bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese von racemischen Aminozuckersäure‐lactonen: xylo‐ und lyxo‐2,3‐Diacetylamino‐5‐acetoxypentan‐4‐olid und ‐2,3,5‐Triacetylaminopentan‐4‐olid
Authors: Egli Markus , Dreiding Andre S.
Published: December 2004

Synthesis of Racemic Aminosugar Lactones: xylo‐ and lyxo‐2,3‐Diacetylamino‐5‐acetoxypentan‐4‐olide and ‐2,3,5‐Triacetylaminopentan‐4‐olide

Starting with 5‐hydroxy‐2‐penten‐4‐olide (1), the tricyclic intermediate 4 was prepared via the chloride 2, the acyl azide 3, and an intramolecular nitrene addition (Scheme 3). Azide ion opened the aziridine ring in 4 at C(α) to give 5, which was transformed via 7 into one of the title compounds, the triacetylated diamino‐hydroxy‐lactone 13 (Scheme 4). An alternative conversion of 4 into 13 involved the synthesis of the N‐acetylaziridine 10, the opening of the 3‐ring of 10 with N to form 12, and a final reductive acetylation (Scheme 5). The third N‐substituent was introduced at C(δ) of 13 by the following sequence: hydrolysis of the AcO group (→14), mesylation (→15), substitution by N (→ 16), and reductive acetylation to yield the other title compound, the triacetylated triaminolactone 17 (Scheme 6). Since the ring opening of aziridines by nucleophiles occurs by inversion, the primary products 5a and 12a of the N reactions as well as the substances derived from them, i.e. 6a, 7a, and 13a‐17a, have the xylo‐configuration (a‐series). Under some of the reaction conditions, the primary xylo‐products suffered a partial epimerization at C(α) to yield mixtures containing the corresponding lyxo‐products (b‐series): The equilibrium between the xylo‐ and lyxo‐isomers was estimated for 5a/5b=1:3, 12a/12b=5:2, 13a/13b=3:1, and 16a/16b=2:1. Since the stereoisomers of the a‐ and the b‐series were always separable, the other lyxo‐products, i.e. 6b, 7b, could be prepared from 5b and 12b.
Synthese und Strukturaufklärung von Merucathinon und Synthese von Cathinon. Inhaltsstoffe von Catha edulis FORSK
Authors: Wolf Jean‐Pierre , Pfander Hanspeter
Published: December 2004

Synthesis and Structure Elucidation of Merucathinone and Synthesis of Cathinone. Constituents of Catha edulis FORSK.

Starting from L‐alanine, two constituents of Catha edulis FORSK., (S)‐4‐amino‐1‐phenylpent‐1‐en‐3‐on ((S)‐3; merucathinone) and (S)‐2‐amino‐1‐phenylpropan‐1‐on ((S)‐1; cathinone) were synthesized.
Synthese von Pentafulvalen durch oxidative Kupplung von Cyclopentadienid mittels Kupfer(II)‐chlorid
Authors: Escher André , Rutsch Werner , Neuenschwander Markus
Published: December 2004

Synthesis of Pentafulvalene by Oxidative Coupling of Cyclopentadienide with Copper(II) Chloride

Starting with a nearly quantitative coupling of cyclononatetraenide 7 to 1, 1′‐dihydrononafulvalene 8 by means of AgBF4, a simple general synthetic concept for fulvalenes is outlined (Scheme 2), consisting in an oxidative coupling of ‘Hückel anions’ like 2 and 7 to 1, 1′‐dihydrofulvalenes 10 with Ag(I) or Cu(II) salts, followed by deprotonation (→11) and oxidation (→12); it has been realised in the case of pentafulvalene (1; overall yield 61%; Scheme 3) and 1,2:5,6‐dibenzopentafulvalene (18; overall yield 66%, Scheme 4). NMR‐spectroscopic investigations show that 1 is a non‐aromatic compound with strongly alternating bond‐lengths, its π‐system being even more localised than that of simple pentafulvenes. In fact, 1 is extremely reactive in concentrated solutions above −50°. Besides of polymerisations, Diels‐Alder dimerisation 1→19 followed by a rearrangement 19→20 takes place (Scheme 5).
Stoffwechselprodukte von mikroorganismen. 238. Mitteilung. Isolierung und Strukturaufklärung von Differolid
Authors: Keller‐Schierlein Walter , Bahnmüller Urs , Dobler Max , Bielecki Jacek , Stümpfel Joachim , Zähner Hans
Published: December 2004

Isolation and Structure Elucidation of Differolide

From cultures of a new actinomycete, Streptomyces aurantiogriseus (PREOBRAZHENSKAYA 1975), strain Tü 3149, a compound C12H12O4 was isolated, which enhances the formation of aerial mycelium and spores of Streptomyces glaucescens. The structure determined by X‐ray diffraction studies was that of racemic dilactone 1 ((±)‐differolide).
1,3‐Butadienyl‐thiocyanate in der Diels‐Alder‐Reaktion mit anschliessender [3,3]‐sigmatroper Umlagerung
Authors: Huber Stefan , Stamouli Peristera , Jenny Titus , Neier Reinhard
Published: December 2004

1,3‐Butadienyl Thiocyanates in the Diels‐Alder Reaction Followed by a [3,3]‐Sigmatropic Shift

(E)‐ and (Z)‐1,3‐Butadienyl thiocyanates 3, 4, and 12–15 have been synthesized selectively. Their use as dienes for Diels‐Alder reactions followed by a [3,3]‐sigmatropic shift to obtain an isomeric isothiocyanate has been studied. The butadienyl thiocyanates are, unfortunately, not very reactive in Diels‐Alder reactions. This disadvantage can be overcome, if a trapping reaction with EtOH is added to the two‐step sequence. This sequence allows to get good yields of the O‐ethyl thiocarbamates 18–23, even if the first two reactions have not favorable equilibrium constants.
Enantioselective Syntheses of α‐Amino Acids from 10‐(Aminosulfonyl)‐2‐bornyl Esters and Di(tert‐butyl) Azodicarboxylate. Preliminary Communication
Authors: Oppolzer Wolfgang , Moretti Robert
Published: December 2004

Succesive treatment of chiral esters 1 with LiN(i‐Pr)2/Me3SiCl and di(tert‐butyl) azodicarboxylate/TiCl4/Ti(i‐PrO)4 gave N,N′ ‐di[(tert‐butoxy)carbonyl]hydrazino esters 9 which on deacylation, hydrogenolysis, transesterification, and acidic hydrolysis furnished (2S)‐α‐amino acids 6 in high enantiomeric purity with efficient recovery of the auxiliary alcohol 7.
Photochemical and Electrochemical Reduction of Carbon Dioxide to Carbon Monoxide Mediated by (2,2′‐Bipyridine)tricarbonylchlororhenium(I) and Related Complexes as Homogeneous Catalysts
Authors: Hawecker Jeannot , Lehn Jean‐Marie , Ziessel Raymond
Published: December 2004

