bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Base‐Labile Anchoring Group for Polymer‐Supported Peptide Synthesis
Authors: Mutter Manfred , Bellof Dieter 
Published: December 2004

AbstractA new base‐labile anchoring group, derived from 9‐(hydroxymethyl)fluorene‐4‐carboxylic acid (HO2CFmoH or HOFmCO2H; 7), for polymer‐supported peptide synthesis os described. The synthesis of 7 starting from 2,2′‐biphenyldicarboxylic acid (1) proceeds in an overall yield of 53%. The group HO2CFmo exhibits properties similar to the well known Fmoc protecting group: It is stable to acidic conditions and cleavable by 15% piperidine in DMF. In combination with acid labile Nα‐protecting groups (e.g. Boc, Ddz, Bpoc, Nps etc.), it renders more flexibility to the stepwise synthesis using polymer supports. The versatility of the new anchoring group in solid‐ and liquid‐phase peptide synthesis is demonstrated for the synthesis of a model peptide.
The Photoisomerization of 1,2,3,4,5‐Pentamethyl‐5‐vinyl‐1,3‐cyclopentadiene
Authors: Burger Ulrich , Etienne Robert 
Published: December 2004

AbstractThe title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone‐sensitized photolysis at 300 nm, the syn‐vinyl‐pentamethylhousene 5, which spontaneously rearranges in a [3,3]0sigmatropic process to give the bicyclo[3.2.0]heptadiene skeleton 2. Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di‐π‐methane rearrangement. The bicyclo[3.2.0]heptadiene derivative 2 give pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.
The Structure of Diastereomeric Oxaprotiline Metabolites. An NMR Study
Authors: Winkler Tammo , Dieterle Walter , Hung Paul , Rihs Grety , Kriemler Hans‐Peter 
Published: December 2004

AbstractThe structure of phenolic metabolites of oxaprotiline, obtained from a study with rats and dogs, are assigned with NMR‐spectroscopic methods in combination with MS data and an X‐ray structure analysis of synthetic (9R*,2′S*)‐2‐chlorooxaprotiline, the metabolites are shown to be (9R*,2′R*)‐2‐hydroxy, 3‐hydroxy‐, and 2‐hydroxy‐3‐methoxyoxaprotiline, and (9R*,2′S*)‐2‐hydroxy‐, 3‐hydroxy‐, and 3‐hydroxy‐2‐methoxyoxaprotiline, as well as 2,6‐dihydroxyoxaprotiline.
An Improved Liquid‐Phase Synthesis of Simple Alkylpyridines
Authors: Grayson J. Ian , Dinkel Rolf 
Published: December 2004

AbstractThe synthesis of pyridines from mixtures of aldehydes or ketones NH3 in the liquid phase has been reinvestigated, using continuous dosage of the carbonyl components to the reaction mixture. The main product from the reaction of acetaldehyde and formaldehyde is 3‐methylpyridine (6), which is also the main product from the reaction of acrolein or a mixture of crotonaldehyde and formaldehyde under the same conditions. The reaction of other aldehydes with formaldehyde give 3,5‐dialklypyridines, e.g. 10, 16. Acetone reacts with either formaldehyde or acetaldehyde to give polysubstituted alkylpyridines. A mechanistic pathway is proposed which accounts for the formation of the observed products.
Monofunctional (Dimethylamino)silane as Silylating Agent
Authors: Szabó Katalin , Ha Ngoc Le , Schneider Philippe , Zeltner Peter , Kováts Ervin sz. 
Published: December 2004

AbstractThe reaction of triorganyl(dimethylamino)silanes with surface‐hydrated silicon dioxide has been studied. These silylating agents are easy to prepare from the corresponding chloro or bromosilanes with dimethylamine. The resulting products are thermally stable and relatively volatile. Reaction with surface‐hydrated silicon‐dioxide preparations at 150–250°C for 170 h yields a dense grafted layer. However, with (dimethylamino)silanes having strongly polar substituents, a retreatment of the surface‐modified silica seems to be necessary in order to attain maximum coverage.
Synthese von N‐(4‐Aminobutyl)‐16‐aza‐19‐nonadecanlactam und N‐(4‐Aminobutyl)‐17‐aza‐20‐icosanlactam (Desoxoinandenin)
Authors: Wälchli Rudolf , Giggisberg Armin , Hesse Manfred 
Published: December 2004

