bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroanatomical analysis of functional brain images: Validation with retinotopic mapping
Authors: Grabowski T. J. , Damasio H. , Frank R. J. , Brown C. K. , Boles Ponto L. L. , Watkins G. L. , Hichwa R. D.
Published: December 2004

The analysis of functional brain images generated by positron emission tomography (PET) has depended on averaging individual images in a common stereotactic space to improve the signal‐to‐noise ratio in activation maps. Although the precise relationship of stereotactic coordinates to sulcul and gyral anatomy is obscured, these techniques have productively enabled exploratory, pixel‐based analysis of PET images. Coregistered three‐dimensional magnetic resonance (MR) datasets, not widely available at the time PET techniques were pioneered, now make it possible to develop complementary hypothesis‐led analysis techniques that respect individual anatomy and, therefore, allow conclusions in terms of sulcal and gyral anatomy. We report the development of such a technique, involving construction of a local standard space within anatomically‐defined boundaries. We validate the technique with a retinotopic mapping paradigm. In the analysis based on this standard space, regions of activation from the contributing subjects superimpose better than they do when Talairach's transformation is used. This approach also allows conclusions to be drawn specifically about striate cortex, whereas analysis of stereotactically transformed data does not distinguish V1 and V2. This approach is likely to be particularly useful for studying brain‐damaged subjects, to whom a universal stereotactic space cannot be applied. © 1995 Wiley‐Liss, Inc.
Localization of semantic processing using functional magnetic resonance imaging
Authors: Shaywitz Bennett A. , Pugh Kenneth R. , Todd Constable R. , Shaywitz Sally E. , Bronen Richard A. , Fulbright Robert K. , Shankweiler Donald P. , Katz Leonard , Fletcher Jack M. , Skudlarski Pawel , Gore John C.
Published: December 2004

The relationship between the functional components of language and the anatomic foci of their neural systems represents a central issue in cognitive neuroscience. Conflicting results from a number of laboratories using positron emission tomography (PET) imaging techniques have led to a significant controversy over the specific neuroanatomic sites engaged by semantic processing. We report here results of an experiment designed to address this controversy, that is, whether semantic processing activates temporal and/or frontal brain regions. In this experiment we used cognitive tasks that emphasized either semantic or phonological information processing but that were similar on both memory search and responce generation components, together with functional magnetic resonance imaging, to examine the neuroanatomic loci of lexical‐semantic as opposed to phonological processing. We studied nine right‐handed men performing two silent generation tasks: rhyme, and semantic category. The former focuses on word form (phonological information) while the latter focuses on word meaning (semantic information). By “phonological” we mean the process of apprehending the sound structures of language. By “semantic” we mean information about the word's contextually specified meanings. Semantic processing makes demands on, and activates widespread areas within, brain including the inferior frontal regions bilaterally and the left posterior temporal region. Phonological processing engages a more restricted neuroanatomic assembly involving primarily anterior left temporal lobe sites. © 1995 Wiley‐Liss, Inc.
Identification of early visual evoked potential generators by retinotopic and topographic analyses
Authors: Clark Vincent P. , Fan Silu , Hillyard Steven A.
Published: December 2004

This study investigated the cortical sources of the early (50‐250 ms) components of the pattern‐onset visual evoked potential (VEP). VEPs were recorded in response to a small circular checkerboard stimulus that was flashed over a range of visual field positions. Temporally and spatially overlapping VEP components were distinguished by differences in retinotopic sensitivity and scalp topography, and by inverse dipole modeling. The C1 component (50‐80 ms) was found to change its polarity and topography systematically as a function of stimulus position in a manner consistent with the retinotopic organization of the striate cortex. The P1 component (comprised of the P75 and P100 subcomponents) had a time course that overlapped the C1 but could be distinguished from the C1 by its differing topography and reduced sensitivity to stimulus position. The P1 generators were localized to the lateral extrastriate cortex. Inverse dipole models were consistent with these striate and extrastriate source locations for the C1 and P1, respectively. The N1 component (120‐180 ms) was found to originate from several spatially distinct generators that differed in their retinotopic organization. © 1995 Wiley‐Liss, Inc.
Etudes sur les matières végétales volatiles XXIV. Composition de l'huile essentielle et du résinoïde de livèche (Levisticum officinale Koch)
Authors: Naves Y. R.
Published: December 2004

