bluuebunny/crossref_metadata_2025_split huggingface dataset:
Übergangsmetall‐katalysierte Additionsreaktionen von 3‐Phenyl‐2H‐azirinen und Acetylencarbonsäureestern
Authors: Inada Akira , Hefmgartner Heinz 
Published: December 2004

Transition Metal Catalyzed Addition Reactions of 3‐Phenyl‐2H‐azirines and Alkyl Acetylene CarboxylatesIn the presence of molybdenum hexacarbonyl, the 3‐phenyl‐2H‐azirines 1 and 7 react with alkyl acetylene carboxylates 2 via the cleavage of the C, N‐double bond to give 2H‐pyrroles 5 or pyrrole 9 (Table), whose structures were deduced from the spectra data, in particular 13C‐NMR. data. The 2H‐pyrrole 5a was also obtained by treatment of a mixture of 1 and 2a with tungsten hexachloride. A tentative mechanism for the formation of the 2H‐pyrroles is formulated.
Kreuzkonjugierte Cyanine und Merocyanine aus Salzen 1‐substituierter 2,3‐Dimethylchinoxaline. 2. Mitteilung Über die oxydative Umwandlung der Farbbasen
Authors: Schelz Dieter 
Published: December 2004

Crossconjugated Cyanines and Meroeyanines, Obtained from Salts of 1‐Substituted 2,3‐Dimethylquinoxslines. 2nd Communication. On the Syntheses of Dehydro‐FormsProducts 3 of the readily oxidized 1 and 2 are found to be sensitive to solvolysis, especially when X and R are electron‐withdrawing substituents. In some cases, the salts 3 could be identified as the oxidation products of the salts 9. The oxidation of 9p (X = 5,6‐benzo, R=CH3) by an alkaline solution of K3Fe(CN)6 leading to the quinoxalinone 10p is compared with the voltammetric oxidation of 81 (X = H, R=4‐C1C6H4) and related to Viehe's [15] c, d‐stabilized radicals. 1H‐NMR.‐spectra of the salts 3 are discussed with regard to the (E/Z)‐isomers,
Iridoide aus Verbascum nigrum L. 182. Mitteilung über organische Naturstoffe
Authors: Seifert Karlheinz , Schöpp Emanuel , Hesse Manfred , Johne Siegfried 
Published: December 2004

Iridoids from Verbascum nigrum L.Two new iridoid glycosides, nigroside 1 (  6‐O‐(3‐O‐einnamoyl‐α‐L‐rhamno‐pyranosyl)aucubin (2), and nigroside 2 (6‐O‐(2‐O‐cinnamoyl‐α‐L‐rhamnopy‐ranosyl)aucubin (3), and the known compound laterioside (1) have been isolated from extracts of the stems of Verbascum nigrum L., and their structures established primarily on the basis of NMR. spectroscopy. Harpagoside (4), a known iridoid glucoside, was also isolated from the roots of this plant.
Synthesis of 1,2‐cis‐Configurated Glycosylphosphonates
Authors: Meuwly Roger , Vasella Andrea 
Published: December 2004

AbstractA synthesis of 1,2‐cis‐configurated, non‐isosteric phosphonate analogues of aldose‐1‐phosphates is described. Treatment of 1‐O‐acyl‐glycoses 1, 7, 13, and 19 with trialkyl phosphite in the presence of trimethylsilyl trifluoromethanesulfonate gave the 1,2‐cis‐configurated glycosylphosphonates 2, 4, 8, 10, 14, 16, 20, and 22 as the major anomers and the 1,2‐trans‐configurated glycosylphosphonates 3, 5, 9, 11, 15, 17, 21, and 23 as the minor anomers. The 1,2‐cis‐configurated phosphonates 4, 10, 16, and 22 were deprotected to give the (β‐D‐glucopyranosyl)phosphonate 6, the (β‐D‐mannopyranosyl)phosphonate 12, the (β‐D‐ribofuranosyl)phosphonate 18, and the (β‐D‐arabinofuranosyl)phosphonate 24, respectively, in high yields. The preferred formation of 1,2‐cis‐configurated phosphonates is explained by postulating an equilibrium between the anomeric phosphonium‐salt intermediates (such as 25 and 26) and a stabilization of the cis‐configurated salts through formation of a pentacoordinated species (such as 28).
Optisch aktive Lycopin‐epoxide und Lycopin‐glycole: Synthesen und chiroptische Eigenschaften
Authors: Meier Heidi , Uebelhart Peter , Eugster Conrad Hans 
Published: December 2004

