bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C‐NMR. Spectra of 4‐Substituted Quinuclidines. Polar effects, Part V
Authors: Becker Konrad B. , Grob Cyril A. 
Published: December 2004

Abstract13C‐NMR. sepctra of 37 4‐substituted quinuclidinium perchlorates, 15 4‐substituted quinuclidines and the corresponding 1‐methylquinuclidinium iodides have been measured. The chemical shifts δ for all compounds lie in the expected range. No correlation is found between δ and the inductive substituent constant σ of the substituent. Abnormal shift differences between quinuclidines bearing a nucleofugal group and the corresponding protonated or N‐methylated quinuclidinum salt are observed for the bridgehead carbon C(4). These differences are ascribed to incipient fragmentation, i.e. C, C‐hyperconjugation in the ground state.
Synthese von Nor‐β‐cyclocitral, Norsafranal und 2, 2′‐Dinor‐β‐carotin
Authors: Kienzle Frank , Minder Rudolf E. 
Published: December 2004

Synthesis of nor‐β‐cyclocitral, norsafranal, and 2, 2′‐dinor‐β‐caroteneThe synthesis of 2, 2′‐dinor‐β‐carotene (10) via norsafranal (5) and nor‐β‐cyclocitral (6) is described.
Isolation by HPLC. and Identification by NMR. Spectroscopy of 11 mono‐, di‐ and tri‐cis isomers of an aromatic analogue of retinoic acid, ethyl all‐trans‐9‐(4‐methoxy‐2,3,6‐trimethylphenyl)‐3,7‐dimethyl‐nona‐2,4,6, 8‐tetraenoate
Authors: Englert Gerhard , Weber Siegfried , Klaus Michael 
Published: December 2004

AbstractPhotoisomerization of an aromatic analogue of retinoic acid, ethyl all‐trans‐9‐(4‐methoxy‐2,3,6‐trimethylphenyl)‐3,7‐dimethyl‐nona‐2,4,6, 8‐tetraenoate 1 in dilute solutions of hexane, benzene, and ethanol yielded multi‐component mixtures of cis isomers which were separated by HPLC. FT‐1H‐NMR. at 270 MHz and, in some cases, homonuclear decoupling and Overhauser experiments as well as 13C‐NMR. were applied to establish the structures of 4 mono‐cis, 4 (of 6 possible) di‐cis, and 3 (of 4 possible) tri‐cis isomers. The structures of 3 isomeric esters, namely (2Z, 4E, 6E, 8E) 6, (2Z, 4Z, 6E, 8E) 9, and (2Z, 4Z, 6Z, 8E) 7 were independently confirmed by direct syntheses. The 1H‐NMR. data of all these compounds and the 13C‐NMR. data of the all‐trans and of 6 cis isomers available in sufficiently large quantities are discussed.
Synthese des Sesquiterpen‐Ketones Shyobunon und seiner Diastereomeren
Authors: Fráter György 
Published: December 2004

Synthesis of the Sesquiterpene Ketone Shyobunon and of its DiastereoisomersShyobunon (12) and 6‐epishyobunon (13) as well as their epimers 10 and 11 were synthetized in five steps from geranyl‐ (1) and nerylsenecionate (2), respectively. Ester enolate rearrangement [5] of 1 and 2 furnished the key intermediates 3 and 4 in high yield and in about 80% stereoselectivity [6] (Scheme 1). Conversion of the acid mixture 3/4 to the cyclohexanone derivatives 7 and 8 succeeded in 35–40% yield by means of cyclization of their acidchlorides with tin tetrachloride to the mixture of 5 and 6, followed by HCl elimination with diazabicyclononene (DBN) (Scheme 2). Selective reduction of 7 to 10 and 11, and 8 to 12 and 13 with triphenyltinhydride completed the synthesis.The relative configuration of 10 and 11 as well as of 12 and 13 were deduced from the 13C‐NMR. spectra (Scheme 4, Table 2). The structure of ‘epishyobunone’ is revised: it has the structure 13, and not 11 as described earlier [1]. This is discussed in connection with the rearrangement of acoragermacrone (16) [18] to shyobunone (12) and 6‐epishyobunone (13) (Scheme 5).
Über Pterinchemie. 65 Mitteilung [1]. Herstellung von (6 R, S)‐5,6,7,8‐Tetrahydro‐L‐biopterin, 7,8‐Dihydro‐L‐biopterin, L‐Sepiapterin, Deoxysepiapterin, (6 R, S)‐5,6‐Dihydrodeoxysepiapterin und 2′‐Deoxybiopterin
Authors: Schircks Bernhard , Bieri Jost H. , Viscontini Max 
Published: December 2004

