bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die stereoisomeren Sinensiaxanthine und Sinensiachrome: Trennung und Bestimmung ihrer absoluten Konfiguration. 7. Mitteilung über Rosenfarbstoffe
Authors: Märki‐Fischer Edith , Eugster Conrad Hans 
Published: December 2004

Stereoisomeric Sinensiaxanthins and Sinensiachromes: Separation and Absolute ConfigurationThe so‐called sinensiaxanthins and sinensiachromes, important apocarotenols from various fruits, have been separated into 2 and 4 stereoisomers, respectively, and their absolute configurations have been determined: (3S,5R,6S)‐5,6‐epoxy‐5,6‐dihydro‐10′‐apo‐β‐carotene‐3,10′‐diol (2), its (9Z)‐stereoisomer 7, the (8R)‐ and (8S)‐epimers of (3S, 5R)‐5,8‐epoxy‐5,8‐dihydro‐ 10′ ‐apo‐β‐carotene‐3, 10′‐diol (4 and 5), and their (9Z)‐stereoisomers 3 and probably 6. Thus, sinensiaxanthins are cleavage products from (Z/E)‐isomeric antheraxanthins or violaxanthins (scission at C(9′)–C(10′)) and sinensiachromes analogously from mutatoxanthins or auroxanthins.
17O‐NMR Spectra of Mesoionic Compounds: The polarized carbonyl group
Authors: Dahn Hans , Ung‐Truong My‐Ngoc 
Published: December 2004

AbstractThe 17O‐NMR spectra of 5 mesoionic compounds have been measured; in two cases, the peak attribution between endo‐ and exocyclic O‐atoms has been made unambiguous by synthesizing specifically O‐labelled samples. The signal of the exocyclic O‐atom appears at particularly high field, closer to the values of enolate than of carbonyl O‐atoms. The cyclic O‐atom resonates close to values of furans (or isoxazol, if bound to N). The exocyclic O‐atom is much more susceptible to structure and substituent variations than the endocyclic, an observation which is in favour of a chain‐conjugated (non‐aromatic) structure 1E.
Synthesis of New Sialidase Inhibitors, 6‐Amino‐6‐Deoxysialic Acids
Authors: Baumberger Franz , Vasella Andrea , Schauer Roland 
Published: December 2004

AbstractThe synthesis of the 6‐amino‐6‐deoxysialic‐acid analogues 4, 5, and 6, is described. Mitsunobu reaction of the 1‐C‐nitroglycal 8, (PPh3, HCOOH, DEAD) gave the formiate 10 with inversion of configuration at C(3) (Scheme 2). Treatment of 10 with aq. NH3 and subsequent protection of the amino function gave the imines 14 and 15 (Scheme 3), which were transformed into the triflates 17. Substitution by azide, deprotection, and N‐acetylation gave the anormeric 2‐acetamido‐3‐azido‐1‐deoxy‐1‐nitro‐D‐mannoses 16 and the enol ether 18. Chain elongation of the nitro azides 16 followed by hydroylsis gave the nonulosonates 20/22, which upon reduction yielded the diols 23 and 24, respectively (Scheme 4). The diol 23 was transformed into the sialic‐acid analogues 5, 6, and 32 by ozonolysis, transfer hydrogenation, hydorgenolysis, and deprotection (Scheme 5), and the diol 24 into 4 by a similar reaction sequence. The sialic‐acid analogues 4 and 6 inhibit bacterial and viral sialidases competitively. The inbibitor constants for this enzyme from Vibrio cholerae are 0.12 mm for 4 and 0.19 mm for 6, respectively. The activity of fowl plague virus sialidase was reduced by 17% and 36% under the influence of 4 and 6, respectively, at a concentration of 0.1 mM. Compound 5 was inactive.
Slowly Interconverting Conformers of The Briarane Diterpenoids Verecynarmin B, C, and D, Isolated from the nudibranch mollusc Armina maculata and the pennatulacean octocoral Veretillum cynomorium of East Pyrenean waters
Authors: Guerriero Antonio , D'Ambrosio Michele , Pietra Francesco 
Published: December 2004

