bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese von Glycofuranosylformamiden, ‐isocyaniden und ‐isocyanaten ausgehend von den entsprechenden Glycosylaziden
Authors: Hiebl Johann , Zbiral Erich
Published: July 2007

Die durch Staudinger‐Reaktion aus den Glycofuranosylaziden 1a, 2b, 3e, 3e, 4d, 4e und 5d gebildeten P‐N‐Ylide reagieren mit Ameisensäure‐Essigsäureanhydrid zu den entsprechenden Glycofuranosylformamiden 1c, 2c, 3g, 4f, 4g und 5e. Als Nebenprodukte entstehen dabei die anomeren Verbindungen 1c,2c und 3g (Ausb. ca. 5%). Unter diesen Bedingungen ergeben α‐ und β‐5‐O‐tert‐Butyldimethylsilyl‐2,3‐O‐isopropyliden‐L‐talofuranosylazid (3e und 3e) dasselbe Formamid 3g. Die Formamide können mit Phosphorylchlorid/Diisopropylamin unter Wasserabspaltung in die Glycofuranosylisocyanide 1d, 2d, 3i und 4h umgewandelt werden. Anschließende Oxidation mit Blei(IV)acetat ermöglicht einen guten Zugang zu den Glycofuranosylisocyanaten 1e, 2d, 3j und 4i.
Thermal degradation of glycosides, II. Thermal effect on acetates of typical triterpenoid and steroid glycosides
Authors: Higuchi Ryuichi , Noguchi Yuko , Kitamura Yoichi , Kim Youn Chul , Komori Tetsuya
Published: July 2007

The termal effect on acetates of triterpenoid and steroid glycosides was examined. Contrary to the case of free glycosides, on heating the acetates of typical triterpenoid and steroid glycosides (including cardiac glycosides) on a melting point apparatus the cleavage reactions of sugar–aglycone and sugar–sugar linkage did not take place, and no aglycones or prosapogenins were obtained. However, two interesting and useful reactions did occur in the course of thermolysis of cardiac glycoside acetates. By taking into account the thermal effect on the glycoside acetates, and their FD mass spectra, an important suggestion on the mechanism of FD mass fragmentation of the glycosidic linkage was obtained.
Synthetic Anthracyclinones, 37. Total synthesis of (+)‐β‐rhodomycinone, (+)‐1‐deoxy‐β‐rhodomycinone, and (+)‐1‐deoxy‐γ‐rhodomycinone by incorporation of (S)‐α‐hydroxybutyric acid
Authors: Krohn Karsten , Hamann Ingo
Published: July 2007

Both enantiomers of the optically active building block 4 for anthracyclinone synthesis have been prepared from α‐hydroxybutyric acid 7. Key steps were the diastereoselective alkylation of the acetal 5 to 8 followed by DIBAH reduction and transacetalization to 10. Coupling of 4 to quinizarine (11) and 1,4,5‐trihydroxy‐9,10‐anthraquinone (3) by two successive Marschalk reactions and benzylic hydroxylation afforded the natural product (+)‐β‐rhodomycinone (18) and (+)‐1‐deoxy‐β‐rhodomycinone (17).
Steroids, XL. 15‐(hydroxymethyl)androstene and ‐estratriene derivatives
Authors: Vincze Irén , Somlai Csaba , Schneider Gyula , Dombi György
Published: July 2007

15α‐Hydroxymethyl‐5‐androstene‐3β,16β,17β‐triol (5d) and 16β‐hydroxy‐15α‐(hydroxymethyl)estratriene derivatives 9 were prepared from the corresponding 15‐hydroxymethylene‐16‐ketones 3 and 4. The configurations of the chiral centers were determined by means of chemical transformations and on the basis of spectroscopic data. The D‐seco derivatives 6 and 8 were identified as the products of a fragmentation and a 1,3‐dicarbonyl fission, respectively.
Zur Synthese von Benzoesäurederivaten aus 3‐Ethoxymethylen‐2,4‐alkandionen und Malonsäuredinitril
Authors: Schmidt Hans‐Werner , Kores Margarete
Published: July 2007

Synthesis of Benzoic Acid Derivatives from 3‐Ethoxymethylene‐2,4‐alkanediones and Malononitrile

Reaction of the 3‐ethoxymethylene‐2,4‐alkanediones 1a–c with malononitrile (2) gives the benzonitrile derivatives 3a–c. Compounds 4a–d are obtained by acid or basic hydrolysis of the nitrile group of 3a–c, Sandmeyer reaction leads to the halogenated benzonitriles 5a–f. Compounds 6a, b are available from 3a and O‐ethyl‐ and O‐allylhydroxylamine hydrochloride.
Synthetic transformation of santonin into (5α,7α,11β)‐3,6‐dioxogermacr‐1‐en‐13,7‐olide, a new intermediate for germacranes and guaianes
Authors: Harapanhalli Ravi S.
Published: July 2007

A seven‐step synthesis of a new intermediate (5α,7α,11β)‐3,6‐dioxogermacr‐1‐en‐13,7‐olide (10) is described starting from (−)‐α‐santonin (1). The key step in the transformation was photolytic skeletal rearrangement of (4α,5β,6α,11β)‐5‐hydroxy‐2‐oxoeudesman‐13,6‐olide (9) to the title compounds, sensitised by mercuric oxide and iodine.
Bausteine von Oligosacchariden, XC. Synthese von Strukturen der inneren Core‐Region von Lipopolysacchariden
Authors: Paulsen Hans , Heitmann Axel C.
Published: July 2007

2‐O‐Acetyl‐3,4,6,7‐tetra‐O‐benzyl‐L‐glycero‐α‐D‐manno‐heptopyranosylchlorid (6) läßt sich mit dem KDO‐Glycosylakzeptor 14 stereoselektiv zu dem α(1→5)‐glycosidisch verknüpften Disaccharid 24 umsetzen, dessen Entblockierung zu L‐α‐D‐Hepp‐(1→5)‐β‐KDOp‐OMe (30) führt. Die Umsetzung von 6 mit 22 führt stereoselektiv zum α(1→3)‐glycosidisch verknüpften Heptosedisaccharid 31, die von 6 mit 35 zum α(1→7)‐glycosidisch verknüpften Heptosedisaccharid 36. Die Entblockierung von 31 führt zu L‐α‐D‐Hepp‐(1→3)‐LD‐Hepp (34), die von 36 zu L‐α‐D‐Hepp‐(1→7)‐LD‐Hepp (39).
Notizen/Notes Formation of Trisubstituted 1,2,4‐Triazoles in the Cyclodehydration of 2‐Hydrazinothiazoles: Competition of Two Reaction Routes
Authors: Veverka Miroslav , Svêtlík Jan
Published: July 2007

The intramolecular cyclodehydration of ethyl (2‐hydrazinothiazol‐4‐yl)acetates 1a – f has been re‐examined. The reactions yield the desired thiazolo[2,3‐c]‐s‐triazoles 2a – f together with the unexpected trisubstituted 1,2,4‐triazoles 3a – f.
Reactions of Organic Anions, 160. Synthesis of Heptafulvene Derivatives by Vicarious Nucleophilic Substitution of Hydrogen in Tropylium Tetrafluoroborate
Authors: Ostrowski Stanisław , Mąkosza Mieczysław
Published: July 2007