[fac‐Re(bpy) (CO)3Cl] (bpy = 2,2′‐bipyridine) is an efficient homogeneous catalyst for the selective and sustained photochemical or electrochemical reduction of CO2 to CO. A quantum yield of 14% and a faradic efficiency of 98% were measured in the presence of excess Cl− ions. The photochemical process took place under visible‐light irradiation and consumed a tertiary amine as electron donor. A formato‐rhenium complex was isolated in the absence of excess Cl− ions. Substitution by Cl− ion generated free formate, but no CO was detected. Luminescence measurements showed that the tertiary amine quenches the metal‐to‐ligand charge‐transfer excited state of the rhenium complex via a reductive mechanism, with a rate constant of 3.4 × 107M−1S−1. The 19e‐complex [Re(bpy) (CO)3X]− produced either photochemically or electrochemically appears to be the active precursor in the CO‐generation process. Detailed spectroscopic studies on 13C‐enriched carbonyl‐rhenium and formato‐rhenium complexes derived from 13C‐enriched CO2 were performed in order to confirm the origin of the products and to study the exchange of the ligands. A mechanism for the present CO2 photoreduction process is presented; it involves separate pathways for CO and formate generation, in which the [Re(bpy) (CO)3X] complex plays the role of both the photoactive and the catalytic center.
New Sesquiterpenoids from Cabreuva Oil
Authors: Maurer Bruno , Hauser Arnold , Ohloff GÜNther
Published: December 2004

Six sesquiterpenoids 1–6, formally derived from (+)‐(S)‐nerolidol by oxidative cyclization, have been isolated for the first time from commercial cabreuva oil. Whereas the two tetrahydrofurans 5 and 6 have already been described, the four bicyclic ethers (cabreuva oxides A–D) 1–4 are new. The structures of 1–4 are confirmed by synthesis and their absolute configurations are shown to be 3S. The organoleptic properties of the synthetic cabreuva oxides are discussed.
Further Saponins from Phytolacca dodecandra L′HERIT
Authors: Dorsaz Anne‐Christine , Hostettmann Kurt
Published: December 2004

Three new bidesmosidic saponins 1–3 have been isolated from the berries of Phytolacca dodecandra L′HERIT (Phytolaccaeae). The structures have been established by spectroscopic (1H‐NMR, 13C‐NMR, FAB‐MS, DCI‐MS, and GC/MS) and chemical methods (acid, basic, and enzymatic hydrolysis). Saponins 1 and 3 are tetra‐ and pentaglycosides of oleanolic acid, whereas 2 is a tetraglycoside of bayogenin. The corresponding prosapogenins 1a‐3a, obtained by cleavage of a glucose unit esterified at C(28), exhibited strong molluscicidal activity against schistosomiasis‐transmitting snails.
The Thermal Reactivity of 5,8α‐Epidioxy‐5α‐cholestan‐3β‐yl Acetate in Acetic Acid
Authors: Fuhrer Hermann , Rihs Grety , Lorenc Ljubinka , Bondarenko Lidija , Kalvoda Jaroslav , Mihailović Mihailo Lj.
Published: December 2004

The thermolysis of the steroidal 5α,8β‐peroxide 1, under acidic conditions afforded in addition to the expected 5,10:8,9‐diseco derivative 2, the rearranged 5α,8β‐epoxide 3, the structure of which was determined by NMR spectroscopy and X‐ray analysis.
Zwei weitere Iridoid‐glycoside und ein Monoterpen‐glycosid aus Sambucus ebulus L. (Caprifloiaceae). 3. Mitteilung über die Inhaltsstoffe der Zwergholunderwurzel
Authors: Gross Gian‐Andrea , Sticher Otto , Anklin Clemens
Published: December 2004

New Iridoid Glycosides and a Monoterpene Glycoside from Sambucus ebulus L. (Caprifloiaceae)

From the roots of Sambucus ebulus L., two novel valeriana‐type ester iridoid glycosides, 6′‐O‐apiosylebuloside (1) and 7,7‐O‐dihydroebuloside (3), along with the open‐chain monoterpene glycoside 5 were isolated. Their structure elucidation is based mainly on one‐ and two‐dimensional NMR methods. 1H,1H‐COSY experiments permitted complete assignment of signals arising from the disaccharide unit in 1. Biogenetically, 3 seems to represent the equivalent of loganin in the valeriana‐type series of iridoid glycosides.
Formation of 2,3‐Dihydrothiophene‐3‐carboxylates from 2(5H)‐Thiophenones via Sequential Cyclization and Ring‐Opening Reactions of 3‐Thiahexa‐1,5‐dienyl Radicals. Preliminary Communication
Authors: Kiesewetter René , Margaretha Paul
Published: December 2004

Methyl 4‐mercapto‐2‐alkenoates 1, obtained by irradiation of 2(5H)‐thiophenones 2 in MeOH, undergo light‐induced S–H bond homolysis to give thio radicals 3 which can be trapped with 2‐butyne to afford 3‐thiahexa‐1,5‐dienyl radicals 12. Intermediates 12 undergo selective 1,5‐ring closure to allylcarbinyl radicals 18, which cyclize to cyclopropylcarbinyl radicals 19. A novel rearrangement of 19 to 23, the direct precursors of title compounds 15 and 17, occurs via two additional ring‐opening and one 1,5‐ring‐closure step.
Photochemical Rearrangement of N‐Substituted 2‐Methyl‐5‐Nitro‐1H‐Imidazoles in the Presence of Water
Authors: Pfoertner Karl‐Heinz , Daly John J.
Published: December 2004

The photochemical behaviour of 2‐methyl‐5‐nitro‐1H‐imidazoles 1 in water‐containing solutions has been studied. In a first reaction step, the photorearrangement of 1 yields 2‐methyl‐2‐imidazoline‐4,5‐dione‐4‐oximes 2. Hydrolysis of 2 and subsequent elimination of water from a supposed intermediate 5 leads to 5‐methyl‐1,2,4‐oxadiazole‐3‐carboxamides 4. The basic structure of 4 was determined by X‐ray analysis of the derivative 4e. Further irradiation destroys the products 4 in part by light‐induced hydrolysis.
Intramolecular Cyclizations of Allenic Acylureas and ‐Amides
Authors: Trifonov Latchezar S. , Orahovats Alexander S.
Published: December 2004

Allenic acids are found to add to dicyclohexylcarbodiimide affording, in the presence of Et2NH, the 4H‐1,3‐oxazin‐4‐ones 5 via 4. Under neutral conditions, they add to diaryl‐ or pyridyl(cyclohexyl)carbodiimides and triphenylketene imine to give the corresponding tricyclo[5.2.2.01,5]undeca‐4,8,10‐trien‐3‐ones 7, 8, 9, and 12. The allenic phenyl ester 13a dimerises, on heating in a [2+2] head‐to‐head fashion, to 14 but fails to undergo intramolecular Diels‐Alder cyclization, to 15.
Functionalisation of saturated hydrocarbons. Part 9. Oxidation of patchouli alcohol by the ‘gif system’: Isolation and organoleptic properties of three new ketonic derivatives
Authors: Barton Derek H. R. , Belœil Jean‐Claude , Billion Annick , Boivion Jean , Lallemand Jean‐Yves , Mergui Simone
Published: December 2004