AbstractThe novel briarane diterpenoids verecynarmin B(=(−)‐(1R*, 10S*, 11R*, 4E, 12Z)‐briara‐4,7,12,17,‐tetraen‐14‐one; (−)‐4); verecynarmin C (=(−)‐(1R*, 10R*, 11S*, 4E, 12Z)−11‐hydroxybriara‐4,7,12,17‐tetraen‐14‐one; (−)‐5); and verecynarmin D (=(−)‐(1R*, 10R*, 11R*, 4E, 12E)‐13‐chloro‐11‐hydroxybriara‐4,7,12,17,‐tetraen‐14‐one; (−)‐6) are reported here as constituents of both the Mediterranean nudibranch mollusc Armina maculata (Rafinesque) and its prey, the pennatulacean octocoral Veretillum cynomorium (PALLAS). The structural assignments rest mainly on (i) establishing that these briaranes occur in solution as two stable conformers which interconvert slowly (ca. 10 time per second at r.t. according to dynamic NMR) by 180° flipping of the C(4)C(5) group in the ten‐membered ring (Scheme 1), (ii) deriving, for both conformers, 1H, 1H coupling constants from 1D spectra, as well as 1H, 1H, 13C, 1H, and 13C, 1H, and 13C, 13C, correlations from 2D experiments; (iii) subjecting the briaranes to SeO2 oxidation at the C(16) methyl group with isomerization at the C(4)=C(5) bond to give, in each case, only one observable molecular species as shown by NMR spectroscopy (Scheme 2).
15N‐Markiertes 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin zur mechanistischen Untersuchung von Reaktionen mit NH‐aciden Heterocyclen
Authors: Ametamey Simon M. , Hollenstein Roger , Heimgartner Heinz 
Published: December 2004

15N‐Labelled 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine for Mechanistic Studies of Reactions with NH‐Acidic HeterocyclesThe synthesis of 3‐(dimethylamino)‐2,2‐dimethyl(1‐15N)‐2H‐azirine (1*) was accomplished via reaction of 1‐chloro‐N,N,2‐trimethyl‐1‐propenylamine (9) and sodium (1‐15N) azide (Scheme 3). The earlier reported reactions of 1 with saccharin (10, Scheme 4), phthalimide (12, Scheme 5), and 2H‐1,3‐benzoxazin‐2,4(3H)‐dione (16, Scheme 6) were repeated with 1*, and the position of the 15N‐label in the products was determined by 15N‐NMR spectroscopy. Whereas the postulated reaction mechanisms for 10 and 12 were confirmed by these experiments, the mechanism for the reaction of 16 had to be revised. With respect to the position of 15N in the products 17 and 18, a new mechanism is formulated in Scheme 7. Treatment of 5,5‐dimethyl‐1,3‐oxazolidine‐2,4‐dione (19) with 1* led to 3,4‐dihydro‐2H‐imidazol‐2‐on 20 in which only N(3) was labelled. The mechanism of a ring expansion and transannular ring contraction as shown in Scheme 8 is in agreement with this finding.
Novel Aplysinopsin‐Type Alkaloids from Scleractinian Corals of the Family Dendrophylliidae of the Mediterranean and the Philippines. Configurational‐assignment criteria, stereospecific synthesis, and photoisomerization
Authors: Guella Graziano , Mancini Ines , Zibrowius Helmut , Pietra Francesco 
Published: December 2004

