bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two‐State Reactivity in Organometallic Gas‐Phase Ion Chemistry
Authors: Shaik Sason , Danovich David , Fiedler Andreas , Schröder Detlef , Schwarz Helmut 
Published: December 2004

AbstractIn contrast to organic reactions, which can almost always be described in terms of a single multiplicity, in organometallic systems, quite often more than one state may be involved. The phenomenon of two states of different multiplicities that determine the minimum‐energy pathway of a reaction is classified as two‐state reactivity (TSR). As an example, the ion/molecule reactions of ‘bare’ transition‐metal‐monoxide cations with dihydrogen and hydrocarbons have been analyzed in terms of the corresponding potential‐energy hypersurfaces. It turns out that, besides classical factors, such as the barrier heights, the spin‐orbit coupling factor is essential, since curve crossing between the high‐ and low‐spin states constitutes a distinct mechanistic step along the reaction coordinates. Thus, TSR may evolve as a new paradigm for describing the chemistry of coordinatively unsaturated transition‐metal complexes. This concept may contribute to the understanding of organometallic chemistry in general and for the development of oxidation catalysts in particular.
Reaction of Hydroxymethyl‐ and Alkyl‐Substituted Azulenes with Manganese Dioxide
Authors: Fallahpour Reza‐Ali , Sigrist Rolf , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that the 2‐(hydroxymethyl)‐1‐methylazulenes 6 are being oxidized by activated MnO2 in CH2Cl2 at room temperature to the corresponding azulene‐1,2‐dicarbaldehydes 7 (Scheme 2). Extension of the MnO2 oxidation reaction to 1‐methyl‐ and/or 3‐methyl‐substituted azulenes led to the formation of the corresponding azulene‐1‐carbaldehydes in excellent yields (Scheme 3). The reaction of unsymmetrically substituted 1,3‐dimethyl‐azulenes (cf. 15 in Scheme 4) with MnO2 shows only little chemoselectivity. However, the observed ratio of the formed constitutionally isometric azulene‐1‐carbaldehydes is in agreement with the size of the orbital coefficients in the HOMO of the azulenes. The reaction of guaiazulene (18) with MnO2 in dioxane/H2O at room temperature gave mainly the expected carbaldehyde 19. However, it was accompanied by the azulene‐diones 20 and 21 (Scheme 5). The precursor of the demethylated compound 20 is the carbaldehyde 19. Similarly, the MnO2 reaction of 7‐isopropyl‐4‐methyalazulene (22) as well as of 4,6,8‐trimethylazulene (24) led to the formation of a mixture of the corresponding azulene‐1,5‐diones and azulene‐1,7‐diones 20/23 and 25/26, respectively, in decent yields (Schemes 6 and 7). No MnO2 reaction was observed with 5,7‐dimethylazulene.
Synthesis of an Isotopically Isomeric Mixture of 1,4,6,8‐Tetramethyl[13C2]azulene and Its Thermal Reaction with Dimethyl Acetylenedicarboxylate
Authors: Fallahpour Reza‐Ali , Hansen Hans‐Jürgen 
Published: December 2004

