bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemie der Amino‐oxime, XIX. Umsetzung von β‐Benzylamino‐oximen mit Sulfurylchlorid
Authors: Gnichtel Horst , Köhler Christoph
Published: July 2007

Chemistry of Amino Oximes, XIX. — Reaction of β‐Benzylamino Oximes with Sulfuryl Chloride

3,4‐Dihydro‐2H‐1,2,6‐thiadiazine 1,1,6‐trioxides 2 were prepared from anti‐β‐benzylamino oximes 1 and sulfuryl chloride. Tetrahydro‐2H‐1,2,6‐thiadiazin 1,1‐dioxides 3 were formed by reduction with NaBH4 and β‐hydroxylimino sulfamic acid derivatives by hydrolysis, alkoholysis, and aminolysis with secondary amines. With primary amines, 2 afforded pyrazolines 7; syn‐β‐benzylamino oximes 9 and sulfuryl chloride yielded pyrazolines 10.
Total synthesis of methynolide
Authors: Ditrich Klaus
Published: July 2007

In this paper the synthesis of methynolide (1), the aglycone of methymycin, a 12‐membered macrolide antibiotic is described. We have used the chiral C‐1 to C‐8 segment 10 which has been combined with the C‐9 to C‐13 segment 9 to form the carbon skeleton of methynolide. Cyclization of the seco‐acid 14 has been accomplished by intramolecular esterification.
1,3‐dipolar cycloaddition reactions of 1‐aryl‐N‐methyl‐2(1H‐azol‐1‐yl)‐ethanimine N‐oxides to olefins
Authors: Mullen George B. , Bennett Grace A. , Swift Patricia A. , Marinyak David M. , Dormer Peter G. , Georgiev Vassil St.
Published: July 2007

The regio‐ and stereoselectivity of the 1,3‐dipolar cycloaddition reaction of 1‐aryl‐N‐methyl‐2‐(1H‐azol‐1‐yl)ethanimine N‐oxides 6 to monosubstituted olefins 7 were investigated. The reaction is regioselective, leading to the corresponding C‐5 substituted isoxazolidines 8/9 as cis/trans diastereomeric mixtures. The cis isomers, which are the predominant species of the mixtures, are readily separated by flash chromatography on neutral silica gel.
Thermal valence rearrangements of heterocycles, 3. A key aziridine intermediate of the Δ4‐isoxazoline‐pyrrole rearrangement
Authors: Mullen George B. , Bennett Grace A. , Georgiev Vassil St.
Published: July 2007

Utilizing the spiro[adamantane‐Δ4‐isoxazoline] precursor 10, a key 2‐acylaziridine intermediate (11) has been isolated, thus providing conclusive evidence that an initial ring contraction may be considered to be the first step of the Δ4‐isoxazoline‐pyrrole rearrangement.
Synthese von [1,1,3‐Trioxo‐1,2‐benzisothiazol‐2(3H)‐yl]keten‐S,S‐acetalen und deren Hydrazinolyse
Authors: Dölling Wolfgang , Herrmann Cornelia , Augustin Manfred
Published: July 2007

Synthesis of [1,1,3‐Trioxo‐1,2‐benzisothiazol‐2(3H)‐yl]ketene S,S‐Acetals and Their Reaction with Hydrazine Hydrate

The previously unknown ketene S,S‐acetals 2, 3, and 4 are prepared by dithiocarboxylation reaction of methylene‐active saccharin derivatives 1 in the presence of sodium hydride/carbon disulfide in dry DMF followed by alkylation. Compounds 2a, 3a, and 4a are treated with hydrazine hydrate (85%) to give 2‐hydrazono‐3,3‐bis(methylthio)propiophenone (6a) and methyl or ethyl pyruvate 6b or 6c, respectively.
Studies on isocyanides. Synthesis of N‐substituted 2‐isocyanocarboxamides
Authors: Bossio Ricardo , Marcaccini Stefano , Pepino Roberto
Published: July 2007

The Ugi four‐component condensation between isocyanides, aldehydes, and ammonium formate affords N‐substituted 2‐formylaminocarboxamides 1 which are dehydrated with POCl3/NEt3 to give the title compounds.
(1S,3S,5S)‐2‐Amino‐3‐methoxymethyl‐2‐azabicyclo [3.3.0]octan: SAMBO — ein neuer chiraler Hilfsstoff
Authors: Martens Jürgen , Lübben Stefan
Published: July 2007

(1S,3S,5S)‐2‐Amino‐3‐methoxymethyl‐2‐ azabicyclo[3.3.0]octane: SAMBO — a New Chiral Auxiliar

(1S,3S,5S)‐2‐Amino‐3‐methoxymethyl‐2‐azabicyclo[3.3.0] octane (SAMBO) (8) was synthesized with an overall yield of 48% starting from the α‐amino acid derivative benzyl (1S,3S,5S)‐2‐azabicyclo[3.3.0]octane‐3‐carboxylate (1) by a six‐step procedure.
Antibiotics from gliding bacteria, XLII. Chemical modification of sorangicin A and structure — Activity relationship I: Carboxyl and hydroxyl group derivatives
Authors: Jansen Rolf , Schummer Dietmar , Irschik Herbert , Höfle Gerhard
Published: July 2007

The synthesis of selectively protected sorangicin A derivatives and their application in the modification of the hydroxyl groups and the carboxyl group in sorangicin A (1) is described. Esters, amides, and sorangicins modified at the hydroxyl groups were prepared and their activities against Staphylococcus aureus, Escherichia coli, and their in vitro inhibition of RNA polymerase were examined. Although no sorangicin A derivatives with superior biological activity were observed, some derivatives completely retained their antibiotic activity or were slightly improved in their activity with certain strains.
Isolierung und Struktur der vier Hauptsaponine aus Solidago gigantea var. serotina
Authors: Reznicek Gottfried , Jurenitsch Johann , Kubelka Wolfgang , Michl Günter , Korhammer Siegfried , Haslinger Ernst
Published: July 2007

Isolation and Structure of the Four Main Saponins from Solidago gigantea var. serotina

The four main saponins from Solidago gigantea Ait. var. serotina (O. Kuntze) Cronq. were isolated. The giganteasaponins 1 — 4 are new bis‐desmosidic triterpensaponins containing 9 or 10 sugar units with bayogenin as aglycone. Their structures were determined by modern NMR techniques and GC/MS without extensive degradation studies.
Biologically active glycosides from Asteroidea, XXIII. Synthesis of acanthacerebroside A
Authors: Sugiyama Shigeo , Honda Masanori , Komori Tetsuya
Published: July 2007

(R)‐2‐Hydroxytetracosanoic acid (2), prepared by using the chiral building block benzyl (R)‐2,3‐epoxypropyl ether (7), was coupled to (2S,3S,4R)‐2‐amino‐1,3,4‐hexadecanetriol (3) to give the ceramide 4. Glycosidation of 4 with D‐glucopyranose affords acanthacerebroside A, (2S,3S,4R)‐1‐O‐(β‐D‐glucopyranosyl)‐2‐[(R)‐2‐hydroxytetracosanoylamino]‐1,3,4‐hexadecanetriol (1).
Synthesis of 3′‐azido‐2′,3′‐dideoxy‐β‐D‐arabino‐hexopyranosyl nucleosides
Authors: Hansen Poul , Lau Jesper , Pedersen Erik B. , Nielsen Carsten M.
Published: July 2007