L'essence de raciune de livèche contient une forte proportion (environ 70%) de dérivés du phtalide parmi lesquels ont été décelés des n‐butylidène‐phtalides, le n‐butyl‐phtalide, l'anhydride sédanonique. La présence de n‐butyl‐dihydro‐phtalides ou de n‐butyl‐tétrahydro‐phtalides est vraisemblable.
Notice sur les variations de potentiel de l'électrode d'ozone et de l'électrode d'oxygène sous l'influence des radiations ultra‐violettes
Authors: Briner E. , Yalda A.
Published: December 2004

L'action des radiations ultra‐violettes diminue d'une manière marquée le potentiel de l'électrode d'ozone et accroît faiblement le potentiel de l'électrode d'oxygène.
Über die Cholin‐esterase des Gehirns und der Erythrocyten. zugleich 3. Mitteilung über die Beeinflussung von Fermentreaktionen durch Chemotherapeutica und Pharmaka
Authors: Zeller Ernst Albert , Bissegger Alfred
Published: December 2004

1. Die Serum‐ChE des Menschen wird durch Percain, Irgamid und Isopropyl‐antipyrin stark, die ChE von menschlichem Gehirn und Erythrocyten werden nur schwach gehemmt. Morphin hemmt alle drei ChE ungefähr gleich stark, Coffein nur die Serum‐ChE.
Metal Complexes with Macrocyclic Ligands. X. On the metal complexation kinetics of two N4‐macrocycles containing a pyridine ring
Authors: Schultz‐Grunow Philipp , Kaden Thomas A.
Published: December 2004

The complexation kinetics of the two macrocycles 1 and 2 with Co2+, Ni2+, Cu2+ and Zn2+ have been measured by pH‐stat techniques. The rates are first order in metal and ligand concentration and depend upon the pH. This results from the different reactivities of the various protonated species of the macrocyclic tetraamines. The resolved rate constants are given in Table 2.

In comparison with other 14‐membered cyclic aliphatic tetraazasystems 1 and 2 react more slowly with metal ions. This might be a consequence of the more rigid structure induced by the pyridine ring.
Inhaltsstoffe des Osmanthus‐Absolues. 4. Mitteilung: Megastigma‐5, 7 (E), 9‐trien‐4‐on und Megastigma‐5, 8 (E)‐dien‐4‐on
Authors: Kaiser Roman , Lamparsky Dietmar
Published: December 2004

Constituents of Osmanthus Absolute, 4th Communication. Megastigma‐5, 7 (E), 9‐triene‐4‐one and Megastigma‐5, 8 (E)‐diene‐4‐one

In continuation of our communications on constituents of Osmanthus absolute, we now report on the occurrence of the two title compounds 1 and 2a in this natural substrate (0.01‐0.02% each). Their structures were confirmed by synthesis starting from β‐ionone via the common intermediate 4‐oxo‐β‐ionol (9). Some further minor components bearing corresponding structural features are tabulated in view of possible biogenetic pathways leading to 1 or 2a, respectively.

In order to clarify the olfactory behaviour, we also synthesized some analogous derivatives in the irone series, these substances being not yet found in nature.
Competing Fragmentation, Substitution and Elimination in the Solvolysis of Alkylated 3‐Chloropropanols and their Ethers. Fragmentation reactions no. 28
Authors: Fischer Walter , Grob Cyril A.
Published: December 2004

The unstrained 3‐chloroalcohols 1a, 2a and 3a do not undergo solvolytic fragmentation in neutral and weakly acidic 80% ethanol, only substitution and elimination products being formed by the limiting SN1‐E1 mechanisms. This also applies to the corresponding ethers 1b and 3b. Addition of sodium hydroxide causes the observed rate constants for the 3‐chloroalcohols to rise steeply by factors of at least 103 to 105. These level off at higher base concentrations due to an opposing ionic strength effect. Whereas 3a fragments quantitatively in the presence of base, 1a and 2a fragment in competition with elimination to the Δ3‐olefins 9a and 10, respectively. 2a also yields 2% of the oxetane 6b.