Tropylium tetrafluoroborate reacts with tertiary carbanions bearing leaving groups at the carbanionic center yielding covalent adducts. Some of them can be transformed into heptafulvenes or tropylium derivatives.
Synthese und Aggregationsverhalten chiraler Cystein‐Amphiphile mit s‐Triazin als verknüpfende Partialstruktur
Authors: Staatz Irina , Granzer Ulrich H. , Roth Hermann J. , Blume Alfred
Published: July 2007

Es werden homologe Liposomenbausteine 3 mit L‐Cystein als chirale hydrophile Kopfgruppe synthetisiert. Als Verknüpfungseinheit zwischen Cystein und den lipophilen Alkylketten dient s‐Triazin. Mittels DSC‐ und Fluoreszenz‐Anisotropie‐Messungen lassen sich die Phasenübergangstemperaturen der Lipide bestimmen. Es kann gezeigt werden, daß eine den Phospholipiden analoge Relation zwischen Art und Länge der Ketten und der Phasenübergangstemperatur besteht. Einschlußversuche mit ionischen wasserlöslichen Farbstoffen ergeben Hinweise auf eine Interaktion der in Phosphatpuffer (pH = 7.0), gebildeten Vesikel mit kationischen, nicht jedoch mit anionischen hydrophilen Substanzen.
A Simple Way to 3‐[(1R,2S,5R and 5S)‐5‐Methoxymethoxy‐2‐methyl‐1,2‐epoxycyclohexyl]propanal, a Synthon for the Total Biomimetic Synthesis of (‐)‐Progesterone
Authors: Daniewski Andrzej Robert , Kiegiel Jaroslaw
Published: July 2007

The cyclohexylpropanals 21 and 22 were obtained in a 5‐step synthesis, starting from the hydroxy diketone 5. Rearrangement of the hydroxy lactones 9 and 10 into epoxy esters 19 and 20, respectively, by potassium hydride in HMPA and 2‐iodopropane was the key step of this synthesis.
Zur Regiochemie von [4 + 2]‐Cycloadditionen mit Methylpyrano[3,4‐b]indol‐3‐onen und unsymmetrischen Dienophilen
Authors: Pindur Ulf , Erfanian‐Abdoust Houshang
Published: July 2007

Die methylierten Pyrano[3,4‐b]indol‐3‐one 1a, 1b reagieren mit acyclischen, unsymmetrischen CC‐Dienophilen nach einer Diels‐Alder‐Reaktion/CO2‐Extrusion zu selektiv funktionalisierten Carbazolen 2. In Abhängigkeit von der Struktur der Reaktionspartner wird keine oder geringe bis hohe Regioselektivität festgestellt. Diethylmesoxalat reagiert mit 1a, 1b regioselektiv zu neuen 2,3‐difunktionalisierten Indolen 4a, 4b, die aus einer regiokontrollierten [4 + 2]‐Cycloaddition und Cycloreversion resultieren, wobei Pyrano[3,4‐b]indoldicarbonsäure‐diethylester 3a, 3b als Intermediate auftreten dürften.
Steroids, XLI. Neighbouring Group Participation, X. Neighbouring Group Participation and Fragmentation During the Solvolysis of the Epimers of 3‐Methoxy‐16‐(tolylsulfonyloxymethyl)‐estra‐1,3,5(10)‐trien‐17‐ol
Authors: Schneider Gyula , Hackler LÁSzló , Wölfling János , Bottka SÁNdor , Sohár PÁL
Published: July 2007

The four possible isomers of 16‐hydroxymethyl‐3‐methoxyestra‐1,3,5(10)‐trien‐17‐ol were converted into the 16‐tolylsulfonyloxymethyl‐17‐acetoxy esters 1b, 3b, 4b, 7b and into the 16‐tolylsulfonyloxymethyl‐17‐tetrahydropyranyl acetals 1c, 3c, 4c, 7c. On alkaline methanolysis of 1b and 7b, the α and β oxetanes 2 and 8 condensed to the D ring in the sterane skeleton were formed, while 3b and 4b yielded the fragmented product 5. Under similar experimental conditions, the acetals 1c, 3c, 4c, 7c were transformed into the 16‐methoxymethyl derivatives 1d, 3d, 4d, 7d.
Eine einfache Synthese von N‐Methyl‐L‐histidin
Authors: Barlos Kleomenis , Hondrelis John , Matsoukas John , Sanida Charicha , Lonergan Greg
Published: July 2007

A Simple Preparation of N‐Methyl‐L‐histidine

N‐Methyl‐L‐histidine is efficiently prepared in two steps starting from Nα‐trityl‐l‐histidine.
Selenonium‐Salze und Selenonium‐ylide von Cyclopentadien, Pentafulvenen, Indol und Pyrrol
Authors: Hartke Klaus , Wendebourg Hans Henning
Published: July 2007

Selenoxide bilden mit Trimethylsilylcyclopentadien (1) die Selenoniocyclopentadienide 3 und 4. Selenoxide und Trifluoracetanhydrid reagieren mit Pentafulvenen zu den Mono‐ und Diselenonium‐Salzen 8 und 6, mit Indol zu dem 3‐Selenonium‐Salz 10 und mit Pyrrol zu den 2‐ und 3‐Selenonium‐Salzen 16 und 17. Die 2‐Isomere lagern mit Trifluoressigsäure quantitativ in die 3‐Isomere um. Deprotonierung von 16 und 17 führt zu den 2‐und 3‐Selenoniopyrroliden 26 und 27.
Crystal Structure and NMR Spectrometric Analysis of Palmarin
Authors: Yonemitsu Michiko , Fukuda Naomichi , Kimura Takeatsu , Komori Tetsuya , Lindner Hans Jörg , Habermehl Gerhard
Published: July 2007

The crystal structure of palmarin (1) has been determined by X‐ray diffraction. The ring C conformation was confirmed to be that of a half chair, and the same result was obtained from 1H‐NMR spectrometry. The ring C of chasmanthin (2) and glucosides of 1 and 2 (palmatoside A, and B) was also decided as a half boat by analysis of the 1H‐NMR spectra.
Synthese von O‐Glycopeptid‐Sequenzen des N‐Terminus von Interleukin‐2
Authors: Paulsen Hans , Adermann Knut
Published: July 2007

Es wird eine Serie von O‐Glycopeptiden mit unterschiedlicher Kettenlänge von 3–10 Aminosäuren synthetisiert, die Struktur‐elemente des N‐Terminus von Interleukin‐2 darstellen. Schlüsselbaustein der Synthesen ist O‐(2‐Acetamido‐3,4,6‐tri‐O‐acetyl‐2‐desoxy‐α‐D‐galactopyranosyl)‐N‐(9‐fluorenylmethoxycarbonyl)‐L‐threonin‐tert‐butylester (9b), der sowohl C‐ wie auch N‐terminal verlängert werden kann. Mit 9b liegt ein Baustein vor, der das Einfügen von glycosylierten Hydroxyaminosäuren mit der bei Peptidsynthesen bewährten Schutzgruppenkombination Fmoc/tBu in Peptidketten erlaubt. Bei dem Aufbau der Ketten wird von Blocksynthesen Gebrauch gemacht. Die Substrate eignen sich zur Überprüfung der Strukturspezifität von Glycosyltransferasen.
Reactions of Organic Anions, 163 Reactions of Nitrobenzophenones with Carbanions Containing Leaving Groups. Vicarious Nucleophilic Substitution of Hydrogen versus Darzens or Wittig‐Horner Reactions
Authors: Ma̧kosza Mieczysłw , Baran Janusz , Dziewońska‐Baran Danuta , Goliński Jerzy
Published: July 2007