AbstractSynthesis of N‐(4‐Aminobutyl)‐16‐aza‐19‐nonadecanelactam and N‐(4‐Aminobutyl)‐17‐aza‐20‐icosanelactam (Desoxoinandenine)According to Scheme 1, the two homologous macrocyclic spermidine derivatives 12 and 23 were synthesized. Key steps in both cases were two different types of ring‐enlargement reactions. Compound 12 was identical with a degradation product of the naturally occurring spermidine alkaloids of inandenine‐type.
Synthesis and Crystal Structure of a Peroxo‐Bridged Binuclear Rhodium (III) Complex and its Superoxo‐Bridged Analogue
Authors: Springborg John , Zehnder Margareta 
Published: December 2004

AbstractThe reaction of the ammonia diol [(NH3)4Rh(OH)2Rh(NH3)4]4+with H2O2 Yields among other products a peroxo‐bridged dimeric species [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](CIO4)3. Its structure was determined by single‐crystal X‐ray diffraction. The crystals are monoclinic with space group P21/n and lattice constants a=12.269 (5) Å, b=10.769(4) Å, c=15.964(4) Å, β=107.17(3)°. The dihedral angle of the RhOORh group in the bimetallic ring deviates by 62δ from planarity. The peroxo‐bridged complex was found to disproportionate in 1M HCIO4 and a red superoxo‐bridged complex. [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](NO3)4, was isolated. Its structure was solved by single‐crystal X‐ray diffraction. The crystals are orthorhombic with space group Pna 2, and lattice constants a=14.997(5) Å, b=11.952(4) Å, C=10.489(4) Å. The dihedral angle off the RhOORh group deviates by 7δ from planarity.
Photoactive cryptands. Synthesis of the sodium cryptates of macrobicyclic ligands containing bipyridine and phenoanthroline groups
Authors: Rodriguz‐Ubis Juan‐Carlos , Alpha Béatrice , Plancherel Dominique , Lehn Jean‐Marie 
Published: December 2004

AbstractThe NaBr cryptates of five macrobicyclic ligands containing bipyridine (bpy) and phenanthroline (phen) groups, i.e, of [bpy.bpy.bpy] 1 [bpy.bpy.phen] 2 [phen.phen.‐phen] 3 [2.1.phen] 4 and [2.2.phen] 5, have been prepared. 1, 2, 4 and 5 have been obtained in high yield by condensation of bis(bromomethyl)bipyridine 6 or ‐phenanthroline 9 with the corresponding macrocyclic diamines in presence of Na2CO3. Direct access to the NaBr complexes of th symmetrical cryptands 1 and 3 was achieved by a one‐step macrobicyclisation procedure. The metal‐ion complexes of ligands 1‐5 have the attractive feature of combining the cation inclusion, nature of cryptates with the photoactivity of bipyridine and phenanthroline groups; they may thus be expected to posses a variety of interesting physical and chemical properties.
Halochrome Molekeln. 6. Mitteilung. Spektrophotometrische Untersuchungen zum acidobasischen Verhalten substituierter 6,6‐Diphenyl‐6H‐chromeno[4,3‐b]indolizine und ihrer Aza‐analogen
Authors: Gunzenhauser Sigmund , Balli Heinz 
Published: December 2004