AbstractFrom the scleractinian coral Tubastraea sp. (Dendrophylliidae) collected at Palawan, Philippines, 3′‐deimino‐3′‐oxoaplysinopsin (4) and 6‐bromo‐3′‐deimino‐3′‐oxoaplysinopsin (6) are now isolated as 5:2 mixtures of (E/Z) stereoisomers. The 3′‐deimino‐2′,4′‐bis(demethyl)‐3′‐oxoaplysinopsin (7) and 6‐bromo‐3′‐demino‐2′,4‐bis(demethyl)‐3′‐oxoaplysinopsin (5) are isolated as 2:3 and 1:1 (E/Z) mixtures, respectively, from another dendrophylliid, Leptopsammia pruvoti, collected near Marseille, Mediterranean coast of France. Larger amounts of these and related compounds, needed for a full structural determination, are obtained by synthesis. Thus, condensations of indol‐3‐carboxaldehyde (9) or of its 6‐bromo derivative 14 with hydantoin (15), 3‐methylhydantoin (11), or 1,3dimethylhydantoin (10) give the prevalent natural aplysinopsins with high stereospecificity. The minor stereoisomers (Z)‐4, (Z)‐6, (E)‐7, and (E)‐5 are obtained by (E/Z) photoisomerization under UV light of the condensation mixtures. The configuration is assigned from larger HC(8)/C(5′) 1H, 13C couplings in the (E) than in the (Z) isomer, and, in the case of 4 and 6, from NOE enhancement at MeN(2′) on irradiation at HC(8). The stereospecificity of the condensations is attributed to steric inhibition to planarity in the rate‐limiting transition states, due to N(2′)/HC(2) repulsion with (Z)‐4 and (Z)‐6, or to C(5′)O/HC(2) repulsion with (E)–7 or (E)‐5. As the aplysinopsins undergo (E/Z ) phostoisomerization also under the daylight conditions of the laboratory, their isomeric composition in nature can not be presently assessed.
Stereospecific Synthesis of 2‐Oxazinyl‐4‐oxoazetidinecarbamates Starting from a 1,2‐Diazepine. A new type of intramolecular transbenzoylation
Authors: Fritz Hans , Henlin Jean‐Michel , Tschamber Théophile , Streith Jacques , Riesen Andreas , Zehnder Margareta 
Published: December 2004

AbstractAzeitidinodiazepines4band4creact with acylnitroso dienophiles5a–c, specifically from their convexe α‐side, but in a non‐regiospecific way, leading thereby stereospecifically to the expected adducts6a–dand7a–d. The three‐dimensional structures of6aand7awere determined by X‐ray analyses which corroborated their NMR data. OsO4cis‐glycolization occurred in good yield with the inverse adducts7aand7eand led to the rearranged products10. These latter ones result from an intramolecular N‐ to O‐transbenzoylation of the short‐lived intermediates9followed by fragmentation of the animal function. X‐Ray analysis of7ashowed the N(10) atom to be pyramidal, a result which demonstrates that it does not have any pronounced benzamide character; otherwise no such N‐ to O‐transbenzoylation would have taken place. Structure and relative configuration of10awere ascertained by X‐ray analysis which confirmed its NMR data as well as the stereochemical outcome of its formation.
Aldehyde Enol Esters as Novel Chain Terminators in Cationic Olefin Cyclizations
Authors: Simmons Dana P. , Reichlin Daniel , Skuy David 
Published: December 2004

AbstractCitronella (1) has been transformed into enol acetates 2 which have been cyclized with various Lewis and Brönsted acids to dihydrocyclocitral (4). Application of this methodology to the synthesis of mono‐ and bicyclic ring systems has been examined.
Synthesis of Ethyl (2RS,3SR)‐1‐Tosyl‐3‐Vinylazetidine‐2‐carboxylate and ethyl (2RS,E)‐3‐ethylidene‐1‐tosylazetidine‐2‐carboxylate (=rac‐ethyl N‐tosylpolyximate)
Authors: Bauman Hans , Duthaler Rudolf O. 
Published: December 2004

