bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibiotika aus Gleitenden Bakterien, XXXVII. Sorangicin A, ein hochwirksames Antibiotikum mit neuartiger Makrolid‐Polyether‐Struktur aus Sorangium cellulosum, So ce12: Spektroskopische Strukturaufklärung, Kristall‐ und Lösungsstruktur
Authors: Jansen Rolf , Höfle Gerhard , Irschik Herbert , Reichenbach Hans , Schomburg Dietmar , Wray Victor
Published: July 2007

Aus dem Myxobakterium Sorangium cellulosum, Stamm So ce12, wurde das hoch aktive Breitspektrumantibiotikum Sorangicin A (1) isoliert. Dessen Struktur wurde überwiegend durch 1D‐ und 2D‐NMR‐Spektroskopie aufgeklärt. Aufgrund einer wahrscheinlich dynamischen Fehlordnung war die Röntgenstrukturanalyse von 1 in einem Molekülteil nicht eindeutig. Die absolute Konfiguration aller 15 Asymmetriezentren konnte mit über 99.5% Wahrscheinlichkeit nach dem Hamilton‐Test festgelegt werden. Die Abhängigkeit der 1H‐NMR‐Spektren vom Wassergehalt und von der Probentemperatur führte zu einem Modell für die Lösungsstruktur von 1 mit einer Wasserbrücke zwischen 21‐Hydroxy‐ und Carbonsäuregruppe.
Terpenes and Terpene Derivatives, XXV. Oreodaphnenol ‐ A Sesquiterpene Alcohol with a New Carbon Skeleton
Authors: Weyerstahl Peter , Marschall‐Weyerstahl Helga , Wahlburg Hans‐Christian
Published: July 2007

From the essential oil of Oreodaphne porosa (commercial “Phoebe oil”) a sesquiterpene alcohol with a new carbon skeleton, oreodaphnenol (1), could be isolated. The structure and relative stereochemistry were deduced from detailed NMR studies and by degradation to the ketone 2.
2,6‐Dicyanbarbaralane durch Phasentransfer‐katalysierte Halogenierung/Dehydrohalogenierung von Bicyclo[3.3.1]nona‐2,6‐dien‐2,6‐dicarbonitril
Authors: Quast Helmut , Mayer Andreas
Published: July 2007

Durch Natriummethanolat in Methan‐[D]ol oder durch Alkalideuteroxid in Deuteriumoxid unter Phasentransfer‐Katalyse werden die γ‐Protonen des Bicyclo[3.3.1]nona‐2,6‐dien‐2,6‐dicarbonitrils (1) gegen Deuterium ausgetauscht. Aus dem so erhaltenen [D4]‐1 wird auf bekanntem Weg das Barbaralandicarbonitril [D2]‐3 hergestellt. Das mit Alkalihydroxid unter Phasentransfer‐Katalyse aus 1 erzeugte Carbanion wird durch Hexachlorethan chloriert. Cyclisierende Dehydrohalogenierung der intermediären chlorierten Dinitrile (vermutlich 2b und 4b) unter den gleichen Reaktionsbedingungen ergibt hauptsächlich 3 (76%) neben 4‐Chlorbarbaralandicarbonitril 5b (11%), die chromatographisch getrennt werden.
Structural Variations of N‐Acetylneuraminic Acid, 11, Synthesis of the 4‐Methylumbelliferyl 2α‐Glycosides of 7‐Epi‐, 8‐Epi‐, and 7,8‐Bis(epi)‐N‐acetylneuraminic Acids, as well as of 7‐Deoxy‐, 8‐Deoxy‐, 9‐Deoxy‐, and 4,7‐Dideoxy‐N‐acetylneuraminic Acids and Their Behaviour Towards Sialidase from Vibrio cholerae
Authors: Zbiral Erich , Schreiner Erwin , Salunkhe Mamikrao M. , Schulz Gerhard , Kleineidam Reinhard G. , Schauer Roland
Published: July 2007