The α,β‐unsaturated D‐sugar aldehyde 2, prepared from tri‐O‐acetyl‐D‐glucal, was converted into 1‐O‐acetyl‐3‐azido‐2,3‐dideoxy‐α‐D‐arabino‐pyranose (3) by reaction with sodium azide in a mixture of acetic acid and water followed by acetylation. Reaction of 3 with silylated pyrimidines using TMS triflate as catalyst followed by deprotection with saturated ammonia in methanol afforded 3′‐azido‐2′,3′‐dideoxy‐β‐D‐arabino‐hexopyranosyl nucleosides 4.
Synthesis of 3‐heptyl‐ and 3‐nonyl‐2,4(1H,3H)‐quinolinediones
Authors: Laschober Rita , Stadlbauer Wolfgang
Published: July 2007

3‐Alkl‐3‐hydroxy‐2,4‐(1H,3H)‐quinolinediones 4, which are metabolites of some Pseudomonas species, were synthesized by oxidation of the corresponding 4‐hydroxy‐2(1H)‐quinolones 3. By halogenation of 3 the 3‐chloro‐ and 3‐bromo‐2,4‐(1H,3H)‐quinolinediones 5 and 7, respectively, are obtained. Exchange of the chloro substitutent in 5 with sodium azide yields the 3‐azido derivatives 8, while reaction with potassium fluoride affords the 3‐fluoroquinolinediones 6.
Synthesis of Vinca alkaloids and related compounds, LIV. Synthesis of (±)‐16‐deethyl‐vincamines, (Deethyl)‐16‐deethyl‐apovincamines, and their 10‐bromo derivatives
Authors: Sápi János , Szabó Lajos , Thurner Angelika , Baitz‐Gács Eszter , Tamás József , Kalaus György , Szántay Csaba
Published: July 2007

A versatile method for introducing a functionalized side chain into enamines 9a and 11a is described. This procedure provides an easy access to 16‐deethyl‐vincamines 16, 17 and 16‐deethyl‐apovincamines 18–21.
A short route to 3′‐deoxy‐3′‐fluorothymidine
Authors: Motawia Mohammed S. , Pedersen Erik B.
Published: July 2007

The 5‐OH‐protected methyl glycosides 2 and 3 were epimerized to give the corresponding epimers 6 and 7 via an oxidation‐reduction procedure. Reaction of 6 with diethylamino‐sulfur trifluoride (DAST) afforded the fluoro sugar 8, which was coupled with thymine to give 3′‐deoxy‐3′‐fluorothymidine (12) after deprotection with saturated ammonia in methanol.
Über neue Säuren im ostindischen Sandelholzöl
Authors: Nikiforov Alexej , Jirovetz Leopold , Machatschek Susanne , Stanek Wolfgang , Buchbauer Gerhard
Published: July 2007

New Acids in the East Indian Sandalwood Oil

Three new terpenoic acids, dihydro‐α‐norcurcumenic acid (2), α‐bergamotenic acid (3), and dihydro‐α‐santalic acid (4), could be identified by means of GC‐MS and GC‐FTIR techniques as genuine constituents of the East Indian sandalwood oil. The former postulated γ‐santalic acid (1) could not be detected. Also a series of pyrolytic experiments did not lead to its formation.
Pheromone synthesis, CXXII. (E)‐ and (Z)‐tetradecenyl formate, potent sex pheromone mimics against the yellow peach moth
Authors: Mori Kenji , Watanabe Hidenori , Fujiwhara Mitsuhiko , Kuwahara Shigefumi
Published: July 2007

Synthesis and biological evaluation of (E)‐ and (Z)‐8‐tetradecenyl formate (3, 4) as pheromone mimics was executed. A 10:1 mixture of the (E)‐ and (Z)‐formate was shown to be as attractive as a 10: 1 mixture of (E)‐ and (Z)‐10‐hexadecenal (1, 2) (genuine pheromone) in a 100‐ng dose against the male yellow peach moth, Dichocrocis punctiferalis.
Reaktionssteuerung durch die Struktur eines Phasentransfer‐Katalysators bei Tribrommethyl‐Anion‐/Dibromcarben‐Umsetzungen
Authors: V. Dehmlow Eckehard , Wilkenloh Jürgen
Published: July 2007

Control of Reactions with Tribromomethyl Anions/Dibromocarbene by the Nature of the Phase Transfer Catalyst

Conversion of (substituted) allyl bromides with bromoform/sodium hydroxide/phase transfer catalyst may be directed towards dibromocarbene addition or substitution by tribromomethyl anion by choice of the catalyst. The observed effects (addition: substitution in the primary step variable between maximally 92:1 and 1:91) are by far the largest reported for specific catalyst influences. Small, hard cations favor the carbene route, sterically shielded and highly delocalized ones favor the substitution process.
Über Pyridinium‐N‐phenolat‐Betaine und ihre Verwendung zur Charakterisierung der Polarität von Lösungsmitteln, XIV. Versuche zur Herstellung eines chiro‐solvatochromen Pyridinium‐N‐phenolat‐Betainfarbstoffs
Authors: Reichardt Christian , Wilk Martina
Published: July 2007

Pyridinium N‐Phenoxide Betaines and Their Application for the Characterization of Solvent Polarities, XIV. — Attempted Synthesis of a Chiro‐Solvatochromic Pyridinium N‐Phenoxide Betaine Dye

Synthesis and UV/VIS spectroscopic properties of the negatively solvatochromic, chiral, (S,S)‐configurated betaine dye 8 are described. There is a linear correlation between the ET′ values of 8 and the ET(30) values of the standard betaine dye 1 (Figure 1). Unfortunately, (S,S)‐8, dissolved in enantiomeric pure (R)‐ and (S)‐configurated alcohols and amines, does not show a measurable chiro‐solvatochromism (Table 2).
Polycyclische Aromatische Alkaloide, V. Synthese von 2‐Bromleptoclinidinon
Authors: Bracher Franz
Published: July 2007

Polycyclic Aromatic Alkaloids, V. – Synthesis of 2‐Bromoleptoclinidinone

4‐Bromo‐2‐nitroacetophenone (6) is selectively reduced to the amine 7 by Fe in aqueous acetic acid. Oxidative amination of quinolinequinone 8 with 7 gives 9. Acid‐catalyzed cyclization of 9, followed by anellation of a pyridine ring, gives the cytotoxic pentacyclic alkaloid 2‐bromoleptoclinidinone (3).
Glycosidation, 14. Stereoselective synthesis of acetal‐β‐glucosides by reaction of 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranose with enol ethers
Authors: Tietze Lutz F. , Lögers Michael
Published: July 2007

