse transcriptase, indicating that purine N(1) is required for the inhibitory activity of the parent 2′,3′‐dideoxyadenosine.
Zur Oxidation von 1,2‐Thiazolen: Ein einfacher Zugang zu 1,2‐Thiazol‐3(2H)‐on‐1,1‐dioxiden
Authors: Schulze Bärbel , Kirsten Gisela , Kirrbach Sabine , Rahm Annette , Heimgartner Heinz 
Published: December 2004

Oxidation of 1,2‐Thiazoles; A Convenient Approach to 1,2‐Thiazol‐3(2H)‐one 1,1‐DioxidesThe 1,2‐thiazoles obtained from 3‐chloroalk‐2‐enals and ammonium thiocyanate (7 → 9, Scheme 1) are easily transformed to 1,2‐thiazol‐3(2H)‐one 1,1‐dioxidcs 10 on treatment with H2O2 in AcOH at 80°. Hydrogenation of 10 in AcOH yields the corresponding saturated 1,2‐thiazolidin‐3‐one 1,1‐dioxides 16 (Scheme 3). Cycloalka[c]‐1,2‐thiazoles 18 are prepared from 2‐[(thiocyanato)methyliden]cycloalkan‐1‐ones and ammonia (Scheme 4). Surprisingly, oxidation of 18a with H2O2 in AcOH yields the tricyclic oxaziridine 19.
Crystal Structures of the Lanthanum(III), Europium(III), and Terbium(III) Cryptates of Tris(bipyridine) Macrobicyclic Ligands
Authors: Bkouche‐Waksman Itka , Guilhem Jean , Pascard Claudine , Alpha Béatrice , Deschenaux Robert , Lehn Jean‐Marie 
Published: December 2004

AbstractThe crystal structures of the LaIII, EuIII, and TbIII complexes of macrobicyclic [bpy.bpy.bpy] ligands, [La3+ ⊂ 1]3 Cl− ( = 3‐La), [Tb3+ ⊂ 1]3 Cl− ( = 3‐Tb), and [Eu3+ ⊂ 2]3 C1− ( = 3‐Eu), have been determined. They confirm the cryptate nature of these species, the cations being bound to the eight N‐sites of the ligand. The macrobicycle presents two open faces, thus allowing additional coordination of two species, Cl− ions or H2O molecules, to the bound cations. These data provide structural support for the photophysical studies of the luminescent properties of the EuIII and TbIII cryptates, which indicated residual coordination of H2O molecules.
Site‐Selectivity in the Fe+‐Mediated CH/CC Bond Activation of Aldimines Short Communication
Authors: Prüsse Tilmann , Schwarz Helmut 
Published: December 2004

AbstractIt is demonstrated for the first time that the site‐selectivity for the Fe+‐mediated CH bond activation of aldimines R1NCHR2 (R1, R2 = alkyl) involves the alkyl chain R1 by a factor ≥ 12 in comparison to the alkenyl part R2. This finding explains previous observations that dehydrogenation of intermediates formed by alkene loss from either R1 or R2 of R1NCHR2/Fe+ preferentially involves the alkyl part.
Monosubstitution von Octa(hydridosilasesquioxan) H8Si8O12 zu R′H7Si8O12 mittels Hydrosilylierung Kurzmitteilung
Authors: Calzaferri Gion , Herren Daniel , Imhof Roman 
Published: December 2004

Monosubstitution of Octa(hydridosilasesquioxane) H8Si8O12 to R′H7Si8O12 by HydrosilylationHydrosilylation of hex‐1‐ene and of styrene by octa(hydridosilasesquioxanes) catalyzed by hexachloroplatinic acid leads to the first monosubstituted octasilasesquioxane R′H7Si8O12 molecules.
Metal complexes with macrocyclic ligands. Part XXXIV. Geometrical and conformational changes during the on/off reaction of the side chain in the CuII complex of 11‐(3‐aminopropyl)‐1,4,7,11‐tetraazacyclotetradecane
Authors: Schiegg André , Riesen Andreas , Kaden Thomas A. 
Published: December 2004