The methyl esters of 7‐epi‐Neu5Ac (1a), 8‐epi‐Neu5Ac (2a), 7,8‐bis(epi)‐Neu5Ac (3a), 7‐deoxy‐Neu5Ac (4a), 8‐deoxy‐Neu5Ac (5a), 9‐deoxy‐Neu5Ac (6a), and 4,7‐dideoxy‐Neu5Ac (7a) were transformed into their peracetylated mixtures of the α‐anomers 1b–7b and β‐anomers 1c–7c. In the next step the 2‐Cl derivatives were prepared with acetyl chloride/HCl which yielded in the following Königs‐Knorr reaction with 4‐methylumbelliferone (MU) the corresponding methylumbelliferyl 2α‐glycosides 7‐epi‐Neu4,5,7,8,9Ac51Me‐αMU (1d), 8‐epi‐Neu4,5,7,8,9Ac51Me‐αMU (2d), 7,8‐bis(epi)‐Neu4,5,7,8,9Ac51Me‐αMU (3d), 7‐deoxy‐Neu‐4,5,8,9Ac41Me‐αMU (4d), 8‐deoxy‐Neu4,5,7,9Ac41Me‐αMU (5d), 9‐deoxy‐Neu4,5,7,8A41Me‐αMU (6d), and 4,7‐dideoxy‐Neu‐5,8,9Ac31Me‐αMU (7d). In the last case also the β‐anomer of 4,7‐dideoxy‐Neu5,8,9Ac31Me‐βMU (7d′) was formed. Zemplen saponification followed by hydrolysis of the ester group with sodium hydroxide, resulted in the sodium salts of the sialic acid MU 2α‐glycosides 7‐epi‐, 8‐epi‐, 7,8‐bis(epi)‐, 8‐deoxy‐, 9‐deoxy‐ and 4,7‐dideoxy‐Neu5Ac‐MU 1e–7e. The enzymatic hydrolysis of these compounds with sialidase from Vibrio cholerae showed only for 3e and 7e significantly reduced rates of cleavage, which is in agreement with the inhibitor constants Ki of the related 2,3‐didehydro sialic acids 7,8‐bis(epi)‐Neu5Ac2en and 4,7‐dideoxy‐Neu5Ac2en1,15).
Chirale Lactole, VIII Ein Weg zur asymmetrischen Induktion bei der Bildung von Zuckern
Authors: Noe Christian R. , Knollmüller Max , Ettmayer Peter
Published: July 2007

Der substituierte Glycolaldehyd 4, der eine enantiomerenreine acetalische Schutzgruppe mit der Konfiguration eines α‐L‐Zukkers am acetalischen Zentrum trägt, wird unter basischen Bedingungen aldolisiert. Die entstehenden Produkte werden nach Reduktion durch Vergleich mit Referenzverbindungen bekannter Absolutkonfiguration charakterisiert. Es entstehen überwiegend L‐Zucker mit L‐Erythrose als Hauptprodukt.
Ring Cleavage of 1,2,3‐Triazolium Ions with Nucleophiles
Authors: Moderhack Dietrich
Published: July 2007

The 1,2,3‐triazolium salts 1 react with a variety of nucleophiles to give products of ring scission like 2–5. The new 1,2,3‐triazolium reaction most probably does not follow the pattern known in the case of isoxazolium and furazanium salts.
NMR‐Spectroscopic Assignment of the Aib‐Methyl Groups in α‐Helical and β‐Turn Environment with the Use of Selectively Deuterated Aib The Solution Conformations of Boc‐Ala‐Aib‐Ala‐OMe
Authors: Leibfritz Dieter , Brunne Roger M. , Weihrauch Thomas , Stelten Johannes , Stohrer Wolf‐Dieter , Haupt Erhard T. K.
Published: July 2007

Boc‐Ala‐Aib‐Ala‐OMe (1a) adopts in the crystal a conformation similar to a β‐turn type II. From 13C‐CP‐MAS spectra the magnetic nonequivalence of the Aib‐Cβ atoms amounts to 6.1 ppm. The pro‐S‐Cβ carbon signal is shifted upfield as can be shown by comparison with the spectra of Boc‐Ala‐(R)‐Aib[D1]‐Ala‐OMe (1b). This assignment corresponds to a downfield shift of the Aib pro‐S‐Cβ carbon in the helix of Boc‐[L‐Glu(OBzl)]4‐Aib‐[L‐Glu(OBzl)]7‐O‐PEG‐M (2a), where it was established with the aid of the (R)‐Aib[D3]‐containing analog (2b), From molecular dynamics simulations of Boc‐Ala‐Aib‐Ala‐OMe we propose two major conformational species in solution that account for the observed MNE of 2.1 ppm, the temperature gradients of the amide protons, the coupling constants, and the distances derived from ROESY spectra.
Ring‐Opening Reactions of Mesoionic [1,2,4]Triazolo[1,5‐c]quinazolines. – Preparation of 1,2,4‐Triazolo[3,4‐b][1,3,4]thiadiazoles by a Translocative Rearrangement
Authors: Molina Pedro , Arques Antonio , Alias Maria Asunción , Saiz Antonio Luis Llamas , Concepción Foces‐Foces Maria De La
Published: July 2007