Preparation of (6 R, S)‐5,6,7,8‐tetrahydro‐L‐biopterine, 7,8‐dihydro‐L‐biopterine, L‐sepiapterine, deoxysepiapterine, (6 R, S)‐5,6‐dihydrodeoxysepiapterine and 2′‐deoxybiopterineWe describe the preparation of (6 R, S)‐5,6,7,8‐tetrahydro‐L‐biopterine (II) by catalytic‐ (reported in our short communication [2]) and natriumdithionite reduction of L‐biopterine (I) and a preparation of 7,8‐dihydro‐L‐biopterine (IV) by treatment of L‐biopterine (I) with natriumdithionite. Whereas oxidation of tetrahydrobiopterine II in the presence of oxygen leads to L‐sepiapterine (III), dihydrobiopterine IV in acetic acid without oxygen gives deoxysepiapterine (VII), 5,6‐dihydro‐deoxysepiapterine (VI) and 2′‐deoxybiopterine (V) by a disproportionation reaction.
Über Pterinchemie. 69 Mitteilung [1]. Konformationsanalyse von 5,6,7,8‐Tetrahydropteroinsäure und 5,6,7,8‐Tetrahydro‐L‐folsäure
Authors: Furrer Hans‐Jürg , Bieri Jost H. , Viscontini Max 
Published: December 2004

Conformational analysis of 5,6,7,8‐tetrahydropteroic acid and 5,6,7,8‐tetrahydro‐L‐folic acidIn the 360‐MHz‐1H‐NMR.‐spectrum of (6R, S)‐9,9‐dideuterio‐5, 6, 7, 8‐tetrahydropteroic acid (racemic) (XIII) (AMX‐System, Fig. 4) and (6R, S)‐9,9‐dideuterio‐5, 6, 7, 8‐tetrahydro‐L‐folic acid (diastereomeric) (XVI) the Ha–C(6) and Ha–C(7) show a vicinal coupling constant of 6,7 Hz and the Ha–C(6) and He–C(7) one of 3,2 Hz. The first coupling constant provides evidence for an approximate trans‐diaxal arrangement of Ha–C(6) and Ha–C(7), and the second for a gauche conformation of Ha–C(6) and He–C(7). The tetrahydropyrazine ring in the racemic 5, 6, 7, 8‐tetrahydropteroic acid (III) and in the diastereomeric 5, 6, 7, 8‐tetrahydro‐L‐folic acid (XVII) exists therefore in a half‐chair conformation with a pseudoequatorial position of the side chain at C(6) (Fig.5).
Synthese von Nucleosiden aus 2‐substituierten Imidazolen
Authors: Wyss Pierre C. , Schönholzer Peter , Arnold Wolf 
Published: December 2004

Synthesis of 2‐Substituted Imidazole NucleosidesCondensation of the trimethylsilyl derivatives of 2‐substituted diethyl and dimethyl imidazole‐4,5‐dicarboxylates (3–5 and 7–9) with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranose (2) in the presence of trimethysilyl trifluoromethanesulfonate provided the 2‐substituted diethyl and dimethyl 1‐(2′,3′, 5′‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl)imidazole‐4, 5‐dicarboxylates 10–15. These were treated with ammonia to afford the 2‐substituted 1‐(β‐D‐ribofuranosyl)imidazole‐4,5‐dicarboxamides 16–21. Treatment of 2‐methyl‐(16) and 2‐ethyl‐1‐(β‐D‐ribofuranosyl)imidazole‐4,5‐dicarboxamide (17) with fuming nitric acid in oleum at −30° yielded the nitric acid esters 23 and 24. Besides the esterification of the sugar hydroxyl groups one H‐atom of the imidazolecarboxamide function at C(5) in these nucleosides was also substituted by the NO2 group.The conformations in solution of 16 and 23 have been determined by 1H‐ and 13C‐NMR. spectroscopy. These studies indicate that the nucleosides exist in dimethyl‐sulfoxide solution preferentially in the S‐gg‐syn‐conformation (16) and N‐gt‐conformation (23). In the crystal structure of nucleoside 23, the ribose was found to be in the O(1′)endo, C(1′)exo twist conformation. The conformation about C(4′), C(5′) is gauche‐trans and the molecule exists in the syn form.
1,2‐Epoxy‐Carotinoide. 1. Mitteilung. Synthese von 1,2‐Epoxy‐lycopin und 1,2,1′,2′‐Diepoxy‐lycopin
Authors: Pfander Hanspeter , Kamber Matthias , Battegay‐Nussbaumer Yvonne 
Published: December 2004