Optically Active Lycopene Epoxides and Lycopene Glycols: Synthesis and Chiroptical PropertiesWe present extensive spectral and chiroptical data on the pure and crystalline lycopene diepoxides 1–3 and glycols 4–9. A first synthetic approach to 1–9 with (+)‐malic acid as starting material afforded 30 as a complex mixture of isomers (Scheme 1). Pure stereoisomers 1–9 were obtained using the enantiomerically pure epoxygeraniol 31 as starting material (Scheme 2). Differentiation of the (5Z)‐from the (all‐E)‐isomers by 1H‐NMR and UV/VIS alone is very difficult.
Ein neues Esteriridoidglycosid aus Sambucus ebulus L. (Caprifoliaceae). 1. Mitteilung über die inhaltsstoffe der Zwergholunderwurzel
Authors: Gross Gian‐Andrea , Sticher Otto , Anklin Clemens 
Published: December 2004

A Novel Ester Iridoid Glucoside from Sambucus ebulus L. (Caprifoliaceae)A novel ester iridoid glucoside, ebuloside (1,), which shows structure elements of the rare 7‐Dehydrologanin derivatives combined with those of the Valerianaceae iridoids, was isolated from the roots of Sambucus ebulus L. Its structure was determined by MS, NMR, and CD spectroscopy as 7‐oxo‐8‐deoxyvalerosidatum.
Photosolvolysis of 2‐Allylated Anilines to 2‐Indanols
Authors: Scholl Bernhard , Jolidon Synèse , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that 2‐allylated anilines (cf. Schemes 2–4, 7, and 8) on irradiation in protic solvents such as H2O. MeOH, and EtOH in the presence of H2SO4 undergo a novel photosolvolysis reaction to yield specifically trans‐2‐hydroxy‐ and trans‐2‐alkoxy‐1‐methylindanes. Intermediates are presumably tricyclo[4.3.0.01,8]nona‐2,4‐dienes formed in an intramolecular [2s + 2s] cycloaddition reaction (cf. Scheme 7). On the other hand, N,N,N‐trimethyl‐2‐(1′‐methylallyl)anilinium salts 18 (Scheme 6) and 2‐(3′‐butenyl)‐N,N‐dimethylaniline (17) lose on irradiation in MeOH or H2SO4/MeOH the ammonium group reductively to yield (1‐methylallyl)benzene (19) and 1‐methylindane (20), respectively.
Crystal Structure of Tricarbonyl‐[2,3‐η:O‐σ‐(7,7‐dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene)]iron
Authors: Barbay Yvan , Ioset Jacques , Roulet Raymond , Chapuis Gervais 
Published: December 2004

AbstractThe product of the reaction of [Fe(benzalacetone)(CO)3] with 7,7‐dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1] hept‐2‐ene is tricarbonyl‐[2,3‐η:O‐σ‐(7,7‐dimethoxy‐5,6‐dimethylidenebicyclo [2.2.1]hept‐2‐ene)]iron. Crystals are monoclinic, space group P21/c with a = 6.612(2), b = 11.610(4), c = 18.604(6) Å, and β = 95.91(2)°. The coordination at the metal atom is trigonal bipyramidal. The equatorial sites are occupied by 2 CO's and by the midpoint of the endocyclic double bond of the organic ligand. The axial sites are occupied by one CO group and the O‐atom of one MeO group of the C(OMe)2 bridge. It is an uncommon example of a d8 metal carbonyl complex bearing an O‐bonded ligand.
Synthesis and Crystal Structure of meso‐Δ,Λ‐μ‐Peroxo‐μ‐hydroxobis[bis(ethylenediamine)rhodium(III)]trifluoromethane Sulfonate
Authors: Springborg Johan , Zehnder Margareta 
Published: December 2004

AbstractThe reaction of the meso‐diol, Δ,Λ‐[(en)2Rh(OH)2Rh(en)2]4+, with aqueous H2O2 and 1 equiv. of NaOH at 90° forms the μ‐peroxo‐μ‐hydroxo‐bridged species Δ,Λ‐[(en)2Rh(O2,OH)Rh(en)2]3+ in a yield of ca. 50%. The compound was crystallized as perchlorate and trifluoromethanesulfonate salts. The structure of the latter salt was determined by single‐crystal X‐ray diffraction. The crystals are triclinic with space group P1 and lattice constants a = 11.895(5), b = 12.491(4), c = 13.053(5) Å, α = 103.98(3), β = 92.59(3), γ = 119.52(6)°. The distances of the metal centres to the bridging peroxo ligand are 1.999(8) and 1.983(6) Å. The OO distance in the peroxo group is 1.521(14) Å, and the dihedral angle of the RhOORh unit deviates 65° from planarity. The peroxo complex reacts reversibly with acid, and spectrophotometric studies suggest that the reaction involves protonation of the peroxo bridge, with pKa = 2.70(2) at 25° in 1M NaClO4.
New Saponins and a Prosapogenin from Polygala chamaebuxus L
Authors: Hamburger Matthias , Hostettmann Kurt 
Published: December 2004