1‐Amino‐5‐aryl‐2‐mercapto‐1H[1,2,4]triazolo[1,5‐c]quinazolin‐4‐ium hydroxides, inner salts (1) undergo ring opening by the action of hydrochloric acid to give 4‐amino‐3‐[2‐(aroylamino)‐phenyl]‐4,5‐dihydro‐5‐thioxo‐1H‐1,2,4‐triazoles3. Reaction of compounds3with phosphorus pentasulfide yields the corresponding 1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazoles6. The molecular structure of6bhas been solved by X‐ray diffraction methods.
Synthesen mit Nitrilen, LXXXIV Farbe und Stereochemie von 3‐(Cyanmethylen)‐2‐indolonen
Authors: Junek Hans , Dworczak Renate , Sterk Heinz , Fabian Walter
Published: July 2007

3‐(Dicyanmethylen)‐2‐indolone (1a–c) und 3‐[Cyan(ethoxycarbonyl)methylen]‐2‐indolone (2a–b) sind auffallend tiefrote Verbindungen. Die Farbigkeit und die Stereochemie dieser Stoffklasse werden untersucht. 1H‐ und 13C‐NMR‐Daten ergaben das Vorliegen von E,Z‐Isomeren in 2a, b, wobei durch Messung des Differenz‐NOE‐Effektes das Auftreten von trans‐s‐cis‐ und trans‐s‐trans‐Konformeren nachgewiesen werden kann. Quantenchemische Berechnungen mittels des semiempirischen AM1‐Verfahrens unterstützen diese spektroskopischen Aussagen. Mit dem INDO/S‐CI‐Verfahren werden die elektronischen Anregungsenergien von 1a, b und 2a, b berechnet und die chromophoren Eigenschaften als intramolekularer Charge‐Transfer‐Übergang diskutiert.
Enantiomerically Pure Building Blocks from Sugars, 9 An Expedient Approach to Pyranoid Ene and Enol Lactones by BF3‐Catalyzed Peroxidation of Glycal and Hydroxyglycal Esters
Authors: Lichtenthaler Frieder W. , Rönninger Stephan , Jarglis Pan
Published: July 2007

An effective and convenient one‐pot procedure, simply involving treatment with boron trifluoride/3‐chloroperbenzoic acid (MCPBA), is detailed for the high‐yield acquisition of enantiomerically pure dihydropyran‐2‐ones from mono‐ and disaccharide‐derived glycal and hydroxyglycal esters. An assessment of the scope of the method is given, a total of 17 examples being ample evidence for its preparative utility and apparent generality. Substantiation of the mechanism presented – BF3‐promoted removal of the allylic acyloxy group, seizure by MCPBA of the allylcarboxonium ion generated, and fragmentation of the resulting hex‐2‐enopyranose 1‐(3‐chloro)perbenzoates on quenching – is provided by characterization of the perester intermediates. Conducting the reaction of glycal esters at room temperature a glycoltype C‐1 – C‐2 bond cleavage occurs instead with the generation of acylated 4,5‐dihydroxypentenals.
Short synthesis of (±)‐4,8‐dimethyl‐1‐oxaspiro[4.5]deca‐3,7‐dien‐2‐one (andirolactone) using the propynoate/cuprate method
Authors: Krause Norbert
Published: July 2007

Racemic 4,8‐dimethyl‐1‐oxaspiro[4.5]deca‐3,7‐dien‐2‐one (andirolactone) (1) was synthesized in two steps with 58% overall yield, starting from 4‐methyl‐3‐cyclohexenone (2) and methyl propynoate (3).
Biologically active glycosides from asteroidea, XXII. Glycosphingolipids from the starfish Astropecten latespinosus, I. Structures of three new cerebrosides, astrocerebroside A, B, and C and of related nearly homogeneous cerebrosides
Authors: Higuchi Ryuichi , Kagoshima Masahiko , Komori Tetsuya
Published: July 2007