AbstractThe synthesis of 3‐ethylideneazetidine‐2‐carboxylic acid (=polyoximic acid; 3) is a approached in two different ways leading to potential precursors of 3. The first way involved a ring closure to a vinyl‐subsatituted azetidin. Thus, Ireland‐Claisen rearrangement of the Boc‐glycinates 6 and 10 of (Z)‐ and (E)‐2‐butene‐1,4‐diol afforded, after exchange of the N‐protecting groups, the isomeric 2‐(tosylamino)‐3‐vinylbutanolides 13 and 14 with high stereoselectivity. Only the cis‐isomer 14 could be further transformed to 3‐(bromomethyl)‐2‐(tosylamino)‐4‐pentenoate 17, and in a smoth cyclization with K2CO3, to trans‐3‐vinylazetidtene‐2‐carboxylaze 18 (Scheme 2). In the second approach, the 3‐ethylidene isomer 19 of 18 was obtained more directly by a [2+2] cycloaddition, together with the two isomers 23 and 24, from methlallene 20 and (tosyliminno)acetate 21 (Scheme 3). The main product of this reaction was, however, 2‐(tosylamino)‐4‐hexinoate 22, the product of an ene reaction.
Acid‐Catalyzed Rearrangements for a Diastereoselective Entry into a New Fused Hexacyclic Heterocycle: (5RS,7aRS,12RS,14aRS,)‐4,5,7a,11,12,14,14a‐octahydro‐5,12‐dimethyl‐diindolo [1,7‐bc: 1′,7′‐gh][2,6] naphthyridine
Authors: Papageorgiou Christos , Borer Xaver 
Published: December 2004

AbstractThe title compound 1 was obtained in 10.3% overall yield via two acid‐catalyzed rearrangements and pyrrolidine formation. Thus, bi‐oxindole 6 afforded exclusively the thermodynamically stable cis‐diazachrysene 7 which, after allylation, followed by aza‐Claisen rearrangement gave alcohol 2. Pyrolytic ring closure of the latter yielded 1 in highly diastereoselective fashion.
Tandem cheletropic additions of sulfur dioxide to [2.2.2]hericene. The ‘barrelene effect’
Authors: Birbaum Jean‐Luc , Vogel Pierre 
Published: December 2004

AbstractAt 20°, [2.2.2]hericene ( = 2,3,5,6,7,8‐hexamethylidenebicyclo[2.2.2]octane;1) adds 2 equiv. of SO2 to give successively mono‐sulfolene 13 and the bis‐sulfolene 14 (for thermodynamic and kinetic data, see Tables 1 and 2). Under forcing conditions (high concentration, long reaction time), no trace of tris‐sulfolene 15 could be detected. The inertia of bis‐sulfolene 14 is attributed to the ‘barrelene effect’ which destabilizes the tris‐sulfolene 15.
Efficient Synthesis of 1,2‐Bis(2,2′‐bipyridinyl)ethane and 1,2‐bis(1,10‐phenanthrolinyl)ethane ligands by oxidative coupling of the corresponding monomeric methylene carbanions
Authors: Lehn Jean‐Marie , Ziessel Raymond 
Published: December 2004

AbstractSeveral dimeric 1,2‐bis (2,2′‐bipyridinyl)ethane (1,2,6,7, and 9 and 1,2‐bis(1,10‐phenanthrolinyl)) ethane (3,4, and 5) ligands have been synthesized in high yield by oxidative coupling of the corresponding monomeric methylene carbanions using as oxidating agents Br2, I2, and 1,2‐dibromoethane. The structure of the compounds obtained from three tetramethyl‐2,2′‐bipyridines and one tetramethyl‐1,10‐phenanthroline have been assigned on the basis of their 1H‐NMR spectra. The electronic absorption and emission properties of these new ligands are reported. They display intense fluorescence spectra.
Synthese der Spermidin‐Alkaloide (±)‐Inandenin‐10‐ol, Inandenin‐10‐on und (±)‐Oncinotin
Authors: Bienz Stefan , Guggisberg Armin , Wälchli Rudolf , Hesse Manfred 
Published: December 2004