Halochromic Molecules. Spectrophotometric Investigation of the Acidobasic Behaviour of Substituted 6,6‐Diphenyl‐6H‐chromeno[4, 3‐b]indolizines and their Aza‐analoguesSubstituted 6,6‐diphenyl‐6H‐chromeno[4,3‐b]indolizines form ring‐opened, intensely coloured (diphenyl)‐indolizinylcarbenium salts with acid. UV/VIS spectra of the coloured salts are discussed on the basis of VEPPPCI calculations. The ϵpH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation equilibria.
The adamantane rearrangement of 1,2‐trimethylenenorbornanes. Part IV. Hydride‐ion abstraction in 1,2‐exo‐trimethylenenorbornane
Authors: Klester Alfred Michael , Ganter Camille 
Published: December 2004

AbstractIn the AlBr3‐catalyzed adamantane rearrangement in CS2of 1,2‐exo‐trimethylenenorbornane (1) to 2‐endo,6‐endo‐trimethylenenorbornane (3), hydride‐ion abstraction occurs at C(6) from theexo‐side. ThekH/kDvalue for competition between1and5(Dexo‐C(6)) was 1.58 ± 0.05, whereas no kinetic isotope effect was operative for competition between unlabeled1and4(Dendo‐C(5)) and between1and6(Dendo‐C(6)).
Über den sterischen Verlauf der Umsetzung von Enaminen aus offenkettigen Aldehyden und Ketonen mit Nitroolefinen zu 2,3‐disubstituierten 4‐Nitroketonen
Authors: Seebach Dieter , Beck Albert K. , Goliński Jerzy , Hay John N. , Laube Thomas 
Published: December 2004

On the Steric Course of the Reaction of Enamines Derived from Open‐Chain Aldehydes and Ketones with Nitro‐olefins Yielding 2,3‐Disubstituted 4‐NitroketonesThe relative configuration of the nitro‐ketone 12 obtained by the title reaction has been proved by a Baeyer‐Villiger degradation and subsequent reduction to the amino‐alcohol (±)‐(u)‐20, the relative configuration of which is identical with a sample prepared from 2‐methyl‐3‐hydroxybutyrate of known configuration (Scheme 1). The stereochemical course of the title reaction is thus as predicted by our topological rule. It is assumed that the other nitro‐ketones 13–18 described here are also formed by (lk)‐combination of the trigonal centers of the educts (diastereoselectivity > 90%, see Formulae and Fig. 1). It is not possible to reverse this relative topicity by employing (Z)‐ instead of (E)‐components of the starting materials, due to the reversibility of the primary step of these Michael additions (Schemes 2 and 3, and Fig. 2).
Photochemical reactions. 141st communication. Photochemistry of α,β‐unsaturated δ,ϵ‐epoxyketones of the ionone series
Authors: Mathies Peter , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn n,π*‐ as well as on π,π*‐excitation, the 4,5‐epoxy‐α‐ionones (E)‐1, (E)‐2, and (E)‐3 undergo (E)/(Z)‐isomerization and subsequent γ‐H‐abstraction leading to the corresponding 4‐hydroxy‐β‐ionones (E/Z)‐9, (E/Z)‐13, and (E/Z)‐17 as primary photoproducts. On photolysis of (E)‐3, as an additional primary photoproduct, the β,γ‐unsaturated σ,ϵ‐epoxy ketone 18 was obtained. The other isolated compounds, namely the 2H‐pyrans 10A + B and 14A + B as well as the retro γ‐ionones 11 and 15A + B, represent known types of products, which are derived from the 4‐hydroxy‐β‐ionones (E/Z)‐9 and (E/Z)‐13, respectively.
Camphorsulfonamide‐Shielded, Asymmetric 1,4‐Additions and Enolate Alkylations; Synthesis of a Southern Corn Rootworm Pheromone. Preliminary Communication
Authors: Oppolzer Wolfgang , Dudfield Philip , Stevenson Thomas , Godel Thierry 
Published: December 2004

AbstractUsing readily accessible 10‐sulfonamido‐isoborneols as regenerable, chiral auxiliaries, highly face‐selective C–C‐bond formations at Cα and Cβ of carboxylates could be conveniently achieved. Thus, conjugated additions of RCu to enoates (1→2) furnished, after saponification, β‐substituted carboxylic acids 3 in 94–98% e.e. Similarly, propionates 12 yielded after deprotonation, enolate alkylation, and reductive ester cleavage the (R)‐alcohols 15 in 78–98% e.e. The acid (+)‐3e was converted to the pheromone (–)‐11.
Asymmetric α‐Acetoxylation of Carboxylic Esters. Preliminary Communication
Authors: Oppolzer Wolfgang , Dudfield Philip 
Published: December 2004