Oxidation of patchouli alcohol (1) using the ‘Gif system’ afforded as major isolated products three new ketonic derivatives 16–18. The structures of these compounds were established by spectral techniques including 2D‐NMR. Ketones 16–18 display interesting organoleptic properties.
3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin als α‐Aminoisobuttersäure(Aib)‐Äquivalent: Cyclische Depsipeptide durch direkte Amid‐Cyclisierung
Authors: Obrecht Daniel , Heimgartner Heinz
Published: December 2004

3‐(Dimethylamino)‐2,2‐dimethyl‐2H,‐azirine as an α‐Aminoisobutyric‐Acid (Aib) Equivalent: Cyclic Depsipeptides via Direct Amid Cyclization

In MeCN at room temperature, 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) and α‐hydroxycarboxylic acids react to give diamides of type 8 (Scheme 3). Selective cleavage of the terminal N,N‐dimethylcarboxamide group in MeCN/H2O leads to the corresponding carboxylic acids 13 (Scheme 4). In toluene/PhSH, phenyl thioesters of type 11 are formed (see also Scheme 5). Starting with diamides 8, the formation of morpholin‐2,5‐ diones 10 has been achieved either by direct amide cyclization via intermediate 1,3‐oxazol‐5(4H)‐ones 9 or via base‐catalyzed cyclization of the phenyl thioesters 11 (Scheme 3). Reaction of carboxylic acids with 1, followed by selective amide hydrolysis, has been used for the construction of peptides from α‐hydroxy carboxylic acids and repetitive α‐aminoisobutyric‐acid (Aib) units (Scheme 4). Cyclization of 14a, 17a, and 20a with HCI in toluene at 100° gave the 9‐, 12‐, and 15‐membered cyclic depsipeptides 15, 18, and 21, respectively.
Triaziridine 7. Mitteilung. Stabile pyramidale Konfigurationen an den Stickstoff‐Atomen von Dialkyl‐und Trialkyl‐triaziridinen
Authors: Hilpert Hans , Hoesch Lienhard , Dreiding André S.
Published: December 2004

Stable Pyramidal configurations at the Nitrogen Atoms of Dialkyl‐and Trialkyl‐triaziridines

Stereochemical features of the recently synthesized nine samples of di‐ and trialkyl‐triaziridines, namely the 1,3‐cyclopentylen‐(series a) and the two stereoisomers of the diisopropyl derivatives (series b and c), containing as the third substituent an H‐atom (2), a CH3 group (3)or a CH2OH group (4), were elaborated on the basis of the 1H‐, 13C‐, and 15N‐NMR spectra. The three N‐atoms of the saturated N3‐homocycle were found to be stable to pyramidal inversion in all cases. According to their NMR spectra, 2–4 of the series a and b possess twofold symmetry (Cs), while 2–4 of series c are asymmetric. Thus, series c has the trans‐configuration at N(2)/N(3) and, consequently, the cis‐configuration at N(1)/N(2), while series a and b have the cis‐configuration at N(2)/N(3) and ‐since the all‐cis‐arrangement is excluded‐the trans‐configuration at N(1)/N(2). The asymmetry of the trans‐configurated 2c turned into twofold symmetry (C2), when a little CF3COOH was added. The 1H‐ and 13C‐NMR data of series b and c of our alkyl‐triaziridines exhibit a shielding effect, according to which there are two types of i‐Pr groups, i‐Pr(a) and i‐Pr(b). They differ in the NMR signals of the H‐ and the C‐atoms of their CH groups: the H‐atoms of i‐Pr(a) are more deshielded by 0.75–1.111 ppm and its C‐atoms are more shielded by 10.0–160.0 ppm as compared to the corresponding atoms of i‐Pr(b). i‐Pr(a) is cis (on the N3‐homocycle) to a large substituent (such as i‐Pr, Me, CH2OH) and to a lone pair, while i‐Pr(b)is cis only to a small (H) or to no substituent and to one or two lone pairs. An analogous effect appears in the NMR signals of the CH3 and CH2OH groups at N(1) of 3 and 4 in the series b and c.
Studies on the Biosynthesis of Tabtoxin (Wildfire Toxin). Origin of the Carbonyl C‐Atom of the β‐Lactam Moiety from the C1‐Pool
Authors: Müller Barbara , Hädener Alfons , Tamm Christoph
Published: December 2004

Re‐isolation of Pseudomonas tabaci strain NCPPB 2730 from its host, the tobacco plant, led to an activation of the bacteria in order to produce the β‐lactam dipeptide tabtoxin (Wildfire toxin, 1). Incorporation of several 14C‐labelled amino acids as well as L‐[methyl‐13C]methionine, L‐[1,2‐13C2]‐ and L‐[3,4‐13C2]aspartate, rac ‐[1,2‐13C2]glycerol, and [1,2‐13C2]acetate into isotabtoxion (2) demonstrated that the building blocks of tabtoxin (1) are L‐threonine, L‐aspartate, the Me group of L‐methionine and a C2‐unit derived from the C3‐pool (Fig. 3). The Me group of L‐methionine provides the carbonyl C‐atom of the β‐lactam moiety. These findings represent a novel pathway in β‐lactam biosynthesis. Mechanistic aspects with respect to the β‐lactam ring formation are discussed. A biradical 16 is proposed as an intermediate during the cyclization of a N‐formyl‐α‐amino ketone 15.
Optisch aktive Alkohole aus 1,3‐Dioxan‐4‐onen: eine praktikable Variante der enantioselektiven Synthese unter nucleophiler Substitution an Acetal‐Zentren
Authors: Seebach Dieter , Imwinkelried René , Stucky Gerhard
Published: December 2004

Optically Active Alcohols from 1,3‐Dioxan‐4‐ones. A Practical Version of Enantioselective Synthesis with Nucleophilic Substitution at Acetal Centers

