bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kupplung von Peptiden mit C‐terminalen α,α‐disubstituierten α ‐ Aminosäuren via Oxazol‐5(4H)‐one
Authors: Wipf Peter , Heimgartner Heinz 
Published: December 2004

Peptide‐Bond Formation with C‐Terminal α,α‐Disubstituted α ‐ Amino Acids via Intermediate Oxazol‐5(4H)‐onesThe formation of peptide bonds between dipeptides 4 containing a C‐terminalα,α‐disubstituted α‐amino acid and ethyl p‐aminobenzoate (5) using DCC as coupling reagent proceeds via 4,4‐disubstituted oxazol‐5(4H)‐ones 7 as intermediates (Scheme 3). The reaction yielding tripeptides 6 (Table 2) is catalyzed efficiently by camphor‐10‐sulfonic acid (Table 1). The main problem of this coupling reaction is the epimerization of the nonterminal amino acid in 4 via a mechanism shown in Scheme 1. CSA catalysis at 0° suppresses completely this troublesome side reaction. For the coupling of Z‐Val‐Aib‐OH (11) and Fmoc‐Pro‐Aib‐OH (14) with H‐Gly‐OBu1 (12) and H‐Ala‐Aib‐NMe2 (15), respectively, the best results have been obtained using DCC in the presence of ZnCl2 (Table 3).
The Synthesis of Trimethylcyclopentane‐carboxylic Acids
Authors: Šolaja Bogdan , Huguet Joan , Karpf Martin , Dreiding André S. 
Published: December 2004

Abstract(1RS, 5SR)‐2,2,5‐Trimethylcyclopentane‐1‐carboxylic acid (17) and (1r, 2RS, 5SR)‐1,2,5‐trimethylcyclopentane‐1‐carboxylic acid (19) are the starting materials for the α‐alkynone routes to (±)‐capnellene and for similar efforts towards ptychanolide. Since 17 and 19 have, so far, been available only by a branching reaction from the same precursor, the cyanohydrin mixture 2/3, a modified synthesis for 17 and a new one for 19 was developed (Scheme 1). The common precursor 2/3 was treated with POCl3 which effected normal dehydration to 6 (47%, major path) in competition with Me migration to 8 and 9 (17%). The minor path to 8 and 9 could be reduced to 3% when SOCl2 was used for the dehydration of 2/3. This reaction was the basis for an improved synthesis of 17 from 1, using the steps b, e, i, r, and v see Scheme 1 in an overall yield of 35%. The POCl3 reaction was also studied with the pure cyanohydrins 2 and 3, the configurations of which were determined by an X‐ray analysis of 2. Me migration did not occur form 2 but only from 3 (25%), which has HOC(1) and HC(5) in a cis position. With SOCl2, 3 underwent only 5% Me migration. The new synthesis of 19 started with 4 using the steps h, n, p, and s (see Scheme 1) in an overall yield of 68%.
Poly(dipeptamidinium)‐Salze: Definition und Methoden zur präparativen Herstellung
Authors: Moser Heinz , Fliri Anton , Steiger Arthur , Costello Gerard , Schreiber Jakob , Eschenmoser Albert 
Published: December 2004

Poly(dipeptamidinium) Salts: Definition and Methods of PreparationPoly(dipeptamidines) are polypeptide derivatives in which the carbonyl oxygen of each second backbone amide group is replaced by an imine nitrogen (see A). So far, such derivatives have been unknown. Polyprotonated salts of them ( = poly(dipeptamidinium) salts) are of interest in view of their intrinsic constitutional relationship to the structure of polynucleotides: the number of covalent bonds between neighboring centers of positive charge in poly(dipeptamidinium) salts is identical to the number of covalent bonds between neighboring centers of negative charge in natural polynucleotides (see D). Poly(dipeptamidinium) polycations and polynucleotide polyanions are constitutionally and electrostatically complementary structures. Since poly(dipeptamidines) are (formally) polymers of dipeptide nitriles, and, since they can be expected to give polypeptides on hydrolysis, the relationship mentioned above deserves attention and experimental study in context with the problem of designing chemical models of biogenesis.This paper describes methods for the chemical preparation, the spectral characterization, and some chemical properties of homodipeptidic poly(dipeptamidinium) salts in the L‐alanyl‐glycyl and L‐phenylalanyl‐glycyl series. The methods of preparation include a stepwise construction of defined lower oligomers (up to hexamer) as well as, in the L‐alanyl‐glycyl series, a one‐operation poly‐condensation procedure leading to polymers containing an average of ca. 20 dipeptamidinium units (Schemes 4,6 and 7).
Structural isomerism in Polycondensates. Part IV. Synthesis and characterization of liquid crystalline poly(azomethines) and low molecular weight model compounds
Authors: Deschenaux Robert , Neuenschwander Peter , Pino Piero 
Published: December 2004