AbstractUsing the readily accessible chiral auxiliaries 1–3 the sulfonamide‐shielded O‐silylated esters 5 underwent π‐face‐selective α‐acetoxylation on successive treatment with Pb(OAc)4 and NEt3 HF to give after recrystallization α‐acetoxy ester 6 in 55–67% yields and in 95–100% d.e. Starting from conjugated enoates addition of RCu and subsequent acetoxylation 10→11→12 yielded α,β‐bifunctionalized esters 12 with >95% configurational control at both Cα and Cβ. Nondestructive removal of the auxiliary (6→7, 6→8 and 12→13) gave either α‐hydroxycarboxylic acids or terminal α‐glycols in high enantiomeric purity. The prepared glycols 8c and 13a are key intermediates for previously reported syntheses of the natural products 16 and 17, respectively.
Synthesis of 1,2‐Dihydropyridines, 2,3‐Dihydro‐4(1H)‐pyridinone, and 1,2,3,4‐Tetrahydropyridines via N‐Acyl N,O‐Hemiacetal Formation
Authors: Roduit Jean‐Paul , Wyler Hugo 
Published: December 2004

AbstractNew procedures are described for the synthesis of α,β‐ethylenic and acetylenic aldehydes from 2‐butene‐ and 2‐butyne‐1,4‐diol, respectively (see Scheme 1). These are applied to the preparation of a particular δ‐acetylamino‐α,β‐ethylenic aldehyde ((E)‐5) as well as of its acetylenic analogue 15. On heating in the presence of a silyl enol ether, the former undergoes a complete dehydrative cyclization affording the N‐acetyl‐1,2‐dihydropyridine 19. The addition of HCl to aldehyde (E)‐5 results in the production of the 4‐chloro‐1,2,3,4‐tetrahydropyridine 22 which is hydrolyzed to the corresponding alcohol 23 on silica gel. Similarly, the addition of HCl or HBr to the δ‐acetyl‐amino‐α,β‐acetylenic aldehyde 15 leads to the previously unknown 4‐halo‐1,2‐dihydropyridines 26; these are easily hydrolyzed to the 2,3‐dihydro‐4(1H)‐pyridinone 27. The ring‐forming process involves a N‐acyl N,O‐hemiacetal as intermediate which is eventually dehydrated.
Selektive Reaktionen an den Tetranortriterpenen Bussein A und B
Authors: Guex Matthias , Tamm Christoph 
Published: December 2004

Selective Reactions of the Tetranortriterpenes Busseins A und BBussein A (1) was transformed to the 1′‐O‐ and 2‐O‐acetyl and the 1′‐O ‐ and 2‐O‐chloroacetyl derivatives 3,5,4, and 6, respectively. By hydrolysis with H2SO4 in MeOH bussein J (7) was obtained from 1 and bussein K (8) from bussein B (2). Treatment of 1 with H2SO4 in H2O and tetrahydrofuran yielded 7, the acid 9, and the dilactone 16. Hydrolysis of 1 with aqueous NH3 in MeOH gave 10; at higher temperature, 12, 13, and 14 were obtained as additional products. With NaOH in aqueous MeOH 7, 10, 15, and 17 – the latter being an isomer of 15 of unknown structure – were formed from 1. Photooxidation of 1 led to 20β,21β:21β,23β‐diepoxybussein A (18).
Variable‐Temperature and Variable‐Pressure17O‐NMR Study of Water Exchange of Hexaaquaaluminium(III)
Authors: Hugi‐Cleary Deirdre , Helm Lothar , Merbach André E. 
Published: December 2004