Carbanions containing leaving groups at the carbanion center react with nitrobenzophenones by two general pathways: addition to the carbonyl group which results in the Darzens or Wittig‐Horner reaction and/or addition to the nitroaromatic ring resulting in the vicarious nuclephilic substitution of hydrogen. The former pathway dominates for p‐nitrobenzophenone, and the vicarious nuclephilic substitution is the major process for o‐nitro‐benzophenone; the extent of these two reactions for m‐nitrobenzophenone depends on the type of carbanion and the reaction conditions.
Umsetzung von Allyl(nonafluorbutyl)sulfonen mit Michael‐Akzeptoren, Synthese von Chrysanthemumsäurederivaten
Authors: Hanack Michael , Auchter Anneliese , Wunde Christian , Stoll Theodor
Published: July 2007

(3‐Methyl‐2‐butenyl)nonafluorbutyl)sulfon (4) reagiert mit 3‐Methyl‐2‐butensäure‐ethylester (2) (Seneciosäure‐ethylester) unter Bildung von Chrysanthemumsäure‐ethylester (3). Als Nebenprodukt wird [5‐Methyl‐1‐(2‐methyl‐1‐propenyl)‐3‐pentenyl]‐[nonafluorbutyl)sulfon (5) erhalten. Das Nonaflon 4 ist durch Umsetzung von 3‐Methyl‐2‐butenylbromid (9) mit Natriumnonafluorbutansulfinat oder durch Umsetzung von Isopren mit Nonafluorbutansulfinsäure zugänglich. (3,3‐Dichlor‐2‐propenyl)(nonafluorbutyl)sulfon (12) reagiert mit Seneciosäure‐ethylester (2) nicht unter Bildung von Permethrinsäure‐ethylester (13), sondern unter Selbstkondensation zu dem Cyclopropylsulfon 15 und dem Disulfon 16.
Stereoisomere Aromastoffe, XXXI Tetrahydro‐2‐methylthiophen‐3‐ol ‐ Struktur und Eigenschaften der Stereoisomeren
Authors: Mosandl Armin , Hener Uwe , Fenske Heinz‐Dieter
Published: July 2007

Tetrahydro‐2‐methylthiophen‐3‐ol (6) wurde synthetisiert und flüssigkeitschromatographisch in cis‐ (6a/6a′) und trans‐Isomere (6b/6b′) getrennt. Durch Umsetzung mit (S)‐Tetrahydro‐5‐oxo‐2‐furancarbonsäurechlorid werden aus 6a/6a′ und 6b/6b′ die diastereomeren Ester 7–10 gebildet, deren flüssigkeitschromatographische Trennung und anschließende Hydrolyse zu den optisch reinen Stereoisomeren 6a, 6a′, 6b und 6b′ führt. Absolute Konfiguration und sensorische Bewertung der Stereoisomeren werden mitgeteilt.
Synthesis of Mono‐ and Sesquiterpenoids, XVI Synthesis of (‐)‐Pereniporins A and B, Sesquiterpene Antibiotics from a Basidiomycete
Authors: Mori Kenji , Takaishi Hideo
Published: July 2007

Starting from (S)‐3‐hydroxy‐2,2‐dimethyl‐1‐cyclohexanone (5), the enantioselective total syntheses of (‐)‐pereniporins A (1) and B (2) were achieved in 33 steps (0.6% overall yield) and in 28 steps (1.8% overall yield), respectively.
Studies Relating to the Configuration and Conformation of 3,5‐Disubstituted Dihydro‐2(3H)‐furanones
Authors: Fischer János , Fodor Tamás , Dobay László , Kiss Béla , Tóth Gábor , Snatzke Günther , Ötvös László
Published: July 2007

Internal prodrug analogues of enalapril were obtained by reduction of (1S)‐N‐[1‐(ethoxycarbonyl)‐3‐oxo‐3‐phenylpropyl]‐(S)‐alanyl‐(S)‐proline tert‐butyl ester (1) to the alcohols 2a and 2b followed by lactonization to (3S,5S)‐ and (3S,5R)‐N‐(tetrahydro‐2‐oxo‐5‐phenyl‐3‐furanyl)‐(S)‐alanyl‐(S)‐proline (4a and 4b), both isolated as the maleates. Their configuration and conformation have been elucidated by a combination of 1D‐ and 2D‐NMR techniques and with the help of CD measurements. In vitro inhibition of angiotensin‐converting enzyme (ACE) by 4a and 4b has been found to be similar to that of enalapril.
Synthese von Marchantin I, einem macrocyclischen Bis(bibenzylether) aus Riccardia multifida
Authors: Dienes Zoltán , Nógrádi Mihály , Vermes Borbála , Kajtár‐Peredy Mária
Published: July 2007

Synthesis of Marchantin I, a Macrocyclic Bis(bibenzyl Ether) from Riccardia multifida

The unambigous synthesis of marchantin (1), a bis(bibenzyl ether) with a 18‐membered ring, by Ullmann, Wittig, and modified Wurtz reaction is reported.
Nitriles in Heterocyclic Synthesis: A Novel Synthesis of 2‐Amino‐3‐pyrrolecarbonitriles
Authors: Hilmy Khalid Mohamed Hassan , Pedersen Erik B.
Published: July 2007

2‐Amino‐3‐pyrrolecarbonitriles are prepared by the reaction of phenacylmalononitrile with primary aromatic amines using a catalytical amount of concd. HCl.
Enantioselective Microbial Reduction of 5‐Acetylisoxazolines – A Novel Method for Stereochemical Control on Yeast Reduction
Authors: Ticozzi Calimero , Zanarotti Antonio
Published: July 2007

The kinetics and the stereoselectivity of the reduction by baker′s yeast of racemic 5‐acetyl‐4,5‐dihydro‐3‐phenylisoxazole 1 to the corresponding alcohol in 2‐propanol/water mixtures are strongly dependent from the 2‐propanol/water ratio; at a ratio of 4.0, the reduction allows a kinetic resolution leading to alcohol 2 and ketone (R)‐1 Subsequent reduction of (R)‐1 with yeast in water and with Aspergillus niger leads to alcohols 3 and 4 with high ee.
1,4‐pentadien‐3‐ones, 31. 1‐(1‐cyclohexenyl)‐1‐propen‐2‐ones: Synthesis, properties, and stereoselective formation of 3‐aryl‐4‐(1‐cyclohexenylcarbonyl)perhydro‐1‐naphthalenones by sequential michael reaction
Authors: Richter Friedrich , Otto Hans‐Hartwig
Published: July 2007