AbstractSodium [1,3‐13C2]cyclopentadienide in tetrahydrofuran (THF) has been prepared from the corresponding labelled [13C2]cyclopentadiene which was synthesized from 13CO2 and (chloromethyl)trimethylsilane (cf. Scheme 10) according to an established procedure. It could be shown that the acetate pyrolysis of cis‐cyclopentane‐1,2‐diyl diacetate (cis‐22) at 550 ± 5° under reduced pressure (60 Torr) gives five times as much cyclopentadiene as trans‐22. The reaction of sodium [1,3‐13C2]cyclopentadienide with 2,4,6‐trimethylpyrylium tetrafluoroborate in THF leads to the formation of the statistically expected 2:2:1 mixture of 4,6,8‐trimethyl[1,3a‐13C2], ‐[2,3a‐13C2]‐, and ‐[1,3‐13C2]azulene (20; cf. Scheme 7 and Fig. 1). Formylation and reduction of the 2:2:1 mixture [13C2]‐20 results in the formation of a 1:1:1:1:1 mixture of 1,4,6,8‐tetramethyl[1,3‐13C2]‐, ‐[1,3a‐13C2]‐, ‐[2,3a‐13C2]‐, ‐[2,8a‐13C2]‐, and ‐[3,8a‐13C2]azulene (5; cf. Scheme 8 and Fig. 2). The measured 2J(13C, 13C) values of [13C2]‐20 and [13C2]‐5 are listed in Tables 1 and 2. Thermal reaction of the 1:1:1:1:1 mixture [13C2]‐5 with the four‐fold amount of dimethyl acetylenedicarboxylate (ADM) at 200° in tetralin (cf. Scheme 2) gave 5,6,8,10‐tetramethyl‐[13C2]heptalene‐1,2‐dicarboxylate ([13C2]‐6a; 22%), its double‐bond‐shifted (DBS) isomer [13C2]‐6b (19%), and the corresponding azulene‐1,2‐dicarboxylate 7 (18%). The isotopically isomeric mixture of [13C2]‐6a showed no 1J(13C,13C) at C(5) (cf. Fig. 3). This finding is in agreement with the fact that the expected primary tricyclic intermediate [7,11‐13C2]‐8 exhibits at 200° in tetralin only cleavage of the C(1)C(10) bond and formation of a C(7)C(10) bond (cf. Schemes 6 and 9), but no cleavage of the C(1)C(11) bond and formation of a C(7)C(11) bond. The limits of detection of the applied method is ≥96% for the observed process, i.e., [1,3a‐13C2]‐ 5 + ADM→ [7,11‐13C2]‐8→[1,6‐13C2]‐9 →[5,10a‐13C2]‐6a (cf. Scheme 6).
Structural and Photophysical Properties of Pseudo‐Tricapped Trigonal Prismatic Lanthanide building blocks controlled by zinc(II) in heterodinuclear df complexes
Authors: Piguet Claude , Rivara‐Minten Elisabeth , Hopfgartner Gérard , Bünzli Jean‐Claude G. 
Published: December 2004

AbstractAn efficient combination of electrospray mass spectrometry (ES‐MS), spectrophotometric and 1H‐NMR titrations in solution is used to characterize the assembly of the segmental ligand 2‐{6‐[1‐(3,5‐dimethoxybenzyl)‐1H‐benzimidazol‐2‐yl]pyridin‐2‐yl}‐1, 1′‐dimethyl‐5,5′‐methylene‐2′‐(5‐methylpyridin‐2‐yl)bis[1H‐ benzimidazole] (L2) with ZnII and 4f metal ions, LnIII. Ligand L2 reacts with Zn(ClO4)2 in MeCN to give successively [Zn(L2)2]2+, where the metal ion is coordinated by the tridentate binding units of the ligands, and the double‐helical head‐to‐head complex [Zn2(L2)2]4+. When L2 reacts with Ln(ClO4)3 (Ln = La, Eu, Lu), LaIII only leads to a well‐defined cylindrical C1‐symmetrical homodinuclear head‐to‐tail complex [La2(L2)3]6+ in solution, while chemical‐exchange processes prevent the 1H‐NMR characterization of [Eu2(L2)3]6+, and LuIII gives complicated mixtures of complexes. However, stoichiometric amounts of LnIII (Ln = La, Ce, Pr, Nd, Sm, Eu, Tb, Y, Lu), ZnII, and L2 in a 1:1:3 ratio lead to the selective formation of the C3‐symmetrical heterodinuclear complexes [LnZn(L2)3]5+ under thermodynamic control. Detailed NOE studies show that the ligands are wrapped about the C3 axis defined by the metal ions, and the separation of dipolar and contact contributions to the 1H‐NMR paramagnetic shifts of the axial complexes [LnZn(L2)3]5+ (Ln = Ce, Pr, Nd, Sm, Eu) in MeCN establishes that ZnII occupies the pseudo‐octahedral capping coordination site defined by the three bidentate binding units, while LnIII lies in the resulting ‘facial’ pseudo‐tricapped trigonal prismatic site produced by the three remaining tridentate units. Photophysical measurements show that [LnZn(L2)3]5+ (Ln = Eu, Tb) are only weakly luminescent because of quenching processes associated with the C3‐cylindrical structure of the complexes. The use of 3d metal ions to control and design isomerically pure ‘facial’ tricapped trigonal prismatic lanthanide building blocks is discussed together with the calculation of a new nephelauxetic parameter associated with heterocyclic N‐atoms coordinated to LnIII.
Pyranosyl‐RNA (‘p‐RNA’): Base‐pairing selectivity and potential to replicate. Preliminary communication
Authors: Pitsch Stefan , Krishnamurthy Ramanarayanan , Bolli Martin , Wendeborn Sebastian , Holzner Armin , Minton Mark , Lesueur Catherine , Schlönvogt Irène , Jaun Bernhard , Eschenmoser Albert 
Published: December 2004