AbstractWith the aim to investigate the influence of structural isomerism on the mesomorphic thermal stability in main chain thermotropic polycondensates, a series of poly(azomethines) and low molecular weight models have been prepared. The model compounds exhibit smectic and/or nematic mesophases whose stabilites are very sensitive to structural modifications. On the basis of the above results, monomers 2, 5, 6, 8, 9, 23, 25, and 26 were selected to synthesize oligomers 27–23. The oligomer 33 obtained from the nonsymmetric diamine 23 has a lower melting point than the symmetric oligomer 28, but a similar liquid crystalline range.
C45‐ und C50‐Carotinoide. 5. Mitteilung
Authors: Wolleb Heinz , Pfander Hanspeter 
Published: December 2004

C45‐ and C50‐Carotenoids. Synthesis of an Optically Active Cyclic C20‐Building Block and of (2R,2′S)‐3′,4′‐Didehydro‐1′,2′‐dihydro‐2‐(4‐hydroxy‐3‐methylbut‐2‐enyl)‐2′‐(3‐methylbut‐2‐enyl)‐β,ψ‐caroten‐1′‐ol (= C. p. 473)The synthesis of the optically active C20‐building block (R)‐16 and of the optically active C50‐carotenoid C.p. 473 (1) starting from (−)‐β‐pinene is reported.
Tetrazinodi(heteroarene): Voltammetrische und cyclovoltammetrische Untersuchung der Oxidation in Methanol, Acetonitril und Dichlormethan
Authors: Hellrung Bruno , Balli Heinz 
Published: December 2004

Tetrazinodi(heteroarenes): Voltammetric and Cyclovoltammetric Studies of the Oxidation in Methanol, Acetonitrile, and DichloromethaneThe oxidation of seven symmetrical [1,2,4,5]tetrazinodi(heteroarenes) with different heterocycles has been investigated by means of dc, ac, and cyclic triangular voltammetry in MeCN and CH2Cl2 (containing Bu4NClO4), MeOH (containing LiCl) and in MeOH/H2O (equimolar mixture). The two step oxidation mechanism has been found of type ‘e‐e’ with quasi‐reversible electrochemical steps. Oxidation potentials and transfer coefficients have been measured (0 to +0.5 V vs. Ag/AgCl/3.5M KCl for the first oxidation step and potential differences of 0.8 to 1.3 V to the second oxidation step), indicating a high radical‐ion stability.
Deoxy‐nitrosugars. 16th Communication. Synthesis of N‐acetyl‐4‐deoxyneuraminic acid
Authors: Baumberger Franz , Vasella Andrea 
Published: December 2004

AbstractThe synthesis of 5‐acetamido‐4‐deoxyneuraminic acid (1) is described. Acetylation of a mixture of the epimeric triols 4 and 5 gave the tetraacetates 7 and 8 (Scheme 1). Ozonolysis of a mixture of these acetates followed by base‐promoted β‐elimination led to the (E) ‐configurated α,β‐unsaturated keto ester 10, which was hydrogenated to give the saturated keto ester 11. Saponification of 11 and hydrolytic removal of the benzylidene group followed by anion‐exchange chromatography gave the 5‐acetamido‐4‐deoxyneuraminic acid (1, Scheme 1 and 2). De‐O‐acetylation (NaOMe/MeOH) of the keto ester 11 gave a mixture of the tert‐butyl ester 12 and the methyl ester 13, which were converted to tert‐butyl N‐acetyl‐4‐deoxyneuraminate (14) and to methyl N‐acetyl‐4‐deoxyneuraminate (15), respectively. Hydrogenolysis of the benzylidene acetal 11 followed by de‐O‐acetylation gave the pentahydroxy ester 16.
Preparation of 3,4‐Fused Cyclopropabenzenes and Cyclopropabenzenyl Cations
Authors: Müller Paul , Rodriguez Domingo 
Published: December 2004

