bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic studies directed toward the pseurotins. Part II. Synthesis of related highly functionalized furan‐3(2H)‐ones
Authors: Dolder Xie Shao Matthys , Tamm Christoph 
Published: December 2004

AbstractThe synthesis of 2,2‐bis(hydroxymethyl)‐4‐methyl‐5‐phenylfuran‐3(2H)‐one (9), 5‐[(1S,2S,Z)‐1,2‐(ethylidenedioxy)hex‐3‐enyl]‐2,2‐bis(hydroxymethyl)‐4‐methylfuran‐3(2H)‐one (24), and 5‐[(1S,2S,Z)‐1,2‐(ethylidenedioxy)hex‐3‐enyl]‐2‐(hydroxymethyl)‐4‐methylfuran‐3(2H)‐one (28), which represent more advanced, suitably functionalized intermediates for the synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, is described.
Optical Absorption Spectra for the Solvated Electron Observed in the Pulse Radiolysis of cis‐ and trans‐ Isomers of 3‐ and 4‐Methylcyclohexanols
Authors: Fujisaki Noboru , Comte Pascal , Infelta Pierre P. , Gäumann Tino 
Published: December 2004

AbstractThe absorption band maximum of solvated electrons, λmax(e−s), in 3‐ or 4‐methylcyclohexanols is observed at longer wavelengths (818–837 nm), if the OH group is axial, and at shorter wavelengths (721–723 nm), if it is equatorial. It is surmised that the size of cavity for the solvated electron is larger in the former case and smaller in the latter.
How good are quartic functions to describe double‐minimum energy profiles? Nitrogen inversion as example
Authors: Ha Tae‐Kyu , Dunitz Jack D. 
Published: December 2004

AbstractEnergy profiles for nitrogen inversion in ammonia (1), aziridine (2), 1 H‐azirine (3), trans‐2,3‐difluoro‐aziridine (4), cis‐2,3‐difluoroaziridine (5), 2,3‐difluoro‐1H‐azirine (6), methanimine (7), and 2,2‐difluoro‐methammine (8) have been calculated at the 6–31 G** and 4‐21G* levels. If the reaction coordinate is chosen as the angle τ between the NH bond and the CNC plane (or the NC line for the imines 7 and 8), the energy is reproduced quite well by a quartic function V(τ) = aτ4 – bτ2 in all cases. Moreover, for this series of molecules the ratio a/b is approximately constant, which means that the inversion barrier is directly proportional to the quadratic force constant of the equilibrium structure along the reaction coordinate. The use of this and other simple relationships for automerization reactions is discussed. Some of the molecules studied show features that can be nicely interpreted in terms of stereoelectronic factors.
Synthese von enantiomerenreinen ‘Grasshopper’‐Ketonen und verwandten Verbindungen
Authors: Baumeler Andreas , Brade Walter , Haag Andreas , Eugster Conrad Hans 
Published: December 2004

Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related CompoundsStarting from our previously described synthon 1, the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4‐(2′,4′‐dihydroxy‐2′,6′,6′‐trimethylcyclohexylidene)but‐3‐en‐2‐ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.
Enantiomeric 3,7‐Dimethylocta‐1,7‐dienes as Useful Chiral Building Blocks. A New Access to Both Optical Antipodes of Natural (E)‐3,7‐Dimethyloct‐2‐ene‐1,8‐diol and (E)‐3,7‐Dimethyloct‐2‐ene‐1,8‐dicarboxylic Acid
Authors: Giersch Wolfgang , Schulte‐Elte Karl H. 
Published: December 2004

AbstractOzonolysis of the easily available monoterpenoids (−)‐1 and (+)‐1 leads in high yield to the ketoaldehydes (−)‐4 and (+)‐4, which serve as convenient intermediates for efficient new routes to both optical antipodes of the naturally occurring octenediol (E)‐2 (Monarch butterfly secretion product) and octene‐dicarboxylic acid (E)‐3 (Callosobruchus chinensis sex pheromone). All steps proceed with almost complete retention of configuration, ensuring the synthesis of the target compounds with high optical purity.
Ein neuer synthetischer Zugang zu Ubichinonen
Authors: Rüttimann August , Lorenz Peter 
Published: December 2004