Acetal‐glycosides are a new class of compounds which is of interest in the development of selective anticancer agents. Cytotoxic aldehydes and ketones may be released by enzymatic or acid‐catalyzed hydrolysis preferentially in the tumour tissue. An alternative synthetic route to acetal‐β‐glucosides 4 was developed in connection with these investigations. The acetyl‐protected acetal‐β‐glucosides 3a–h are obtained anomerically pure in 63–95% yield by reaction of 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranose (1) with an enol ether 2a–h in the presence of catalytic amounts of p‐toluenesulfonic acid in dry tetrahydrofuran at room temperature. Deacetylation with potassium carbonate in methanol gives the free acetal‐β‐glucosides 4a–h.
An improved preparation of 2‐methylene‐ and 2,3‐dimethylenecephalosporins
Authors: Gunda Tamas E.
Published: July 2007

The one‐step reductive cleavage and reduction of 3‐acetoxymethyl‐2‐methylenecephalosporin sulphoxides provides easy access to 2,3‐dimethylenecephems.
Unsymmetrically substituted furoxans, XII. Phenylfuroxancarboxylic acids and their derivatives
Authors: Fruttero Roberta , Ferrarotti Bruno , Serafino Anna , Gasco Alberto
Published: July 2007

Synthesis and structure of the two isomeric furoxancarboxylic acids 3 and 14 and of a few of their derivatives 10–13, 15, 16 is reported. 1,3 Dipolar cycloaddition reactions of the product obtained by thermal decomposition of 4‐phenyl‐3‐furoxancarboxylic acid and thermal equilibration of furoxan derivatives are also discussed.
Approach to chiral vicinal diacylamines by Bamberger ring cleavage of substituted imidazoles
Authors: Altman Janina , Grinberg Mircea , Wilchek Meir
Published: July 2007

Ring cleavage of ethyl 3‐[4(5)‐imidazolyl]propanoate (1) with (−)‐menthyl chloroformate introduces chiral carbamate substituents on the double bond which, upon hydrogenation, induces preferred formation of ethyl (4S)‐4,5‐bis[(−)‐menthyl‐oxycarbonylamino]pentanoate (5) (5:1 ratio of diastereomers). The ring cleavage benzoylation product of (S)‐histidine methyl ester, with a chiral center in the side chain, gives rise to (2S,4R)/(2S,4S)‐2,4,5‐tribenzamidopentanoates (13, 14), in 2:1 ratio upon hydrogenation.
Synthesis of compounds with juvenile hormone activity, XXVIII. Synthesis of (−)‐juvenile hormone I, the antipode of the natural compound
Authors: Mori Kenji , Fujiwhara Mitsuhiko
Published: July 2007

The synthesis of the unnatural (10S,11R)‐(−)‐juvenile hormone I [(−)‐JH I, (−)‐1] is described.
Cycloadditionen, 18. 5‐Aminoisoxazole durch Cycloaddition von Nitriloxiden an Inamine
Authors: Himbert Gerhard , Kuhn Hildegard , Barz Michael
Published: July 2007

Cycloadditions, 18. — 5‐Aminoisoxazoles by Cycloaddition of Nitrile Oxides to Ynamines

Ten differently substituted ynamines 1a–j react with five nitrile oxides 3a–e to give the 5‐aminoisoxazoles 4a–z. The stannyl‐substituted ynamine 1c furnishes the same compounds (e.g. 4a–d) by reaction with the hydroximoyl chlorides 2a–d. Two representatives of 4–b and p ‐ can be transformed into the corresponding 1‐azirine‐3‐carboxamides 6a and b.
Bonellin: Aufklärung der absoluten Konfiguration
Authors: Montforts Franz‐Peter , Müller Claudia Margrit , Lincke Anngret
Published: July 2007

Bonellin: Determination of Its Absolute Configuration

The absolute configuration of bonellin (3), the physiologically active pigment of the marine echiuroid worm Bonellia viridis, has been established as (S) by ozonolytic degradation. Ozonolysis forms the imide 5 the configuration of which was confirmed by CD spectroscopic comparison with 5 from degradation of vitamin B12.
Reductive transformations of 5,6‐dihydro‐4H‐1,2‐oxazines: Synthesis of 4‐hydroxy ketoximes, N‐hydroxypyrrolidine derivatives, and other nitrogen‐containing compounds
Authors: Hippeli Claudia , Reißig Hans‐Ulrich
Published: July 2007

6‐Siloxy‐substituted 1,2‐oxazines 1 are transformed into 4‐hydroxy ketoximes 2 by reduction with NaBH4 in ethanol. Reductive Beckmann rearrangement converts the oxime 2a into the 1,4‐amino alcohol 7. Diisobutylaluminum hydride (DIBAH) induces a novel reductive ring contraction of 1 to provide either N‐hydroxypyrrolidine derivatives 8 or nitrones 9. Other 1,2‐oxazines lacking the 6‐siloxy substituent are also studied under these reaction conditions. Catalytic hydrogenolysis either gives the acyclic amine 16 or it stops at the stage of the proline derivative 21. Mechanistic features of these synthetically valuable transformations are discussed.
Reaktion von 2,3,4‐Tri‐O‐acetyl‐α‐L‐rhamnopyranosylbromid mit ethanolischer Trimethylamin‐Lösung
Authors: Bognár Rező , Farkas István
Published: July 2007

Reaction of 2,3,4‐Tri‐O‐acetyl‐α‐L‐rhamnopyranosyl Bromide with an Ethanolic Solution of Trimethylamine

Reaction of 2,3,4‐tri‐O‐acetyl‐α‐L‐rhamnopyranosyl bromide (1) with an ethanolic solution of trimethylamine yielded 2,3‐di‐O‐acetyl‐1,2‐O‐(1‐ethoxyethylidene)‐β‐L‐rhamnopyranose (2) instead of 1,4‐Anhydro‐2,3‐di‐O‐acetyl‐α‐L‐rhamnopyranose (3) as was earlier described in the literature. The structure of compound 2 was established by analysis and spectroscopical data.
Synthese von (R)‐Lasiodiplodin aus Polyhydroxybuttersäure
Authors: Braun Manfred , Mahler Ulrike , Houben Sabine
Published: July 2007

Synthesis of (R)‐Lasiodiplodin from Polyhydroxybutyric Acid

The twelve‐membered macrolide (R)‐lasiodiplodin (1), a fungal metabolite of Botrysdiplodia theobromae, has been synthesized in a nine‐step procedure. (R)‐1,3‐Butanediol (6), which is easily available by reductive depolymerization of the biopolymer polyhydroxybutyric acid (PHB), proves itself as a suitable enantiomerically pure building block.
Solanum alkaloids, 117. Synthesis of the steroid alkaloid soladunalinidine and other 5α‐spirosolan‐3‐amines
Authors: Quyen Le Thi , Ripperger Helmut , Schreiber Klaus
Published: July 2007