AbstractA series of 3,4‐disubstituted (4a, b) or 3,4‐fused (4c‐e) 1,1‐di‐fluorocyclopropabenzenes, including the very strained 1,1‐difluoro‐3,4‐dihydro‐1 H‐cyclobuta[a]cyclopropa[d]benzene (4e) have been synthesized and characterized. Dissolution of these difluoro derivatives in fluorosulfonic acid affords the fluoro cations 3a–e. 1H‐, 19F‐, and 13C‐NMR data of the cations are reported and discussed with respect to those of the precursors.
The Relative Stabilities of Substituted cis‐ and trans‐1,2,3,4,4a,9,10,10a‐Octahydrophenanthrenes, Including Configurational Corrections in the Elad‐Ginsburg Morphine Synthesis
Authors: Duthaler Rudolf O. , Ginsburg David 
Published: December 2004

AbstractThe relative configuration of the title compounds has been determined by 1H‐NMR measurements at 300 MHz. In contradistinction to prevailing opinion, it was found that 4‐oxo derivatives prefer the cis‐configuration. While the cis/trans ratio is 82:18 for the parent 1,2,3,4,4a,9,10,10a‐octahydrophenanthrene‐4,9‐dione, the trans‐isomers of C(5)‐substituted derivatives cannot be detected under the conditions of equilibration. The cis‐configuration is retained upon acetalization of the 4‐oxo derivative. A warning is issued regarding the assigned configurations of certain intermediates in the Elad‐Ginsburg synthesis of morphine.
Sarcodictyeone, a ring‐reduced, optically active linear tetraprenylquinone from the mediterranean stolonifer Sarcodictyon roseum ( = Rolandia rosea)
Authors: D'Ambrosio Michele , Guerriero Antonio , Fabbri Daniele , Pietra Francesco 
Published: December 2004

AbstractThe Mediterranean stolonifer Sarcodictyon roseum ( = Rolandia rosea) (Cnidaria, Anthozoa, Alcyonaria, Stolonifera, Clavulariidae) contains the first example of a chiral, optically active prenyl derivative of a reduced benzoquinone, sarcodictyenone (= (+)‐(4R*,5R*)‐5‐geranylgeranyl‐4‐hydroxy‐2‐methylcyclohex‐2‐en‐1‐one; (+)‐1a).
Nukleophile Addition von Lithiumorganylen an das N,N‐Diethyl‐10‐(trimethylsilyl)‐1, 6‐methano[10]annulen‐2‐carboxamid
Authors: Neidlein Richard , Kramer Walter , Wirth Wolfgang 
Published: December 2004

Nucleophilic Addition of Lithiumorganyles to N,N‐Diethyl‐10‐(trimethylsilyl)‐1,6‐methano[10]annulene‐2‐carboxamideReaction of lithiumorganyles with N,N‐diethyl‐10‐(trimethylsilyl)‐1,6‐methano[10]annulene‐2‐carboxamide followed by quenching with H2O or MeI yields 2,3‐dihydro derivatives of 1,6‐methano[10]annulene.
Generation and Reactions of Lithiated tert‐Butyl and 2,6‐Di(tert‐butyl)‐4‐methylphenyl Cyclopropanecarboxylates
Authors: Häner Robert , Maetzke Thomas , Seebach Dieter 
Published: December 2004

Abstracttert‐Butyl and 2,6‐di(tert‐butyl)‐4‐methylphenyl (BHT) cyclopropanecarboxylates (4, 6, 24, 25) are lithiated with LiN(i‐Pr)2 and t‐BuLi, respectively. Reactions with alkyl halides, aldehydes, acyl chlorides, and heteroelectrophiles give α‐substituted BHT esters which can be cleaved (t‐BuOK/H2O/THF) to the corresponding carboxylic acids or reduced (LiAlH4/THF) to the cyclopropanemethanols.
Stoffwechselprodukte von Mikroorganismen. 237. Mitteilung. (2S, 3R, 4R, 6R)‐2,3,4‐Trihydroxy‐6‐methylcyclohexanon aus zwei Actinomyceten‐Stämmen
Authors: Müller André , Keller‐Schierlein Walter , Bielecki Jacek , Rak Gabriele , Stümpfel Joachim , Zähner Hans 
Published: December 2004

(2S, 3R, 4R, 6R)‐2,3,4‐Trihydroxy‐6‐methylcyclohexanone from Two Strains of ActinomycetesA tetrazolium‐blue positive compound was isolated from two strains of acinomycetes. Its constitution and relative configuration 1 were determined by spectroscopic methods, and the absolute configuration by degradation to (+)‐(R)‐methylsuccinic acid.
Synthesis of 3β‐Hydroxy[21‐14C]‐5β‐pregn‐8(14)‐en‐20‐one from Chenodeoxycholic Acid
Authors: Deluca MóNica E. , Seldes Alicia M. , Gros Eduardo G. 
Published: December 2004