A New Synthetic Route to UbiquinonesUbiquinones 11 have been prepared employing a new strategy: as key step, the Diels‐Alder reaction of 1,1,2‐trichloroethene 3 with 2,5‐bis[(trimethylsilyl)oxy]‐3‐methylfuran (2) has been used for the construction of the quinone part. After methanolysis of the [4 + 2] adducts 4a/4b, further reaction with cyclopentadiene and substitution of the Cl‐atoms by MeO groups, the intermediate 7 is obtained. Diketone 7 can easily be alkylated with the desired polyprenyl side chain 9 (X = Br) using a strong base to yield, after a retro‐Diels‐Alder reaction, the corresponding ubiquinones 11 in high yields.
Synthese von 2,4‐Diamino‐thieno[2,3‐d]pyrimidin‐Derivaten
Authors: Link Helmut 
Published: December 2004

Synthesis of 2,4‐Diamino‐thieno[2,3‐d]pyrimidinesCondensation of 2‐aminothiophene‐3‐carbonitrile (4) with guanidine or sequential addition of CS2 and NH3 to 4 provides 2,4‐diaminothieno[2,3‐d]pyrimidine (7). This compound yields, after sequential addition of sec‐BuLi and either [3‐(trifluoromethyl)benzene]sulfenyl chloride (8) or the corresponding disulfide 9, followed by acidic work up, 2,4‐diamino‐6‐{[3‐(trifluoromethyl)phenyl]thio}thieno[2,3‐d]pyrimidine (10). In another approach, 2‐amino‐5‐{[3‐(trifluoromethyl)phenyl]thio}thiophene‐3‐carbonitrile (11) obtained from 4 and 8 is transformed to 10 by condensation with guanidine. Corresponding to the second route, 2,4‐diamino‐6‐[(naphth‐2‐yl)thio]thieno‐[2,3‐d]pyrimidine (16) is synthesized. Oxidation of 10 with m‐chloroperbenzoic acid gives 2,4‐diamino‐6‐{[3‐(tri‐fluoromethyl)phenyl]sulfinyl}thieno[2,3‐d]pyrimidine (13).
Thermal 1,6‐Electrocyclization Reactions of Acceptor‐Substituted 2,3‐Divinyl‐1H‐indoles Yielding Functionalized Carbazoles
Authors: Pindur Ulf , Adam Reinhard 
Published: December 2004

AbstractThree new synthetic procedures for and thermal 1,6‐electrocyclizations of acceptor‐substituted 2,3‐divinyl‐1H‐indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)‐catalyzed coupling and Wittig procedures.
Synthese von einigen 2H‐Pyran‐2‐on‐Derivaten
Authors: Kvita Vratislav , Sauter Hanspeter 
Published: December 2004

The Synthesis of Some 2H‐Pyran‐2‐one DerivativesDerivatives of 6‐unsubstituted 2H‐pyran‐2‐one have been synthesized by several different methods. The 4‐chloro‐2H‐pyran‐2‐one (9) is the most important, since it serves as starting material for the synthesis of different 4‐substituted 2H‐pyran‐2‐ones (Scheme 2). Also described are simple transformations of cumalic‐acid derivatives producing 5‐(2,2‐dichlorovinyl)‐2H‐pyran‐2‐one (23), 2‐oxo‐2H‐pyran‐2‐carbonitrile (26), and 4,5‐bis(trifluoromethyl)‐2H‐pyran‐2‐one (32) (Scheme 3 and 4).
Tetrahydrolipstatin: Thermal and Hydrolytic Degradation
Authors: Stalder Henri , Schneider Pierre R. , Oesterhelt Gottfried 
Published: December 2004

AbstractThe thermal and hydrolytic degradation of tetrahydrolipstatin (THL, 1) was investigated. All main degradation products were isolated, characterized, and synthesized. Labile intermediates unavailable to isolation were detected and identified by GC/MS analysis of their silylated derivatives, and whenever possible, compared with independently prepared reference compounds. The identified degradation products represent at least 97% of the total degradation mixture. Two main reaction pathways arc proposed. Pharmacological data are reported for the degradation mixture and the main degradation products.
Neoflor und 6‐Epineoflor aus Blüten von Trollius europaeus; Hochfeld‐1H‐NMR‐Spektren von Neoxanthin und (9′Z)‐Neoxanthin
Authors: Märki‐Fischer Edith , Eugster Conrad Hans 
Published: December 2004