Syntheses of the Spermidine Alkaloids (±)‐Inandenin‐10‐ol, Inandenin‐10‐one, and (±)‐OncinotineNew syntheses of the title compounds using two‐ring‐enlargement reactions are described. Starting from the aldehyde 1, the corresponding 4′‐aza derivative 15 could be obtained by reductive amination with the appropriate and protected spermidine derivative 14 (Scheme 4). Enlargement of the carbocyclic ring in 15 by five members gave, after further transformations, the hydroxylactam 18. Transamidation of 18, the second ring‐enlargement step, led to (±)‐inandenin‐10‐ol (7;22.9% overall yield) and, after oxidation, to inandenin‐10‐one (8; 22.5%, overall yield). (±)‐Oncinotine 6 was synthesized by two pathways (Scheme 6): protection of the terminal NH2 group by treatment with the Nefkens reagent and replacement of the OH group by Cl gave 24, which by thermal transamidation followed by direct ring closure led to the oncinotine derivative 26. The same intermediate could be obtained in higher yield via 28 by oxidation and protection of 18 followed by transamidation and reductive ring closure. Treatment of 26 with hydrazine finally gave (±)‐oncinotine 6 in 15.9% overall yield.
Synthese des Flechtenmakrolids (+)‐Aspicilin mit Photolactonisierung als Schlüsselreaktion
Authors: Quinkert Gerhard , Heim Nana , Glenneberg Jürgen , Döller Uwe , Eichhorn Mathias , Billhardt Uta‐Maria , Schwarz Christine , Zimmermann Gottfried , Bats Jan W. , Dürner Gerd 
Published: December 2004

Synthesis of the Lichen Macrolide (+)‐Aspicilin Using Photolactonization as a Key Reaction(+)‐Aspicilin, obtained from a lichen source of the Black Forest, has been proven to have the absolute configuration depicted by formula la. It is easily built up from phenol (14a), 1,9‐nonanediol (13a), and (−)‐(S‐) methyloxiarane (6) (cf. Scheme 2). The latter building block provides the first stereogenic center C(17). The heterocycle is produced by photolactonization, fairly early during the course of the synthesis. The second stereogenic center is generated diastereoselectively at C(6) in compound 8, conveniently available from photolactone 9a or 9b/9c. Its absolute configuration depends on the kind of reducing agent and is controlled by long‐range conformational transmission of chiral information. To explore the cause of stereoselection, 2D‐NMR spectroscopy, X‐ray structural analysis, and/or computer‐aided conformational search followed by energy minimization have been used extensively, revealing the importance of the local conformation of the lactone moiety. Compound 8, on treatment with Yamamoto's reagent, affords pre‐target compound 7a almost exclusively. The latter compound, on pyridine‐accelerated dihydroxylation with OsO4, gives preferentially (+)‐Aspicilin.
The Structure of the Polycyclic Nonadecapeptide Ro 09‐0198
Authors: Kessler Horst , Steuernagel Stefan , Will Martin , Jung Günther , Kellner Roland , Gillessen Dieter , Kamiyama Tsutomu 
Published: December 2004

AbstractThe conventional determination of the amino‐acid sequence of the peptide antibiotic Ro 09‐0198 was prevented by four cyclizations via side chains. The joint application of NMR spectroscopy at highest field and automated Edman degradation yielded a complete determination of the connectivity pattern. The three‐dimensional structure derived from NOE data exhibits an interesting separation of amino acids with hydrophilic and hydrophobic side chains.
The Reaction Volume for the Equilibrium between the Lanthanide (III) ennea‐ and octaaqua lons as a diagnostic aid for their water‐exchange mechanisms. Preliminary Communication
Authors: Laurenezy Gabor , Merbach André E. 
Published: December 2004