Abstract3β‐Hydroxy[21‐14C]5β‐pregn‐8(14)‐en‐20‐one (17) was prepared from chenodeoxycholic acid (1a). The synthetic sequence involved: (i) degradation of the bile‐acid side chain to an etianic acid; (ii) formation of the 8(14)‐double bond; (iii) inversion of the configuration at C(3); (iv) construction of the acetyl side chain at C(17) with the required isotopic label at C(21). Structures of all described products were confirmed by chemical and spectroscopic (IR, 1H‐NMR, 13C‐NMR, MS) methods.
Highly Stereoselective Photochemical Oxidative Addition Reactions. Preliminary Communication
Authors: Chassot Laurent , von Zelewsky Alex 
Published: December 2004

AbstractCyclometallated complexes of the type cis‐bis(2‐phenylpyridine)platinum(II) (C22H16N2Pt) and cis‐bis(2‐(2′‐thienyl)pyridine)platinum(II) (C18H12N2S2Pt) undergo thermal or photochemical oxidative addition (TOA or POA) reactions with a number of substrates. TOA (with CH3I, CH3CH2I etc.) yield mixtures of several isomers which rearrange slowly (within ca. one week at room temperature) to one of the possible cis‐isomers. CH2Cl2, CHCl3, or (E)ClCHCHCl, e.g., do not react thermally. POA yield directly complexes of Pt(IV) with the halide and a σ‐bonded C‐atom in cis‐position. The configuration, as assigned by extensive use of 1H‐NMR data, can be characterized for the two chelating ligands C …︁ N and C′ …︁ N′ by C,C′‐cis; N,N′‐cis and C(chelate), Cl‐trans.
[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication
Authors: Fráter Georg , Müller Urs , Günther Wulf 
Published: December 2004

Abstract[2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis‐ethyl propenyl ether showed a ca. 3:1 diastereo‐selectivity. A two‐step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)‐compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis‐ benzyl 1‐hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (−)‐blastmycinone. Accordingly, the preferred transition state has been deduced as 15.
Metaboliten der 1,5‐Dihydroimidazo[2,1‐b]chinazolin‐2(3H)‐one. Synthese und Reaktionen einiger 1,5‐Dihydro‐3‐hydroxyimidazo[2,1‐b]chinazolin‐2(3H)‐one
Authors: Stalder Henri 
Published: December 2004

Metabolites of 1,5‐Dihydroimidazo[2,1‐b ]quinazolin‐2(3H)‐ones. Preparation and Reactions of Some 1,5‐Dihydro‐3‐hydroxyimidazo[2,1‐b]quinazolin‐2(3H)‐onesHydroxylated 1,5‐dihydroimidazo[2,1‐b]quinazolin‐2(3H)‐ones 2–4 and 6 were isolated as metabolites of imidazoquinazolinones 1a and 1b, respectively. The synthesis of 1,5‐dihydro‐3‐hydroxy‐3‐methylimidazo[2,1‐b]quinazolin‐2(3H)‐ones 3, 4, and 6, and the preparation of some derivatives thereof is described.
Reaktion von 3‐(Dimethylamino)‐2H‐azirinen mit 1,3‐Thiazolidin‐2‐thion
Authors: Ametamey Simon M. , Prewo Roland , Bieri Jost H. , Heimgartner Heinz , Obrecht Jean Pierre 
Published: December 2004

Reaction of 3‐(Dimethylamino)‐2H‐azirines with 1,3‐Thiazolidine‐2‐thioneReaction of 3‐(dimethylamino)‐2H‐azirines 1 and 1,3‐thiazolidine‐2‐thione (6) in MeCN at room temperature leads to a mixture of perhydroimidazo[4,3‐b]thiazole‐5‐thiones 7 and N‐[1‐(4,5‐dihydro‐1,3‐thiazol‐2‐yl)alkyl]‐N′,N′‐dimethylthioureas 8 (Scheme 2), whereas, in i‐PrOH at ca. 60°, 8 is the only product (Scheme 4). It has been shown that, in polar solvents or under Me2NH catalysis, the primarily formed 7 isomerizes to 8 (Scheme 4). The hydrolysis of 7 and 8 leads to the same 2‐thiohydantoine 9 (Scheme 3 and 5). The structure of 7a, 8c, and 9b has been established by X‐ray crystallography (Chapt. 4). Reaction mechanisms for the formation and the hydrolysis of 7 and 8 are suggested.
Intramolecular Carbenoid Reactions of Pyrrole Derivatives. A Total Synthesis of (±)‐Ipalbidine
Authors: Jefford Charles W. , Kubota Tadatoshi , Zaslona Alexander 
Published: December 2004