Neoflor and 6‐Epineoflor from Flowers of Trollius europaeus; Highfield 1H‐NMR Spectra of (all‐E)‐Neoxanthin and (9′Z)‐NeoxanthinRe‐isolation of the very polar carotenoids from flowers of the title plant furnished two epimeric pentahydroxy compounds. Based on spectroscopical and chiroptical arguments and by chemical correlation with neoxanthin, their structures were established as 11 (proposed name neoflor) and 12 (6‐epineoflor), Decoupling experiments and COSY‐2D‐1H‐NMR spectra allowed a complete assignement of the vinyl protons of the two isomers, and furthermore, for the first time, also of those of (all‐E)‐neoxanthin and (9′Z)‐neoxanthin.
Carbonyliron Complexes of Allenic Acids, Esters, Amides, and Imides
Authors: Trifonov Latchezar S. , Orahovats Alexander S. , Heimgartner Heinz 
Published: December 2004

AbstractOn irradiation in the presence of Fe(CO)5, the allenic amides and imides showed a similar course of complexation to that of esters and lactones, respectively, e.g. the amides of type 10 led to diiron complexes of type 11 (Scheme 3), whereas the imide 12 yielded a mixture of a dinuclear and two mononuclear complexes (13–15, Scheme 4). The racemic ester 6 also gave mononuclear (7a, 7b, and 9) and dinuclear complexes (8a and 8b; Scheme 2). In case of the allenic acid 4, only complexation of type 5 was observed (Scheme 1).
Synthesis and Biological Evaluation of 14‐Alkoxymorphinans. Part 8. 14‐methoxymetopon, an extremely potent opioid agonist
Authors: Schmidhammer Helmut , Schratz Andrea , Mitterdorfer Jörg 
Published: December 2004

Abstract14‐Methoxymetopon (= 5,14‐O‐dimethyloxymorphone; 4)and 14‐ethoxymetopon (5) were synthesized from 14‐hydroxy‐5‐methylcodeinone (6). In the AcOH‐writhing test in mice, compound 4 was found to be ca. 20000 times more potent than morphine.
2H/1H Isotope Shifts for 6Li‐NMR: First Experimental Detection and Applications to Structural Problems in the Field of Organolithium Compounds
Authors: Eppers Oswald , Günther Harald 
Published: December 2004

AbstractDeuterium‐induced isotope effects on 6Li chemical shifts, transmitted over two bonds, 2Δ(6Li)(2H/1H), have been measured for the first time for methyllithium and the system methyllithium/lithium iodide. The observed shifts are to low field and range from 15 to 20 ppb per CD3 group. The multiplicity and intensity distribution of the 6Li signals resulting for mixtures of CH3‐ and CD3‐containing samples in the limit of slow inter‐ as well as intra‐aggregate exchange yield information about the size of the various clusters present in diethylether solution. It is expected that these isotope shifts can facilitate structural investigations of organolithium compounds. In some cases, the results of such measurements are expected to be less ambiguous then the conclusions based on multiplets that arise from scalar 13C,6Li spin‐spin coupling.
The Gas‐Phase Ion/Molecule Reactions of C3H5X (X = C1, Br, I)
Authors: Gäumann Tino , Zhu Zhiqing , Kida Marcia C. , Riveros José M. 
Published: December 2004

AbstractThe ion/molecule reactions of the molecular ion, the C3H ion, and the C3H ion obtained from 3‐chloropropene. 1‐bromopropene, 2‐bromopropene, 3‐bromopropene, bromocyclopropane. and 3‐iodopropene have been studied with their neutral precursor in a Fourier‐transform mass spectrometer (FT/ICR). The molecular ions react to yield primarily C6H except for the ion derived from 1‐bromopropene that is unreactive. The kinetics of the 3‐bromopropene molecular ion reveals that 18% of these ions must possess a different structure which is unreactive. The fact that C3H ions obtained from 2‐bromopropene are the only ones to undergo proton transfer is taken as evidence that only this parent compound gives rise to 2‐propenyl cations by low‐energy electron impact. The C3H ions generated in these systems are shown to be roughly an equal mixture of propargylium ions that react to yield C6H and unreactive cyclopropenium ions.
A New General Synthesis of 2,2‐Dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones and Their Application for the in situ Preparation of Electron‐Rich Dienes in Carbonyl‐Alkyne Exchange Reactions with Acetylenes
Authors: Obrecht Daniel 
Published: December 2004