AbstractTwo glycosides 2 and 3 of the formerly undescribed triterpene 3β,23,27,29‐tetrahydroxyolean‐12‐en‐28‐oic acid (4) have been isolated from the aerial parts of Polygala chamaebuxus L. In addition, a prosapogenin, obtained by basic hydrolysis of a mixture of bidesmosidic saponins, has been identified as tenuifolin (1). The structures have been established by spectroscopic (IR, 1H‐and 13‐C‐NMR, DCI‐ and FAB‐MS) and chemical methods (acid, basic, and enzymatic hydrolysis, acetylation, bromination).
Synthesis of (5R,8S,10R)‐6‐(Allyloxy)‐ and (5R,8S,10R)‐6‐(Propyloxy)ergolines from the 6‐Methyl Precursors
Authors: Nordmann René , Gull Peter 
Published: December 2004

AbstractNovel (5R,8S,10R)‐6‐(allyloxy)‐ and (5R,8S,10R)‐6‐(propyloxy)ergolines have been synthesized by use of a Meisenheimer [2,3]‐sigmatropic rearrangement of a (5R,8S,10R)‐6‐allyl‐ergoline N6‐oxide as key step.
Isolement et identification de deux glucosyl‐lutéolines mono‐C‐substituées et de la diglucosyl‐6,8‐lutéoline di‐C‐substituée dans les tiges feuillées de Passiflora incarnata L
Authors: Congora C. , Proliac A. , Raynaud J. 
Published: December 2004

Isolation and Identification of two Mono‐C‐glucosyl‐luteolins and of the Di‐C‐substituted 6,8‐Diglucosyl‐luteolin from the Leavy Stalks of Passiflora incarnata L.The present work on Passiflora incarnata presents the isolation and the structural identification of C‐glycosylluteolins, i.e. of orientin (1), homoorientin (2) and lucenin 2 (3). The latter compound is new for this plant.
Interactions between Oxygen Lone‐Pair Orbitals and Double‐Bond π‐Orbitals in β,γ‐Unsaturated, Bicyclic Ketones; a PE‐Spectroscopic Investigation
Authors: Carrupt Pierre‐Alain , Gabioud Raphy , Rubello Albino , Vogel Pierre , Honegger Evi , Heiloronner Edgar 
Published: December 2004

AbstractThe HE(Iα) photoelectron (PE) spectra of 2,3,5,6‐tetramethylidene‐2‐bicyclo[2.2.1]heptanone (12), 5,6‐dimethylidene‐2‐bicyclo[2.2.1]heptanone (14), 5,6‐dimethylidene‐2‐bicyclo[2.2.2]octanone (16), and 5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanone (17) have been recorded, Comparison with the PE data of other β,γ‐unsaturated ketones and parent alkenes, and with the result of ab initio STO‐3G calculations, confirm the existence of significant interactions between the oxygen lone‐pair orbital no and the double‐bond π orbital(s). It is argued that the major contributions to the basis energy shifts and to the cross term between the no and π orbitals are due to a ‘through‐bond’ mechanism.
The Radical Anions of 1,2‐diphenylcyclohexene and Structurally Related Compounds. Conformational ESR and ENDOR studies
Authors: Gerson Fabian , Martin Williiam B. 
Published: December 2004