AbstractBase pairing in p‐RNA (β‐D‐ribopyranosyl‐(4′ → 2′)‐oligonucleotides) is not only stronger than in DNA and RNA, but also more selective in the sense that it is strictly confined to the Watson‐Crick mode. Homopurine sequences (tested up to decamers) exist as single strands under conditions where they undergo reverse‐Hoogsteen self‐pairing in homo‐DNA or Hoogsteen self‐pairing in DNA. This exceptional pairing selectivity is rationalized as hinging on two structural features of p‐RNA: the large inclination between backbone axis and base‐pair axes in p‐RNA duplexes, and the higher rigidity of the p‐RNA backbone compared with RNA, DNA, and homo‐DNA. The most important consequence of the pairing selectivity refers to the potential of p‐RNA to replicate. Replicative copying of sequence information by nonenzymatic template‐controlled ligation is not hampered by self‐pairing of guanine‐rich templates, as it is known to be the case in the RNA series. We have demonstrated two replicative cycles in which G‐rich p‐RNA‐octamer templates induce sequence‐selective ligation of tetramer‐2′‐phosphate derivatives to complementary C‐rich octamer sequences, and in which the latter, with comparable efficiency, induce corresponding ligation reactions back to the original G‐rich octamers. Ligation is most satisfactorily achieved after pre‐activation of the 2′‐phosphate groups as 2′,3′‐cyclophosphate derivatives; in this version, the process does not proceed as oligocondensation, but as a genuine oligomerization. This is of considerable promise for the search for potentially natural conditions under which homochiral p‐RNA strands might self‐assemble and self‐replicate.
Preparation of the PdCl2 Complex of TADDOP, the Bis(diphenylphosphinite) of TADDOL: Use in enantioselective 1,3‐diphenylallylations of nucleophiles and discussion of the mechanism
Authors: Seebach Dieter , Devaquet Edmée , Ernst Alexander , Hayakawa Michiya , Kühnle Florian N. M. , Bernd Schweizer W. , Weber Beat 
Published: December 2004

AbstractReaction of the tartrate‐derived diol (R,R)‐α,α,α′,α′‐tetraphenyl‐2,2‐dimethyl‐1,3‐dioxolane‐4,5‐dimethanol (TADDOL) with chlorodiphenylphosphane gives a new bis(diphenylphosphanyl) ligand (TADDOP). The complex 4 formed with PdCl2 has been crystallized and its structure determined by X‐ray diffraction (Fig.1). The complex is used for Pd‐catalyzed enantioselective 1,3‐diphenylallylations of various nucleophiles which give products with enantiomer ratios of up to 88:12 (Scheme 2). Crystallization procedures lead to the enantiomerically pure (> 99:1) product 11 derived from dimethyl malonate. The structure of the TADDOP complex 4 is compared with those of other transition‐metal complexes containing chelating bis(diphenylphosphanyl) ligands (Fig.2). A crystallographic data base search reveals that the structures of transition‐metal complexes containing two Ph2P groups (superpositions in Fig.3) fall into one of two categories: one with approximate C2 symmetry and the other with C1 symmetry (20 and 19 examples, resp.). A mechanistic model is proposed which correlates the conformational chirality (δ or λ) of the four Ph groups' arrangement in such complexes with the topicity of nucleophile approach on Pd‐bound trans,trans‐1,3‐diphenylallyl groups (Scheme 3 and Table).
Multiple Cyclopropanations of C70. Synthesis and characterization of bis‐, tris‐, and tetrakis‐adducts and chiroptical properties of bis‐adducts with chiral addends, including a recommendation for the configurational description of fullerene derivatives with a chiral addition pattern
Authors: Herrmann Andreas , Rüttimann Markus , Thilgen Carlo , Diederich François 
Published: December 2004