AbstractThe substituted 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones of type II and III have been prepared by acid‐catalyzed cyclization of the corresponding substituted acetylenic ketones I in good to excellent yields (Scheme 1). These 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones II and III have been used for the in situ preparation of highly reactive dienes of type IV–VI (Scheme 2) in carbonyl‐alkyne exchange reactions with electron‐poor alkynes VII to yield the highly substituted aromatic compounds VIII and IX. These reactions proceed in good yields and with excellent degree of regioselectivity. Aryl‐substituted 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones III (R1 = Ar) subsequently yield highly substituted biaryls. Reaction mechanisms are presented for the formation of the 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones as well as for the carbonyl‐alkyne exchange reactions with electron‐poor acetylenes.
Structural and Luminescence Study of the 3:2 Complex between Europium Nitrate and the B Isomer of Dicyclohexyl‐18‐crown‐6
Authors: Moret Emmanuel , Nicolò Francesco , Plancherel Dominique , Froidevaux Pascal , Bünzli Jean‐Claude G. , Chapuis Gervais 
Published: December 2004

AbstractThe crystal and molecular structure of bis[dinitrato‐(2,4,8,15,18,21‐hexaoxatricyclo[20.4.0.09,14]hexacosane)europium(III)]pentakis(nitrato)europiate(III) [Eu(NO3)2LB]2([Eu(NO3)5]), has been determined at 170 K from single‐crystal X‐ray diffraction. The complex crystallizes in the monoclinic space group P21/n (ITC No. 14): a = 16.338(3) Å, b = 15.704(3) Å, c = 24.474(4) Å, β = 97.73(1)°, Z = 4. The structure was refined to a final R value of 0.058 (Rw = 0.060). The asymmetric unit contains three independent ions lying on general positions: [Eu(NO3)5]2− and two distinct [Eu(NO3)2LB]+ cations with the macrocyclic ligand in the cis‐anti‐cis conformation (B‐isomer). The EuIIIions are 10‐coordinate with the following mean bond lengths: Eu–O(nitrate) = 2.48(2) Å in the anion and 2.45(2) Å in the two cations, Eu–O(ether) = 2.56(8) and 2.55(5) Å. Small but significant differences are observed between the two complex cations, especially with respect to the positions of the cyclohexyl substituent. A conformational analysis performed on the six O‐atoms of the complex cations confirms the predictions of a simple model. The metal ion sites of the complex have been probed by high‐resolution excitation and emission spectra at 296 and 77 K. The 5D0←7F0 excitation spectrum displays two main bands along with several other minor components. A detailed analysis of the corresponding and selectively excited emission spectra leads to the observation of three types of spectra corresponding to the three crystallographically different EuIII ions. Moreover, three minor sites are identified, one anionic and two cationic, with a population equal to ca. 10% of the population of the main sites. We interpret this finding as reflecting the presence of molecules with slightly different conformations.
Michael Reactions of α‐Unsubstituted Trisubstituted 1H‐Pyrroles
Authors: Lüönd Rainer , Neier Reinhard 
Published: December 2004

AbstractTo obtain stable derivatives of α‐unsubstituted pyrroles, the reaction of the test pyrrole 9 with a series of chalcones 14a–h were studied. Michael adducts 16b–h could be isolated. In order to synthesize coloured derivatives, the reaction of different pyrroles 9, 21, 23, and 25 with diphenylpropynone 19 was investigated. In these cases, too, Michael‐addition products were formed. The intense absorption band around 400 nm makes the identification of these derivatives easy.
2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains
Authors: Terradas Fernand , Wyler Hugo 
Published: December 2004