These results support a concerted base‐induced fragmentation mechanism which competes with intramolecular base‐induced elimination (Ei) in the case of the acyclic chloroalcohols 1a and 2a. The formation of small amounts of the oxetane 6b from 2a is attributed to intramolecular nucleophilic substitution at the tertiary carbon atom.
Investigation of the Head‐Space of Roasted Meat II. Synthesis of substituted 2, 4, 5‐trithia‐hexanes
Authors: Dubs Paul , Stüssi Rita
Published: December 2004

Substituted 2, 4, 5‐trithiahexanes 1, a class of substances recently found in roasted meat, have been synthesized via two different routes.
Clark‐ähnlicher Wasserstoffdetektor
Authors: Grüniger Hans‐Rudolf , Sulzberger Barbara , Calzaferri Gion
Published: December 2004

Clark‐like Hydrogen Detector

A quantitative hydrogen detector, similar to the Clark oxygen electrode, has been proposed by Green et al. [1] in 1967. Such a detector gives a signal which is directly proportional to the hydrogen partial pressure without consuming any hydrogen itself. We have taken up the proposal of Green et al., and have realized a very sensitive and under many circumstances also a selective detector, which is easy to handle and which can be used in gaseous phase as well as in aqueous solution. Sensitivity of 0.1 Torr or even better can be achieved. The main differences to the Clark electrode are that a platinized platinum electrode has to be used instead of a blank platinum electrode and that a more positive potential has to be applied. We give a detailed description of the construction and the handling of the Clark‐like hydrogen detector.
Totalsynthese von (+)‐D‐Homo‐19‐nortestosteron
Authors: Gutzwiller Jürg , Labler Ludvik , Meier Werner , Fürst Andor , Eder Ulrich , Sauer Gerhard , Wiechert Rudolf
Published: December 2004

Total Synthesis of (+)‐D‐Homo‐19‐nortestosterone

A novel total synthesis of (+)‐D‐homo‐19‐nortestosterone (2) is described starting from (4a S, 5S)‐5‐(t‐butoxy)‐4a‐methyl‐4, 4a, 5, 6, 7, 7‐hexahydro‐3 H‐naphthalen‐2‐one (3) as a chiral building block for the rings C and D. The key step involves combining of the derived reactive one‐carbon atom adducts 5 and 6 with the β‐keto ester 16, a synthon for the rings A and B, to give the Δ9‐4, 5‐secosteroid 21. 21 was readily transformed to the title compound 2 by hydrogenation and subsequent ring closure. Hydrogenation of the derived 3, 5‐dione 22 followed by base‐catalyzed cyclization gave the 17a‐t‐butoxy compound 27 and the 9β, 10α‐D‐homosteroid 29 as by‐product.
Synthesis and properties of chiral macrotricyclic ligands. Complexation and transport of chiral molecular cations and anions
Authors: Lehn Jean‐Marie , Simon Jacques , Moradpour Alexandre
Published: December 2004

The optically active macrotricyclic cryptands1and2, containing the binaphthyl group as chiral unit, have been synthesized. These compounds contain lateral cavities which may serve as anchoring sites for polar groups of the substrates and a central, chiral cavity large enough for including more or les completely the bulk of a molecular ion. Their complexation properties towards molecular ions give evidence for the occurrence of two types of processes: (a) direct complexation of primary ammonium cations, like phenylethyl ammonium chloride, occurs with either1or2; (b) cascade binding, involving first complexation of an alkali cation followed by pairing with a molecular anion, takes place with2. Process (b) may be considered as ametallo‐receptormodel system where binding of an anionic substrate is dependent on initial binding of a cation. In both cases (a) and (b) weak resolution of chiral racemic substrates has been observed by extraction and transport (through a bulk liquid membrane) experiments. This indicates that in the complex the bulk of the substrate should be located close to the chiral unit and therefore more or less in the central cavity. In the case of cryptand2, the resolution achieved for the (±)‐mandelate anion is markedly affected by the nature of the complexed cation.
Synthese von 1, 3, 4‐Oxadiazolen und 4, 5‐Dihydro‐1, 2, 4‐triazinen aus 3‐Dimethylamino‐2, 2‐dimethyl‐2 H‐azirin und Carbohydraziden
Authors: Link Helmut
Published: December 2004