1,2‐Epoxy‐Carotenoids. Synthesis of 1,2‐Epoxy‐lycopene and 1,2,1′,2′‐Diepoxy‐lycopeneThe synthesis of the naturally occuring 1,2‐epoxy‐lycopene and of 1,2,1′,2′‐diepoxy‐lycopene is described.
Citrus‐Carotinoide. 2. Mitteilung. Synthese von (3R)‐β‐Citraurin, (3R)‐β‐Citraurol und (3R)‐β‐Citraurinin; Aufklärung der Konfiguration von Citrus‐Carotinoiden
Authors: Pfander Hanspeter , Lachenmeier Andreas , Hadorn Martin 
Published: December 2004

Citrus‐Carotenoids. Synthesis of (3R)‐β‐Citraurin, (3R)‐β‐Citraurol and (3R)‐β‐Citraurinene; Determination of the Configuration of Citrus‐Carotenoids(3R)‐β‐Citraurin, (3R)‐β‐citraurol and (3R)‐β‐citraurinene were prepared starting from (3R)‐3‐acetoxy‐β‐ionone. Comparison of the chiroptical data of β‐citraurin from orange peels with those of the synthetic compound confirmed the 3R‐configuration of the natural pigment.
Über die Stereoselektivität der α‐Alkylierung von (1R, 2S) (+)‐cis‐2‐hydroxy‐cyclohexancarbonsäureäthylester
Authors: Fráter György 
Published: December 2004

The Stereoselectivity of the α‐Alkylation of (+)‐(1R, 2S)‐cis‐Ethyl‐2‐hydroxy‐cyclohexanecarboxylateIn continuation of our work on the stereoselectivity of the α‐alkylation of β‐hydroxyesters [1] [2], we studied this reaction with the title compound (+)‐2. The latter was prepared through reduction of 1 with baker's yeast. Alkylation of the dianion of (+)‐2 furnished (−)‐4 in 72% chemical yield (Scheme 1) and with a stereoselectivity of 95%. Analogously, (−)‐7 was prepared with similar yields. Oxidation of (−)‐4 and (−)‐7 respectively furnished the ketones (−)‐6 (Scheme 3) and (−)‐8 (Scheme 4) respectively, each with about 76% enantiomeric excess (NMR.). It is noteworthy that yeast reduction of rac‐6 (Scheme 3) is completely enantioselective with respect to substrate and product and gives optically pure (−)‐4 in 10% yield, which was converted into optically pure (−)‐6 (Scheme 3).The alkylation of the dianionic intermediate shows a higher stereoselectivity (95%) from the pseudoequatorial side than that of 1‐acetyl‐ or 1‐cyano‐4‐t‐butyl‐cyclohexane (71% and 85%) [9] or that of ethyl 2‐methyl‐cyclohexanecarboxylate (82%). The stereochemical outcome of the above alkylation is comparable with that found in open chain examples [1] [2].Finally (+)‐(1R, 2S)‐2 was also alkylated with Wichterle's reagent to give (−)‐(1S, 2S)‐9 in 64% yield. The latter was transformed into (−)‐(S)‐10 and further into (−)‐(S)‐11 (Scheme 5). (−)‐(S)‐10 and (−)‐(S)‐11 showed an e.e. of 76–78% (see also [11]). Comparison of these results with those in [11] confirmed our former stereochemical assignment concerning the alkylation step.
Heterotricyclodecane XXVII. Ein weiterer Zugang zu 2,6‐Dioxatricyclo [3.3.2.03,7]decan
Authors: Buchs Peter , Ganter Camille 
Published: December 2004