AbstractESR, ENDOR, and TRIPLE resonance studies have been performed on the radical anions of 1,2‐diphenylcyclohex‐1‐ene (4), 1,2‐di(perdeuteriophenyl)cyclohex‐1‐ene ((D10)4) the trans‐configurated 3,4‐diphenyl‐8‐oxabicyclo[4.3.0]non‐3‐ene (5) and its 2,2,5,5‐tetradeuterio derivative (D4)5, and 2,3‐diphenyl‐8,9,10‐trinorborn‐2‐ene (6). The spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} exhibit strong temperature dependence along with a specific broadening of ESR hyperfine lines and proton ENDOR signals. The coupling constant, which bears the main responsibility for these features, is that of the β‐protons in the quasi‐equatorial positions of the cyclohexene ring, and the experimental findings are readily rationlized in terms of relatively modest conformational changes without invoking the inversion of the half‐chair form. The hyperfine data for the β‐protons in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} closely resemble the corresponding low‐temperature values for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document}, However, the ‘unusual’ features observed for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} are absent in the ESR and ENDOR spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document}, because the half‐chair conformation of the cyclohexene ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} is deprived of its flexibility. Although the boat form of this ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} is also rigid, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} are temperature‐dependent, due to an interconversion between two propeller‐like conformations of the phenyl groups. The pertinent barrier is 30 ± 5 kJ·mol−1. An analogous interconversion presumably takes place in \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} as well, but, unlike \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document}, it is not amenable to experimental study.
Diasterio‐ und enantioselektive Reduktion von β‐Ketoestern mit Cyclopentanon‐, Cyclohexanon‐, Piperidon‐ und Tetralon‐Struktur durch nicht fermentierende Bäcker‐Hefe
Authors: Seebach Dieter , Roggo Silvio , Maetzke Thomas , Braunschweiger Hans , Cercus Jacques , Krieger Manfred 
Published: December 2004

Diastereo‐ and Enantioselective Reduction of beta;‐Keto Esters Derived from Cyclopentanone, Cyclohexanone, Piperidone and Tetralone by ‘Non‐fermenting’ Baker's YeastUnder ‘non‐fermenting’ conditions, i.e. in tap water, in the absence of nutrients baker's yeast (25–380 g/g of substrate, aerobic) reduces β‐keto esters such as those mentioned in the title with better selectivity than under the normally employed ‘fermenting’ conditions (sugar and nutrients, CO2 development). With the β‐ keto esters containing the tetralone substructure, large amount of yeast are required (250–380 g/g); the substrate disappears in the biomass, and the desired reduction product can be extracted after reaction times of up to a week at 30°. The configuration of most products(16–24) is established. Generally, the (R)‐β‐keto ester is reduced faster than the (S)‐enantiomer (the two esters are in equilibrium under the reactio conditions), and the hydride transfer takes place preferentially from the diastereotopic Re‐face. The β‐hydroxy esters thus available are useful starting materials for syntheses of enantiomerically pure compounds (EPC).
Nonafulvalen: Synthese durch oxidative Kupplung von Cyclononatetraenid und Valenzisomerisierung
Authors: Escher André , Neuenschwander Markus , Engel Peter 
Published: December 2004

Nonafulvalene: Synthesis by Oxidative Coupling of Cyclononatetraenide and Valence IsomerisationFollowing a general strategy (Scheme 2) for the synthesis of fulvalenes by oxidative coupling of Hückel anions, the synthesis of nonafulvalene (1), has been realised (Scheme 3). The most tricky step is a twofold deprotonation of bi(cyclononatetraenydl) 3 with K(t‐BuO) to give 4; it is only possible after equilibration 3⇄3a; otherwise, deprotonation of one cyclononatetraene unit of 3 followed by oxidative coupling with AgBF4 gives quater(cyclononatetraenyl) 12 as an isomeric mixture. The reaction of 3 with Kgives potassium cct‐cyclononatetraenide 11 (M = K; Scheme 5) and not the dianion 4 as reported in the literature. Nonafulvalene (1)is extremely reactive due to its very easy valence isomerisation to geve an isomeric mixture of tetrahydro‐dibenzopentafulvalenes 13 (Scheme 4). The structure of crystalline isomer (E‐anti)‐13 has been proved by X‐ray analysis.
Solubilization of Peptides in Non‐polar Organic Solvents by the Addition of Inorganic Salts: Facts and Implications
Authors: Seebach Dieter , Thaler Adrian , Beck Albert K. 
Published: December 2004

AbstractThe solubility of open‐chain peptide derivatives (12 examples) in non‐polar, ether‐type organic solvents may be greatly increased by addition of salts (LiCl, LiBr, LiI, LiBF4, LiClO4, NaI, MgBr2 CaBr2, ZnCl2) or of titanates (Ti(OEt)4, Ti(OCHMe2)4). Examples are reported (Tables 2–6) in which this solubilizing effect leads to peptide concentrations more than one‐hundred‐fold those in the absence of salt (cf, BocAlaGlyGlyGlyOH in THF from 2g·1−1 to ≥ 300 g·1−1 with 6 equiv. of LiCl), 1H‐NMR Spectra of one of these solutions are reported (Fig. 1). There are no indications for epimerizations of stereogenic centres on the peptide backbone. Possible applications of these solutions in peptide chemistry are discussed.
Catechol‐O‐methyltransferase‐Inhibiting Pyrocatechol Derivatives: Synthesis and Structure‐Activity Studies
Authors: Borgulya Janos , Bruderer Hans , Bernauer Karl , Zürcher Gerhard , Prada Mosé Da 
Published: December 2004