AbstractThe regioselectivity of multiple cyclopropanations of C70 with 2‐bromopropanedioates in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as base (Bingel reaction) was investigated in a systematic study. Bisadduct formation occurred preferentially at the 66 bonds formed by the most pyramidalized sp2‐C‐atoms at the two opposite poles of the fullerene and, in the reaction with achiral bis[(ethoxycarbonyl)methyl]2‐bromopropanedioate (13a), yielded three constitutionally isomeric bis(methano)fullerenes (Scheme 2). Two of them, C2‐symmetrical (±)‐1 and (±)‐2, are chiral; a fact which had not been considered in previous investigations. Formation of the third, C2v‐symmetrical isomer 3 was observed for the first time. Configurational descriptions for fullerene derivatives which possess a chiral chromophore as a result of specific functionalization patterns are proposed. Cyclopropanations of C70 with optically active bis[(S)‐1‐phenylbutyl] 2‐bromopropanedioate (13b) yielded five optically active, C2‐symmetrical bis‐adducts 7–11 which could be separated by preparative HPLC and fully characterized (Scheme 3, Fig.4). Compounds 7/8 and 9/10 represent two constitutionally isomeric pairs of diastereoisomers, and their circular dichroism (CD) spectra show pronounced Cotton effects mainly due to strong chiroptical contributions from the chirally functionalized fullerene chromophores (Fig.7). Since the addition patterns on the fullerene surface in each pair of diastereoisomers have an enantiomeric relationship, their CD spectra closely resemble those expected for two enantiomers. In the third constitutional isomer 11, the addition pattern on the fullerene surface is C2v‐symmetrical, and optical activity only results from the chiral addends. Its CD spectrum shows weak Cotton effects mainly from induced circular dichroism originating from the perturbation of the achiral fullerene chromophore by the attached chiral addends. Addition of diethyl 2‐bromopropanedioate (2 equiv.) to the C2‐symmetrical racemic bis‐adduct (±)‐2 yielded a mixture of tris‐adducts and one major, C2‐symmetrical tetrakis‐adduct (±)‐4 which was isolated in pure form (Scheme 4). Starting from the achiral C2v‐symmetrical bis‐adduct 3, one single Cs‐symmetrical tris‐(5) and one C2v‐symmetrical tetrakis‐adduct (6) were obtained as major products which were isolated and fully characterized (Scheme 5). The regioselectivity for introduction of a second addend in the same hemisphere of C70 is high and resembles the preferred pattern of bis‐addition seen in the functionalization of C60.
Synthesis and Evaluation as Glycosidase Inhibitors of 1H‐Imidazol‐2‐yl C‐Glycopyranosides
Authors: Granier Thierry , Vasella Andrea 
Published: December 2004

AbstractThe (1H‐imidazol‐2‐yl)ulose 8 and the 1H‐imidazol‐2‐yl C‐glycopyranosides 23 and 24 have been prepared from tetra‐O‐benzylgluconolactone 6 in two and six steps, respectively. The imidazoles 8 and 24 are moderate competitive inhibitors of sweet‐almond β‐glucosidase (pH 6.8, Ki ≈ 0.79 and 0.64 mM, respectively), while 23 is a competitive inhibitor of yeast α‐glucosidase (pH 6.8, Ki ≈ 0.26 mM). Addition of 2‐lithiated 1‐[(dimethylamino)methyl]‐1H‐imidazole to 6 gave the ulose 7 (68%), which was deprotected to 8. Reduction of 7 with NaBH4 yielded a 12:88 mixture 10/11. Attempts to selectively mesylate HOC(1) of these diols failed, while dinitrobenzoylation led to 19/20, which cyclized easily (NaH) to a 25:75 mixture of 21 and 22 which were separated and debenzylated to the C‐glycosides 23 and 24.
From Epiraikovenal, an Instrumental Niche‐Exploitation Sesquiterpenoid of Some Strains of the Marine Ciliated Protist euplotes raikovi, to an unusual intramolecular tele‐dienone‐olefin [2+2] photocycloaddition
Authors: Guella Graziano , Pietra Francesco , Dini Fernando 
Published: December 2004

AbstractIt is shown that strains of the marine ciliate Euplotes raikovi are subtly variable in their production of secondary metabolites. Strains GA8 and 39W from Mediterranean and SB8 from Californian coasts produce the sesquiterpenoid epiraikovenal (3), while strains GA8 and SB8 also produce secoepiraikovenal (4), which play an instrumental niche‐exploitation role and have also taxonomic significance. Comparison of 3 and 4 with raikovenal (2) and its putative biogenetic precursor 1, which have similar roles in the conspecific strain Morl from Casablanca coast in the Atlantic Ocean, inspired us the first case of intramolecular tele‐dienone‐olefin [2+2] photocycloaddition, exemplified here by the transformation of 1 into ent‐3. This served also to unequivocally clarify the stereochemical relationship between 3 and 2.
Neighboring‐Group Participation in the Gas Phase. Loss of benzaldehyde from [(benzyloxy)methyl]dialkylsilyl‐substituted 1,3‐dithianes
Authors: Fässler Jürg , Huber Priska , Bratovanov Svetoslav , Bigler Laurent , Bild Norbert , Bienz Stefan 
Published: December 2004