AbstractAn enzyme is extracted from the red peel of Amanita muscaria which cleaves the C(2)–C(3) and the C(4)–C(5) bond of the aromatic ring of L‐dopa (1) to form a mixture of 4,5‐secodopa (= salt of 6‐amino‐2‐hydroxy‐4‐(2′‐oxoethylidene)hept‐2‐enedioic acid; 2) and 2,3‐secodopa ( = salt of 7‐amino‐5‐formyl‐2‐hydroxyocta‐2,4‐dienedioic acid; 3), two hitherto hypothetical biosynthetic intermediates (see Scheme). Though isolation of these products has not been possible, structural evidence is inferred from reaction products, kinetics, and spectroscopical characteristics in comparison with known compounds. Secodopas 2 and 3 are characterized in dilute solution by HPLC and UV/VIS spectroscopy (anions; λmax 424 and 414 nm, resp., ϵ420 = 25500; on acidification, shift to 380 and 372 nm, resp.). They cyclize without enzyme catalysis, optimally at pH 4.5–5; 3 produces muscaflavin (5) and 2 betalamic acid (4). The products arc identified by direct comparison with authentic samples in HPLC, by 1H‐NMR of 5, and by condensation of 4 with L‐proline to form the well known betalain indicaxanthin (7). The enzymatic conversion of L‐dopa (1) via 2 to betalamic acid (4; (S)) and its condensation with L‐proline leads to pure natural indicaxanthin (7; (2S,115)); correspondingly, the enzymatic conversion of D‐dopa to (R)‐betalamic acid and its condensation with L‐proline produces isoindicaxanthin ((2S,11R)) which is unknown in nature. Particularly relevant is the fact that the same enzyme cleaves pyrocatechol to produce a solution of the enolate form of the known 2‐hydroxy‐6‐oxohexa‐2,4‐dienoate (secopyrocatechol; 9; see Fig. 5). Dissociation constants of the corresponding enolic functions in the cleavage products are determined by spectrometric titration and compared to those of known systems.
C‐Alkylation of Peptides through Polylithiated and LiCl‐Solvated Derivatives Containing Sarcosine Li‐Enolate Units
Authors: Seebach Dieter , Bossler Hans , Gründler Hansjörg , Shoda Shin‐Ichiro , Wenger Roland 
Published: December 2004

AbstractThe tripeptide and hexapeptide derivatives Boc‐Gly‐Sar‐MeLeu‐OH (5b), Boc‐Ala‐Sar‐Sar‐OH (6b), Boc‐Ala‐Sar‐MeLeu‐OH (7b), and Boc‐Abu‐Sar‐MeLeu‐Val‐MeLeu‐Ala‐OH (12b) can be poly‐deprotonated (tri‐ and pentalithio derivatives K and P, respectively), and thus C‐alkylated on sarcosine (Sar) moieties with MeI and allyl or PhCH2Br. The polylithiated species are solubilized in THF, and their reactivity modified by excess base (lithium diisopropylamide (LDA)), by added LiCl, and/or the cosolvent N,N′‐dimethylpropyleneurea (DMPU). Optimization of the reaction conditions for methylation in the cases of 7b (Table 3) and 12b (Scheme 8) gave products in which the Sar residue of the educt has been transformed into a Me‐D‐Ala unit in yields of 80 (9c/8c) and 67% (14c/13c), respectively, and with a diastereoselectivity of ca. 4:1. Less selective methylations and benzylations were observed with the tripeptides 5b and 6b containing only one stereogenic center; also, excess base and alkyl halide may lead to double alkylations in those latter two cases (Tables 1 and 2). No epimerization of stereogenic centers was detected under the strong‐base conditions. The analysis of the products was accomplished by a combination of NMR and FAB‐MS spectroscopy, as well as by hydrolysis to the parent amino acids, subsequent formation of derivatives with isopropyl isocyanate, and GC analysis on the chiral column Chirasil‐Val®.
Quantitative Structure‐Affinity Relationships of Dopamine D2 Receptor Antagonists: A Comparison between Orthopramides and 6‐Methoxysalicylamides
Authors: de Paulis Tomas , El Tayar Nabil , Carrupt Pierre‐Alain , Testa Bernard , van de Waterbeemd Han 
Published: December 2004