Abstract3‐Nitro‐ and 3‐cyanopyrocatechols bearing electron‐withdrawing substituents at C(5) have been found to inhibit the enzyme catechol‐O‐methyltransferase. Structure‐activity studies are discussed on the basis of the pharmocological data of 50 compounds (cf, Chapt. 4, Tables 1–7). Some 3‐nitro‐5‐aroylpyrocatechols (Type A2, Table 1) fulfil the requirements for a clinical candidate, being orally active, specific, reversible, and relatively short‐acting. The chemical work involved is illustrated by describing a choice of exemplary syntheses, dealing with compounds 9, 11, 14, 18, 22, 24, 25, 35, 41, and 42 (Chapt. 5, Schemes 1–10).
Photochemical Synthesis of Cyclic 2‐(2,2‐Dimethylpropylidene)‐1,3‐dicarbonyl Compounds
Authors: Hobel Klaus , Margaretha Paul 
Published: December 2004

AbstractPhotolysis (λ = 254 nm) of 4‐(t‐Bu)‐substituted [b]‐fused bi‐ and tricyclic pyrandiones 5 affords title compounds 4 in good yields as well as small amounts of spiroalkanediones 8. The alkyl‐substitution pattern at C(4) of the pyran ring in 5 determines the relative amount of α vs. β‐cleavage products obtained from the primarily formed acyl‐vinyloxy biradical.
The Carbonyl Group as Homoconjugated Electron‐Releasing Substituent. Regioselective electrophilic additions at bicyclo[2.2.1]hept‐5‐en‐2‐one, bicyclo[2.2.2]oct‐5‐en‐2‐one, and derivatives
Authors: Carrupt Pierre‐Alain , Vogel Pierre 
Published: December 2004

AbstractIn CHCl3, CH3CN, or AcOH, benzeneselenenyl chloride (PhSeCl), bromide (PhSeBr), and acetate (PhSeOAc), 2‐nitrobenzenesulfenyl chloride (NO2C6H4SCl), and 2,4‐dinitrobenzenesulfenyl chloride ((NO2)2C6H3SCl) added to bicyclo[2.2.1]hept‐5‐en‐2‐one (5) in an. anti fashion with complete stereo‐ and regioselectivity, giving adducts 20–24 in which the chloride, bromide, or acetoxy substituent (X) occupies the endo position at C(6) and the Se‐ or S‐substituent (E) the exo position at C(5), The addition 5+ (NO2)2C6H3SCl→24 was accompanied by the formation of (1RS, 2RS)‐2‐(2,4‐dinitrophenylthio)cyclopent‐3‐ene‐l‐acetic acid (25). The latter was the major product in AcOH containing LiClO4. The additions of PhSeCl and PhSeBr to bicyclo[2.2.2]oct‐5‐en‐2‐one (6) were less stereoselective (proportion of exo vs. endo mode of electrophilic attack was ca. 3:1) but highly regioselective gazing adducts 27/28 and 29/30, respectively, the regioselectivity being the same as that of the electrophilic additions of 5. The reaction of PhSeCl with a 4:1 mixture of 2‐exo‐chloro‐ and 2‐endo‐chlorobicyclo[2.2.1]hept‐5‐ene‐2‐carbonitriles (12) was slower than addition 5+ PhSeCl; it gave adducts 31/32 (4:1) in which the PhSe moiety occupies the exo position at C(6) and the Cl atom the endo position at C(5). The addition of PhSeCl to 2‐chlorobicyclo[2.2.1]oct‐5‐ene‐2‐carbonitriles (13) was very slow and gave adducts with the same regioselectivity as 12 + PhSeCl, but opposite with that of reactions of the corresponding enones 5 and 6. PhSeX (X = Cl, Br, OAc) added to 2‐cyanobicyclo[2.2.1]hept‐5‐en‐2‐yl acetates (14) with the same regioselectivity as 12 + PhSeCl. The additions of PhSeCl, PhSeBr, NO2C6H4SCl, and (NO2)2C6H3SCl to 2‐(bicyclo[2.2.1]hept‐5‐en‐2‐ylidene)propanedinitrile (49) were not regioselective, showing that a dicyanomethylidene function is not like a carbonyl function when homoconjugated with a π system. The results are in agreement with predictions based on MO calculations suggesting that a carbonyl group homoconjugated with an electron‐deficient centre can behave as an electron‐donating, remote substituent because of favourable n(CO)↔σC(1), C(2)↔p(C(6) hyperconjugative interaction.
Enantioselective Synthesis: Steric and electronic effects of the substrates upon stereoselectivity in the gold(I)‐catalyzed aldol reaction with chiral ferrocenylamine ligands, preliminary communication
Authors: Togni Antonio , Pastor Stephen D. 
Published: December 2004