By means of the high‐performance liquid chromatography (HPLC), three new cerebrosides (ceramide monohexosides), as‐trocerebroside A (8), B (10), and C (18), together with a known cerebroside, acanthacerebroside A (17), were isolated from a molecular species of cerebroside obtained from the less polar fraction of the chloroform/methanol extract of the starfish Astropecten latespinosus. On the basis of chemical and spectral evidences, their structures were determined. The structures of the nearly homogeneous cerebrosides, which appeared to be pure from HPLC and negative FAB mass spectrum, were also described.
Reaktionen der Trialkylsilyl‐trifluormethansulfonate, IX. Elektrophile Silylierung elektronenreicher Alkene
Authors: Schulz Dieter , Simchen Gerhard
Published: July 2007

Reactions of Trialkylsilyl Trifluoromethanesulfonates, IX. — Electrophilic Silylation of Electron‐Rich Alkenes

Ketene O,O‐, O,S‐, and O,N‐acetals 1, 7, and 9 are converted into the C‐silylated derivatives 4, 8, and 11, respectively, by reaction with trimethylsilyl triflate (2a)/tertiary amine or sodium hydride. The ambident character of the ketene O,O‐acetals 1 in the silylation with 2a is studied.
Amphiphilic carbohydrate‐based mesogens, V. Mesogenic 1‐O‐alkyl‐D‐glucitols from alkyl D‐glucopyranosides
Authors: Dahlhoff Wilhelm V.
Published: July 2007

The endocyclic acetal bonds of alkyl D‐glucopyranosides (hexyl to decyl, 1a – e) are regioselectively hydroborated with ethyldiboranes(6) in the presence of 9‐methylsulfonyloxy‐9‐borabicyclo[3.3.1]nonane (MSBBN) after conversion to their 2,3,4,6‐tetra‐O‐diethylboryl derivatives 2a – e. Subsequent deboronations give the mesogenic 1‐O‐alkyl‐D‐glucitols 3a – e.
Monosaccharide mit Stickstoff im Ring, XXXIX. Synthese von modifizierten α‐L‐Fucosidase‐Inhibitoren, die 1,5‐Didesoxy‐1,5‐imino‐L‐fucit als Basisstruktur enthalten
Authors: Paulsen Hans , Matzke Michael , Orthen Bruno , Nuck Rolf , Reutter Werner
Published: July 2007

Monosaccharides Containing Nitrogen in the Ring, XXXIX. — Synthesis of Analogues of 1,5‐Dideoxy‐1,5‐imino‐L‐fucitol, Inhibitors of α‐L‐Fucosidase

Variation of the side chain in the 1,3‐dithiane derivative 1 of D‐galactose leads to a series of analogues of 1,5‐dideoxy‐1,5‐imino‐L‐fucitol (deoxyfuconojirimycin) (33), which are potent inhibitors of α‐L‐fucosidase. Cleavage of the dithioacetal in 5 followed by reduction of the aldehyde 6 and deblocking results in 1,5‐dideoxy‐1,5‐imino‐L‐galactitol (8). The aldehyde 6 is converted by Wittig reaction to 10 and 14 via 9 and 13, which are homologues of 1,5‐dideoxy‐1,5‐imino‐L‐fucitol (33). Cyclization of the Wittig product 15 yields the γ‐lactam 18. After reduction of the acetylated γ‐lactam 19 and subsequent deblocking the trihydroxyindolizidine 24 is obtained, which is an analogue of castanospermine with L‐fuco configuration. The chloride 30, which is available from 27, can be converted by intramolecular substitution and removal of the blocking groups to the bicyclic aziridine derivative (3R,4S,5R,6S) ‐1‐azabicyclo[4.1.0]heptane‐3,4,5‐triol (32). First results on the inhibitory activities of all new analogues on α‐L‐fucosidase are presented.
Natural product chemistry, 140. Synthesis of some new acridones
Authors: Reisch Johannes , Herath H. M. T. Bandara , Kumar N. Savitri
Published: July 2007