A Further Approach to 2,6‐Dioxatricyclo[3.3.2.03,7]decaneA further synthesis of 2,6‐dioxatricyclo[3.3.2.03,7]decane (10) is described by bridging the 9‐oxabicyclo[4.2.1]non‐7‐en‐3endo‐ol (9). The latter compound was prepared by ring expansion starting from the known 8‐oxabicyclo[3.2.1]oct‐6‐en‐3‐on (1).
Synthese von optisch aktiven, natürlichen Carotinoiden und strukturell verwandten Naturprodukten. V. Synthese von (3R, 3′R)‐, (3S, 3′S)‐ und (3R,3′S; meso)‐Zeaxanthin durch asymmetrische Hydroborierung. Ein neuer Zugang zu Optisch aktiven Carotinoidbausteinen. Vorläufige Mitteilung
Authors: Rüttimann August , Mayer Hans 
Published: December 2004

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. V. Synthesis of (3R, 3′R)‐, (3S, 3′S)‐ and (3R,3′S; meso)‐zeaxanthin by Asymmetric Hydroboration. A New Approach to Optically Active Carotenoid Building UnitsThe synthesis of (3R, 3′R)‐, (3S, 3′S)‐ and (3R,3′S; meso)‐zeaxanthin (1), (19) and (21) is reported utilizing asymmetric hydroboration as the key reaction. Thus, safranol isopropenylmethylether (4) is hydroborated with (+)‐ and (−)‐(IPC)2BH to give the optically pure key intermediates 5 and 7 resp., which are transformed into the above‐mentioned C40‐compounds.
Synthese von optisch aktiven, natürlichen Carotinoiden und strukturell verwandten Naturprodukten. VII. Synthese von (3R)‐3‐Hydroxyretinol, (3R)‐3‐Hydroxyretinal und (3R)‐3‐Hydroxyretinsäure
Authors: Mayer Hans , Santer Jean‐Marie 
Published: December 2004

Synthesis of optically active natural carotenoids and structurally related compounds. VII. Synthesis of (3R)‐3‐hydroxyretinol, (3R)‐3‐hydroxyretinal and (3R)‐3‐hydroxyretinoic acidThe synthesis of (3R)‐3‐hydroxyretinol, (7), (3R)‐3‐hydroxyretinal (9) and (3R)‐3‐hydroxyretinoic acid (5) according to the building principle C15 + C5 = C20 is reported utilizing the optically active C15‐phosphonium salt 2 and the C5‐aldehyde ester 3.
Reactions of oxygenated cobalt (II) complexes. XIII. Diastereoisomeric forms of μ‐peroxo‐μ‐hydroxo‐bis[bis(ethylenediamine) cobalt(III)]. Preparation, X‐ray structure determination and reactivity
Authors: Fallab Silvio , Zehnder Margareta , Thewalt Ulf 
Published: December 2004

AbstractOxygenation of solutions containing bis(ethylenediamine) cobalt(II) ions leads to a mixture of diastereomeric forms of μ‐peroxo‐μ‐hydroxo‐bis[bis(ethylenediamine) cobalt(III)] cations. The existence of a meso‐isomer has now been proved by its isolation as perchlorate and by an X‐ray structure determination. The crystals are monoclinic with space group P21/n and lattice constants: a = 19.280, b = 11.984, c = 11.654 Å, β = 99.190°.The UV./VIS. spectra of the isomers are practically identical but show different kinetic behaviour. In acidic solution the meso‐isomer decomposes 4 times faster than the racemic form. In alkaline solution the meso‐isomer isomerizes to the racemic form. A mechanism which explains all the kinetic observations has been devised.
Photochemische Reaktionen. 109. Mitteilung [1]. Zur Photochemie konjugierter δ‐Keto‐enone und β,γ,δ,ϵ‐ungesättigter Ketone
Authors: Eichenberger Herbert , Tsutsumi Kentaro , de Weck Guy , Wolf Hans Richard 
Published: December 2004