Secondary alcohols in enantiomeric excesses above 90% are accessible from 2‐substituted 6‐methyl‐1,3‐dioxan‐4‐ones (Scheme 4). The dioxanones are prepared from aldehydes and readily available (R)‐or (S)‐3‐hydroxybutanoic acid. Treatment of the dioxanones with silyl nucleophiles or triisopropoxy(methyl)titanium in the presence of [Cl3TiX] yields the corresponding 3‐alkoxy acids in diastereoselectivities ≥ 95%. The ‘chiral auxiliary’ is removed from the alkoxy acids by treatment with LiN(i‐Pr)2 to give the secondary alcohols with ≤ 90% ee. cis/trans‐Mixtures (9:1) of the dioxanones furnish products of the same configurational purity as those obtained from pure cis‐isomers. In comparison with other variants of enantioselective synthese with nucleophilic substitution at acetal centers, the following advantages of the dioxanone method are noteworthy: (i) (R)‐ and (S)‐3‐hydroxybutanoic acids are both readily available; (ii) reactions are not sensitive to changes in conditions; (iii) the ‘chiral auxiliary’ is removed simply by base elimination, no oxidation is required; (iv) no chromatographic purification steps are necessary. The overall reaction described here is an enantioselective nucleophilic addition to aldehydes with concomitant dehydration of enantiomerically pure 3‐hydroxybutanoic to crotonic acid.
Sequencing of Tentoxin by Using Fast‐Atom‐Bombardment (FAB)/High‐Resolution (HR)/Tandem Mass Spectrometry (MSMS). Scope and Limitation of a Novel Strategy
Authors: Eckart Klaus , Schwarz Helmut
Published: December 2004

The recently developed FAB/MSMS methodology (i.e.) ionization of an underivatized peptide by using fast‐atom‐bombardment (FAB) combined with tandem mass spectrometry (MSMS) is applied for the sequencing of the cyclotetrapeptide tentoxin (12). The scope and limitation of the strategy is discussed in detail. Possible resolutions to overcome problems related to (i) the resolution of isobaric fragment ions and (ii) the distinction of sequencevs. retro‐sequence are investigated. The novel strategy is compared with conventional techniques. Significant improvement of the presently used FAB/MSMS methodology can be achieved by combining this approach with accurate mass measurements.
Angular Distortions at Tetracoordinate Carbon Planoid Configurations in Substituted Spiro[4.4]nonanes
Authors: Luef Wolfgang , Keese Reinhart , Bürgi Hans‐Beat
Published: December 2004

The configuration of the spiro centre in polycyclic compounds containing a spiro[4.4]nonane substructure is analyzed in terms of symmetry coordinates. As revealed by X‐ray structures of such compounds, the local distortions around the quaternary C‐atom are dominated by a decrease of the ring‐bond angles at the spiro centre and a twist of one ring relative to the other. The planoid deformations given by the planarization index PC are comparatively small for spiro[4.4]nonanes, which contain either no additional bridges between the rings or only α,β′–or β,β′‐polymethylene bridges. This indicates that the local strain in the spiro C(C)4 fragments is rather small.
Syntheses of Diamino‐dideoxylyxose Derivatives using Acylnitroso Dienophiles
Authors: Defoin Albert , Fritz Hans , Schmidlin Christian , Streith Jacques
Published: December 2004

N‐Acylnitroso derivatives 6 which were prepared by in‐situ oxidation of the corresponding hydroxamic acids 5 reacted instantaneously and in high yields with dihydropyridine 4. The Diels‐Alder adducts 8 were formed regiospecifically with the acylnitroso dienophiles 6a–c, whereas the dienophiles 6d–f gave mixtures of both regioisomers 7 and 8. These and some other results [2] were best explained by the FMO theory. The Diels‐Alder adducts 7 and 8 gave the corresponding ‘anti’‐cis‐glycols when reacted with OsO4/N‐methylmorpholine N‐oxide. Hydrogenolysis of the N–O bond followed by peracetylation led to the expected aminolyxose derivatives 14 and 16. A similar sequence, using 4 and the hydroxamic‐acid derivative 18 of (+)‐D‐mandelic acid led, with a poor asymmetric induction, to a mixture of the expected optically active aminolyxose compounds 19A/19B.
Potassium Carboxylates by Direct Carbonylation of Potassium Alkoxides
Authors: Rautenstrauch Valentin
Published: December 2004

Reaction of the K+ alkoxide of linalool (1) in benzene with CO at 425–440 bar and 120–130° for 12–30 h gave the K+ salt of 2,6‐dimethyl‐2‐vinyl‐5‐heptenoic acid (4a) in a ca. 25% yield based on ca. 65% converted alkoxide. Reaction of the [K+ ⊂ 18‐crown‐6] alkoxide of 1 with CO at 50–55 bar and 40° for 90–140 h gave a mixture containing mainly the [K+ ⊂ 18‐c‐6] salts of 4a (ca. 62%) and of the homogeranic acids 3a and 6a (together ca. 27% of the mixture) in a ca. 35% combined yield based on 50–60% converted alkoxide. The uncomplexed or complexed K+ alkoxide of (S)−1 gave, with ca. 85% net retention, the K+ salt of (S)‐4a. Reaction of the [K+ ⊂ 18‐c‐6] alkoxide of geraniol (2) with CO at 50 bar and 40° for 65–70 h gave myrcene (10) and geranyl formate (11) in a ca. 40–50% yield each based on ca. 85% converted alkoxide. Reaction of the [K+ ⊂ 18‐c‐6] alkoxide of 3‐pentyl‐1,4‐pentadien‐3‐ol (14) at 50 bar and r.t. for 70 h gave a mixture of the [K+ ⊂ 18‐c‐6] salts of 2‐pentyl‐2‐vinyl‐3‐butenoic acid (15a) (67%) and the 4‐pentyl‐2,4‐hexadienoic acids 18a and 19a (together 23% of the mixture) in a ca. 90% combined yield based on ca. 65% converted alkoxide.
Facile Hetero‐Diels‐Alder Reaction of α,β‐Unsaturated Acyl Cyanides and Enol Ethers: Syntheses of 2‐Alkoxy‐3,4‐dihydro‐2H‐Pyran‐6‐carbonitriles
Authors: John Robert A. , Schmid Vincent , Wyler Hugo
Published: December 2004

2‐Ethoxy‐3,4‐dihydro‐2H‐pyran‐6‐carbonitriles are obtained in high yield by stereospecific endo‐mode cyclo‐additions of α,β‐unsaturated acyl cyanides and ethyl vinyl ether at room temperature. The nitrile group is converted to some other functionalities.
Coralloidin C, D, and E: Novel Eudesmane Sesquiterpenoids from the Mediterranean Alcyonacean Alcyonium coralloides
Authors: D'Ambrosio Michele , Guerriero Antonio , Pietra Francesco
Published: December 2004