Synthesis of 1,3,4‐Oxadiazoles and 4,5‐Dihydro‐l,2,4‐triazines from 3‐Dimethylamino‐2,2‐dimethyl‐2 Hazirine and Carbohydrazides

3‐Dimethylamino‐2, 2‐dimethyl‐2 H‐azirine (1) reacts with aromatic carbohydrazides to give 2‐(1‐amino‐1‐methylethyl)‐5‐aryl‐1, 3, 4‐oxadiazoles (7, 10, 11). With ethyl carbazate the azirine 1 forms the aminoester 15, which is easily cyclized to the 4, 5‐dihydro‐1, 2, 4‐triazin‐3 (2H)‐one 16. From the reaction of 1 with oxamohydrazide (17) and oxalodihydrazide 19 the 4, 5‐dihydro‐1, 2, 4‐triazin‐3‐carboxamide 18 and the symmetric compound 20, respectively, have been isolated. Reactions supporting the structures of the new compounds are described.
«Push‐Pull»‐Acetylene als Hilfsmittel zur Synthese von Amiden
Authors: Neuenschwander Markus , Lienhard Ulrich , Fahrni Hans‐Peter , Hurni Beat
Published: December 2004

Amide Synthesis by Means of ‘Push‐Pull’‐Acetylenes

‘Push‐Pull’‐acetylenes react easily with carbon acids, Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one‐pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, ‘push‐pull’‐acetylenes could be excellent reagents for peptide synthesis.
«Push‐Pull»‐Acetylene als Hilfsmittel zur Synthese von Peptiden
Authors: Neuenschwander Markus , Fahrni Hans‐Peter , Lienhard Ulrich
Published: December 2004

Peptide synthesis by Means of ‘Push‐Pull’‐Acetylenes

‘Push‐pull’‐acetylenes 1 are excellent reagents for peptide synthesis: Addition of ‘push‐pull’‐acetylenes to solutions of N‐protected amino acids (or vice versa) gives enol esters 5, which react selectively with the amino function of a second amino acid. In this way serine, tyrosine, 4‐hydroxyproline, cysteine as well as histidine are linked to form dipeptide esters without protection of the second functional group (OH, SH or NH). The amount of racemization is very low. Similarly tri‐ as well as tetrapeptides are available. The versatility of the reaction is discussed.
Über die Synthese von 1‐Aryl‐und 1‐Alkyl‐2, 3‐dimethyl‐chinoxalinium‐perchloraten. 2. Mitteilung. Synthese und 1H‐NMR.‐Spektren von 2,3‐Dimethyl‐1‐phenyl‐6‐X‐chinoxalinium‐perchloraten
Authors: Schelz Dieter
Published: December 2004

On the Synthesis of 1‐Aryl‐ and‐1‐Alkyl‐2, 3‐dimethyl‐quinoxalinium Perchlorates. 2nd Communication

1. Mitt.: [1].

. Synthesis and
1
H‐NMR.
Spectra of 2, 3‐Dimethyl‐1‐phenyl‐6‐X‐quinoxlinium Perchlorates

The synthesis of the title compounds (5) which have been useful as precursors for a lot of conventional and new‐type dyes [2‐8] has yet been limited to examples with XH [2] [3] [11] [15] and with electron‐donating [4] [12] or at best slightly electron‐accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron‐accepting substituents: N‐monosubstituted o‐phenylendiamines 4, were condensed with 2, 3‐butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products ‐ mostly substituted at position 6 of the quinoxalinium ring ‐ are chracterized by 1H‐NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6. Correlations of chemical shifts with Hammett's σp [18] are given by equations (1)‐(5).
Allylic Reactions of Benzocyclopropenes. Discrimination of halogen substituents in 1, 1‐Dihalogenobenzocyclopropenes
Authors: Müller Paul , Etienne Robert , Pfyffer Jean , Pineda Nelson , Schipoff Michel
Published: December 2004