Abstract[(Benzyloxy)methyl]dialkylsilyl‐substituted 1,3‐dithianes show in CI‐MS an abundant loss of benzaldehyde from the [M + H]+ quasi‐molecular ion. The fragmentation is explained with an intramolecular redox process, where a hydride is proposed to be transferred from the benzyl position to a neighboring thionium ion. This would form a particle that could readily lose benzaldehyde as a neutral fragment. The CI‐MS results provide an explanation for the unusual instability of (benzyloxy)methyl‐substituted silanes towards acids. In fact, the formation of benzaldehyde was established in the decomposition of a (benzyloxy)methyl‐substituted acylsilane in the presence of Lewis or Brønsted acids and ethanethiol. The CI‐MS study, therefore, represents a useful method to recognize unusual reactions that are – or might be – important in solution.
Formation and Thermal Rearrangement of Dimethyl Tricyclo[6.2.2.01,7]dodeca‐2,4,6,9,11‐pentaene‐9,10‐dicarboxylates
Authors: Fallahpour Reza‐Ali , Hansen Hans‐Jürgen 
Published: December 2004

AbstractThe high‐pressure reaction of 1‐methylazulenes 1 with excess of dimethyl acetylenedicarboxylate (ADM) in hexane at 30° and at pressures up to 7 kbar affords the tricyclic compounds 2 in reasonable‐to‐good yields (cf. Table 1). The crystalline compounds 2 decompose on melting into the starting materials and undergo rearrangement to the corresponding heptalene‐1,2‐dicarboxylates 6. The X‐ray crystal‐structure analyses of 2f and 2g (cf. Fig. 1) reveal the presence of a perfectly planar seven‐membered ring and comparably long C(1)–C(10) as well as C(1)–C(11) bonds (cf. Tables 2 and 3). The thermolysis of 2g in different solvents leads in aprotic media to the formation of the starting azulene 1g and, depending upon the polarity of the solvents, to varying amounts of the corresponding heptalene‐1,2‐dicarboxylate 6f (cf. Table 11). The formed amounts of 1g depends linearly on the ET values of the solvents (cf. Fig. 4). The same is valid for the thermolysis of 2g in protic media (cf. Table 10 and Fig.3). However, in these cases instead of the heptalene‐1,2‐dicarboxylate 6g, the corresponding (E)‐ and (Z)‐isomers of the 1‐(azulen‐1‐yl)ethene‐1,2‐dicarboxylates 7g are formed. The other tricyclic compounds 2 exhibit the same behavior on thermolysis in MeCN and BuOH (cf. Tables 8 and 9, resp.). The results show that the tricyclic compounds 2 undergo at temperatures up to 110° two competing reactions, namely heterolysis of the C(1)–C(10) bond, leading to the formation of heptalenes 6 in polar aprotic media, and the (E)‐ and (Z)‐ethene‐1,2‐dicarboxylates 7 in polar protic media, and concerted homolysis of the C(1)–C(10) and C(8)–C(9) bonds in the sense of a retro‐Diels‐Alder reaction in apolar media, yielding the starting azulenes and ADM, the amount of which decrease with increasing polarity of the solvent. The kinetic and activation parameters measured for 2g and the other tricyclic compounds 2 are collected in Tables 12–15. The tricyclic compounds 2a and 2b show in polar aprotic media (MeCN) a different behavior in that they form, instead of heptalenes, the corresponding 3,4‐dihydrocyclopent[cd]azulene‐1,2‐dicarboxylates 16a and 16b, respectively (Scheme 4). Experiments with [8‐2H]‐2a showed that these compounds are not formed via intramolecular H‐shifts (cf. Schemes 8 and 9).
Nucleic‐Acid Analogs with Restricted Conformational Flexibility in the Sugar‐Phosphate Backbone (‘Bicyclo‐DNA’). Part 5. Synthesis, Characterization, and Pairing Properties of Oligo‐α‐D‐(bicyclodeoxynucleotides) of the Bases Adenine and Thymine (α‐Bicyclo‐DNA)
Authors: Bolli Martin , Lubini Paolo , Leumann Christian 
Published: December 2004