AbstractThe transverse relaxation rate of H2O in Al(H2O)has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the17O‐NMR line‐broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchange with bulk H2O, whereas at low temperatures quadrupolar relaxation is prevailing. Low‐temperature fast‐injection17O‐NMR was used to extend the accessible kinetic domain. The samples studied contained Al3+(0.5m), Mn2+(0.2–0.5m),H+(0.2–3.1m) and17O‐enriched (20–40%) H2O. Non‐coordinating perchlorate was used as counter ion. The following H2O exchange parameters were obtained:k= (1.29 ± 0.04) s−1, ΔH* = (84.7 ± 0.3) kJ mol−1, ΔS* = +(41.6 ± 0.9)J K−1mol−1, and ΔV= +(5.7 ± 0.2) cm3mol−1, indicating a dissociative interchange,Id, mechanism. These results of H2O exchange on Al(H2O)are discussed together with the available complex‐formation rate data and permit also the assignment of Idmechanisms to these latter reactions.
Esters of 1‐O‐Demethylthiocolchicines: Formation of Isomers in Chloroform Solution
Authors: Kerekes Peter , Brossi Arnold , Flippen‐Anderson Judith L. , Chignell Colin F. 
Published: December 2004

Abstract1‐O‐Acetyl‐1‐O‐demethylcolchicine, and acylated 1‐O,2‐O‐didemethylthiocolchicines, in contrast to 2‐O‐acetyl‐, 2‐O,3‐O‐diacetyl‐ and 3‐O‐acetyl analogs, showed after standing in CHCl3 solution significant changes in optical rotation, a duplication of 1H‐NMR signals, and the formation of new isomers on TLC. Solid‐state X‐ray diffraction of O‐acetylated colchinoids and thio analogs, showed out of planar arrangements of the aromatic substituents, but the analysis could not help to explain the structures of the newly formed isomers in CHCl3 solution.
Total Synthesis of (−)‐Crinine. Use of Tandem Cationic Aza‐Cope Rearrangement/Mannich Cyclizations for the Synthesis of Enantiomerically Pure Amaryllidaceae Alkaloids
Authors: Overman Larry E. , Sugai Soji 
Published: December 2004

AbstractThe total synthesis of enantiomerically pure (−)‐crinine (1) in 10 steps and 6% overall yield from cyclopentene oxide is reported. The key step was the rearrangement of 7 upon reaction with AgNO3 at 25°C to give cis‐perhydroindolone 8 in 81% yield.
Konformation und Dynamik von [6]Paracyclophan‐8,9‐dicarbonsäure‐dimethylester. Eine 1H‐ und 13C‐NMR Studie
Authors: Günther Harald , Schmitt Peter , Fischer Hartmut , Tochtermann Werner , Liebe Jörg , Wolff Christian 
Published: December 2004

Conformation and Dynamics of Dimethyl [6]Paracyclophane‐8,9‐dicarboxylate. A 1H‐ and 13C‐NMR StudyThe 1H‐ und 13C‐NMR spectra of dimethyl [6]paracyclophane‐8,9‐dicarboxylate have been assigned and analyzed in the slow‐exchange limit (−20°C) for the ring‐inversion process of the methylene bridge using several 2D‐NMR techniques. The vicinal 1H, 1H coupling constants of the methylene chain show a Karplus‐type dependence on torsional angles. The observed values indicate that the solution conformation of 1 closely resembles that found in the crystal. No significant changes in the 1H‐NMR shielding properties of the boat‐shaped benzene ring were detected. The 13C chemical shifts of the methylene C‐atoms can be explained without invoking ring current contributions, which are too small for unambiguous identification. A lineshape analysis for the AB⇌BA exchange system of the aromatic protons yielded ΔH≠ = 43.25 ± 0.72 kJ/mol, ΔS≠ = −51.27 ± 2.66 J/K mol, and ΔG≠(298) = 58.53 kJ/mol for the dynamic process corresponding to an inversion of the methylene bridge.
Synthesis of a Glyoxalase I Inhibitor from Streptomyces griseosporeus NIIDAet OGASAWARA
Authors: Mirza Sohail , Molleyres Louis‐Pierre , Vasella Andrea 
Published: December 2004