On rearrangement, 1‐ethynyl‐1‐cyclohexanol (1) yields 1‐acetyl‐1‐cyclohexene (2). At −78°C in the presence of LDA, 2 reacts with aldehydes/ketones yielding the aldols 5/8, which are dehydrated to the title compounds 6 or 9. At room temp., a reaction between the lithium derivative of 2 and 6 ensues, yielding the bicyclic products 10. These can also be prepared independently from isolated 6 and 2 with LDA or butyllithium in high yields. The stereochemistry is elucidated by spectroscopic methods, and the minimum energy conformation of 10a is calculated. The stereoselective formation of 10 is explained by a lithium‐controlled sequential Michael reaction.
Synthese von (1α,7α,8β)‐(±)‐7‐Hydroxy‐1‐(hydroxymethyl)pyrrolizidin, der Necin‐Base rac‐Platynecin
Authors: Röder Erhard , Bourauel Thomas , Wiedenfeld Helmut
Published: July 2007

Synthesis of (1α,7α,8β)‐(±)‐7‐Hydroxy‐1‐(hydroxymethyl)pyrrolizidin, the Necine rac‐Platynecine

rac‐Platynecine (rac‐7) can easily be obtained in high yields from diethyl (±)‐cis‐2,3‐pyrrolidinedicarboxylate (rac‐1) by N‐alkylation to ethyl (±)‐cis‐2,3‐bis(ethoxycarbonyl)‐1‐pyrrolidinepropionate (rac‐2), Dieckmann reaction to ethyl (1α,8β)‐(±)‐6‐ethoxycarbonyl‐7‐oxo‐1‐pyrrolizidinecarboxylate (rac‐3), subsequent saponification, decarboxylation, reduction to (1α,7α,8β)‐(±)‐pyrrolizidine‐1,7‐carbolactone (rac‐6), and further reduction to the desired title compound rac‐7.
Chemie und Stereochemie der Iridoide, XIV. Aucubin und Scandosid aus Catalpol
Authors: Weinges Klaus , Ziegler Hans Jürgen
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XIV. — Aucubin and Scandoside from Catalpol

Aucubin (9), scandoside (10), and its methyl ester [“feretoside” (11)] were obtained, in good yields, from catalpol (1). The absolute configurations of 9–11 were established by correlation to catalpol, whose X‐ray crystal structure has previously been determined.
Synthese von L‐Prolin‐haltigen O‐Glycopeptiden
Authors: Paulsen Hans , Merz Gunnar , Brockhausen Inka
Published: July 2007

Synthesis of L‐Proline‐Containing O‐Glycopeptides

The synthesis of a number of L‐proline‐containing O‐glycopeptides in which 2‐acetamido‐2‐deoxy‐α‐D‐galacto‐pyranose is α‐glycosidically linked to L‐threonine is described. For N‐terminal extension with amino acids the building block 3 is preferred. For C‐terminal extension a new intermediate is developed, that includes the Aloc/tBu combination of protective groups which can be synthesized with high yield and stereoselectivity. The Aloc group shows a low steric hindrance and is very stable. Therefore, the carbohydrate‐containing compound 68 can also be coupled C‐terminally with low‐reactive L‐proline derivatives in good yields. The synthesized O‐glycopeptides shall be used in the investigation of the dependence of the protein structure on the glycosyltransferase activity of the biosyntheses of mucins.
Chemie und Stereochemie der Iridoide, XIII. Synthese von enantiomerenreinem (1R,2S,2″Z)‐(+)‐Methyljasmonat aus Catalpol
Authors: Weinges Klaus , Lernhardt Ulrich
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XIII. — Synthesis of Enantiomerically Pure Methyl (1R,2S,2″Z)‐(+)‐Jasmonate Starting from Catalpol

Enantiomerically pure methyl (1R,2S,2″Z)‐(+)‐jasmonate (2), which was recognized as a component of the fragrance of the jasmine flower oil, was synthesized starting from catalpol (3). 2 is easily epimerized to 1. Thus, it is necessary to use very mild conditions in the course of the synthesis and purification. These results raise the question whether 2 exists as a natural product in the flower of jasmine and 1 arises during the isolation.
Synthesis and structure of some condensed quinazolines
Authors: Badawy Mohamed A. , Abdel‐Hady Sayed A. , Mahmoud Ahmed H. , Ibrahim Yehia A.
Published: July 2007

Condensation of 2‐hydrazino‐4(3H)‐quinazolinone (1) with bielectrophilic reagents gives the corresponding triazoloquinazolines 8, the structures of which were established by selective synthesis through deamination of their N‐amino derivatives. The synthesis of methyl‐substituted derivatives of these angular tricyclic systems and their linear isomers was also achieved starting with 3‐methyl‐ and 1‐methyl‐2‐hydrazino‐quinazolinone.
Xylaral, ein Hydroxyphthalid‐Derivat aus Fruchtkörpern von Xylaria polymorpha (Ascomycetes)
Authors: Gunawan Sonny , Steffan Bert , Steglich Wolfgang
Published: July 2007

Xylaral, a Hydroxyphthalide Derivative from Fruiting Bodies of Xylaria polymorpha (Ascomycetes)

Fruiting bodies of Dead Man's Fingers, Xylaria polymorpha, contain a hydroxyphthalide derivative, xylaral (1), which exhibits a violet colour reaction with aqueous ammonia. 1 is a homologue of cyclopaldic acid (5) with a C14‐side chain containing an enone moiety.
Functionally substituted vinyl carbanions, 42. Synthesis of the top half of chlorothricolide
Authors: Hirsenkorn Rolf , Schmidt Richard R.
Published: July 2007

β‐Lithiated functionally substituted acrylates 2a–c prove to be versatile building blocks for spirotetronate syntheses useful in top half syntheses of the aglycon chlorothricolide 1 of the macrolide antibiotic chlorothricin. The electrophilic‐nucleophilic cyclohexanone derivatives 27‐cis/trans (with relative cis or trans relationship of the carboxylate group) required in this synthesis design are obtained via a cycloaddition route from pentenone in five steps. Generation of the dilithiated species from the acrylates 2a–c affords then the corresponding spirotetronates 32a–c, which serve as versatile intermediates in top half syntheses for different strategies in chlorothricolide total syntheses. Hydroxylation in the vinylic α‐position of the tetronate moiety and selective phenylselenylation provide the spirotetronates 39a‐cis/trans and 41a, which meet the requirements of a top half molecule. The same is true for a different strategy, which provides the aldehydes 42b‐cis/trans. The latter are then converted into the fully functionalized spirotetronates 44b‐cis/trans by treatment with vinylmagnesium bromide and subsequent hydroxylation at the vinylic α‐position. The investigations delineate similar convenient strategies for the syntheses of kijanolide and te‐tronolide, which are the aglycon portions of the structurally related macrolide antibiotics kijanimicin and tetrocarcin, respectively.
Heterocyclische β‐Enaminoester, 52. Neue Wege zu kondensierten Pyrimidinen über Iminophosphorane
Authors: Wamhoff Heinrich , Wintersohl Heinrich , Stölben Stephan , Paasch Joachim , Nai‐Jue Zhu , Fang Guo
Published: July 2007

Heterocyclic β‐Enamino Esters, 52. — New Approaches to Condensed Pyrimidines via Iminophosphoranes