The steroid alkaloid soladunalinidine [5α‐tomatidan‐3β‐amine, (25S)‐5α,22βN‐spirosolan‐3β‐amine, 2], isolated from Solanum dunalianum, is synthesized from tomatidine (5α‐tomatidan‐3β‐ol, 1) via 5α‐tomatidan‐3‐one (4) and its oxime 5 which is reduced to 2 as well as to its ring‐E‐opened (22S) and (22R) dihydro products 6 and 9, the N(22,26)‐chloro‐N(3)‐(2‐hydroxy‐benzylidene) derivatives 8 and 11 of which are recyclized to N(3)‐(2‐hydroxybenzylidene)soladunalinidine (3). The 5α‐spirosolan‐3‐amines stereoisomeric at C‐22 and C‐25, 5α‐solasodan‐3α‐amine (13) and ‐3β‐amine (15), are obtained in an analogous sequence of reactions from soladulcidine (5α‐solasodan‐3β‐ol, 12).
Spectroscopic studies of the solvent polarities of room‐temperature liquid ethylammonium nitrate and its mixtures with polar solvents
Authors: Herfort Ina‐Maria , Schneider Hermann
Published: July 2007

The maximum wavelength of the solvatochromic absorption band of Dimroth‐Reichardt's dye I, 2,4,6‐triphenylpyridinium N‐4‐(2,6‐diphenylphenoxide) betaine, has been determined at 25°C from the ultraviolet‐visible spectra of solutions of this dye in ethylammonium nitrate (EAN) and its mixtures with several polar solvents. The related molar transition energy, ET(30) in kcal/mol, of the long‐wavelength absorption band increases sharply, when EAN is dissolved at low concentrations in the various solvents. The pronounced blue shift of the absorption band is attributed to the hydrogen‐bond interaction between the ethylammonium cation and the ground state of the betaine molecule.
Enzym‐katalysierte Reaktionen, 7. Enantioselektive Veresterung racemischer Cyanhydrine und enantioselektive Hydrolyse oder Umesterung racemischer Cyanhydrinester mittels Lipasen
Authors: Effenberger Franz , Gutterer Beate , Ziegler Thomas , Eckhardt Elisabeth , Aichholz Reiner
Published: July 2007

Enzyme‐Catalyzed Reactions, 71). – Enantioselective Esterification of Racemic Cyanohydrins and Enantioselective Hydrolysis or Transesterification of Cyanohydrin Esters by Lipases

Pure cyanohydrin enantiomers (S)‐1/(R)‐1 and their O‐acyl derivatives (R)‐3/(S)‐3 are obtained from three different lipasecatalyzed reactions: i) enantioselective hydrolysis of aliphatic and aromatic racemic cyanohydrin esters 3, ii) enantioselective acylation of racemic cyanohydrins 1, iii) enantioselective transesterification of 3 with primary alcohols. Both the cyanohydrin esters and the free cyanohydrins (which are prone to racemization) are isolated as enantiomers with high optical purity on a preparative scale. Hydrolysis of the racemic butyrates 3b, e with Candida cylindracea lipase and pseudomonas sp. lipase, respectively, for example, affords the free (S)‐cyanohydrins (S)‐2‐hydroxypentanenitril [(S)‐1a] and (S)‐mandelonitrile [(S)‐1b)] in high yield with 97 and 96% ee, respectively. (S)‐1a is obtained with the same optical purity by candida sp. lipase‐catalyzed transesterification of 3b with 1‐octanol.
Synthesis of 6H‐1,2‐oxazines by hetero Diels‐Alder reactions of nitroso alkenes towards methoxyallenes
Authors: Zimmer Reinhold , Reißig Hans‐Ulrich
Published: July 2007

Regioselective hetero Diels‐Alder reactions of in‐situ generated nitroso alkenes 2–4 with methoxyallene derivatives 1 provide 4H‐1,2‐oxazines 5–7 with an exo‐methylene group at C‐5. These primary cycloadducts are smoothly transformed into conjugated 6H‐1,2‐oxazines 11–13 by base or acid catalysis. The bicylic nitroso alkene 17 and methoxyallene (1a) combine to give the tricyclic 1,2‐oxazine 18, thus demonstrating that an exo‐transition state is favoured in this [4+2] cycloaddition. The reaction of the sterically hindered methoxyallene 1h with nitrosostyrene affords the cycloadduct 22 in low yield. 22 is very likely formed by a two‐step Diels‐Alder reaction via a zwitterion. Allene derivatives lacking a methoxy group are not sufficiently reactive towards nitroso alkenes and do not provide 1,2‐oxazines.
Investigations on different coupling reagents for the synthesis of a cyclopeptide analog of neuropeptide Y
Authors: Hoffmann Eike , Beck‐Sickinger Annette G. , Jung Günther
Published: July 2007

The short‐cut analog of neuropeptide Y (NPY), NPY 1YESK‐Ahx‐25RHYINKITRQRY‐NH2, was synthesized on the amide anchor 5‐(4‐aminomethyl‐3,5‐dimethoxyphenoxy)valeric acid (ADPV) attached to polystyrene/1% divinylbenzene by using the 9‐fluorenylmethoxycarbonyl/tert‐butyl (Fmoc/tBu) strategy. Side‐chain‐to‐side‐chain cyclization of residues Glu2 to Lys30 of this linear heptadecapeptide amide was carried out by using different activating reagents under high‐dilution conditions of the free peptide. The use of diphenylphosphoryl azide (DPPA) with the addition of triethylamine gave the highest yield of cyclic peptide. Replacing the tertiary amine by dipotassium hydrogen phosphate as an insoluble inorganic base did not improve the cyclization. Complete cyclization was achieved within four hours by using 2‐(1H‐benzotriazol‐1‐yl) ‐1,1,3,3‐tetramethyluronium tetrafluoroborate (TBTU) in combination with 1‐hydroxybenzotriazol (HOBt) as activating agent, but the separation from excess TBTU resulted in lower yields. Reactions were monitored by HPLC and kinetic investigations were made. The identity and purity of the final product magnified image were proven by various analytical methods including atmospheric pressure ionization mass spectrometry (API‐MS). The receptor binding constant of the cyclic analog was found to be comparable to that of NPY.
Synthesis and circular dichroism of steroids with a 1,4‐benzodioxane chromophore: On the absolute configuration of (−)‐silandrin
Authors: Antus Sándor , Baitz‐Gács Eszter , Snatzke Günther , Tóth Tamás S.
Published: July 2007

Starting from cholesterol the three possible stereoisomeric 1,4‐benzodioxanes 24, 31, 32 and a series of analogues with 2βH,3βH configuration (25–27, 29, 30) have been synthesized. The α band of the 1,4‐benzodioxane chrompohore has been unequivocally identified in the CD spectra between 325–300 nm. For its Cotton effect the same helicity rule is valid as for homochirally analogous tetralins: the P/M helicity of the heteroring leads to a positive/negative CD within the α‐band. The (2′R,3′R) configuration of 6 has been established by a comparison of its CD data with those of 39 and with the help of the above‐mentioned helicity rule. This allows the assignement of the (2S,2′R,3′R) configuration of (−)‐silandrin (3).
Synthesis and spectroscopic characterization of 15N‐labeled hexaaminobenzene derivatives
Authors: Wolff J. Jens , Limbach Hans‐Heinrich
Published: July 2007