Reaction of 1, 1‐dichloro‐2, 5‐diphenylbenzocyclopropene (10a) with 1 equiv. of silver fluoride yields 1‐chloro‐1‐fluoro‐2, 5‐diphenylbenzocyclopropene (10c). Both 10a and 10c react with excess silver fluoride to give the difluoro compound 10b. Both 10b and 10c are also prepared via cyclo‐additions of 1, 2‐dichloro‐3, 3‐difluorocyclopropene (14) or 1, 2, 3‐flurocyclopropene (13) with diphenylbutadiene and subsequent aromatization with base. Similarly. 1‐chloro‐1‐fluorobenzocyclopropene (16) is accessible from butadiene and 13.
Studies on Radical Cations I. Molecular and electronic structure of [3]radialene cation produced by γ‐irradiation in condensed phase
Authors: Bally Thomas , Haselbach Edwin , Lanyiova Zuzana , Baertschi Peter
Published: December 2004

γ‐Irradiation of tris (methylidene)‐cyclopropane (‘[3]radialene’) 1 in a rigid electron scavenging matrix (butylchoride/i‐pentane, 1:1) at 77 K leads to formation of its molecular cation 1+. Slight softening of the matrix by a temperature increase of 3–5 K results in formation of a newly absorbing species, tentatively assigned arising from structrral relaxation of 1+ by π‐bond rotation: magnified image
2‐Stannyl‐1, 3‐dithiane Herstellung, Sn/Li‐Transmetallierung und Verwendung für Cyclisierungen
Authors: Seebach Dieter , Willert Ingrid , Beck Albert K. , Gröbel Bengt‐Thomas
Published: December 2004

2‐Stannyl‐1,3‐dithianes. Preparation, Sn/Li‐Transmetallation, and Use for Cyclizations

In order to test the possibility of generating nucleophilic 2‐lithio‐1, 3‐dithiane centers in the presence of electrophilic groups in the same molecule, the stannylated dithianes 1‐3 were prepared or generated. Solutions of the lithio derivatives 2a and 2b could either be obtained by metallation of 1 with lithiumdiisopropylamide (LDA) or by transmetallation of 3 with alkyllithium reagents. Alkylations of 2 led to the alkyl‐stannyl‐dithianes 4‐7. Additions of the trimethylstannylated lithiodithiane 2a to aldehydes and ketones at low temperature led ‐ after hydrolysis ‐ to the adduct alcohols 8; warming up to room temperature before hydrolysis furnished keten thioacetals 9 only with acetone (→ 9b) and cyclohexanone (→ 9c) as carbonyl component, while still the simple adducts 8a and 8d were isolated with benzaldehyde and cyclohexenone, respectively. Methyl benzoate and benzoic acid anhydride reacted with 2a to produce the tin‐free derivatives 12 and 14, respectively.

It is shown that the Sn/Li‐exchange at the 2‐position of dithianes 4‐7, 15 and 16 takes place within minutes at −78°, whereas H/Li‐metallation does not occur at all at this temperature. In situ preparation of the cyclization products 17‐19 from halo‐epoxides is described. The overall yields of Sn/Li‐exchange (3 → 2), epoxyalkylation (2 → 15 and 16, repectively), Sn/Li‐exchange in 15and 16, cyclization (→ 17–19) are twice as high (up to 80%) with the tributylin than with the trimethyltin derivatives. The intramolecular 1, 3 nucleophilic reaction 20a → 17 is complete within 5 min at −78°. The total yields of cyclization products by the tin route (3b → 16 → 20b → 18 + 19) and by direct metallation (1, 3‐dithiane →21b → 20b → 18 + 19) are 63 and 30%, respectively.
An Efficient Synthesis of Methyl (±)‐Jasmonate and (Z)‐Jasmone
Authors: Näf Ferdinand , Decorzant René
Published: December 2004

An efficient synthesis of methyl (±)‐jasmonate and (Z)‐jasmone is described. The Key step is a phase‐transfer reaction between cyclopentane (9) and 1, 4‐dibromo‐2‐pentene (6a/b) to give the spiro [2.4]hepten‐4‐ones 4a and 4b.
Claisen‐Umlagerung von 2‐Propinyl‐(3‐pyridyl)‐und Allyl‐(3‐pyridyl)äthern
Authors: Bruhn Jens , Zsindely Janos , Schmid Hans , Fráter György
Published: December 2004

Claisen Rearrangement of 2‐Propinyl (3‐Pyridyl) and Allyl (3‐Pyridyl) Ethers

Verbindungen vom Typ 1 werden mit Ausnahme von 17 und 25 als Äther benannt. Der systematische Name von 1 ist: 3‐(2‐Propinyl)oxy‐pyridin.