Photochemistry of Conjugated δ‐Keto‐enones and β,γ,δ,ϵ‐Unsaturated KetonesOn 1π,π*‐excitation the δ‐keto‐enones 5–8 are isomerized to compounds B (18, 22, 26, 28) via 1,3‐acyl shift and to compounds C (19, 23, 27, 29) via 1,2‐acyl shift, whereas the β,γ,δ,ϵ‐unsaturated ketone 9 gives the isomers 32 and 33 by 1,2‐and 1,5‐acyl shift, respectively. Furthermore, isomerization of 6 to 24, dimerization of 8 to 30 and addition of methanol to 8 (8 → 31) is observed. Unlike 7 and 8 the acyclic ketones 5, 6 and 9 undergo photodecarbonylation on 1π,π*‐excitation (5 → 20, 21; 6 → 20, 25; (E)‐9 → 35–38).Evidence is given, that the conversion to B as well as the photodecarbonylation of 5,6 and 9 arise from an excited singulet state, but the conversion to C as well as the dimerization of 8 from the T1‐state.
Benzylidène‐5‐hydroxy‐4‐dihydro‐2,5‐thiophènecarboxanilides‐3‐(Z): Synthèse et isomérisation en benzyl‐5‐hydroxy‐4‐thiophènecarboxanilides‐3
Authors: Jaunin Roland 
Published: December 2004

(Z)‐5‐Benzylidene‐2,5‐dihydro‐4‐hydroxy‐3‐thiophenecarboxanilides: Synthesis and Isomerization into 5‐Benzyl‐4‐hydroxy‐3‐thiophenecarboxanilidesUpon treatment with an arylamine in boiling xylene, the esters I yield predominantly the corresponding anilides II, along with a small but variable amount of the isomeric thiophene derivatives III (Table 1). On the other hand, the derivatives III can be readily prepared by base‐ or acid‐catalyzed isomerization of II. Esters I can also be isomerized to the corresponding thiophene derivatives IV (Scheme 6), but only in the presence of a strong acid (Table 4). The two series of isomers reported in Tables 2 and 3 present spectral differences which allow unambiguous structural assignments. The (Z)‐configuration for compounds of Table 2 is confirmed by a NOE study carried out on the O‐methyl derivatives 6a and 7a.
Synthesis of (R)‐ and (R)‐4‐methyl‐6‐2′‐methylprop‐1′‐enyl‐5,6‐dihydro‐2H‐pyran (Nerol oxide) and Natural Occurrence of its Racemate
Authors: Ohloff Günther , Giersch Wolfgang , Schulte‐Elte Karl H. , Enggist Paul , Demole Edouard 
Published: December 2004

AbstractFollowing a known procedure, a mixture of (−)‐(2S,3R)‐ and (+)‐(2R,3R)‐2,3‐epoxy‐citronellols (5) was prepared from (−)‐(R)‐linalool (3)viaepoxy alcohol4and then reduced to (−)‐(R)‐3‐hydroxy‐citronellol (6). Sensitized photooxygenation of (−)‐(R)‐diol6led in part to (−)‐(R)‐triol8which was cyclodehydrated by dilute acid to a mixture of diastereoisomeric tetrahydropyran‐4‐ols9and10. Dehydration of hydroxy ethers9and10afforded (−)‐(S)‐nerol oxide (11) and (+)‐(R)‐nerol oxide (12), respectively, with an optical purity of 91%. Nerol oxide isolated from Bulgarian rose oil (0.038%) proved to be racemic. These results shed some light on the formation of nerol oxide in plants.
Synthesis of the Sesquirose Oxides from Rose Oxide
Authors: Ohloff Günther , Giersch Wolfgang , Decorzant René , Büchi George 
Published: December 2004

AbstractThe eight stereoisomeric sesquirose oxides 9 to 16 were prepared from the four optically active rose oxides 1 to 4. The spectral data, optical rotations and the olfactive properties of 9 to 16 are given.
Synthesis of Enantiomeric 3‐Oxa‐analogues of cis‐Rose Oxide and of Some Sesquiterpenoid Homologues
Authors: Ohloff Günther , Giersch Wolfgang 
Published: December 2004