Methyl 6‐amino‐2,3‐dimethoxybenzoate (6) which was obtained from 6‐formyl‐2,3‐dimethoxybenzoic acid (1), was treated with phloroglucinol to give two new acridone alkaloids, 1,3,8‐trihydroxy‐7‐methoxy‐9‐acridone (7) and 1,3‐dihydroxy‐7,8‐dimethoxy‐9‐acridone (8). Methylation of 7 and 8 gave another four new acridone alkaloids, 1,8‐dihydroxy‐3,7‐dimethoxy‐9‐acridone (9), 1,8‐dihydroxy‐3,7‐dimethoxy‐10‐methyl‐9‐acridone (10), 1‐hydroxy‐3,7,8‐trimethoxy‐10‐methyl‐9‐acridone (11) and 1,3,7,8‐tetramethoxy‐10‐methyl‐9‐acridone (12).
Synthesis of the α‐methyl ketoside of 5‐amino neuraminic acid methyl ester and its corresponding 5‐myristoyl and 5‐cyclopropanoyl derivative
Authors: Schrell Andreas , Whitesides George M.
Published: July 2007

This communication describes the first synthesis of the α‐methyl ketoside of an N‐unprotected neuraminic acid in the form of its methyl ester (Neu5NH21Me‐α‐2Me) (5a). This compound is a valuable intermediate for the synthesis of unnatural N‐substituted sialic acids. Syntheses of Neusmyristoyl1me‐α‐2Me (5b) and Neuscyclopropanoyl1me‐α‐2Me (5c) are presented.
Lascivol, der Bitterstoff des Unverschämten Ritterlings, Tricholoma lascivum (Agaricales)
Authors: Eizenhöfer Thomas , Fugmann Burkhard , Sheldrick William S. , Steffan Bert , Steglich Wolfgang
Published: July 2007

Lascivol, the Bitter Component of Tricholoma lascivum (Agaricales)

The structure of lascivol (1), the bitter principle of the toadstool Tricholoma lascivum, has been elucidated by chemical and spectroscopic studies including a single crystal X‐ray structure analysis. 1 is degraded to dimethyl L‐glutamate (6) and 5‐methoxy‐2,4‐dimethylindole (5) by acid methanolysis.
Synthese von Metallkomplexen mit Bis(phenalenyl)imin‐Liganden
Authors: Hofmann Michael , Musso Hans
Published: July 2007

Synthesis of Metal Complexes with Bis(phenalenyl)imine Ligands

Synthesis of model pigments and their metal chelates with Zn, Co, Ni, and Mn (26a–d) are described. The former are obtained from 2,4‐dihydro‐4,9‐dihydroxy‐1,2,4‐phenalenethione (14b) by connecting two molecules in a ninhydrin‐like reaction with nitrogen to the ligand 8. These models confirm the structure of the zinc complex 2 isolated from the ascomyces Roesleria hypogea. Isolation of the rearranged ester 18 proves this compound to be an intermediate in the mechanism of the degradation process of phenalenetriones 14 to acenaphthoquinones 16.
Pheromone synthesis, CXXI. Synthesis of (4R*,5R*,6S*,7E,9E)‐4,6,8‐trimethyl‐7,9‐undecadien‐5‐ol and its isomers to determine the relative stereochemistry of the female specific compound of the woodroach Cryptocercus punctulatus
Authors: Mori Kenji , Itou Masamichi , Brossut Rémy
Published: July 2007

By synthesizing some isomers of 4,6,8‐trimethyl‐7,9‐undeca‐dien‐5‐ol, (4R*,5R*,6S*,7E,9E)‐relative stereochemistry was assigned to the isomer isolated as the female specific compound of the tergal glands secretion of the woodroach Cryptocercus punctulatus.
Asymmetric induction of four chiral centers by hetero Diels‐Alder reaction of a chiral nitroso dienophile
Authors: Werbitzky Oleg , Klier Konrad , Felber Helena
Published: July 2007

The Diels‐Alder reaction of cis‐5,6‐diacetoxy‐1,3‐cyclohexadiene (1), which has a meso configuration, with the chiral nitroso dienophile 2 occurs with induction of four asymmetric centers in very high optical yield (ee = 94%) and leads to the dihydro oxazine 3 (89%). The influence of the reaction temperature on the asymmetric induction was investigated and the absolute configuration of the product determined. Reductive cleavage of the N  O bond of 3 presents a simple route to enantiomerically pure derivatives of (1R)‐conduramine A1 (82%).
Über Pyridinium‐N‐phenolat‐Betaine und ihre Verwendung zur Charakterisierung der Polarität von Lösungsmitteln, XV. Sind solvatochrome vinyloge γ‐Pyridon‐Betainfarbstoffe bessere empirische Indikatoren der Lösungsmittelpolarität?
Authors: Reichardt Christian , Milart Piotr , Schäfer Gerhard
Published: July 2007

Pyridinium N‐Phenoxide Betaines and Their Application for the Characterization of Solvent Polarities, XV. — Are Solvatochromic Vinylogous γ‐Pyridone Betaine Dyes Better Empirical Indicators of the Solvent Polarity?