AbstractA new method for alkaloid synthesis is described. The rhodium(II)‐acetate‐catalyzed decomposition of 3‐(4‐acetoxyphenyl)‐1‐diazo‐4‐(pyrrol‐1‐yl)‐2‐butanone (5d) gave 6‐(4‐acetoxyphenyl)‐5,6‐dihydro‐7(8H)‐indolizinone (6d) in 82% yield via an intramolecular carbenoid reaction. The latter compound was converted in four steps in 13% overall yield to (±)‐ipalbidine (1b).
The radical anion of 1,2:9,10‐dibenzo[2.2]paracyclophane.. An ESR, ENDOR, and TRIPLE resonance study
Authors: Gerson Fabian , Martin William B. , Wong Henry N. C. , Chan Chin Wing 
Published: December 2004

AbstractThe radical anion of 1,2:9,10‐dibenzo[2.2]paracyclophane (3) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck‐benzene rings, and of the four inner and four outer protons in the side‐benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2‐dimethoxyethane; counterion: K+). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane (1) points to similar nodal properties of the singly occupied orbitals in and . Notwithstanding this similarity, seems to associate less readily than with alkali metal counterions, since tight ion pairs of with K+ are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane‐1,9‐diene (2), are not apparent for in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative 4 which has a CH3 substituent in one of the side‐benzene rings of 3.
3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin als Aib‐Äquivalent: Synthese von Aib‐Oligopeptiden
Authors: Obrecht Daniel , Heimgartner Heinz 
Published: December 2004

3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine as an Aib Equivalent; Synthesis of Aib Oligopeptides3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) reacts with carboxylic acids at 0–25° to give 2‐acylamino‐N,N,2‐trimethylpropionamides ( = 2‐acylamino‐N,N‐dimethylisobutyramide, acyl‐Aib‐NMe2) in excellent yields (Scheme 2 and 3). Examples of α‐amino‐, α‐hydroxy‐, and α‐mercapto‐carboxylic acids are given. On treatment with HCl in toluene, the terminal dimethylamide group is selectively converted to the corresponding carboxylic acid (→acyl‐Aib) via an amide cleavage (Scheme 4 and 5); 1,3‐oxazol‐5(4H)‐ones are intermediates of this amide hydrolysis. This reaction sequence has been used for the extension of peptide chains (Scheme 6). The synthesis of Aib‐oligopeptides using this methodology is described (Scheme 8).
Photochemical Synthesis of Octahydro‐ and 3a,4,5,6,7,7a‐Hexahydro‐benzo[b]thiophenes from Methyl (E)‐4‐Mercapto‐2,6‐heptadienoate and Alkenes or Alkynes via Consecutive Radical Ring Closure. Preliminary Communication
Authors: Kiesewetter René , Margaretha Paul 
Published: December 2004

AbstractOn irradiation (λ = 300 nm) in MeOH 5‐(2‐propenyl)‐2(5H)‐thiophenone (1c) affords methyl (E)‐4‐mercapto‐2,6‐heptadienoate (2c) which undergoes light‐induced homolysis of the S–H bond to give the alkylthio radical 3c. This species can be trapped by 2,3‐dimethyl‐2‐butene or 2‐butyne to afford octahydrobenzo‐[b]thiophene 9 or 3a,4,5,6,7,7a‐hexahydrobenzo[b]thiophene 13, respectively, as main products via consecutive radical ring closure. In the absence of unsaturated hydrocarbons, 3c cyclizes to give methyl (E)‐3(thiolan‐2‐yl)‐2‐propenoate (8).
Complexes of 3,3′‐Oxybis[(diphenylphosphino)methylbenzene] with Ni(II), Pd(II), Pt(II), Rh(I), and Ag(I). How Important is Backbone Rigidity in the Formation of trans‐Spanning Bidenatate Chelates??
Authors: Marty Werner , Kapoor Pramesh N. , Bürgi Hans‐Beat , Fischer Erwin 
Published: December 2004