The Mediterranean alcyonacean Alcyonium (=Parerythropodium) coralloides (Pallas, 1766) is shown to contain the novel eudesmane sesquiterpenoids coralloidin C (=(–)−(4R,10S)‐eudesma‐5,7(11)‐dien‐15‐yl acetate; (–)−4), coralloidin D (=(–)−(10R*)‐eudesma‐4,7(11)‐diene‐12,13‐diyl diacetate; (–)−7), and coralloidin E (=(+)−(4R*,10R*)‐eudesma‐5,7‐dien‐11‐ol;(+)−8). The absolute configuration of (–)−4 is derived by the exciton‐coupling method, applied to deacetylcoralloidin Cp‐anisate ((–)−6). Coralloidin E((+)−8), being also obtained on treatment of deacetylcoralloidin A (=(+)−(4R*, 8R*, 10R*)‐eudesma‐5,7(11)‐dien‐8‐ol; (+)−2) with (COCl)2 in DMSO, is configurationally correlated to coralloidin A (=(+)−(4R*, 8R*, 10R*)‐eudesma‐5,7(11)‐dien‐8‐yl acetate; (+)−1). Under acidic conditions, (+)−2 undergoes a complex rearrangement giving (+)‐(3R*, 4S*, 5R*, 6R*, 7S*)‐arist‐10‐(1)‐en ‐3‐ol ((+)−9), which is also obtained, together with (+)−8, on attempts to mesylate (+)−2.
Complete Sequence Determination and Localisation of One Imino and Three Sulfide Bridges of the Nonadecapeptide Ro 09–0198 by Homonuclear 2D‐NMR Spectroscopy. The DQF‐RELAYED‐NOESY‐Experiment
Authors: Kessler Horst , Steuernagel Stefan , Gillessen Dieter , Kamiyama Tsutomu
Published: December 2004

The constitution of the nonadecapeptide Ro 09–0198 (1) has been established by homonuclear two‐dimensional NMR spectroscopy. The peptide contains three sulfide bridges and a bridge formed from the side chain of a lysine residue (lysinoalanine moiety). Only the composition was known before, thus the complete sequencing and the elucidation of the bridges had to be performed. Of special importance was the application of the RELAYED‐NOESY experiment. This technique was improved by the introduction of a double‐quantum filter to reduce the tailing around the diagonal. The resulting sequence of 1 exhibits a surprizing analogy of this immunopotentiating peptide to the ACE inhibitor ancovenin.
Light‐Induced, Thermal, and Acid‐Catalyzed π‐Skeletal Rearrangements of Five‐Ring‐Annelated Heptalenes
Authors: Weber Roland H. , Brügger Paul , Jenny Titus A. , Hansen Hans‐Jürgen
Published: December 2004

It is shown that, upon irradiation in CDCl3 solution, 5,6,8,10‐tetramethylheptalene‐1,2‐dicarboxylic anhydride (6) rearranges to its double‐bond‐shift (DBS) isomer 7 in an equilibrium reaction (Scheme 2). The isomer 7 is DBS stable at −50°. At ca. 30°, a thermal equilibrium with 97.8% of 6 and 2.2% of 7 is rapidly established. Similarly, the ‘ortho’‐anhydrides 9 and 11 (Schemes 4 and 5) can be rearranged to their corresponding DBS isomers 12 and 13, respectively. Whereas 12 is DBS stable at 30° (at 100° in tetralin, 94.0% of 9 are in equilibrium with 6.0% of 12), the i‐Pr‐substituted isomer 13 is already at 30° in thermal equilibrium with 11 leading to 98.7% of 11 and 1.3% of 13. It is shown by rearrangement of diasteroisomeric ‘ortho’‐anhydrides of known relative and absolute configuration (Scheme 6) that the DBS in such five‐ring‐annelated heptalenes occurs with retention of the configuration of the heptalene skeleton as already established for other heptalene compounds. It is found that the DBS process may also take place under acid catalysis (e.g. HCl/CH3OH), thus yielding 9 from 12 (Scheme 9). The ‘ortho’‐anhydrides 21 and 23 (Scheme 10) which are isomeric with 9 and 11 (Scheme 3) undergo rapid DBS' already at room temperature. The thermal equilibrium 21⇄22 consists of 18% of 21 and 82% of 22 at 30° and that of 23⇄24 of 17% of 23 and 83% of 24 at −30°. From these equilibrium mixtures, the pure DBS isomer 22 can be obtained by crystallization. Again, these rapid DBS' occur with retention of configuration of the heptalene skeleton (Fig. 4).
Ringerweiterung durch Fragmentierung. Synthese von 15‐Pentadecanolid (Exaltolid®)
Authors: Milenkov Branimir , Guggisberg Armin , Hesse Manfred
Published: December 2004

Ring Enlargement by Fragmentation. Synthesis of 15‐Pentadecanolide (Exaltolide®)

The title compound was synthesized from 1‐(3′‐hydroxypropyl)‐2‐oxocyclododecane‐1‐carbonitrile (3), using two different routes (Scheme). The CN group of 3 was converted to the Me3N+ residue in 5 which underwent, upon NaH treatment, a fragmentation leading to the ring‐enlargement product 6. The same product was observed after heating the ring‐enlarged dimethylamine oxide 14, prepared from 3 by Bu4NF treatment and conversion of the CN into the dimethylamine‐oxide moiety. Ozonolysis of the methylidene double bond in 6 and reduction of the resulting C = O to a CH2 group gave Exaltolide® (8).
Verecynarmin A, a Novel Briarane Diterpenoid Isolated from Both the Mediterranean Nudibranch Molluse Armina maculata and its Prey, the Pennatulacean Octocoral Veretillum cynomorium
Authors: Guerriero Antonio , D'Ambrosio Michele , Pietra Francesco
Published: December 2004

The briarane diterpenoid verecynarmin A (=(−)).(8R,9S,11R,12aR,4Z,6Z)‐11,12‐epoxy‐8,8a,9,10,12,12a,13‐octahydro‐1,5,8a,12‐tetramethylbenzo[4,5]cyclodeca[1,2‐b]furan‐9‐yl acetate; ((−)‐1) is shown to be contained in both the Mediterranean nudibranch mollusc Armina maculata(RAFINESQUE) and its prey, the pennatulacean octocoral Veretillum cynomorium(PALLAS). The structure is mainly solved by 1D‐NMR, 2D‐NMR, and NOE studies of (−)‐1. However, the relative configurations at the epoxide and angular methyl centres, as well as the preferred conformation, are established by shift‐reagent and NOE studies of diol(−)‐4 obtained by epoxide‐ring opening of (−)‐1 with LiA1H4. The absolute configuration is established via deacetylation of (−)01 followed by Horeau's esterification.
2,4‐Bis(4‐methylpheylthio)‐1,3,2λ5,4λ5‐dithiadiphosphetan‐2,4‐dithion: Ein neues Reagens zur Schwefelung von N,N‐disubstituierten Amiden
Authors: Wipf Peter , Jenny Christjohannes , Heimgartner Heinz
Published: December 2004

2,4‐Bis(4‐methylphenylthio)‐1,3,2λ5,4λ5‐dithiadiphosphetane‐2,4‐dithione: A New Reagent for Thiation of N,N‐Disubstituted Amides

As a new reagent for the thiation of amides, the easily accessible 2,4‐bis(4‐methylphenylthio)‐1,3,2λ5,4λ5‐dithiadiphosphetane‐2,4‐dithione (9) shows a remarkable selectivity. This selectivity – the preferred thiation of N,N‐disubstituted amides – is complementary to the one of the well known Lawesson reagent. Thiation of diamides of type 2 with 9 leads via cyclization of the corresponding dithiodiamides to 1,3‐thiazole‐5(4H)‐thiones 1 (Scheme 3).
Sterospecific Syntheses and Spectroscopic Properties of Isomeric 2,4,6,8‐Undecatetraenes. New Hydrocarbons from the Marine Brown Alga Giffordia mitchellae. Part IV.
Authors: Boland Wilhelm , Schroer Nora , Sieler Christiane , Feigel Martin
Published: December 2004