AbstractThe pseudolactones 6 and 12 were prepared in a straightforward way from methyl α‐D‐glucopyranoside and methyl α‐D‐mannopyranoside, respectively. The pseudolactone 6 reacted with tert‐butyl lithioacetate to give the protected, trihydroxylated cyclohexenone carboxylate 7 (51 %). The sterically hindered, L‐ribo‐configurated pseudolactone 12 reacted with diethyl ethylphosphonate and dimethyl methylphosphonate to give the protected trihydroxycyclohexenones 17 (49 %) and 18 (62 %), respectively. The hydroxymethylated cyclohexenone 21 was obtained from 18 by treatment with Me2AlSPh and then formaldehyde, oxidation of the product 19, and elimination. Deprotection of 21 gave 2, identical with KD16‐Ul. Esterification of 2 gave 1, identical with the title compound. Alternatively, 1 was obtained in higher yields by esterification of 21, followed by deprotection of the hydroxy groups. This synthesis gave 1 and 2 from methyl α‐D‐mannopyranoside in an overall yield of 18 and 20 %, respectively, confirming their absolute configuration.
Photochemistry of 4‐Thia‐2‐cycloalkenones. Part 2
Authors: Anklam Elke , Lau Sabine , Margaretha Paul 
Published: December 2004

AbstractMethyl 2‐allyl‐3‐oxo‐2,3‐dihydrothiophene‐2‐carboxylate (2) photocyclizes selectively to methyl 2‐oxo‐7‐thiatricyclo[3.2.1.03,6]octane‐1‐carboxylate (4). In contrast, 4‐thia‐2‐cyclohexenone 3, on irradiation, affords only low yields of dimers, cycloadducts (2‐methylpropene) or RH reduction products (i‐ProH).
Direct Clay‐Catalyzed Friedel‐Crafts Arylation and Chlorination of the Hydrocarbon Adamantane
Authors: Chalais Stéphane , Cornélis André , Gerstmans André , Kołodziejski Wacław , Laszlo Pierre , Mathy Arthur , Métra Pierre 
Published: December 2004

AbstractMultiple chlorinations and arylations at the tertiary positions of adamantane are promoted by FeCl3‐doped K10 montmorillonite in CCl4 or in aromatic solvents. The process, remarkably easy to implement, can be tailored to selective formation of monosubstituted 1‐adamantyl derivatives or 1,3‐disubstituted adamantanes. The process achieves alkylation at the meta‐ and para‐positions of toluene leading to a purely statistical distribution and displays no substrate specificity in competition experiments between toluene and benzene.
The Novel Adamantane Isomer Tricyclo[4.4.0.03,9]decane (2‐Homotwistbrendane)
Authors: Känel Hans‐Ruedi , Ganter Camille 
Published: December 2004

AbstractTwo synthetic approaches to the novel C10H16 hydrocarbon tricyclo[4.4.0.03,9]decane (1; 2‐homotwistbrendane), one of the 19 members of the adamantaneland, and its Lewis‐acid‐catalyzed rearrangement are described. One route starts from tricyclo[4.3.0.03,8]nonan‐2‐one (2; 2‐twistbrendanone). The missing tenth C‐atom is introduced by ring enlargement (Tiffeneau‐Demjanov method). Starting from methyl 8,9,10‐trinorborn‐5‐ene‐2‐endo‐carboxylate (8), ring enlargement by one C‐atom, regio‐ and stereoselective introduction of a C1 unit to a 2‐endo,6‐endo‐disubstituted bicyclo[3.2.1]octane, and ring closure by acyloin condensation are the key steps in the second approach.
New Furano‐sesquiterpenoids from Mediterranean Sponges
Authors: Guella Graziano , Mancini Ines , Guerriero Antonio , Pietra Francesco 
Published: December 2004