AbstractEnantioselectivity in the gold(I)‐catalyzed aldol reaction with chiral ferrocenylamine ligands is strongly dependent upon both the steric and electronic effects of the substrates. In the reaction of pyridine‐2‐, 3‐, and 4‐carbaldehydes with ethyl 2‐isocyanoacetate, surprisingly and significantly different enantioselectivities were observed in the formation of the cis‐ and trans‐dihydro‐oxazoles that must be due to electronic rather than steric effects. The first example of double stereodifferentiation in the gold(l)‐catalyzed aldol reaction is reported.
2′, 3′‐Dideoxy‐3′‐fluorotubercidin and Related Dideoxyribonucleosides:. Synthesis via a 2′‐deoxy‐3′‐oxoribofuranoside intermediate and conformation studies
Authors: Rosemeyer Helmut , Seela Frank 
Published: December 2004

AbstractAn efficient synthesis of the unknown 2′‐deoxy‐D‐threo‐tubercidin (1b) and 2′, 3′‐dideoxy‐3′‐fluorotubercidin (2) as well as of the related nucleosides 9a, b and 10b is described. Reaction of 4‐chloro‐7‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine (5) with (tert‐butyl)diphenylsilyl chloride yielded 6 which gave the 3′‐keto nucleoside 7 upon oxidation at C(3′). Stereoselective NaBH4 reduction (→8) followed by deprotection with Bu4NF(→9a)and nucleophilic displacement at C(6) afforded 1b as well as 7‐deaza‐2′‐deoxy‐D‐threo‐inosine (9b). Mesylation of 4‐chloro‐7‐{2‐deoxy‐5‐O‐[(tert‐butyl)diphenylsilyl]‐β‐D‐threo‐pentofuranosyl}‐7H‐pyrrolo[2,3‐d]‐pyrimidine (8), treatment with Bu4NF (→12a) and 4‐halogene displacement gave 2′, 3′‐didehydro‐2′, 3′‐dideoxy‐tubercidin (3) as well as 2′, 3′‐didehydro‐2′, 3′‐dideoxy‐7‐deazainosne (12c). On the other hand, 2′, 3′‐dideoxy‐3′‐fluorotubercidin (2) resulted from 8 by treatment with diethylamino sulfurtrifluoride (→10a), subsequent 5′‐de‐protection with Bu4NF (→10b), and Cl/NH2 displacement. 1H‐NOE difference spectroscopy in combination with force‐field calculations on the sugar‐modified tubercidin derivatives 1b, 2, and 3 revealed a transition of the sugar puckering from the 3′T2′ conformation for 1b via a planar furanose ring for 3 to the usual 2′T3′ conformation for 2.
Structural Aspects of the Enantioselectivity of Tartrates with α‐Amino‐alcohol Salts. Part II. Crystal structures of (1R, 2S)‐norephedrine hydrochloride and (1R, 2R)‐ norpseudoephedrine hydrochloride
Authors: Egli Martin , Dobler Max 
Published: December 2004

AbstractEnantioselective host‐guest complexes between α‐amino‐alcohol salts and chiral tartrates can not be crystallised up to now. To study structural aspects of their enantioselectivity, crystal structures of the components were determined. Norephedrine was used as a reference guest α‐amino‐alcohol. (1R, 2S)‐Norephedrine hydrochloride (monoclinic, space group P21 Z = 4, a = 8.455, b = 10.331, c = 12.570 Å, β = 107.45°) and (1R, 2R)‐norpseudoephedrine hydrochloride (monoclinic, space group P21 Z = 2, a = 5.493, b = 8.052, c = 11.986 Å, β = 104.62°) both adopt M‐synclinal conformations with respect to the ammonium and hydroxy groups. Rather short intramolecular N…︁O distances indicate interaction between ammonium and hydroxy groups.