Efficient syntheses of [15N6]‐labeled hexaaminobenzene (6), hexakis(dimethylamino)benzene (7) and 2,2′,2″‐trimethylbenzotris(imidazol) (1) are described. The compounds are characterized by 15N CPMAS NMR spectroscopy.
Substituent effects in the 1,3‐dipolar cycloaddition reactions of 2‐methylenecephalosporins with diazoalkanes
Authors: Pitlik János , Csaba Jászberényi J. , Komáromi István
Published: July 2007

The 2‐methylenecephalosporins 1 undergo stereoselective 1,3‐dipolar cycloaddition reactions with diazoalkanes to give exclusively the spirocyclopropylcephalosporins 3. Substituens at C‐3, C‐4 and C‐7 of the cephalosporin nucleus do not display a significant effect on the reactivity of the 2‐exo double bond. However, reduction of the sulfoxides to sulfides has an inactivating influence. Reactions with substituted diazoalkanes proceed more slowly in every case. The results are explained by theoretical (PM3, AM1 and MNDO) calculations.
Biologically active glycosides from asteroidea, XXVIII. Glycosphingolipids from the starfish Asterias amurensis versicolor Sladen, 1. Isolation and structure of six new cerebrosides, asteriacerebrosides AF, and two known cerebrosides, astrocerebroside A and acanthacerebroside C
Authors: Higuchi Ryuichi , Jhou Jian Xin , Inukai Kazuyoshi , Komori Tetsuya
Published: July 2007

Six new cerebrosides, asteriacerebroside A (1), B (2), C (3), D (4), E (7) and F (8), have been isolated from the two cerebroside molecular species obtained from the less polar fraction of the chloroform/methanol extract of the starfish Asterias amurensis versicolor Sladen. The structures of these cerebrosides have been determined on the basis of chemical and spectroscopic evidences. Two known cerebrosides, astrocerebroside A (5) and acanthacerebroside C (6), have also been isolated and characterized. Reversed‐ and normal‐phase HPLC were effective in isolating these cerebrosides, showing the very close similarity in their structures. Mass spectrometry of dimethyl disulfide derivatives of the cerebrosides was useful for the determination of the double‐bond position in the cerebrosides.
Functionally substituted vinyl carbanions, 44. Synthesis of odd‐numbered 13‐crown‐4 derivatives possessing a functional group and their application in C‐lithiation of acrylates
Authors: Jatzke Harald , Schmidt Richard R.
Published: July 2007

The synthesis of symmetrically hydroxy‐substituted 13‐crown‐ 4 derivatives 2 and 3 is reported. To this end, diol 7 is first deprotonated with potassium tert‐butoxide and then treated with ditosylate 6 in the presence of lithium perchlorate as a template. Base‐catalyzed addition of 2 and 3 to methyl propiolate affords β‐alkoxy‐substituted acrylates 1a and 1b, respectively. Treatment of 1a with LDA in THF generates the β‐C‐lithiated species 1a‐A as indicated by quenching with CH3OD and reaction with propanal; thus, β‐deutero derivative 1a‐(β‐D) and tetronate 4a, respectively, are obtained. Competition experiments between 1a and methyl β‐methoxyacrylate (1c) with LDA in THF exhibit for 1a a higher thermodynamic but practically the same kinetic acidity.
Synthese chiraler Bausteine aus D‐glucosamin‐hydrochlorid
Authors: Giannis Athanassios , Henk Thomas
Published: July 2007

Synthesis of Chiral Building Blocks from D‐Glucosamine Hydrochloride

Wittig‐reaction of 2‐acetamido‐2‐deoxy‐D‐glucose (1) with the semistabilized ylide Ph3PCHPh yielded the epimeric chain‐elongated derivatives 2 and 3 in different amounts depending on the reaction conditions. Reaction of 2‐(tert‐butoxycarbonylamino)‐2‐deoxy‐D‐glucose (5) with Ph3PCHPh yielded the compound 8, or after intramolecular cyclisation, the derivatives 6 or 7. Compound 3 was transformed in three steps into the amino alcohol 10. The 3‐amino‐1,2‐diol derivative 17 and also the N,O‐protected α‐hydroxy‐β‐amino acid derivative 16 were obtained from 7. The N‐protected homophenylalanine derivatives 12 and 14 were available in two steps from 2 or 8.
Synthesis of 4‐nitro‐2H‐isoindole derivatives
Authors: Wojciechowski Krzysztof
Published: July 2007

Oxidation of nitro derivatives of 3,4‐dihydro‐1H‐2,3‐benzothiazine 2,2‐dioxides 1a–e in the presence of a base leads to nitro‐2H‐isoindole derivatives, 3a–e.
Natural product chemistry, 145. Synthesis of rac‐acridone‐coumarin dimers (acrimarins)
Authors: Reisch Johannes , Herath H. M. T. Bandara , Kumar N. Savitri
Published: July 2007

Three new rac‐acridone‐coumarin dimers (acrimarins) 5, 6 and 7 have been obtained by condensation of (E)‐suberenol (1) with the corresponding acridones 2, 3 and 4.
Reactions of lithium salts of O‐alkyl oximes with halogens: A highly stereoselective oxidative coupling of 5,6‐dihydro‐3‐methyl‐4H‐1,2‐oxazine
Authors: Shatzmiller Shimon , Lidor Ramy , Bahar Eliezer , Goldberg Israel
Published: July 2007

Lithiation of 5,6‐dihydro‐3‐methyl‐4H‐1,2‐oxazine (4) in an unpolar solvent system (hexane/THF) at −65°C followed by reaction with Cl2,Br2, or I2 affords cleanly and stereoselectively 6 (RS,RS) of which an X‐ray structure analysis is described. In contrast, attempts to couple the halogenated 1,2‐oxazine derivative 5c have given, under various reaction conditions, equal amouts of 6 and 8 (meso). A mechanism of this reaction is discussed.
Reactions of 4‐(dicyanomethylene)‐3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one towards active methylene compounds
Authors: Metwally Saoud A. M. , El‐Naggar Galal M. , El‐Emary Talaat I.
Published: July 2007

The reaction of some active methylene compounds with 4‐(dicyanomethylene)‐3‐methyl‐1‐phenyl‐2‐pyrazoline‐5‐one (1a) has been investigated. This reaction involves a Michael addition to afford 4‐spirocyclobutenes 3 or cyclopyran‐2‐pyrazoline‐5‐ones 4, depending on the active methylene derivatives used. A possible rationalization of the reaction pathway is proposed.
Synthese von 6‐Methoxy‐2,5‐dimethyl‐2H‐isoindol‐4,7‐dion, einem Alkaloid aus Reniera‐Arten
Authors: Schubert‐Zsilavecz Manfred , Schramm Hans Wolfgang
Published: July 2007

Synthesis of 6‐Methoxy‐2,5‐dimethyl‐2H‐isoindole‐4,7‐dione, an Alkaloid from Reniera Species