AbstractA large series of orthopramides (= 2‐methoxybenzamides), 6‐methoxysalicylamides, and 2,6‐dimethoxy‐benzamides were examined for their affinity to the dopamine D2 receptor. The binding data were correlated with physicochemical parameters and 13C‐NMR chemical shifts using the cross‐validated partial least‐squares method and multiple linear regression analysis. The results quantitate the influence of electronic factors and lipophilicity to D2 receptor binding. They also show that the N‐[(1‐ethylpyrroIidin‐2‐yl)methyl] and N‐(1‐benzylpiperidin‐4‐yl) side‐chains affect the mode of binding of these compounds.
Synthesis of Aristotelia‐type alkaloids. Part VII. Syntheses of (±)‐sorelline, (±)‐serratenone, and (±)‐aristotelin‐19‐one
Authors: Burkard Stefan , Borschberg Hans‐Jürg 
Published: December 2004

AbstractThe imine obtained by condensing indole‐protected 2‐(indol‐3‐yl)acetaldehyde (5) with the terpinylamine derivative (±)‐4 was cyclized in 51% yield to the 19‐substituted hobartine derivative (±)‐20 upon exposure to anhydrous HCOOH. This pivotal intermediate was further elaborated into the indole alkaloids (±)‐serratenone ((±)‐22) and (±)‐sorelline ((±)‐29). In the course of these investigations, a novel rearrangement was uncovered; a Lewis acid‐catalyzed 1,3‐migration of an arylsulfonyl group from the indole N‐atom into the benzene ring. The discovery that synthetic (±)‐aristotelin‐19‐one ((±)‐34) has decidedly different spectroscopic properties than aristolasicone, a metabolite for which the structure has been recently proposed, led to a revision of the structure of the latter.
Axially Dissymmetric Diphosphines in the Biphenyl Series: Synthesis of (6,6′‐Dimethoxybiphenyl‐2,2′‐diyl)bis(diphenylphosphine)(‘MeO‐BIPHEP’) and Analogues via an ortho‐Lithiation/Iodination Ullmann‐Reaction Approach
Authors: Schmid Rudolf , Foricher Joseph , Cereghetti Marco , Schönholzer Peter 
Published: December 2004

AbstractThe new axially dissymmetric diphosphines (R)‐ and (S)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis(diphenyl phosphine) ((R)‐ and (S)‐5a; ‘MeO‐BIPHEP’) and the analogues (R)‐ and (S)‐5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho‐lithiation/iodination reaction of the (m‐methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10. The bis(phosphine oxides) 10 subsequently are resolved with (−)‐(2R,3R)‐ and (+)‐(2S,3S)‐O‐2,3‐dibenzoyltartaric acid and reduced to diphosphines 5. The Ullmann reaction constitutes a new and efficient route to 2,2′‐bis(phosphinoyl)‐substituted biphenyl systems. Absolute configurations were established for (R)‐5a by X‐ray analysis of the derived Pd complex (R,R)‐17a, and for 5b and 5c by means of 1H‐NMR comparisons of the derived Pd complexes 16 or 17, respectively, and by means of CD comparisons. The MeO‐BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′‐dimethylbiphenyl‐2,2′‐diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.
A Direct Route to 3‐(D‐Ribofuranosyl)pyridine Nucleosides
Authors: Piccirilli Joseph A. , Krauch Tilman , MacPherson Lawrence J. , Benner Steven A. 
Published: December 2004

AbstractA route for synthesizing C‐nucleosides with 2,6‐substituted pyridines as heterocyclic aglycones is described. Condensation of appropriately substituted lithiated pyridines with ribono‐1,4‐lactone derivatives yields hemiacetal 4a–g (Table 1), which can be reduced by Et3SiH and BF3·Et2O to the corresponding C‐nucleoside (see Scheme 1 for 4d → β‐D‐5). Conditions are presented that optimize the amount of the 2,6‐dichloropyridine‐derived β‐D‐anomer β‐D‐5 formed (Table 3). Aminolysis of β‐D‐5 yields the diaminonucleoside 14 (Scheme 3).
Über die Reaktion einiger 2H‐Pyran‐2‐on‐Derivate mit primären Aminen
Authors: Kvita Vratislav , Sauter Hanspeter , Rihs Grety 
Published: December 2004

On the Reaction of Some 2H‐Pyran‐2‐one Derivatives with Primary AminesThe versatile reactivity of 6‐unsubstituted 2H‐pyran‐2‐ones towards aliphatic and aromatic amines has been studied. It was found that the result of the reaction depends not only on the substitution of 2H‐pyran‐2‐ones and on the structure of amines, but also on the stoichiometric ratio of reacting compounds.