The new negatively solvatochromic betaine dyes 11 and 12 are synthesized. Their solvatochromism is weaker compared with that of the standard betaine dye 1, used to introduce the ET(30) scale of solvent polarity.
Constituents of holothuroidea, II. Six newly identified biologically active triterpenoid glycoside sulfates from the sea cucumber Cucumaria echinata
Authors: Miyamoto Tomofumi , Togawa Kenichi , Higuchi Ryuichi , Komori Tetsuya , Sasaki Takuma
Published: July 2007

From the whole body of sea cucumber Cucumaria echinata (Cucumariidae), we recently identified six genuine holostane‐type triterpenoid glycoside sulfates designated as cucumechinoside A (1), B (2), C (3), D (4), E (5), and F (6). The structures 1–6 were determined on the basis of chemical and spectral investigations. Antitumor activities of these cucumechinosides and their solvolized compounds (10, 11, and 12) against murine lymphoma L 1210 and human epidermoid carcinoma KB cell in vitro were examined, and their antifungal and antiprotozoal activities were also investigated.
Total synthesis of cedrusin and its methyl ether
Authors: Antus Sándor , Baitz‐Gács Eszter , Bauer Rudolf , Gottsegen Agnes , Seligmann Otto , Wagner Hildebert
Published: July 2007

A simple synthesis of the racemates of two naturally occurring neolignans 1 and 2 was achieved starting from caffeic acid ethyl ester and the methyl ferulate 6, respectively.
Benzofuran dioxetanes, a new class of mutagenic agents: Synthesis by photooxygenation of benzofuran derivatives
Authors: Adam Waldemar , Albrecht Olaf , Feineis Erich , Reuther Irene , Saha‐Möller Chantu R. , Seufert‐Baumbach Petra , Wild Dieter
Published: July 2007

Tetraphenylporphine‐sensitized photooxygenation of benzofuran derivatives1afforded the corresponding benzofuran dioxetanes2in good yields. Allylic hydroperoxides3were formed regioselectively from 2,3‐dimethyl‐substituted benzofurans as minor products, except in the case of the benzofuran1d, which gave predominantly the hydroperoxide3d. The relative reactivities of the benzofurans toward singlet oxygen depended on the nature of substituents at the C‐2 and C‐3 positions of the furan rings. The benzofuran dioxetanes2were strongly mutagenic in the Salmonella typhimurium strain TA 100, their mutagenicity depending on the type of substituents of the dioxetane and of the benzo rings.
Antibiotics from gliding bacteria, XLIII. Phenoxan: A novel inhibitor of HIV‐1 infection in cell cultures from Polyangium sp., strain Pl VO19 (Myxobacteria)
Authors: Jansen Rolf , Kunze Brigitte , Wray Victor , Reichenbach Hans , Jurkiewicz Elke , Hunsmann Gerhard , Höfle Gerhard
Published: July 2007

Guided by a biological screening with a cell assay, the first HIV‐1 inhibitor from a gliding bacterium, phenoxan (1), was isolated. The structure of 1 was determined by spectroscopic methods to be a substituted oxazole‐γ‐pyrone, showing a remarkable similarity to aureothin (2) and spectinabilin (3).
Synthese von 2‐Desoxy‐α‐O‐glycopeptiden mit dem N‐Iodsuccinimid‐(NIS‐) Verfahren
Authors: Kottenhahn Matthias , Kessler Horst
Published: July 2007