2‐Propinyl (3‐pyridyl) ether (1), synthesized from the corresponding 3‐pyridinol, was heated in DMF or decane at 208° in a sealed tube. In this way the furopyridines 2 and 3 were formed, and furthermore the pyranopyridine 4 if decane was used as solvent (Scheme 1). The same reactions took place with (2‐methyl‐3‐pyridyl) 2‐propinyl ether (14). In DMF only 15, and in decane 16 as well as 15 were formed (Scheme 3). The rearrangement of the pyridine derivative 17, which is substituted in both O‐positions to the ether moiety, gave in both DMF and decane the diastereoisomeric tetracyclic compounds 18 and 19. The same kind of reaction took place with 25 (Scheme 4).

In the thermolysis of the allyl 3‐pyridyl ether (27) cyclization was observed, too. The isolated product has the structure of the dihydrofuropyridine 28 (Scheme 6). The substituted allyl 3‐pyridyl ether 30 reacted in the same way to the dihydrofuropyridine 31 (Scheme 6).
Cob(I)alamin als Katalysator. 1. Mitteilung. Reduktion von gesättigten Nitrilen in wässeriger Lösung
Authors: Fischli Albert
Published: December 2004

Co(I)alamin as Catalyst. 1. Communication. Reduction of Saturated Nitriles in Aqueous Solution

Using cob(I)alamin as homogeneous catalyst in the presence of aqueous acetic acid saturated nitriles 5a–m are reduced to the corresponding aldehydes 6a–m in good yields. A possible reaction mechanism for this reduction is discussed.
Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1‐ (3′‐O‐Phosphoryl‐2′‐deoxy‐β ‐D‐ribofuranosyl)‐2(1H)‐pyridone‐(3′‐5′)‐1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐2 (1H)‐pyridone
Authors: Cerletti Nico , Séquin Urs , Tamm Christoph , Zürcher Werner
Published: December 2004

The dinucleoside phosphate ΠdpΠd (4) was synthesized from the monomers 1‐(5′‐O‐monomethoxytrityl ‐ 2′ ‐ deoxy ‐ β ‐ D ‐ ribofuranosyl) ‐ 2 (1 H) ‐ pyridone ((MeOTr) Πd, 2) and 1‐(5′‐O‐phosphoryl‐3′‐O‐acetyl‐2′‐deoxy‐β‐D‐ribofuranosyl)‐(1H)‐pyridone (pΠd(Ac), 3). Its 6.4% hyperchromicity and an analysis of the 1H‐NMR. spectra indicate that the conformation and the base‐base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.
13C‐NMR. Spectra of 4‐Substituted Quinuclidines. Polar effects, Part V
Authors: Becker Konrad B. , Grob Cyril A.
Published: December 2004

13C‐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‐carotene

The 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

Photoisomerization 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 Diastereoisomers

Shyobunon (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′‐deoxybiopterine

We 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 acid

In 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 Nucleosides

Condensation 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‐lycopene

The 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‐cyclohexanecarboxylate

In 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.
Oxidation Products of Retinylidene Dimedone
Authors: Acton Nancy , Brossi Arnold
Published: December 2004

Several oxidation products of the retinoid retinylidene dimedone (RD) have been synthesized and characterized for biological testing in the expectation that they may be found as metabolites of RD.
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]decane

A 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 Units

The 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 acid

The 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

Oxygenation 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 Ketones

On 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‐thiophenecarboxanilides

Upon 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

Following 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

The 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

The 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

Chemical 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

The 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

Hydrogen 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 Group

Treated 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

A 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 Ligands

The 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

The 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

Thermal 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 Analogues

The 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‐Methylpterin

The 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.