AbstractA conformational analysis of the (3′S,5′R)‐2′‐deoxy‐3′,5′‐ethano‐α‐D‐ribonucleosides (a‐D‐bicyclodeoxynucleosides) based on the X‐ray analysis of N4‐benzoyl‐α‐D‐(bicyclodeoxycytidine) 6 and on 1H‐NMR analysis of the α‐D‐bicyclodeoxynucleoside derivatives 1‐7 reveals a rigid sugar structure with the furanose units in the l′‐exo/2′‐endo conformation and the secondary OH groups on the carbocyclic ring in the pseudoequatorial orientation. Oligonucleotides consisting of α‐D‐bicyclothymidine and α‐D‐bicyclodeoxyadenosine were successfully synthesized from the corresponding nucleosides by phosphoramidite methodology on a DNA synthesizer. An evaluation of their pairing properties with complementary natural RNA and DNA by means of UV/melting curves and CD spectroscopy show the following characteristics: i) α‐bcd(A10) and α‐bcd(T10) (α = short form of α‐D)efficiently form complexes with complementary natural DNA and RNA. The stability of these hybrids is comparable or slightly lower as those with natural β‐d(A10) or β‐d(T10)( β = short form ofβ‐D). ii) The strand orientation in α‐bicyclo‐DNA/β‐DNA duplexes is parallel as was deduced from UV/melting curves of decamers with nonsymmetric base sequences. iii) CD Spectroscopy shows significant structural differences between α‐bicyclo‐DNA/β‐DNA duplexes compared to α‐DNA/β‐DNA duplexes. Furthermore, α‐bicyclo‐DNA is ca. 100‐fold more resistant to the enzyme snake‐venom phosphodiesterase with respect to β‐DNA and about equally resistant as α‐DNA.
Mechanism of Transfer of a Basic Drug across the Water/1,2‐Dichloroethane Interface: The case of quinidine
Authors: Reymond Frédéric , Girault Hubert H. , Steyaert Guillaume , Carrupt Pierre‐Alain , Testa Bernard 
Published: December 2004

AbstractThe electrochemical transfer of quinidine across the H2O/1,2‐dichloroethane interface was investigated by cyclic voltammetry, so as to determine its lipophilicity. The formal transfer potential was measured as a function of the pH of the aqueous phase. Both singly and doubly protonated quinidine cations can transfer across the interface, and their formal Gibbs free energies of transfer were observed to be 7.7 and 31.2 kJ mol−1, respectively. Between pH 0 and 3, only the doubly charged quinidine was present in the aqueous phase and was observed to transfer. Between pH 3 and 6, the transfer of both cations occurred. The proportion of doubly charged quinidine decreased progressively in this pH range and disappeared completely above pH 6. The overall process was analyzed using a thermodynamic model. The relationship between the various forms of quinidine in both phases and pH was established and found to be in good agreement with the experimental results. With this model, the acid‐base equilibrium constants in the organic phase could be calculated as pKa1o = 9.66 ± 0.21 and pKa2o = 14.20 ± 0.16 (the subscripts a1o and a2o refer to the first and second dissociation constants). This study illustrates how the partition of ionic species can be taken into account in the determination of lipophilicity and in the description of the passive transfer of organic drugs.
Synthesis and Tritium Labelling of 6β‐Amino‐4,5α‐epoxymorphinans and their 14‐hydroxy derivatives as potential affinity labelling probes with μ opioid agonist activity
Authors: Ötvös Ferenc , Tóth Géza , Lovas Sándor , Simon Csaba , Hosztafi Sándor 
Published: December 2004

AbstractThe synthesis of 6β‐(methylfumaramido) and 6β‐chloroacetamido derivatives 1b and 1c of 6β‐amino‐7,8‐ didehydromorphinan and the corresponding 14‐hydroxy derivatives 1e and 1f are described. The 7,8‐dihydro derivatives of these compounds were synthesized in inactive (2b,c,e,f) as well as in tritiated form (3b,c,e,f).
Synthesis of 6‐Substituted 1‐Deazapurine 2′‐Deoxyribonucleosides
Authors: Wenzel Thomas , Seela Frank 
Published: December 2004

AbstractThe synthesis of 6‐substituted 1‐deazapurine 2′‐deoxyribonucleosides is described. Glycosylation of the 1‐deazapurine (imidazo[4,5‐b]pyridine) anions with the α‐D‐halogenose 5 gives stereoselectively N7‐ and N9‐ regioisomers. 1H‐NMR NOE and 13C‐NMR spectroscopy are used for unambiguous assignment of isomers, and 15N‐NMR chemical shifts are correlated with σpara Hammett constants and point charges.