AbstractThe equilibrium between [Ce(H2O)9]3+ and [Ce(H2O)8]3+ has been followed in aqueous solution at 298 K by variable‐pressure UV spectroscopy at 295 nm. The dervied volume of reaction for the dissociation of this enneaaqua ion is ΔV0 = +10.9 cm3. mol−1. This value, together with the previously determined activation volume, ΔV≠ = −6 cm3. mol−1, for H2O exchange on [Ln(H2O)8]3+ (Ln = Tb to Tm), allows the assignment of an associative interchange Ia mechanism on these octaaqua ions.
Bathophenanthroline‐ruthenium(II) complexes as non‐radioactive labels for oligonucleotides which can be measured by time‐resolved fluorescence techniques
Authors: Bannwarth Willi , Schmidt Dieter , Stallard Robert L. , Hornung Claudia , Knorr Reinhard , Müller Francis 
Published: December 2004

AbstractThe specific attachment of bathophenanthroline‐ruthenium(II) complexes as non‐radioactive label molecules to synthetically 5′‐NH2‐modified oligonucleotides is described. After excitation by light pulses, the fluorescence of these labels can be measured by a time‐resolved mode woth high sensitivity. No quenching takes place due to coupling of the Ru complexes to the DNA. Ru‐complex‐labelled oligonucleotides still hybridize specifically to complementary DNA sequences, and no quenching is observed in the course of the hybridization process.
Crystal Structure and Electron‐Density Distribution of Two [1.1.1] Propellane Derivatives at 81 K
Authors: Seiler Paul , Belzner Johannes , Bunz Uwe , Szeimies Günter 
Published: December 2004

AbstractThe molecular structure and electron‐density distribution of two [1.1.1]propellane derivatives have been determined from accurate single‐crystal X‐ray diffraction measurements at 81 K. The crystals of these highly reactive compounds (both are liquid at room temperature) were grown directly on the X‐ray diffractometer at ca. 208 and 228 K, respectively. Both compounds crystallize in the space group P21/c with one molecule in the asymmetric unit. The symmetry of the propellane C‐atom skeleton is close to D3h for both molecules. The distances between the two bridgehead C‐atoms are 1.587 and 1.585 Å, and the mean lengths of the propellane side bonds are 1.525 and 1.528 Å, respectively. The deformation density peaks of the propellane side bonds (ca. 0.25 e/Å3) lie somewhat outside the internuclear connection lines and so correspond to ‘bent bonds’ as expected. On the other hand, the difference electron density between the bridgehead nuclei is slightly negative in both molecules. An interesting feature, observed in these difference maps, is presence of a diffuse, positive difference density at each inverted C‐atom, outside the bridgehead bond, a probable site of electrophilic attack.
Photochemistry of Thiophen‐2(5H)‐ones
Authors: Kiesewetter René , Margaretha Paul 
Published: December 2004

AbstractMechanistic evidence for the light‐induced ring opening of thiophen‐2(5H)‐ones 1 in alcohols affording α, β‐unsaturated mercapto esters 2 is presented. Regio‐and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S‐heterocycles 16 and 18, of 3‐thiahex‐5‐enyl radicals 4 to (tetrahydrothien‐3‐yl)methyl radicals 6 and of (2,3‐dihydrothien‐3‐yl)methyl radicals 30 (type 7, but‐3‐enyl radicals) to cyclopropane‐methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3‐dimethylbut‐2‐ene affords [2 + 2] cycloadducts 14 albeit in very low yields.
A New Method for the Preparation of (E)‐3‐Acylprop‐2‐enoic Acids
Authors: Obrecht Daniel , Weiss Bettina 
Published: December 2004

AbstractA new method for the preparation of (E)‐3‐acylprop‐2‐enoic acids ( = (E)‐3‐acylacrylic acids) of type II via acid‐catalyzed isomerization of the corresponding 3‐acylprop‐2‐ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.
Biosynthesis of Homoterpenes in Higher Plants
Authors: Boland Wilheim , Gäbler Andreas 
Published: December 2004