The heterocyclic and carbocyclic 2‐(triphenylphosphoranyl‐ideneamino)‐3‐carboxylates 1a, b, 4a–d, and 8a, b, d react with isocyanates in a novel type of pyrimidine annulation to give heterocondensed 2‐alkoxy‐4‐pyrimidinones 3a–d, 5a–h, furthermore 14‐17 (revised constitutions) as well as 4(3H)‐quinazolinones 9a–g, 10a, b. The constitution of model compound 3a has been established by X‐ray analysis. — Crossover experiments reveal that partially saturated enamino esters, such as 1a, b, 4a–d, undergo strictly an intramolecular 1,3‐shift of the ester alkoxide; a mechanism accounting for this annulation reaction is discussed. Under these conditions, the anthranilates 8 afford a stabilized carbodiimide to which alcohols or amines add before condensation occurs to 4(3H)‐quinazolinones 9a–c, 10a, b; however, with the phenyl esters 8b, d the intramolecular 1,3‐migration of the phenoxide is clearly favoured to afford 9f,g. — Reaction of the iminophosphoranes 19a,b of the 1,4‐dihydropyridines 18a,b with acetylenedicarboxylates results in 1‐addition and Aza‐Wittig annulation to give the pyrido[1,2‐a]pyrimidines 21a–c.
EPC‐synthesis and fungistatic activity of a gloeosporone analog with an ω‐hydroxybutyl instead of the pentyl side chain on the macrocyclic ring
Authors: Seebach Dieter , Adam Geo , von dem Bussche‐Hünnefeld Christoph , Gisi Ulrich , Binder Heinz
Published: July 2007

(+)‐5′‐Oxa‐gloeosporone (2), an analog of the natural germination self‐inhibitor (−)‐gloeosporone (1), is synthesized, largely following our previously published route to the parent compound. Thus, the hydroxybutyl side chain of 2 was introduced by hydroboration of a butenyl group (→ 14) which had been carried along throughout the synthesis up to the stage of the 14‐membered yne‐lactone 13. Silyl protection (→ 15), oxidation of the acetylene to a 1,2‐diketone moiety (→ 16), and deprotection with spontaneous intramolecular hemiacetal formation completed the synthesis of (+)‐2. The (+)‐oxa‐gloeosporone 2 exhibits an in vitro and in vivo antifungal activity spectrum with 14 microorganisms very similar to both the natural (1) and the unnatural enantiomer (ent‐1) of gloeosporone, indicating that neither the sense of chirality nor the side‐chain structure is important for the mode of action.
Synthese von 2‐(2‐Aminoethyl)thiophen über aktivierte Arylsulfonylaziridine
Authors: Fikentscher Rolf , Brückmann Raif , Betz Rainer
Published: July 2007

Synthesis of 2‐(2‐Aminoethyl)thiophene via Activated Arylsulfonylaziridines

Activated arylsulfonylaziridines react with 2‐lithiothiophene under ring cleavage to afford sulfonamides 2, reductive cleavage of which with sodium bis(2‐methoxyethoxy)aluminium hydride yields 2‐(2‐aminoethyl)thiophene (3).
Reaktionen von Dinatrium‐dicyandithioacetat und Natrium‐dicyanthioacetamiden mit γ‐Bromcrotonsäure‐Derivaten
Authors: Wobig Dieter
Published: July 2007

Reactions of Disodium Dicyanodithioacetate and Sodium Dicyanothioacetamides with Derivatives of γ‐Bromocrotonic Acid

The dicyanodithioacetate 3 reacts with the derivatives of γ‐bromocrotonic acid 4a and 4b to give the thieno‐[2,3‐b]thiophenes 5a and 5b. 3 can also be alkylated successively with two different alkylating reagents. In this way the compounds 5c, 6a, and 6b are prepared. Reactions of the dicyanothioacetamides 8a and 8b with 4a and 4b yield the thiazolidines 9a–d.
Ozonolyse von Olefinen, I. Ozonolyse von 1,4‐Cyclohexadien und säurekatalysierte Folgereaktionen von Primärspaltprodukten
Authors: Mittelbach Martin , Poklukar Norbert , Junek Hans
Published: July 2007

Ozonolysis of Olefins, I. — Ozonolysis of 1,4‐Cyclohexadiene and Acid‐Catalysed Reaction of Primary Cleavage Products

The reaction of 1,4‐cyclohexadiene (1) with ozone under different reaction conditions was investigated. Complete ozonolysis of 1 in chloroform led to a highly explosive ozonide. Oxidative ozonolysis gave malonic acid in 30% yield, ozonolysis in alcoholic solutions of HCl gave alkyl 3,3‐dialkoxypropionates 3 in 60–70% yield and small amounts of the 1,1,3,3‐tetraalkoxypropane 4 as well as dialkyl malonate 5. Partial ozonolysis of 1 in HCl/methanol led to a mixture of 3, 5, and the corresponding (Z)‐3‐hexene derivatives 6a–c. Depending on the reaction time and concentration of HCl, also the two methanol addition products 7b and 7d could be obtained. To verify the structure of these two compounds, 4‐methoxycyclohexene (8) was ozonized in HCl/methanol, which gave a mixture of 7a–d.
Synthese von Undecose‐Derivaten als D‐Galactose‐Analoga zur spezifischen Modifikation Galactose‐bindender Proteine
Authors: Lehmann Jochen , Scheuring Markus
Published: July 2007

Syntheses of Undecose Derivatives as D‐Galactose Analogues for Specific Modification of Galactose‐Binding Proteins

A series of undec‐ and dodecoses containing functional groups was obtained from 1,2:3,4‐di‐O‐isopropylidene‐α‐D‐galacto‐hexodialdo‐pyranose‐(1,5) (1) using Wittig and Grignard reactions to bring about chain elongation. The compounds resemble 6‐C‐alkylated D‐galactose derivatives which should have affinity to some galactose‐binding proteins. One potential photoaffinity reagent, 8‐azi‐6,7,8,9,10‐pentadeoxy‐D‐galacto‐undecose (12), was prepared from 6,7,9,10‐tetradeoxy‐1,2:3,4‐isopropylidene‐α‐D‐galacto‐8‐undecosulopyranose‐(1,5) (10). Compound 11 is suitable for syntheses of “spacer‐modified” oligosaccharides.
Reactions of organic anions, 164. Formation of gem‐dichlorocyclopropanes from perhalomethanes and alkenes in a phase‐transfer catalytic (PTC) system
Authors: Fedoryński Michał , Dziklińska Anna , Jończyk Andrzej
Published: July 2007

Perhalomethanes YCCl3 (Y = Cl, Br) react with alkenes in the phase‐transfer catalytic system to give gem‐dichlorocyclopropanes.
Isolierung und NMR‐spektroskopische Untersuchungen von (−)‐1‐O‐Benzyl‐β‐D‐primverosid aus grünen Früchten von Prunus laurocerasus
Authors: Weinges Klaus , Schick Hartmut , Lautenschläger Michael , Schilling Gerhard
Published: July 2007

Isolation and NMR‐Spectroscopic Investigations of (−)‐1‐O‐Benzyl‐β‐D‐primveroside from Green Fruits of Prunus laurocerasus