AbstractSolution studies of the Cu2+ complex with 11‐(3‐aminopropyl)‐1,4,7,11‐tetraazacyclotetradecane(L) indicate that, depending on the pH and on the age of the solution, different species are present. Dissolving the solid [CuL](ClO4)2 in slightly acidic solution gives the protonated complex AH, characterized by an absorption maximum at 574 nm, by a relatively fast proton‐induced dissociation kinetics and by the typical colour change in basic solution to give the deprolonated form A with coordinated side chain. AH slowly interconverts in acidic solution to a new species BH, which has an absorption maximum at 547 nm, and which is kineticaily more stable against acid dissociation and shows no coordination of the amino group of the side chain. In alkaline solution, however, the deprotonated form B deliver A in a base induced reaction. The X‐ray diffraction studies of A and BH allow to determine the geometry of the metal ion and the configuration of the macrocycle. In A, the Cu2+ is pentacoordinated by the five N‐atoms of the ligand and the macrocycle is in the RRSR configuration, whereas in BH the Cu2+ is octahedrally coordinated by the four N‐atoms of the macrocycle and two axial perchlorate O‐atoms with the macrocycle in the RRRS configuration. The amino group of the side chain is protonated and not coordinated. Thus, the on/off equilibrium of the side chain not only changes the geometry of the metal ion, as is generally found, but also alters the macrocyclic moiety.
Unimolecular Gas‐Phase Oxidation of Terminal Hydroxy Groups in [FeO(CH2)nOH]+ Complexes (n = 2–8). A Case for OH Bond Activation by Late Transition‐Metal Ions. Preliminary Communication
Authors: Prüsse Tilmann , Schwarz Helmut 
Published: December 2004

AbstractIn contrast to Fe+/diol complexes, gas‐phase dehydrogenation of the corresponding FeII alkoxides, [FeO(CH2)nCH2OH]+, is a highly specific process in the course of which oxidation of the terminal OH group takes place. Based on labeling studies, this is the exclusive mechanism for n = 2 and 3 (Scheme: path ); for higher homologues, as for example [FeOf(CH2)7CH2OH]+, the labeling data demonstrate that an additional mechanism is operative, involving the dehydrogenation of internal positions of the alkyl chain (path ). The Fe+‐mediated oxidation –CH2OH → –CHO +H2: constitutes one of the rare examples of O‐H bond activation by late cationic transition‐metal ions.
Reaction of the 5‐Azoniafulvene Ion with Enamines: A New Approach to Pyrrolizines
Authors: Schärer Daniel , Jindra Vladimir , Bringhen Alain O. , Burger Ulrich 
Published: December 2004

AbstractThe synthesis of N,N‐dimethyl‐N‐[(pyrro‐1‐yl)methyl]anilinium chloride (14) and of the corresponding p‐toluidinium salt 15 is described. These salts, when dissolved in polar solvents, are shown to be in equilibrium with 1‐(chloromethyl)pyrrole (17) and thereby potentially with the 5‐azoniafulvene ion (2). Consequently, they react under very mild conditions (MeCN, 60°) with enamines to give pyrrolizine derivatives in acceptable yield (40–50°). The process is rationalized in terms of an initial Mannich‐type reaction which is immediately followed by acyclization.
A Molecular‐Mechanics Analysis of Complexes of the Sexidentate Macrocycles cis‐ and trans‐6,13‐Dimethyl‐1,4,8,11‐tetraazacyclotetradecane‐6,13‐diamine
Authors: Bernhardt Paul V. , Comba Peter 
Published: December 2004

AbstractMolecular‐mechanics calculations of the sexidentate coordinated complexes of the pendant arm macrocyclic hexaamines trans‐ (L1) and cis‐6,13‐dimethyl‐3,4,8,11‐tetraazacyclotetradecane‐6,13‐diamine (L2) reveal that the trans‐isomer shows a preference toward small metal ions, whereas the L2 may coordinate a wider range of metal ions without significant intramolecular strain. Conformational disorder in previously reported crystal structures of complexes of L1 is interpreted, and predictions for some, as yet, unknown complexes of L2 are made.
Energy Transfer from a Lumazine (= Pteridine‐2,4(1H,3H)‐dione) Chromophore to Bathophcnanthroline‐ruthenium(II) Complexes during Hybridization Processes of DNA
Authors: Bamwarth Willi , Müller Francis 
Published: December 2004

AbstractWe incorporated 6,7‐dimethyllumazine chromophores and a [RuII(bathophenanthroline)] complex into different oligodeoxynucleotides, the former via the corresponding phosphoramidites of the 2′‐deoxynucleosides and the latter specifically by the phosphonate approach at the 5′‐end of synthetic oligonucleotides, directly in the course of their synthesis on solid support. Efficiency measurements of this energy‐transfer system with the lumazine as energy donor and the Ru complex as energy acceptor allowed us to distinguish between the hybridized and the non‐hybridized state of oligonucleotides. Thus, the approach should be of value in DNA probe technology for the detection of single‐stranded DNA targets.
9‐(2′‐Deoxy‐β‐D‐xylofuranosyl)adenine Building Blocks for Solid‐Phase Synthesis and Properties of Oligo(2′‐deoxy‐xylonucleotides)
Authors: Roscmeycr Helmut , Krečmerova Marcela , Seela Frank 
Published: December 2004