AbstractThe synthesis, spectral properties and sensory evaluation of chiral oxa‐analogues of cis‐rose oxide, and of eight corresponding sesquiterpenoid homologues, are described.
Natural Abundance 13C‐NMR. of Vitamin D3 Metabolites
Authors: Williams Thomas H. , Greeley David N. , Baggiolini Enrico G. , Partridge John J. , Shiuey Shian‐Jan , Uskokovié Milan R. 
Published: December 2004

AbstractChemical shifts of 13C‐ and 1H‐NMR. spectra of vitamin D3 metabolites (2–7) are assigned. Substituent effect parameters due to hydroxyl groups are deduced by comparison with vitamin D3.
Two New Sesquiterpenoid Ketones from Cassia Oil
Authors: Thomas Alan F. 
Published: December 2004

AbstractThe synthesis of 2‐methyl‐6‐(4′‐methylphenyl)‐l‐hepten‐3‐one (1) and 2‐methyl‐6‐(4′‐methylphenyl)‐3‐heptanone (2), constituents of the oil of Cinnamomum cassia, is described.
Cob(I)alamin as Catalyst. 8th Communication. Cob(I)alamin and Heptamethyl Cob(I)yrinate During the Reduction of α,β‐Unsaturated Carbonyl Derivatives
Authors: Fischli Albert , Daly John J. 
Published: December 2004

AbstractHydrogen bonds as presented in Figure 2 cannot account for the enantioselective attack of cob(I)alamin (4(I)) or heptamethyl cob(I)yrinate (5(I)) on one of the two enantiotopic faces of the substrates. The attack of the strongly nucleophilic 3d orbital is preferentially directed to the re‐side of the starting materials with (Z)‐configuration and leads, after the highly stereoselective reductive cleavage of the Co, C bond, to saturated products with (S)‐configuration in varying enantiomeric excesses (see Schemes 1, 3 and Table 1).
Dérivés de sucres à groupement gem‐dihalogénoéthényle
Authors: Tronchet Jean M. J. , Bonenfant Alain‐P. 
Published: December 2004

Carbohydrate Derivatives Bearing a gem‐Dihalogenoethenyl GroupTreated with the appropriate Wittig reagent, aldehydosugar derivatives (1–13) led in good to excellent yields to the expected gem‐difluoro, gem‐chlorofluoro‐and/or gem‐dichloroenoses (14–29). Examples of their dibromo analogues had been previously described (see e.g. [1]) but the diiodo derivatives could not be isolated, The influence of the conditions on the yields is reported as well as spectroscopic properties (particularly the long‐range 13C, 19F‐ and 1H, 19F‐coupling constants) of these new enoses.
The Synthesis of β,γ‐ and α,β‐Unsaturated Aldehydes via Polyene Epoxides
Authors: Rosenberger Michael , Jackson William , Saucy Gabriel 
Published: December 2004

AbstractA substitute for the Darzens glycidic ester synthesis for converting unsaturated ketones or aldehydes into the homologated β,γ‐ or α,β‐unsaturated aldehydes employing sulfur ylides is described. The carbonyl group is converted into the unsaturated oxirane which is then rearranged to the new aldehyde. High yields of isomerically pure aldehydes are available by this method and the process is of practical importance in the conversion of β‐ionone into the β‐C14‐aldehyde, a key intermediate in the Isler synthesis of vitamin A. The efficient preparation of α‐ and β‐cyclocitral by the novel process is also described.
Synthese, spektroskopische Eigenschaften und elektrochemisches Verhalten von Ruthenium(II)‐Komplexen mit zweizähnigen Stickstoffliganden
Authors: Belser Peter , Zelewsky Alex Von 
Published: December 2004