Giffordene (=(2Z,4Z,6E,8Z)‐2,4,6,8‐undecatetraene; 9f) and five steroisomers are new C11H16 hydrocarbons from the marine brown alga Giffordia mitchellae. Their synthesis is based on non‐stereoselective Wittig reactions of (E)‐2‐alkenals with appropriate acetylenic phosphoranes and subsequent chromatographic separation of the resulting (E/Z)‐pairs. The uniform enynes (>98% purity) are then stereospecifically reduced to (Z)‐alkenes with Zn(Cu/Ag) in aq. MeOH at r.t. 13C‐ and 1 H‐NMR data of the new tetraenes are presented. Biosynthetically, giffordene (9f) originates from dodeca‐3,6,9‐trienoic acid via an unstable (3Z,5Z,8Z)‐1,3,5,8,‐undecatetraene followed by a thermally allowed antarafacial 1,7‐sigmatropic hydrogen shift to the (2Z,4Z,6E,8Z)‐isomer9f.
Strukturaufklärung ungewöhnlicher Umlagerungsprodukte von S‐(1‐Alkenyl)sulfoximiden mit Hilfe der Stossaktivierungsmassenspektrometrie (CAD‐MS)
Authors: Veith Hans‐Jürgen , Gais Hans‐Joachim , Erdelmeier Irene
Published: December 2004

Structure Determination of Unusual Rearrangement Products of S‐(1‐Alkenyl)sulfoximides by Collisionally Activated Dissoication Mass Spectrometry (CAD‐MS)

The Molecular ions of s‐(l‐alkenyl)‐‐N‐(p‐tolyl)sulfoximides 1 are transformed into the N(phenylsufenyl)sulfonamides 3+ by a 1,2‐migration of the alkenyle group to the O‐atom of the sulfoximide function followed by a 2,3‐sigmatropic rearrangement. The structure of the production e has been unambiguouslydetermined by the CAD method, showing the identity of the ion e (m/z368) obtained from 1a and from 4a.
Raspailynes, Novel Long‐Chain Acetylenic Enol Ethers of Glycerol from the Marine Sponges Raspailia pumila and Raspailia ramosa
Authors: Guella Graziano , Mancini Ines , Pietra Francesco
Published: December 2004

The sponges Raspailia pumila and ramosa (Demospongiae, Tetractinomorpha, Axinellida) from the North‐East Atlantic are shown to contain a series of novel long‐chain enol ethers of glycerol where the enol ether CC bond is conjugated, in sequence, to both an acetylenic and an olefinic bond. Polar extracts give raspailynes hydroxylated at their (1Z5Z)‐1,5‐alkadien‐3‐ynyl chain, like raspailyne Al ( = (+)‐(S)‐3‐[((1Z,5Z)‐16‐hydroxy‐hexadeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; (+2) and isoraspailyne A ( = (+)‐3‐[((1Z,5Z)‐17‐hydroxyocta‐deca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐[propanediol; (+)‐3). Less polar extracts give 3 different types of raspailynes not hydroxylated at the chain. Raspailynes of the first type have either the (1Z,5Z)‐configuration in a linear chain such as raspailyne B2 (( = (−)‐(s)‐3‐[((1Z,5Z)‐trideca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; (−)‐4), raspailyne Bl ( = (−)‐3‐[((1Z,5Z)‐tetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol;(−)‐5), and raspailyne B ( = 3‐[((1Z,5Z)‐pentadeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 6) or the (1Z,5Z)‐pentadeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 6)or the (1Z,5Z)‐configuration in a chain ending with an isopropyl group, like isoraspailyne Bl ( = 3‐[((1Z,5Z)‐12‐methyltrideca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 7) and isoraspailyne B ( = 3‐[((1Z,5Z)‐13‐methyltetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 8). Raspailynes of the second type have the (1Z,5E)‐configuration, like isoraspailyne Bla ( =3‐[((1Z,5E)‐tetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 9) and isoraspailyne Ba ( = 3‐[((1Z,5E)‐13‐methyltetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol; 10). Raspailynes of the third type have the (1E,5Z)‐configuration, like isoraspailyne Blb ( = 3‐[((1E,5Z)‐tetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2,‐propanediol; 11). The (S)‐configuration for (+)‐1,((+)‐2, and (−)‐4 is derived from chemical correlations.
Complexes of 2,2′,2″‐Nirtilotriphenol. Part IV. Cage Compounds with Phosphorus(III) and Phosphorus(V)
Authors: Müller Edgar , Bürgi Hans Beat
Published: December 2004

The ligand 2,2′,2″‐nitrilotriphenol reacts with P(III) and P(V) compounds to form corresponding phosphorus complexes. Syntheses and NMR data of 2,2′,2″‐nitrilotriphenyl phosphite (II), 2,2′,2″‐nitrilotriphenyl phosphate (III) and of a hydrolysis product of II, 2,2′‐[N‐(2‐hydroxyphenyl)imino]diphenly phosphonate (IV), are reported, as well as crystal structures of II and IV. Phosphite II shows a bicycloundecane framework; no NċPinteraction is present. The phosphonate IV shows two coordinated and one dangling phenol group; the N‐atom does not interact with the P‐atom. Strong acids protonate II as well as III to form cations: in these, NMR evidence indicates coordination of the N‐atom to the P‐atom.
Oxidative Breaking of Long‐Chain Acetylenic Enol Ethers of Glycerol of the Marine Sponges Raspailia pumila and of Model Compounds with Aerial Oxygen
Authors: Guella Graziano , Mancini Ines , Pietra Francesco
Published: December 2004

The raspailynes (novel long‐chain enol ethers of glycerol having the enol ethers double bond conjugated in sequence, to an acetylenic and an olefinic bond, isolated from the North‐East‐Atlantic sponges Raspailia pumila and R. ramosa) are stable under normal hydrolytic conditions for enol ethers. In contrast, when their solutions are evaporated, these lipids such as raspailyne Bl (=(−))‐3‐[(1Z,5Z)‐(tetradeca‐1,5‐dien‐3‐ynyl)oxy]‐1,2‐propanediol;(−‐2) rapidly react with aerial O2 under normal laboratory‐daylight conditions, with rupture of the C=C enol ether bond to give 1‐O‐formylglycerol (3) and an aldehyde (such as tridec‐4‐en‐2ynal(4) from (−)‐2). This reaction must be caused by triplet O2, since thermally generated singlet O2 has no effect on (−)‐2 in solution. That the mere presence of an enol‐ether moiety conjugated to an acetylenic group is responsible for such a behaviour is demonstrated with the model compounds 1‐methoxypentadec‐1‐en‐3‐yn‐5‐ol (6a) and its 5‐O‐acetyl or 5‐O‐tetra‐hydropyranyl derivatives 6b and 6c, respectively. Resistance to both hydroytic conditions and singlet O2 of these compounds is thought to arise from electron depletion at the enol‐ether C(beta;) atom by the acetylenic group. Plausible reaction pathways for enol‐ether bond rupture in these compounds by aerial O2 are outlined.
β‐Cleavage of Bis(homoallylic) Potassium Alkoxides. Preparation of 3‐Hydroxypropyl and 4‐Hydroxybutyl Propenyl Ketones from γ‐ and δ‐Lactones. Synthesis of (±)‐Rose oxide
Authors: Snowden Roger L. , Linder Simon M. , Muller Bernard L. , Schulte‐Elte Karl H.
Published: December 2004