6‐Methoxy‐2,5‐dimethyl‐2H‐isoindole‐4,7‐dione (4) can easily be obtained in high yields in a one‐pot synthesis by heating sarcosine (2) and paraformaldehyde in the presence of 3‐methoxy‐2‐methyl‐1,4‐benzoquinone (1).
Concave reagents, 9 Alcoholysis of diphenylketene catalyzed by concave pyridines and open‐chain analogs
Authors: Lüning Ulrich , Baumstark Roland , Schyja Wolfgang
Published: July 2007

Pseudo‐first‐order rate constants k(obs) for the (concave) pyridine‐catalyzed addition of ethanol to diphenylketene have been determined photometrically. The catalytic activity of the concave pyridines 1 or 2 is determined by their basicity and by their size. This effects a difference in k(obs) of up to three orders of magnitude. The decrease in catalytic activity by the concave shielding can be overcome by introduction of basicity‐increasing substituents into the pyridine ring (i.e. 1q). An amine–alcohol complex is probably the reactive species in this catalysis as the slope β of 0.3‐0.5 in a Brønsted plot supports.
Synthese von cis‐konfigurierten Bis(trifluormethyl)pyrethroiden
Authors: Rothermel Reinfried , Hanack Michael
Published: July 2007

Synthesis of cis‐Configurated Bis(trifluoromethyl)pyrethroids

trans‐2,2‐Bis(trifluoromethyl)cyclopropanecarboxylates 2a, b are converted into the cis‐diastereomers by base‐catalyzed epimerization via the bicyclic lactones 3a, b. Dehydration of cis‐2a and cleavage of the ester function leads to the fluorinated chrysanthemic acid 4b, which is converted into the pyrethroids 4d, e. cis‐2b is oxidized by pyridinium chlorochromate to give methyl cis‐3‐formyl‐2‐2‐bis(trifluoromethyl)‐cyclopropanecarboxylate (hexafluorocaronaldehydic acid methyl ester) (5). This compound, which is very sensitive to isomerization, is converted into the pyrethroid esters 6a, b predominately retaining the cis configuration; however, by introducing the 2,2‐dichlorovinyl side chain the trans diastereomer is obtained. The starting materials trans‐2a, b are prepared by the reaction of aldehydes 9a, b with 2,2‐dichlorohexafluoropropane and triphenylphosphine followed by cyclopropanization of the resulting 1,1‐bis(trifluoromethyl)olefins 10a, b with (ethoxycarbonylmethylene)dimethylsulfurane (14).
New stereoisomers of quinic acid and their lactones
Authors: Scholz‐Böttcher Barbara M. , Ernst Ludger , Maier Hans Gerhard
Published: July 2007

Heating of (−)‐quinic acid [(−)‐1] at reflux temperature with 90% acetic acid/concd. H2SO4 (67/1) yields a mixture of six stereoisomeric quinic acids (four meso forms and two pairs of enantiomers), four γ‐quinides (four pairs of enantiomers), and three δ‐quinides (two meso forms and one enantiomeric pair). The 1H‐ and 13C‐NMR spectra for most of these compounds are given. The fully trimethylsilylated derivatives of all the compounds are characterized by high‐resolution GC/MS. The existence of neo‐quinic acid (6), its γ‐ (10) and δ‐lactone (12), of epi‐δ‐quinide (13), of two meso‐quinic acids, and of another γ‐quinide is reported for the first time. The structures and configurations of neo‐quinic acid, neo‐γ‐, neo‐δ‐, and epi‐δ‐ quinide are derived from their NMR spectra. All stereoisomeric quinic acids and their γ‐and δ‐lactones are also formed under the roasting conditions of coffee.
2,2′‐Binaphthyliden‐1,1′ ‐dione – Farbe und Struktur
Authors: Göltner Christine , Laatsch Hartmut
Published: July 2007

2,2′‐Binaphthylidene‐1,1′ ‐diones – Colour and Structure

The UV spectra of deep purple to green 2,2′‐binaphthylen‐1,1′‐diones 3 may be explained by substituent increments with high reliability. This allows assistence in structure elucidation of substituted 1‐naphtholes 1a by UV/Vis measurements of their oxidation products, or colour adjustment of 3 for use in diagnostic purposes. Also highly soluble derivatives of 3 were synthesized for the first time.
Synthesis of Shikonin and Alkannin
Authors: Braun Manfred , Bauer Claus
Published: July 2007

The enantiomeric naturally occurring naphthoquinones shikonin [(R)‐1] and alkannin [(S)‐1] have been synthesized in a thirteen‐step procedure in 44 to 65% e.e. The stereogenic centers of (R)‐1 and (S) are created by the reaction of naphthaldehyde 3 with (R)‐ and (S)‐2‐hydroxy‐1,2,2‐triphenylethyl acetate (2), respectively. In order to find out a rationalization for the unexpectedly low diastereoselectivity in this aldol addition, a series of substituted aromatic aldehydes 12a–h has been treated with (R)‐2.
Metallkomplexe mit Tetrapyrrol‐Liganden, LX. Pseudo‐Sandwichkomplexe: Komplexe drei‐ und vierwertiger Metall‐Ionen mit Porphyrin‐ und Schiff‐Base‐Liganden
Authors: Buchler Johan N. W. , Hammerschmitt Peter
Published: July 2007

Metal Complexes with Tetrapyrrole Ligands, LX. – Pseudo Sandwich Complexes: Complexes of Metal(III) and ‐(IV) Ions with Porphyrin and Schiff‐Base Ligands

The synthesis of novel metal complexes with a porphyrinate, (P)2–2), and an ethylenebis(salicylidenealdiminate) or similar tetradentate open chelate, (L‐4)2−, as ligands is described. Their general formula [M(P)(L‐4)]n is realized with n = o and M = ZrIV or HfIV or n = −1 with M = YIII or TbIII; in the latter, an additional Li+ ion warrants electroneutrality. These complexes are prepared from the metal monoporphyrinates MIV(P)X2 or MIII(P)X (X = acetylacetonate) and the corresponding Schiff‐base derivatives, H2(L‐4) or Li2(L‐4), respectively. 1H‐NMR data prove the square antiprismatic configuration of the ZrIV species at 295 K which is abandoned at 373 K when the (P)2− and (L‐4)2− freely rotate about each other. Electrochemical measurements show that oxidations and reductions involve only the porphyrin ligands. The redox potentials experience shifts that can be understood in terms of the Hammett parameters σ of the substituents at (L‐4)2−.
Untersuchung des stereochemischen Einflusses von Substituenten in 3‐Stellung an Cholsäurederivaten mit Hilfe von 1D‐ und 2D‐NMR‐Methoden
Authors: Wollborn Ute , Leibfritz Dieter
Published: July 2007

1D‐ and 2D‐NMR Studies on the Stereochemical Influence of C‐3 Substituents in Derivatives of Cholic Acid1)