The TLC of the acetylated aqueous extracts of the green fruits of Prunus laurocerasus reveals two spots corresponding to pentaacetyl‐glucopyranose and hexaacetyl‐1‐O‐benzyl‐β‐D‐primveroside (2), which can be quantitatively separated by flash chromatography. Saponification of 2 yields the free 1‐O‐benzyl‐β‐D‐primveroside (1) which affords D‐primverose (3) upon hydrogenolysis. The direct hydrogenolysis of 2 yields hexaacetyl‐β‐D‐primverose (4). The structures of compounds 1–4 have been verified by NMR spectroscopy.
Synthesis of the three stereoisomers of auxin‐glutaric acid to confirm the non‐existence of Kögl's auxin‐a and ‐b
Authors: Mori Kenji , Kamada Atsushi , Kido Masaru
Published: July 2007

All of the three possible stereoisomers of (5S,1′S)‐4‐carboxy‐5‐methyl‐1‐(1′‐methylpropyl)heptanoic acid were synthesized and their stereostructures assigned unambiguously by 13C‐NMR and X‐ray analyses. The melting points and the specific rotations of the three isomeres were quite different from those reported for Kögl's auxin‐glutaric acid and its two stereoisomers. This fact indicates the non‐existence of Kögl's auxin‐a and ‐b.
Dithio‐ und Thionester, 50. α,β‐Acetylenische Thioamide, Dithioester und Thionester
Authors: Hartke Klaus , Gerber Hans‐Dieter , Roesrath Ulrich
Published: July 2007

Dithio and Thiono Esters, 50. – α,β‐Acetylenic Thioamides, Dithio Esters, and Thiono Esters

α,β‐Acetylenic amides 5 and thioamides 7 have been obtained by a palladium‐catalysed condensation of the terminal acetylenes 3 with N,N‐dimethylcarbamoyl chloride (4) or ‐thiocarbamoyl chloride (6). Sulfhydrolysis of the α,β‐acetylenic thioamidium salts 19 or amidium salts 21 leads to the formation of the α,β‐acetylenic dithio esters 22 or thiono esters 23. Both types may also be prepared by a palladium‐catalysed condensation of the terminal acetylenes 3 with methyl carbonodithiochloridate (25) or O‐methyl carbonothiochloridate (26). The thiono esters 23 are also accessible from 26 and the alkyne Grignard reagents 29. Finally, reactions of 22 and 23 with amines, thioles, alkylating agents, and cyclopentadiene are described.
Über die Inhaltsstoffe der Propolis, II
Authors: Seifert Michael , Haslinger Ernst
Published: July 2007

Constituents of the Propolis, II1)

Extraction of the propolis (bee glue) with n‐hexane yields a solution of hydrocarbons, fatty acids, aromatic esters, and waxes. The latter have been separated by fractionating crystallisation; the other compounds were isolated by column and thin‐layer chromatography. Their structures have been determined by GC/MS, NMR, and chemical degradation. The following classes of compounds have been found: monoester waxes, diester waxes, diacylglycerol ether, aromatic esters, keto waxes, hydroxy waxes, and fatty acids.
Bausteine von Oligosacchariden, XCVIII. Synthese von Oligosacchariden der inneren Core‐ und Lipoid‐A‐Region von Lipopolysacchariden
Authors: Paulsen Hans , Brenken Mathias
Published: July 2007

Building Units of Oligosaccharides, XCVIII. – Synthesis of Oligosaccharides of the Inner Core and Lipoid A Region of Lipopolysaccharides

Glycosidic coupling of the Hep‐Kdo disaccharide bromide 9 with the Lipoid A analogous disaccharide 10 gives the tetrasaccharide 11 which was deprotected to yield the tetrasaccharide L‐α‐D‐Hepp‐(1→5)‐α‐Kdop‐(2→6)‐β‐D‐GlcpNhm‐(1→6)‐D‐GlcNhm (18). In a further block synthesis 10 was glycosylated with the Hep‐[Kdo]‐Kdo donor 24. Deprotection of the corresponding pentasaccharide 25 furnished L‐α‐D‐Hepp‐(1→5)‐[α‐Kdop]‐(2→4)‐α‐Kdop‐(2→6)‐β‐D‐GlcpNhm‐(1→6)‐D‐GlcNhm (31). Sheep erythrocytes can be coated with these oligosaccharides 18 and 31. The resulting complexes are used as synthetic antigens and immunogens containing the disaccharide L‐α‐D‐Hepp‐(1→5)‐α‐Kdop and the branched trisaccharide L‐α‐D‐Hepp‐[α‐Kdop‐(2→4)]‐α‐Kdo as antigenic determinants.
Organic azides in heterocyclic synthesis, 14. Synthesis of 3,6‐diaminopyridazine from 6‐azidotetrazolo[1,5‐b]pyridazine
Authors: Deeb Ali , Sterk Heinz , Kappe Thomas
Published: July 2007

6‐Azidotetrazolo[1,5‐b]pyridazine („3,6‐Diazidopyridazine”︁, 1) reacts at ambient temperature with phosphanes or phosphites 2a–c to yield the phosphazenes 3a–c. In contrast to literature reports, the tetrazolopyridazines 1, and 3a,b react with phosphanes to yield 3,6‐bis(phosphoranylideneamino)pyridazines 4; however, the required temperature is rather high (180°C). The use of phosphites instead of phosphanes leads to „Michaelis‐Arbuzov‐type”︁ rearrangements; thus, 3a reacts in boiling 2d to afford 6, and heating of the trimethoxyphosphazene 3c in refluxing 1,2‐dichlorobenzene yields the methylamino derivative 7.
Inter‐ and intramolecular hetero‐Diels‐Alder reactions, 32. Iridoids, 26. Synthesis of bridged homoiridoids from secologanin by tandem‐Knoevenagel‐hetero‐Diels‐Alder reactions
Authors: Tietze Lutz F. , Bärtels Christoph
Published: July 2007

The tandem‐Knoevenagel‐hetero‐Diels‐Alder reaction of the chiral enantiomerically pure monoterpene glucoside secologanin (1) with 1,3‐dicarbonyl compounds 6a–d and the analogous compounds 11a–b in the presence of ethylenediammonium diacetate as catalyst leads to the bridged cycloadducts 8a–d and 13a–b in 60–70% yield, except for 8d. Compound 8b can be transformed into 9 by treatment with methanol and into 10 by treatment with water. The cycloadditions are highly regio‐ and stereoselective, affording only the bridged but not the annulated compounds as single diastereomers.
Properties and reactions of substituted 1,2‐thiazetidine 1,1‐dioxides: Acylation of β‐sultams at C‐4, reduction of 4‐acyl‐β‐sultams, and stereochemistry of 4‐(α‐hydroxyalkyl)‐β‐sultams
Authors: Müller Martin , Otto Hans‐Hartwig
Published: July 2007

Acylation of N‐silylated and 2,3‐substituted 1,2‐thiazetidine 1,1‐dioxides (β‐sultams) results in the formation of 4‐acylated β‐sultams 2 and 8. The desilylation of 2 to 3 is easily done with TBAF either on silica gel or in ethanolic solution. The acylated β‐sultams are reduced by sodium borohydride yielding α‐hydroxyalkyl β‐sultams 11 and 12, obtained as mixtures of diastereoisomers. These are separated by CC. The stereochemistry of the acylated and of the α‐hydroxylated β‐sultams is elucidated by spectroscopic methods, and compared to that of the antibiotic drug thienamycin.
Synthesis of substituted phenyl‐, biphenyl‐, and terphenylcarbaldehydes by coupling of arylpalladium complexes with alkyl‐ and aryl‐grignard reagents
Authors: Jendralla Heiner
Published: July 2007