Starting from γ‐ and δ‐lactones 1–3, a two‐step preparation of 3‐hydroxypropyl and 4‐ hydroxybutyl propenyl ketones 10–18 is described, involving as the key step the β‐cleavage of the bis(homoallylic) potassium alkoxides 4a–9a. The novel methodology is illustrated by a short synthesis of (±)‐rose oxide(20).
A Torquospecific 1,5‐Electrocyclization
Authors: Gesche Paul , Klinger François , Riesen Andreas , Tschamber Théophile , Zehnder Margareta , Streith Jacques
Published: December 2004

Saponification of homodiazepine 1a and 1b, in the absence of any proton donors, led to the formation of the 6π electron anionic species A which, by virtue of a 1,5‐electrocyclization, is in equilibrium with the allylic anion B. This latter tricyclic species is thermodynamically less favoured than its bicyclic isomer A. Nevertheless, B could be trapped by acylation and led tupe‐2 compounds which are the major reaction products. This is due to the fact that B is more nucleophilic and, therefore, much more reactive than A. The transoid topology of the tricyclic products 2 was demonstrated by 1H‐NMR and by an X‐ray diagram of 2d. The transoid geometry of 2 is a consequence of a torquospecific 1,5‐electrocyclization (of A), which is due to a steric, and possibly even to an electronic factor.
Pulse Radiolytic Studies of 1‐Halo‐2‐(methylthio)ethanes in Hexane and 1,2‐Dichloroethane: Formation of an Intermolecular Species with a Three‐Electron Bond between Sulfur and Iodine
Authors: Anklam Elke , Mohan Hari , Asmus Klaus‐Dieter
Published: December 2004

1‐Iodo‐2‐(methylthio)ethane was synthesized via a ring‐opening reaction of thiirane with MeI in MeCN. The S‐centered radical cation of this compound undergoes an intermolecular stabilization with the I substituent of a second unattacked substrate molecule to yield an magnified image bonded radical cation. The oxidation was initiated by solvent radical cations in irradiated 1,2‐dicloroethane and hexane solutions. The 2ρ/ρ* three‐electron‐bonded species exhibits an optical absorption band at 410 nm, detectable by pulse radiolysis. During its decay, a new, longer‐lived absorption band is formed at 380 nm which is assigned to . The latter is suggested to result from anchimeric assistance in the generation of a cyclic sulfonium salt. The radical cations of 1‐bromo‐and 1‐chloro‐2‐(methylthio)ethane are assumed to undergo raped cyclization to the sulfonium salt without stabilization in any intermolecular S‐Br or S‐Cl interaction.
Azomalonic Ester Syntheses. Part I. One‐Step Synthesis of Triazolo[1,4]benzodiazepines from Azomalonates. Preparation of Novel Polyaza Tricycles from Diethyl (2‐Chloroacetamido)malonate
Authors: Heckendorn Roland
Published: December 2004

A useful synthetic principle for the preparation of N‐heterocycles consists in the base treatment of azoma‐lonates carrying electrophilic centers in the side chain. Thus, pharmacologically active triazolo[1,4]benzodiazepine‐carboxamides can be prepared in one step from azomalonates derived from 2‐aminobenzophenones and diethyl (2‐chloroacetamido)malonate. The same malonate coupled with diazotized 3‐amino‐2‐chloropyridine leads in 2 steps to 3 novel pyridotriazoloazines. Similarly, N‐protected 2‐amino‐diphenylamine derivatives are converted into triazoloquinoxaline‐carboxylic acids. The heteocycles are further characterized by functional‐group inter‐conversion. Some mechanistic aspects of the azomalonic‐ester synthesis are discussed.
Asymmetric Induction at C(β) and C(α) of N‐Enoylsultams by Organomagnesium 1,4‐Addition/Enolate Trapping
Authors: Oppolzer Wolfgang , Poli Giovanni , Kingma Arend J. , Starkemann Christian , Bernardinelli Gérald
Published: December 2004

The 1,4‐addition of alkylmagnesium chlorides to conjugated N‐enoylsultams and subsequent ‘enolate trapping’ with aq. NH4Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π‐face defferentiation as demonstrated by the conversions 1→2, 1→4, and 8→9. This holds also for the regioselective 1,4‐addition of EtMgC1 to a dienoylsultam (15→16). Reactive conformations 1≠, 8≠, 13, and 14 are postulated in agreement with X‐ray evidence which also served for the structure determination of the product 9j.
Aminierende reduktive Kupplung aromatischer Aldehyde mit niervalenten Titan‐Reagenzien zu 1,2‐Diarylethylendiaminen
Authors: Betschart Claudia , Seebach Dieter
Published: December 2004

Preparation of 1,2‐Diarylethylenediamines by Aminative Reductive Coupling of Aromatic Aldehydes with Low‐Valent Titanium Reagents

In a novel McMurry‐ Type one‐pot reaction, aromatic aldehydes and secondary amines are poupled of give the N, N, N′, N′‐tetraalkyl‐1,2‐diarylethylendiamines 1–22 (Table 3). To this end, a lithium dialkylamide is added to an aromatic aldehyde to give the adduct B which is then treated with 1 equiv. of TiC14 to yield a coloured suspension of a reagent synthetically equivalent to a iminium salt (C/D in Scheme 4). After treatment with a low‐valent Ti reagent which is prepared by reduction of TiC14 with either K or, preferably, Mg, the coupling products are isolated in 23 to 81% yield as a 1:1 mixture of the diastereoisomers (meso‐ and rac‐form). These are separated either by chromatography or by crystallization and characterized.
Synthesis and Reactions of Optically Active 1,3‐Diols
Authors: Rösslein Lukas , Tamm Christoph
Published: December 2004