Synthesis, Spectroscopic Data and Electrochemical Behavior of Ruthenium(II) Complexes with Bidentate LigandsThe syntheses of coordination compounds of ruthenium (II) with bidentate nitrogen donors (aa) is described. The ligands (aa) used are related to dipyridyl, but differ from the latter in size of the π‐electron systems. In some ligands, e.g. 10, the two halves of the molecule are forced to be non planar by the aliphatic bridge between the two rings accomodating the nitrogen ligand atoms. The syntheses of the complexes Ru(dipy)2(aa)2+, Ru(dipy)(aa)2+2 and Ru(aa)2+3 ((aa) 1–17) are described. Generally the crystalline salts with PF−6 as counter‐ion have been obtained. The complexes are characterized by elementary analysis, electronic spectra, infrared spectra, cyclic voltammograms, proton nuclear magnetic resonance spectra and, for those which have been obtained in optically active forms also by circular dichroism. In the discussion special emphasis is given to the change of properties compared to the well investigated Ru(dipy)2+3 complex. In the visible range of the spectrum all complexes show one or several spin allowed charge transfer transitions at longer wave lengths then Ru(dipy)2+3. The ground state oxidation potential to the 3+ state are little affected by substitution of one or more of the dipy ligands in Ru(dipy)2+3 by the ligands (aa), whereas the reduction behavior is strongly influenced by such substitutions. The 1H‐NMR. spectra indicate rigid conformations of some of the nonplanar (aa)‐ligands in the complexes.
The Enantioselective Synthesis of (+)‐Estradiol from 1,3‐Dihydrobenzo[c]thiophene‐2,2‐dioxide by Successive Thermal SO2‐Extrusion and Cycloaddition Reactions. Preliminary communication
Authors: Oppolzer Wolfgang , Roberts David Anthony 
Published: December 2004

AbstractThe optically pure steroid (+)‐15 has been synthesized from the easily accessible (+)‐carboxylic acid 11 by a sequence of 7 steps in 50% overall yield. The key steps are the regioselective deprotonation/alkylation 7+13 → 14 and the thermal SO2‐extrusion/cycloaddition 14 → 15 (Scheme 3). The compound (+)‐15 has been readily converted to the naturally occurring (+)‐estradiol (17) in 60% yield.
trans/cis Isomerization of Astaxanthin Diacetate/Isolation by HPLC. and Identification by 1H‐NMR. Spectroscopy of Three Mono‐cis‐ and Six Di‐cis‐Isomers
Authors: Euglert Gerhard , Vecchi Max 
Published: December 2004

AbstractThermal and iodine‐catalyzed photochemical trans/cis isomerization of synthetic, racemic astaxanthin diacetate (3,3′‐dihydroxy‐β,β‐carotene‐4,4′‐dione diacetate) yielded multi‐component mixtures of cis‐isomers. Separation and isolation of 10 different cis‐isomers in quantities between 10 and 70 μg was achieved by HPLC. Investigation of their 270‐MHz‐FT‐1H‐NMR. spectra led to the identification of 9 of these isomers, namely the 9‐, 13‐, and 15‐mono‐cis‐, the 9,9′‐, 9,13‐, 9,13′‐, 9,15‐, 13,13′‐, and 13,15‐di‐cis‐astaxanthin diacetate.
Etude par spectrométrie de masse de la fragmentation du désoxy‐3‐di‐O‐isopropylidène‐1,2: 5,6‐méthylidène‐3‐α‐D‐hexofurannose et de quelques analogues substitués en C(3′)
Authors: Glangetas Alain , Gülacar Fazil O. , Tronchet Jean M. J. , Buchs Armand 
Published: December 2004

Electron Impact Mass Spectrometry of the 3‐Desoxy‐1,2: 5,6‐di‐O‐isopropylidene‐3‐methylidene‐δ‐D‐hexofuranose and Some C(3′)‐Substituted AnaloguesThe mass spectra of the 3‐desoxy‐1,2:5, 6‐di‐O‐isopropylidene‐3‐methylidene‐ α‐D‐ribo‐hexofuranose and of some C(3′)‐mono‐ and ‐disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed.
Über Pterinchemie. 74. Mitteilung. Zum Verlauf der katalytischen Reduktion von 6‐Methylpterin
Authors: Ganguly Abhoy N. , Sengupta Pradip K. , Bieri Jost H. , Viscontini Max 
Published: December 2004

On the Pathway of the Catalytic Reduction of 6‐MethylpterinThe catalytic hydrogenation of 6‐methylpterin (I) in neutral or weekly acidic solution begins, as for the 7‐methylpterin, by the thermodynamically controlled reduction of the 7,8‐double bond. It is not possible to say, according to our experiments, which double bound, either the 5,6 or the 7,8, is first reduced in strongly acidic solution. However, a 5,8‐reduction can be excluded.