The structural effects of C‐3 sustituents on two derivates of cholic acid have been studied by 1D‐as well as homonuclear and heteronuclear 2D‐NMR spectra. The stereochemical structure of ring A is derived from homonuclear vicinal coupling constants. The consequences of C‐3 substitution on 1H and 13C chemical shifts, on stereochemical and electronical effects are discussed.
Synthesis of oxime‐based macrocyclic systems by oxidative coupling of an aza‐allyl anion derivative – cyclooligomerization of dioxime diethers
Authors: Shatzmiller Shimon , Menashe Naim , Shalom Eytan , Bahar Eliezer
Published: July 2007

Reaction of the dilithium salts of the dioxime diethers 1 gives the polyoxime‐based macrocyclic systems 2–4. Temperature and lithium effects indicate that mixed aggregates play an important role in the formation of these heterocyclic systems by oxidative coupling. An X‐ray structure analysis of 3f has been carried out showing that the thermodynamically unfavored Z configuration is a characteristic feature of this reaction product.
Efficient and diastereoselective synthesis of (+)‐ and (−)‐grandisol and 2‐[(1R,2S)‐2‐isopropenylcyclobutyl]ethanol (demethylgrandisol) in high purity
Authors: Hoffmann Norbert , Scharf Hans‐Dieter
Published: July 2007

Acetone‐sensitized [2 + 2] photocycloaddition of ethylene to chiral butenolides 3 and 15 yields diastereomeric cyclobutanes, which are transformed to (+)‐(1) and (−)‐grandisol (ent‐1) (overall yield 34–36%) and to 2‐[(1R,2S)‐2‐isopropenylcyclobutyl]ethanol (demethylgrandisol) (2) (overall yield 25%) in five steps.
Oxime von Derivaten der 2‐Acetamido‐2,4‐didesoxy‐D‐xylo‐hexose und der entsprechenden Uronsäure
Authors: Györgydeák Zoltán
Published: July 2007

Oxime Derivatives of 2‐Acetamido‐2,4‐dideoxy‐D‐xylo‐hexose and of the Corresponding Uronic Acid

Oximes and O‐methyl oximes of 3‐O‐protected 2‐acetamido‐2,4‐dideoxy‐D‐xylo‐hexose and of methyl 2‐acetamido‐2,4‐dideoxy‐D‐xylo‐hexuronate (14, 15, 16, 18, 19 and 26) have been prepared from 2‐acetamido‐2‐deoxy‐D‐glucopyranose. Their structures have been elucidated by 1H‐ and 13C‐NMR data.
Enzymes in Organic Synthesis, 8. Synthesis of enantiomerically pure prostaglandin intermediates by enzymatic transesterification of (1S*,5R*,6R*,7R*)‐(±)‐7‐hydroxy‐6‐hydroxymethyl‐2‐oxabicyclo[3.3.0]octan‐3‐one
Authors: Weidner Judith , Theil Fritz , Kunath Annamarie , Schick Hans
Published: July 2007

Lipase Amano PS is a suitable biocatalyst for the highly regio‐ and enantioselective transesterification of the racemic prostaglandin building block (1S*,5R*,6R*,7R*)‐(±)‐7‐hydroxy‐6‐hydroxymethyl‐2‐oxabicyclo[3.3.0]octan‐3‐one (rac‐1) yielding (1S,5R,6R,7R)‐(−)‐6‐acetoxymethyl‐7‐hydroxy‐2‐oxabicyclo[3.3.0]octan‐3‐one (2) and the unreacted (1R,5S,6S,7S)‐(+)‐enantiomer ent‐1.
Diels‐Alder reactions of 2,3‐dimethylenecephalosporins
Authors: Gunda Tamas E. , Kövér Katalin E.
Published: July 2007

2,3‐Dimethylenecephalosporin esters 1 undergo Diels‐Alder reaction with ethyl methacrylate and O‐ethyl S‐methyl dithiooxalate. The structure of the former reaction product 3a is in accordance with 1H‐NMR data as well as with theoretical considerations (FMO, MMX)
Conversion of (−)‐α‐narcotine into (+)‐papaveroxinoline and (+)‐macrantaline
Authors: Rozwadowska Maria D. , Banaszyński Slawomir
Published: July 2007

(−)‐α‐Narcotine (5), a phthalideisoquinoline alkaloid, is converted into two secoberbines: (+)‐papaveroxinoline (3) and (+)‐macrantaline (1). The reaction sequence involves reduction of 5 to the diol 6 followed by selective monoacetylation to (+)‐3. Hydrogenolysis of the latter affords (+)‐1.
Synthesis of 3,5‐dichloro‐6‐ethyl‐2,4‐dihydroxybenzoic acid – the aromatic constituent of lipiarmycin A3
Authors: Alexy Markus , Scharf Hans‐Dieter
Published: July 2007

3,5‐Dichloro‐6‐ethyl‐2,4‐dihydroxybenzoic acid (5, homodichloroorsellinic acid) is the polysubstituted aromatic carboxylic acid found in the macrolide antibiotic lipiarmycin A3. A convenient synthesis of the title compound from ethyl 2‐pentenoate and ethyl acetoacetate is described (five steps, 41% overall yield).
Solution structure of phalloidin obtained by NMR spectroscopy in [D6]DMSO and molecular dynamics calculation in vacuo and in water
Authors: Kessler Horst , Wein Thomas
Published: July 2007

Homo‐ and heteronuclear NMR techniques have been used to assign all proton and most of the carbon resonances of phalloidin (1) [cyclic(L‐alanyl‐D‐threonyl‐L‐cysteinyl‐cis‐4‐hydroxy‐L‐prolyl‐L‐alanyl‐L‐mercapto‐L‐tryptophyl‐4,5‐dihydroxy‐L‐leucyl) cyclic (3→6) sulfide], a toxic bicyclic heptapeptide of the poisonous mushroom Amanita phalloides. Intramolecular proton–proton distances derived from rotating‐frame NOE experiments have been used as constraints in energy minimization and molecular dynamics calculations using GROMOS. Charge reduction of solvent‐exposed NH protons has been used to minimize artifacts in the in vacuo calculation. The structure has been proven to be unstable without constraints in vacuo. Hence, a procedure is proposed in which first restrained MD in vacuo is performed and refinement is carried out by restrained or unrestrained MD in water.
Synthese von 5,15‐diarylsubstituierten Porphyrinen über Aminomethylierung von Bis(4‐ethyl‐3‐methyl‐2‐pyrryl)phenylmethanen
Authors: Hombrecher Hermann K. , Horter Gaby
Published: July 2007

Synthesis of 5,15‐Diaryl‐Substituted Porphyrins by Aminomethylation of Bis(4‐ethyl‐3‐methyl‐2‐pyrryl)phenylmethanes

The synthesis of unsymmetrically diarylsubstituted porphyrins 11a‐g (yields 5–19%) is described. Aminomethylation of dipyrromethane 6a with Mannich reagent 9 in acetonitrile leads to the intermediate 10, which is directly converted into the porphyrins 11 by acid‐catalysed coupling with the dipyrromethanes 6.
Zur Reaktion von Dialkylphosphiten mit α‐Enonen, II. 2:1‐Addukte aus Dimethylphosphit und α‐Enonen: Darstellung von (1‐Hydroxy‐1,3‐alkandiyl)diphosphonaten und 5‐Dimethoxyphosphoryl‐2‐methoxy‐1,2‐oxaphospholan‐P‐oxiden
Authors: Öhler Elisabeth , Zbiral Erich
Published: July 2007