The ‘syn’‐1,3‐diols 3,4 and 5 with a C7, C6, and C5 chain, respectively, were synthesized from methyl hydrogen 3‐hydroxyglutarate (2; Schemes 1 and 2). The latter is available in (R)‐ and (S)‐configuration. Octyl (3R)‐4‐chloro‐3‐hydroxybutanoate (17) is an alternative starting material for the preparation of 5 (Scheme 3.) The epoxide 20, derived from 5 in a one‐pot reaction, is a versatile synthon, which selectively reacts with a great number of nucleophiles (Scheme 4).
Dendryphiellin A, the First Fungal Trinor‐eremophilane. Isolation from the marine deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT
Authors: Guerriero Antonio , D'Ambrosio Michele , Pietra Francesco , Cuomo Vincenzo , Vanzanella Fortunato
Published: December 2004

The novel metabolite dendryphiellin A ( = (+)‐(1R,2S,8aR)‐ 1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*, 2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoate; (+)‐1) is isolated from cultures of the marine deuteromycete Dendryphiella salina. There is no precedent in fungi for trinor‐eremophilanes or for branched C9 carboxylic acids, the two classes of compounds constituting (+)‐1. The structure is secured by NMR spectroscopy and hydrolysis of (+)‐1 to give the side‐chain moiety ((6R*,2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoic acid (2)) intact, whilst the trinor‐ermophilane moiety is decomposed. The absolute configuration at the trinor‐eremophilane moiety is established from exciton coupling between the dienone and the diene‐ester functions.
New Pterocarpinoids from Dolichos marginata ssp. erecta
Authors: Gunzinger Jan , Hostettmann Kurt , Msonthi Jerome D.
Published: December 2004

Four new pterocarpinoids, sphenostylin A, B, C, and D (1–4), have been isolated from the CHCl3 extract of the root bark of Dolichos marginata ssp. erecta (Leguminosae) by preparative liquid chromatography. The structures have been established by spectroscopic methods (UV, 1H‐NMR, 13C‐NMR, EI‐MS, DCI‐MS, CD) and chemical transformations. The isolated compounds showed weak antifungal activity against Cladosporium cucumerinum.
Free‐Energy Dependence of the Ion Yield of Photo‐Induced Electron‐Transfer Reactions in Solution
Authors: Vauthey Eric , Suppan Paul , Haselbach Edwin
Published: December 2004

A study of photo‐induced electron‐transfer reactions in MeCN with 9,10‐dicyanoanthracene as acceptor and 21 electron donors with transient photoconductivity measurements is reported. The free‐ion yield and the rate constant of back electron transfer are determined. For exergonic reactions, the ‘Marcus‐inverted’ region is observed. The fit with the theory is best, when a nearly solvent‐independent Coulomb term is used in the calculation of the energy balance.
The dimeric and polymeric anhydride of 2,3‐O‐isopropylidene‐β‐D‐ribofuranose. An NMR study
Authors: Winkler Tammo , Ernst Beat
Published: December 2004

The 1H‐ and 13C‐NMR data of the dimeric anhydride 1 of 2,3‐O‐isopropylidene‐β‐D‐ribofuranose are reported together with the 1H‐NOE values. The data show that the products of the polymerization of 1,5‐anhydro‐2,3‐O‐isopropylidene‐β‐D‐ribofuranose are α‐ and β‐D‐ribofuranans and not an α‐D‐ribofuranan and a β‐D‐ribofuranan and a β D ribo‐pyranan as claimed before [2] [3].
Spectroscopic and Electrochemical Behavior of Cyclometalated Pd(II) Complexes
Authors: Maestri Mauro , Sandrini Diana , Balzani Vincenzo , von Zelewsky Alex , Jolliet Philippe
Published: December 2004

The absorption and emission spectra, emission lifetimes, luminescence quantum yields, and electrochemical behavior of the complexes Pd(Phpy)2, Pd(Thpy)2, and Pd(bhq)2 (Phpy−, Thpy−, and bhq−, and bhq− are the deprotonated forms of 2‐phenylpyridine, 2‐(2‐thienyl)pyridine, and benzo[h] quinoline, respectively) have been studied, and the results obtained have been compared with those available for Pt(II) and Pt(IV) complexes containing the same ligands. The intense ligand‐centered absorption bands below 340 nm are strongly perturbed by matalation, and the absorption features in the 340–450‐nm region are likely to include contributions from formally metal‐to‐ligand charge‐transfer transitions. The structured luminescence spectra observed at 77 K (lifetimes are 0.48, 0.28 and 2.6 ms for Pd(Phpy)2, Pd(Thpy)2, and Pd(bhq)2, respectively) have been assigned to transitions having mainly ligand‐centered character, with an increasing metal‐to‐ligand charge‐transfer contribution in going from Pd(bhq)2 to Pd(Phpy)2 and to Pd(Thpy)2. The complexes Pd(phpy)2 and Pd(thpy)2 show two reversible one‐electron reduction waves, whereas reduction of Pd(bhq)2 is irreversible, as is the oxidation of the three complexes.
Herstellung enantiomerenreiner, α‐alkylierter Lysin‐, Ornithin‐ und Tryptophan‐Derivate
Authors: Gander‐Coquoz Marlyse , Seebach Dieter
Published: December 2004

Synthesis of Enantiomerically Pure, α‐Alkylated Lysine, Ornithine, and Tryptophan Derivatives

The imidazolidinones 9 and 10 as well as the oxazolidinone 18a were prepared in several steps by known methods from lysine and ornithine with an overall yield of ca. 20%. After double deprotonation with LDA, the corresponding dianionic derivatives could be diastereoselectively alkylated with electrophiles (MeI, C6H5CH2Br, C6H5CHO, CH3CHO). Acid hydrolysis led to the two enantiomeric 2‐methyl‐ and 2‐benzyllysines and to the enzyme inhibitor (S)‐2‐methylornithine. Several α‐alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1‐(tert‐butyloxycarbonyl)‐3‐(bromomethyl)indole (26). Alkaline hydrolysis of the five‐membered auxiliary ring of 30b followed by treatment with HCl afforded (S)‐2‐methyltryptophan (31).
Notiz zur Synthese Eines Optisch Aktiven Ace‐Hemmers mit Amino‐oxo‐benzazepin‐1‐alkansäure‐Struktur mittels enantiokonvergierender kristallisationsinduzierter Racemat‐Trennung
Authors: Boyer Stephen K. , Pfund Rolland A. , Portmann Robert E. , Sedelmeier Gottfried H. , Wetter Hansjürg F.
Published: December 2004

Note on the Synthesis of an Optically Active ACE Inhibitor with Amino‐oxo‐benzazepine‐1‐alkanoic‐Acid Structure by Means of an Enantioconvergent Crystallization‐Based Resolution

An enantioselective synthesis of the potent angiotensin‐converting enzyme inhibitor (1′S,3S)‐3‐[(1′‐(ethoxy‐carbonyl)‐3′‐phenylpropyl)amino]‐2,3,4,5‐tetrahydro‐2‐oxo‐1H‐1‐benzazepine‐1‐acetic acid hydrochloride (3) is described which user a crystallization‐based resolution of a racemic amino intermediate with concomitant racemization of the unwanted enantiomer.