Novel arylcarbaldehydes 4 (R3 = alkyl or aryl) are prepared from arylcarbaldehydes 1 via arylpalladium complexes 3.
Reaction of α‐lithio O‐alkyloximes with diiodomethane – a synthesis of α‐iodomethylene oxime ethers
Authors: Shatzmiller Shimon , Lidor Ramy , Babar Eliezer
Published: July 2007

Regiocontrolled deprotonation (e. g. lithiation) of acetone O‐methyloxime (1), 5,6‐dihydro‐3‐methyl‐4H‐1,2‐oxazine (9a) and 4,5‐dihydro‐3‐methylisoxazole (9b) is achieved within 1 minute at −65°C in hexane/THF. The lithiated compounds react very fast at low temperature (−65°C) with diidomethane to give mainly the corresponding α‐iodomethylene oxime ethers 6 and 11a, b. A radical mechanism of this reaction is discussed.
Untersuchungen an 1,3‐Thiazinen, 43. Newman‐Kwart‐Umlagerung bei Thiocarbazoylierungen von Tetrahydro‐2H‐1,3‐thiazin‐2‐on und Thiazolidin‐2‐on
Authors: Hanefeld Wolfgang , Von Gösseln Hans Joachim
Published: July 2007

Investigations on 1,3‐Thiazines, 43. – Newman‐Kwart Rearrangement in the Course of Thiocarbazoylation of Tetrahydro‐2H‐1,3‐thiazin‐2‐one and Thiazolidin‐2‐one

Thiocarbazoylation of tetrahydro‐2H‐1,3‐thiazin‐2‐one (1) with thiocarbazic acid chlorides leads to N‐thiocarbazoyl derivatives 5 and N‐carbazoyl‐tetrahydro‐2H‐1,3‐thiazin‐2‐thiones 8, which are interpreted as products of an O‐thiocarbazoylation to 6, subsequent Newman‐Kwart rearrangement to 7 and final S→N transcarbazoylation. Thiocarbazoylation of thiazolidin‐2‐one (9) yields an isolable Newman‐Kwart rearrangement product 12 and its product 13 of S→N transcarbazoylation.
Herkunft der Methylsubstituenten in F‐Säuren
Authors: Scheinkönig Josef , Spiteller Gerhard
Published: July 2007

Origin of the Methyl Substituents of F Acids

Feeding experiments with L‐[methyl‐13C]methionine on suspension cultures of Saccharum spec. demonstrate that the furan methyl groups of F acids 1 are derived from methionine. Specific incorporation of 13C label was confirmed by GC/MS analysis of the tetrahydrofuran derivatives 2.
1,3,2λ5‐Benzothiazaphosphole 2‐Oxide and 1,3,2λ5‐benzoxazaphosphole 2‐oxide derivatives, new and versatile phosphorylating reagents
Authors: Jacob Peter , Richter Wolfgang , Ugi Ivar
Published: July 2007

The synthesis of the highly reactive five‐membered cyclic phosphorylating reagents 6a and 12 is described. The reagent 6a monophosphorylates alcohols without ring opening, whereas 12 diphosphorylates with ring opening yielding phosphate triesters.
Synthesis and Reactions of α‐Bromo‐N‐alkoxyimidates
Authors: Shatzmiller Shimon , Bercovici Sorin
Published: July 2007

The reaction of alkyl hydroxamates 2 with (C2H5)3O · BF4 in CH2Cl2 affords N‐alkoxyimidates 3. The direct alkylation of hydroxamic acids 1 with 1,2‐dibromoethane gives the 5,6‐dihydro‐1,4,2‐dioxazine derivatives 4. The reactions of the acyclic imidates 3 as well as the cyclic N‐alkoxyimidates 4 with N‐bromosuccinimide in CCl4 produces the α‐bromoimidates 5a–d and 6a–d. The α‐bromine atom in the bromides 5b, d and 6a, b, d can be displaced by fluorine and azido substituents to yield the α‐fluoro‐N‐alkoxyimidates 7b, d and 10a, b, d and the α‐azido compounds 8b, d and 11a, b, d, respectively. The reduction of the azides 8b, d and 11a, b, d affords the α‐aminoimidates 9b, d and 12a b, d, respectively. The reaction of the bromides 6a–d with benzene derivatives 14a–d in the presence of AgBF4 affords the aromatic substitution products 15a–d. Acid‐catalyzed hydrolysis of 15a, c gives the arylsubstituted carboxylic acids 16 and 17.
Synthesis of (+)‐Artemeseole
Authors: Narjes Frank , Schaumann Ernst
Published: July 2007

The synthesis of the monoterpene (+)‐artemeseole (1b) is accomplished by starting from (Z)‐dienol 5. Sharpless epoxidation of 5 gives oxirane 4. Attempted opening of the epoxide ring in 4 or in derivatives 8a, b by various allyl or acetylide anions gives side reactions, but the desired coupling with a C3 unit is achieved in the reaction of silyl‐protected oxirane 8b with 9 or 13 giving 17 and 19a, respectively. Alkenol 19a is further converted into oxirane 21 by desilylation, tosylation, and base‐induced epoxide formation. Anion generation from 21 by reductive desulfurization yields (dialkenylcyclopropyl)methanol 3. Acid‐catalyzed cyclization to a tetrahydrofuran completes the synthesis of 1b.
Novel Prenylated 2‐Quinolinones from East Asian Zanthoxylum Species
Authors: Brader Günter , Wurz Gerald , Greger Harald , Hofer Otmar
Published: July 2007

In addition to already known 2‐quinolinones [flindersine (3), N‐methylflindersine (4), 8‐methoxyflindersine (5), zanthobungeanine (6), glycolone (1), O‐methylglycosolone (2)], four novel derivatives have been isolated and identified by spectroscopic methods. The roots of Zanthoxylum schinifolium and Z. simulans contain the novel prenylated schinifoline (7) and N‐methylschinifoline (8), whereas the leaves of Z. simulans predominantly form N‐acetoxymethylflindersine (10). From the roots of Z. scandens zascanol epoxide (9) has been isolated whose prenyl side chain is characterized by an epoxide ring and a terminal hydroxy group.
Syntheses of α‐Aminophosphonic Acids, VI. Synthesis of Diastereomerically Pure 1‐Aminocyclopropylphosphonic Acids
Authors: Groth Ulrich , Lehmann Lutz , Richter Lutz , Schöllkopfh Ulrich
Published: July 2007

The lithium or potassium derivative of diethyl isocyanomethylphosphonate (1) reacts with epoxides in the presence of boron trifluoride–diethyl ether to provide the diethyl 3‐hydroxy‐1‐isocyanoalkylphosphonates rac‐3. The corresponding mesylates rac‐4 undergo a base‐mediated cyclization to the diethyl 1‐isocyanocyclopropylphosphonates rac‐5. Acidic hydrolysis affords the diethyl 1‐aminocyanocyclopropylphosphonates rac‐6, which upon treatment with trimethylsilyl iodide yield the 1‐aminocyclopropylphosphonic acids rac‐7. A base‐mediated cycloalkylation of 1 with dibromoalkanes 10 gives the diethyl 1‐isocyanocycloalkylphosphonates 11, which are suitable precursors for the achiral 1‐aminocycloalkylphosphonic acids.
Synthesis of Aniline Derivatives with Potential Toxicological Implications to the Spanish Toxic Oil Syndrome
Authors: Ferrer Marta , Galceran Montserrat , Sánchez‐Baeza Francisco , Casas Josefina , Messeguer Angel
Published: July 2007