Reaction of Dialkyl Phosphites with α‐Enones, II. – 2:1 Adducts from Dimethyl Phosphite and α‐Enones: Synthesis of (1‐Hydroxy‐1,3‐alkanediyl)diphosphonates and 5‐Dimethoxyphosphoryl‐2‐methoxy‐1,2‐oxaphospholane P‐Oxides

On NaOCH3‐catalyzed reaction with two equivalents of dimethyl phosphite (2), various α‐enones 1 are transformed into the diphosphonates 5 (e.g. 5a, 5b, 5e, 5f), which, depending on the structure of the enone, can further react with ring closure to give the 1,2‐oxaphospholanes 6 (e.g. 6c, 6g, 6h), or with phosphonate‐phosphate rearrangement of the α‐hydroxyphosphonate moiety to yield compounds 7 (e.g. 7d). The formation of the 2:1 adducts is believed to occur via addition of 2 to the carbonyl group of the (3‐oxoalkyl)phosphonates 4, formed from thermodynamically controlled 1,4 addition of 2 to 1. Compounds 4 could also be treated with 2 to yield 2:1 adducts (e.g. 4c → 5c, 4d → 5d, 4d → 7d).
Improved synthesis of α‐L‐Fuc(1→4)‐β‐D‐GlcNAc and α‐L‐Fuc(1→6)‐β‐D‐GlcNAc building blocks: A convergent strategy employing 4‐O→6‐O acetyl migration; NOE data of the protected α‐1,4‐linked disaccharide
Authors: Peters Thomas , Weimar Thomas
Published: July 2007

The synthesis of the two ethylthio disaccharide building blocks 10 and 17 was achieved by coupling of fucosyl bromide 9 with the acceptor alcohols 6 and 7 under in situ anomerization conditions. The selectively protected 2‐deoxy‐2‐phthal‐imidoglucose derivative 7 was derived from 6 by utilizing an optimized acetyl migration reaction. The ethylthio function in disaccharides 10 and 17 was activated with bromine, and excess bromine was removed with cyclohexene. The sensitive 1,6‐linkage in the disaccharide 10 proved to be stable under these activating conditions. The disaccharide bromides 11 and 18 were treated with methanol to afford after deblocking the methyl glycosides 16 and 23. Homonuclear 1H‐NOE data were obtained for the protected 1,4‐linked disaccharide 17 suggesting that its preferred solution conformation is rather similar to the solution conformation of the deblocked disaccharide 23 in aqueous solution as known from literature data.
Synthesis of sphingosine relatives, IX. Synthesis of (2S,3R,4E)‐1‐O‐(β‐D‐glucopyranosyl)‐N‐ [24‐(linoleoyloxy)tetracosanoyl]‐4‐sphingenine. The structure proposed for the esterified cerebroside in the epidermis of guinea pigs
Authors: Mori Kenji , Nishio Hiroyuki
Published: July 2007

(2S,3R,4E)‐1‐O‐(β‐D‐Glucopyranosyl)‐N‐[24‐(linoleoyloxy)tetracosanoyl)‐4‐sphingenine (1) was synthesized from D‐glucose (A), (2S,3R,4E)‐4‐sphingenine (sphingosine, B), 24‐hydroxytetracosanoic acid (C) and linoleic acid (D). The 1H‐NMR spectrum of synthetic 1 was different from that of the esterified cerebroside which was isolated as a tissue‐characteristic compound in the epidermis of footpad and dorsal skin of guinea pigs.
Synthetic and stereochemical studies on phthalideisoquinoline hemiacetals
Authors: Rozwadowska Maria D. , Matecka Dorota
Published: July 2007

The two new phthalideisoquinoline hemiacetals rac‐egenine (3) and rac‐corytensine (4) are prepared by stereoselective DIBAL reduction of rac‐bicuculline (1) and rac‐adlumidine (2), respectively. The identity of egenine (3) with decumbensine as well as of corytensine (4) with epi‐α‐decumbensine and humosine A is postulated. The configuration around the anomeric center in natural (+)‐egenine (3), (+)‐corytensine (4) and (−)‐narcotine hemiacetal (7) is deduced as (7′S), (7′R) and (7′R), respectively.
Natural product chemistry, 142. Synthesis of gravacridonol
Authors: Reisch Johannes , Voerste A.
Published: July 2007

Gravacridonol (2), naturally occurring in the roots of Ruta graveolens, has been synthesized in one step from rutacridone (1) in a yield of 23%.
Über die Reaktion von 2‐Diazo‐1,3‐diketonen mit 1,3‐ambident‐nucleophilen Phosphor‐Yliden: Eine neue Synthese von Monoheteroatom‐Fünf‐ und ‐Sechsringen
Authors: Capuano Lilly , Drescher Stefan , Huch Volker
Published: July 2007

Reaction of 2‐Diazo‐1,3‐diketones with 1,3‐Ambident‐Nucleophilic Phosphorus Ylides: A New Synthesis of Monoheteroatomic Five‐ and Six‐Membered Rings

The thermolysis of 2‐diazo‐1,3‐diketones 1 with 1,3‐ambidentnucleophilic 3‐imino‐ 3, 3‐thioxo‐ 10 or 3‐oxophosphoanes 11 proceeds either by Wittig reaction, leading to the formation of the pyrrole 7 or thiophene nucleus 12, or competitively via a mechanism which involves both Wolff rearrangement and Wittig reaction by the acylcarbonyl, whereby 2‐pyridones 8, 2‐pyrones 14 or the indenyl acetophenone 15, respectively, are formed. The rates of these processes are strongly determined by substituent effects. As an exception to the general pattern of behavior, the cyclic acyl ketene derived from diazodimedone undergoes Wittig reaction with 3 through the ketene carbonyl, giving the quinoline derivative 9. The structure of 9 was confirmed by X‐ray diffraction analysis.
Isolierung und Strukturaufklärung von Ergokonin A und B; zwei neue antifungische Sterol‐Antibiotika aus Trichoderma koningii
Authors: Augustiniak Hermann , Forche Edgar , Reichenbach Hans , Wray Viktor , Gräfe Udo , Höfle Gerhard
Published: July 2007

Isolation and Structure Elucidation of Ergokonin A and B; Two New Antifungal Sterol Antibiotics from Trichoderma koningii

Isolation and structure elucidation by 2D‐NMR spectroscopy of the two new antifungal sterol antibiotics ergokonin A (1) and B (2a) from Trichoderma koningii are described. The structures of 1 and 2a are derived from ergosterol and characterized by an 18‐carboxy group. In addition ergokonin A (1) is esterified at the 3‐hydroxy group with (2S,3S)‐3‐hydroxyleucine 3‐O‐sulfate (3c). In the course of structure elucidation of the amino acid residue the stereoisomers of 3‐hydroxyleucine N‐sulfamate and 3‐O‐sulfate (3b, c) have been synthesized and characterized by NMR spectroscopy.