AbstractThe bidentate diphosphine ligand, 3,3′‐oxybis[(dipenylphosphino)methylbenzene] (1) forms monomeric, trans‐square‐planar complexes MX2(1) (M = Ni, Pd, Pt; X = Cl−, Br− I−, and, in part, N, NCS−, CN−, NO) as well as Pt(H)Cl(1), Pt(H)Br(1), and RhCl(CO)(1). Polymeric species have been observed with substitutionally inert metal centres: trans‐[PtCl2(1)]2 and cis‐[PtCl2(1)]n (mean value of n ≈ 4–5) 31P‐NMR, and selected IR and UV/VIS parameters are reported. Ligand 1 shows a marked preference for trans‐spanning and monomeric chelate formation, despite its various degrees of freedom of internal rotation in the lignad backbone. The readily available ligand 1 as well as analogues with other donor atoms, therefore, appear useful in most potential applications of trans‐spanning chelate ligands. The crystal structure of AgCl(1)·0.5 (CH3)2CO·0.39 C6H12 (space group C2/c,a = 21.02 Å, b = 14.57 Å, c = 24.79 Å, β = 99.77°, V = 7531.4 Å3, Z = 8) confirms the presence of three‐coordinate Ag(I), with a coordination intermediate between a trigonal‐planar and a T‐shaped geometry (P‐Ag‐P = 145.61(8)°).
Nucleotides. Part XXVI.. A new synthesis of 9‐(′‐D‐ribofuranosyl)uric acid and its 5′‐monophosphate
Authors: Schulz Bernd S. , Pfleiderer Wolfgang 
Published: December 2004

AbstractSyntheses for 9‐(β‐D‐ribofuranosyl)uric acid (16) and its 5′‐monophosphate 14 have been achieved starting from guanosine and applying the 2‐(p‐nitrophenyl)ethyl group for protection of the aglycon moiety as well as the phosphate function. A more efficient and direct approach to 14 uses O6, O8‐dibenzyl protection and phosphorylation by the Yoshikawa procedure. The various protected intermediates have been characterized by spectroscopic means and elemental analysis.
Ring‐Open Analogues of Adenine Nucleoside. Aminoacyl Derivatives of Cyclo‐ and Acyclo‐Nucleosides
Authors: Hakimelahi Gholam H. , Zarrinehzad Morteza , Jarrahpour Ali A. , Sharghi Hashem 
Published: December 2004

AbstractThe synthesis of acyclic analogues of ribo‐ and deoxyribonucleosides is described. These compounds (Table 3) are both poor substrates and poor inhibitors of adenosine deaminase. The synthesis of dinucleotides from these analogues is also described, and the activity along with the inhibitory properties of some of them are studied against deaminase enzyme. These nucleotides are resistant to degradation by phosphodiesterases. HCl impregnated on silica gel is an excellent reagent for the preparation of the chloromethyl ether precursors of acyclo‐nucleosides. A general and rapid procedure is developed for the preparation and isolation of the 5′‐aminoacyl derivatives of robo‐ and arabinonucleosides. Quinoline has a marked effect on aminoacylations without racemization. Compounds 35a, b possess remarkable antiviral effects in vitro. A procedure is also developed for the conversion of acyclo‐ribonucliosides 13e, f to acyclo‐deoxyribonucleosides 11e, f.
Data bank: The PE Spectra of Paracyclophanes with Unsaturated Bridges and of Related Molecules
Authors: Yang Zhong‐Zhi , Kovač Branka , Heilbronner Edgar , Lecoultre Jacques , Chan Chin Wing , Wong Henry N. C. , Hopf Henning , Vögtle Fritz 
Published: December 2004

AbstractThe PE spectroscopic data for a series of [2.2]paracyclophanes with olefinic and/or aromatic bridges, and of a few related molecules are reported, together with tentative assignments based on simple MO models.
Neuartige Triterpen‐Lactone aus Helenium autumnale L.
Authors: Matusch Rudolf , Häberlein Hanns 
Published: December 2004

Novel Triterpene Lactones of Helenium autumnale L.Three novel triterpene lactones 1–3 could be detected by investigating a pentane extraxt of the Helenium autumnale L. (Asteraceae) roots. The structures are especially elucidated by 1H‐ and 13C‐NMR spectroscopy. The lactones 1‐3 formally represent Diels‐Alder products of a reaction between a sesquiterpene lactone and an α,β‐unsaturated sequiterpene aldehyde.