The synthesis of anilides 2 from several saturated and unsaturated fatty acids 1 required for toxicological studies related to the Spanish Toxic Oil Syndrome is reported. In addition, a simple procedure for the microscale determination of the position of a carbon–carbon double bond of a fatty acid residue is described. This procedure involves epoxidation of the sample with 3,3‐dimethyldioxirane followed by oxidative cleavage with periodic acid to yield the corresponding carbonyl derivatives which are easily identifiable by GC‐MS analysis. Finally, the synthesis of anilino derivatives 5–8 formally derived from glycerol is also reported. For this purpose, a common precursor, i.e. 3‐(phenylamino)propane‐1,2‐diol (4) is prepared, and convenient procedures for its chemoselective acylation at either the hydroxy or the amino group have been developed.
Electroorganic synthesis, 57. Synthesis of advanced prostaglandin precursors by Kolbe electrolysis, II. – Preparation of coacids and anodic initiated tandem radical‐addition / radical‐coupling reaction with (1′R,4′S,3R/S)‐3‐(cis‐4‐acetoxycyclopent ‐2‐enyloxy)‐3‐ethoxypropionic acid
Authors: Weiguny Jens , Schäfer Hans J.
Published: July 2007

The α‐silyl‐substituted carboxylic acids 4 and 10 were prepared and with other coacids subjected to a mixed Kolbe electrolysis with β‐cyclopentenyloxypropanoate 1. The stereochemical course of this cyclization reaction was determined on the basis of the 4‐methyl‐substituted product 23 by 1H‐NMR‐NOE spectroscopy. Conversion of the bicyclic reaction products 21b–d to advanced prostaglandin precursors such as lactone 30 was achieved in few steps. magnified image
Eine neue Strategie zur Festphasensynthese von O‐Glycopeptiden über 2‐Azidoglycopeptide
Authors: Paulsen Hans , Bielfeldt Tim , Peters Stefan , Meldal Morten , Bock Klaus
Published: July 2007

A New Strategy for the Solid‐Phase Synthesis of O‐Glycopeptides via 2‐Azido‐glycopeptides

The building blocks Fmoc‐Thr(α‐D‐GalN3Ac3)‐OPfp (8) and Fmoc‐Ser(α‐D‐GalN3Ac3)‐OPfp (9) were synthesized. Both building blocks are active esters which can directly be used for the solid‐phase synthesis of O‐glycopeptides. The obtained glycopeptides carry an 2‐azido‐2‐deoxy‐D‐galactosyl residue α‐linked to Thr or Ser. The conversion of the 2‐azido into the 2‐acetamido groups was achieved with thioacetic acid on solid support, and subsequently the sugar residues of the polymer bound glycopeptides were deacetylated with hydrazine hydrate in methanol. The subsequent cleavage from the resin with TFA/water gave after RP‐HPLC purification directly the desired deprotected O‐glycopeptides. magnified image
Synthesis of Dopamines Labelled with 13C in the α‐ or β‐Side Chain Position and Their Application to Structural Studies on Melanins by Solid‐State NMR Spectroscopy
Authors: Crescenzi Orlando , Kroesche Christoph , Hoffbauer Wilfried , Jansen Martin , Napolitano Alessandra , Prota Giuseppe , Peter Martin G.
Published: July 2007

Solid‐state NMR spectroscopy was applied to the analysis of melanins prepared by peroxidase‐H2O2 oxidation of dopamines specifically 13C labelled in the α‐ or β‐side chain positions. A surprisingly diverse pattern of signals indicated the presence of uncyclized dopamine and noradrenaline‐derived units, in addition to indole and carbonyl carbon atoms. These structural features, coupled with the results obtained from elemental analysis of dopamine melanin samples prepared under different conditions, point to a pigment formation process more complex than previously believed. magnified image
Constituents of Holothuroideae, V. Isolation and Structure of Cerebrosides from the Sea Cucumber Pentacta australis
Authors: Higuchi Ryuichi , Inagaki Masanori , Togawa Kenichi , Miyamoto Tomofumi , Komori Tetsuya
Published: July 2007

Four new cerebrosides, PA‐0‐1, PA‐0‐5, PA‐2‐5 and PA‐2‐6, were isolated from the two cerebroside mixtures, PA‐0 and PA‐2, obtained from the less polar fraction of the methanol extract of the sea cucumber Pentacta australis. The structures of these cerebrosides were determined on the basis of chemical and spectroscopic evidence. Another cerebroside, PA‐1‐4, isolated in a pure state from a different cerebroside mixture PA‐1, was found to be identical with the known glucocerebroside CE‐2c obtained from the related sea cucumber Cucumaria echinata of the same family. Reversed‐phase HPLC was effective in isolating these cerebrosides, showing the very close similarity of their structures. An analysis of the mass spectrum of the dimethyl disulfide derivatives of cerebrosides was also useful for the determination of the double‐bond position in the sea cucumber cerebroside. magnified image
New Effective Transformations of Monosaccharides by Selective Inversion
Authors: Miethchen Ralf , Rentsch Daniel
Published: July 2007

Regio‐ and stereoselective acetalizations of methyl α‐D‐lyxopyranoside (1), methyl β‐L‐arabinopyranoside (6), methyl α‐D‐galactopyranoside (11), and methyl β‐D‐galactopyranoside (13) with chloral, including an inversion of the configuration at C‐3, were achieved with dicyclohexylcarbodiimide as a coagent. Additionally, the formed methyl 3,4‐O‐(2,2,2‐trichloroethylidene)‐α‐D‐arabinopyranoside 2, methyl 2,3‐O‐(2,2,2‐trichloroethylidene)‐β‐L‐lyxopyranoside 7, methyl 2,3‐O‐(2,2,2‐trichloroethylidene)‐α‐D‐gulopyranoside 12, and methyl 2,3‐O‐(2,2,2‐trichloroethylidene)‐β‐D‐gulopyranosides 14 and 15 contain an N‐cyclohexylcarbamoyl group vicinal to the chloral acetal moiety; the compounds 12 and 15, moreover, a formyl group in 6‐position. The formyl and carbamoyl functions may be cleaved stepwise with methanolic sodium methoxide. Deformylation of the 6‐O‐formyl derivative 15 affords the urethane 16 with simultaneous migration of the carbamoyl group from the 4‐ to the 6‐position. The fluorination of 3 and 8 with anhydrous hydrogen fluoride/nitromethane/acetic anhydride, giving the glycosyl fluorides 4 and 9 without any cleavage of the cyclic chloral acetal functions, is described. BF3‐catalyzed glycosylations of chloro‐ethanol with the fluorides 4 and 9α/β yield the α‐glycoside 5 and the anomeric mixture 10α/β, respectively, showing that neither a cyclic chloral acetal function in 3,4‐O‐nor in 2,3‐O‐position affects such reactions.