AbstractA mixture of sponges of the East Pyrenean Mediterranean is shown to contain the known sponge products longifolin (1), avarol ((+)‐3), and avarone (4) and the terrestrial‐plant product sesquirosefuran (2), besides to the new furano‐sesquiterpenoids tavacfuran (= 3‐methyl‐2‐[(3′Z)‐3′‐methyl‐4″‐methyl‐2″‐furyl‐3′‐butenyl]furan; (5) and tavacpallescensin (= 5,10‐dihydro‐6,9‐dimethyl‐4H‐benzo[5,6]cyclohepta[1,2‐b]furan; 6) and the new furano‐butenolide sesquiterpenoids tavacbutenolide‐1 (= (±‐4‐ethoxy‐2‐methyl‐4‐)[(2′E)‐2′‐methyl‐4′‐(3″‐methyl‐2″‐furyl)‐2′‐butenyl]‐2‐buten‐4‐olide; (±)‐7) and tavacbutenolide‐2 (= (±)‐4‐ethoxy‐3‐methyl‐4‐[2′E)‐3′‐methyl‐4′‐(4″‐methyl‐2″‐furyl)‐2′‐butenyl]‐2‐buten‐4‐olide; (±)‐8). Structural assignments are based on NMR data and on the synthesis of the (E)‐isomer of 5. The sponge Dysidea tupha of the same area is also shown to contain the two sesquiterpenoids ent‐furodysinin ((−)‐14), which is enantiomeric to a product of a Dysidea sp. of Australian waters, and tuphabutenolide ((+)‐15).
Synthesen von Carotinen mit ψ‐Endgruppen und (Z)‐Konfiguration an terminalen konjugierten Doppelbindungen
Authors: Zumbrunn Albrecht , Uebelhart Peter , Eugster Conrad Hans 
Published: December 2004

Syntheses of Carotenes with ψ‐End Groups and (Z)‐Configuration at Terminal Conjugated Double BondsFive carotenes bearing (5Z)‐ψ‐end groups were synthesized and carefully characterized: (5Z)‐lycopene (6), (5Z5′Z)‐lycopene (7), (5′Z)‐neurosporene (8), (5′Z)‐β,ψ‐carotene (12), and (5′Z)‐ε,ψ‐carotene (14).
Totalsynthese von Decarboxybetalainen durch photochemische Ringöffnung von 3‐(4‐Pyridyl)alanin
Authors: Hilpert Hans , Siegfried Marc‐André , Dreiding André S. 
Published: December 2004

Total Synthesis of Decarboxybetalaines by Photochemical Ring Opening of 3‐(4‐Pyridyl)alanineA photochemical approach is presented for the total synthesis of the decarboxybetalaines, which were previously known from the mild decarboxylation of the natural plant colorants, the betalaines: Irradiation of rac‐3‐(4‐pyridyl)alanine (1) yielded the rac‐2‐decarboxybetalamic‐acid‐imine (4, 86%), presumably via a Dewar pyridine 2, a cyclic aminal 3 and an electrocyclic ring opening. The imine‐zwitterion 4 was treated with three amines, namely (S)‐cyclodopa (6), (S)‐proline (7), and indoline (8), to afford three decarboxybetalaines, namely (2S)‐17‐decarboxybetanidine (9, red, 34%), (2S)‐13‐decarboxyindicaxanthine (10, yellow, 56%), and rac‐16‐decarboxyindobetalaine (11, orange, 78%), respectively. The structures of these coloring matters were confirmed by their electrophoretic behavior and their spectroscopic properties. 17‐Decarboxybetanidine 9 was shown to be a ca. 1:1 mixture of two C(15)‐epimers 9a and 9b, separable by chromatography. The configuration of 9a was determined as (2S, 15S) and that of 9b as (2S, 15R), by correlating their optical rotations with those of betanidine (12a) and isobetanidine (12b), respectively. The decarboxybetalaines 9, 10, and 11 did not show the double‐bond isomerism at C(β), (Cγ) of the chromophore which had been found characteristic for the corresponding betalaines 12, 13, and 14.