AbstractIn higher plants, the two homoterpenes 4,8‐dimethyinona‐1,3,7‐triene (1) and 4,8,12‐trimethyltrideca‐1,3,7,11‐tetraene (2) are synthesized from the regular terpene alcohols nerolidol and geranyllinalool by fragmentation into the homoterpene and butenone. The biosynthetic pathway is evidenced by conversion of (2H)nerolidol in Hoya purpureo‐fusca, Magnolia liliiflora nigra, Robinia pseudoacacia, and Philadelphus coronarius.
Isotope Effects on the Lipophilicity of Deuterated Caffeines
Authors: Bechalany Antoine , El Tayar Nabil , Carrupt Pierre‐Alain , Testa Bernard , Falconnet Jean‐Bernard , Cherrah Yahia , Benchekroun Youssef , Brazier Jean‐Louis 
Published: December 2004

AbstractIn the present study, it is confirmed that the deuteration of CH groups is accompanied by a small but genuine decrease in lipophilicity. The lipophilicity of deuterated isotopomers of caffeine was measured by reversed‐phase HPLC. Overall, lipophilicity was shown to decrease when going from unlabelled caffeine to the three isomeric trideuterated caffeines, then to the three isomeric hexadeuterated caffeines, and finally to nonadeuterated caffeine. In addition, position‐specific effects were also proven. E.g. (7‐methyl‐2H3)caffeine experienced a smaller isotope effect than its two positional isomers. Both a cavity factor (decreased volume of deuterated isotopomers) and intramolecular electronic effects are postulated to operate.
Synthese von (R)‐β, β‐Carotin‐2‐ol und (2R, 2′R)‐β, β‐Carotin‐2,2′‐diol
Authors: Gut Samuel , Wolleb Heinz , Pfander Hanspeter 
Published: December 2004

Synthesis of (R)‐β, β‐Caroten‐2‐ol and (2R, 2′R)‐β, β‐Carotene‐2,2′‐diolStarting from geraniol, the two carotenoids (R)‐β, β‐caroten‐2‐ol (1) and (2R, 2′R)‐β, β‐carotene‐2,2′‐diol (3) were synthesized. The optically active cyclic building block was obtained by an acid‐catalysed cyclisation of the epoxide (R)‐4. The enantiomeric excess of the product was > 95 %.
A Regiospecific Photochemical Rearrangement of 2‐Azabenzotricyclo[5.2.2.01,5]‐ to 2‐Azabenzotricyclo[6.2.1.01,5]undecatrienone
Authors: Trifonov Latchezar S. , Dimitrov Valentin S. , Orahovats Alexander S. 
Published: December 2004

AbstractThe 2‐azatricyclo[5.2.2.01,5]undeca‐4,8,10‐trien‐3‐ones 1a and 1b gave on irradiation the 2‐azatricyclo‐[6.2.1.01,5]undeca‐4,6,9‐trien‐3‐ones 2a and 2b, respectively. The rearrangement was found to be solvent‐, oxygen‐, and wavelength‐independant.
Synthèse énantiospécifique des acides (+)‐(2R)‐ et (−)‐(2S)‐éthyl‐6‐dihydro‐3,4‐méthyl‐2‐oxo‐4–2H pyranecarboxylique‐5
Authors: Deschenaux Pierre‐François , Kallimopoulos Thomas , Stoeckli‐Evans Helen , Jacot‐Guillarmod André 
Published: December 2004

Enantiospecific Synthesis of (+)‐(2R)‐ and (−)‐(2S)‐6‐Ethyl‐3,4‐dihydro‐2‐methyl‐4‐oxo‐2H‐pyran‐5‐carboxylic AcidThe two enantiomers (−)‐(2S)‐ and (+)‐(2R)‐6‐ethyl‐3,4‐dihydro‐2‐methyl‐4‐oxo‐2H‐pyran‐5‐carboxylic acid ((S)‐ and (R)‐7) have been synthesized from (+)‐(3S) and (−)‐(3R)‐3‐hydroxybutanoates, respectively (Scheme 1). By reduction and decarboxylation, the tetrahydro‐2H‐pyranols (2R, 4R, 6S)‐ and (2S, 4S, 6R)‐13, respectively, were obtained with an enantiomeric excess of ≥ 93%.