AbstractThe 9‐(2′‐deoxy‐à‐D‐threo‐pentofuranosyl)adenine (=9‐(2′‐deoxy‐à‐D‐xylofuranosyl)adeninc, xAd; 2) was protected at its 6‐NH2 group with cither a benzoyl (5a) or a (dimethyfamino)methylidcnc (6a) residue and with a dimethoxytntyl group at 5′‐OH (5b, 6b). Compounds 5b and 6b were then converted into the 3′‐phosphonates 5c and 6c; moreover, the 2‐cyanoethyl phosphoramidite 6d was synthesized starting from fib. The DNA building blocks were used for solid‐phase synthesis of d[(xA)122‐A] (8). The latter was hybridized with d[(xT)12‐T] (Tm = 35°); in contrast, with d(T12), complex formation was not observed. Moreover, xAd and xTd were introduced into the self‐complementary dodccamcr d(G‐T‐A‐G‐A‐A‐T‐T‐C‐T‐A‐C) (12) at different positions lo give the oligomcrs 13–16. All oligonucleotides were characterised by temperature‐dependent CD and UV spectroscopy, and in addition, 14 by T‐jump experiments. From concentration‐dependent Tm measurements, the thermodynamic paraneters of the melting as well as the tendency of hairpin formation of the oligonucleotides were deduced. Oligemer 14 was hydrolyzed by snake‐venom phosphodiesterase in a discontinuous way implying a fast hydrolysis of unmodified 3′‐ and 5′‐flanks followed by a slow hydrolysis of the remaining modified tetramer. In contrast to this, oligonucleotide 16 was hydrolyzed in a continuous reaction. In both cases, calf‐spleen phosphodiesterase hydrolyzed the oligomer only marginally.
Synthese von Makrocyclen durch Ringerweiterung von 14gliedrigen cyclischen Imiden
Authors: Koch Thomas , Ognyanov Vassil I. , Hesse Manfred 
Published: December 2004

Synthesis of Macrocyles by Ring Enlargement of 14‐Membered Cyclic ImidesIn the presence of a base, cyclododecanone derivative 2, activated in α‐position by an allyloxycarbonyl group, underwent ring enlargement with isocyanates to give 14‐membered imides (Schemes 1–3). Cleavage of the activating group gave new 14‐membered imides which could be transformed by further ring‐enlargement reactions into new macrocyclic compounds.
Endohedral fullerene‐noble gas clusters formed with high‐energy bimolecular reactions of C (x = 60, 70; n = 1, 2, 3)
Authors: Weiske Thomas , Hrušák Jan , Bohme Diethard K. , Schwarz Helmut 
Published: December 2004

AbstractResults are reported for high‐energy beam experiments which establish the formation of endohedral carbon cluster‐noble gas compounds by bimolecular reactions of C (x = 60, 70; n = 1, 2, 3) with He and C with Ne. The ions were accelerated up to 8 ke V in a four‐sector mass spectrometer and allowed to collide with the noble gas in a collision chamber at room temperatur. Product ions were monitored with a B/E = constant linked scan. Within the sensivity of the experiments, no carbon cluster‐gas compounds were observed in the reactions of C with H2, D2, O2, Ar, and SF6, or of C with O2. The observed fall in the cross‐section for carbon cluster‐noble gas compounds with increasing size of the noble gas, the observation of unimolecular loss of C2 from mass‐selected CxHe+ ions, and the elimination of carbon fragments instead of He observed in the formation of the collision‐induced CxHen+ product ions are taken as evidence for endohedral compound formation. Results of ab initio molecular‐orbital calculations for the perpendicular penetration of the plane of ionized benzene with He, Ne, and Ar indicate that sufficient kinetic energy should be available in the collisions with C to penetrate the C cage at the collision energies of the experiments.
Radical Cations and Radical Anions of Three Bridgehead Azopolycycloalkanes: A fluid‐solution ESR study
Authors: Gescheidt Georg , Lamprecht Axel , Rüchardt Christoph , Schmittel Michael 
Published: December 2004

AbstractThe radical mono‐ions of three azoalkanes in which the azo group is connected to the polycyclic alkane moieties at the bridgehead C‐atoms, i.e. 1,1′‐azonorbornane (1), 1,1′‐azotwistane (2), and 1,1′‐azobicyclo[3.2.1]octane (3), were studied in fluid solution by ESR spectroscopy. According to the ESR parameters and MO models, the radical cations of 1–3 should be considered as σ radicals, whereas the corresponding radical anions are π radicals. INDO calculations point to a a remarkable dependence of the 14N‐coupling constants on the geometry at the N‐atoms in the radical cations of aliphatic azo compounds.