Synthesis of 2‐Deoxy‐α‐O‐glycopeptides by the N‐Iodosuccinimide (NIS) Procedure

Glycosidation of amino acid/peptide derivatives of serine, threonine, or hydroxyproline with glycals like tris‐O‐acetyl‐D‐glucal 1 or tris‐O‐acetyl‐D‐galactal 2 and N‐iodosuccinimide (NIS) gives 2‐deoxy‐2‐iodo‐α‐O‐glycopeptides with high yields and excellent anomeric purity. Disaccharide glycals like per‐O‐acetyl‐D‐cellobial 15, per‐O‐acetyl‐D‐lactal 16, and 2′,3′,4′,6′‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl‐(1 – 3)‐4,6‐di‐O‐benzyl‐D‐galactal 17 can also be used as glycosyl donors in this process. They give moderate to good yields of α‐O‐glycoside with formation of small amounts of β‐O‐glycopeptide. The NIS procedure is especially favored for the direct and stereoselective glycosidation of larger peptide fragments, which is very difficult with classical techniques. The so‐formed 2‐deoxy‐2‐iodo‐α‐O‐glycopeptides were deiodinated by using different methods and then deacetylated in the sugar moiety.
Epitope analysis: N4‐Formylation of the D‐benzylpenicilloyl antigenic structure
Authors: Schneider Conrad H. , De Weck Alain L.
Published: July 2007

Acetic anhydride treatment of 6‐(benzylpenicilloylamido)‐hexanoic acid bis(benzylammonium) salt (1a) in formic acid gave the N4‐formylated derivatives 2a and 2b as diastereomeric mixtures. The inhibitory capacity of these haptens was assessed in a precipitating system involving anti‐D‐α‐benzylpenicilloyl antibody and D‐α‐benzylpenicilloyl antigen.
Antibiotics from gliding bacteria, XLIV. Ambruticins VS: New members of the antifungal ambruticin family from Sorangium cellulosum
Authors: Höfle Gerhard , Steinmetz Heinrich , Gerth Klaus , Reichenbach Hans
Published: July 2007

A group of six new antifungal metabolites (ambruticins VS‐1 to ‐5, VS‐3 N‐oxide) was isolated from the myxobacterium Sorangium cellulosum. They were separated by RP chromatography and identified as (5S,6R)‐5‐amino‐6‐hydroxypolyangioic acids 1b–e, 2b and methyl ester 2a by spectroscopic methods.
Circular dichroism, XCV. Chiroptical properties of stereoisomeric conjugated oximes, I
Authors: Frelek Jadwiga , Huang Liang , Kerek Francis , Snatzke Günther , Szczepek Wojciech J.
Published: July 2007

The CD of ketoximes of defined (E)/(Z configuration and some of their O‐derivatives of steroids (4‐en‐3‐ones, 4‐en‐6‐ones, 5‐en‐7‐ones, 4,6‐dien‐3‐ones) and monoterpenoids (verbenone, carvone) have been investigated. All show two Cotton effects around 250 nm (band II) and 230 nm (band III), which usually have opposite signs. For the first‐mentioned one a rule is proposed for the correlation between CD and absolute configuration. Most of the (Z)‐oxime derivatives give an additional Cotton effect around 290 nm (band I), whose sign is always opposite to that of band II.
Photochemie von Aminoketonen, 14. Synthese und transannulare Photocyclisierung von 2‐Benzoyl‐1,4‐bis(tosyl)piperazinen
Authors: Wessig Pablo , Legart Frank , Hoffmann Berit , Henning Hans‐Georg
Published: July 2007

Photochemistry of Amino Ketones, 141). – Synthesis and Transannular Photocyclisation of 2‐Benzoyl‐1,4‐bis‐(tosyl)piperazines

1,1‐Dialkyl‐1,2‐bis(tosylamino)ethanes 4 are prepared in a three‐step reaction starting with dialkyl ketones 1. With strong bases in dimethylformamide compounds 4 react regioselectively with 1,2‐dibromoalkyl phenyl ketones 5 to afford the 2‐benzoyl‐1,4‐bis(tosyl)piperazines 6. On irradiation (≥ 300 nm) the piperazines 6a, b, f, g, without substituents in position 6, undergo Norrish‐II cleavage yielding open‐chain products. Depending on the ring conformations the 2,2‐dialkylpiperazines 6c, d, e form diazabicycloalkanes 10 and 11 on irradiation.
Darstellung und Reaktionen von N‐Phenacyl‐N‐tosylhydroxylaminen und ‐hydrazinen
Authors: Wessig Pablo , Henning Hans‐Georg
Published: July 2007

Preparation and Reactions of N‐Phenacyl‐N‐tosylhydroxylamines and ‐hydrazines

O‐Alkyl‐N‐phenacyl‐N‐tosylhydroxylamines 3 were prepared in two steps from O‐alkylhydroxylamines 1. In the presence of a base the N‐tosylhydroxylamines 3 undergo rearrangement and cleavage to N‐tosylphenacylamine (5) and aldehydes 6. N‐Alkul‐N′‐phenacyl‐N,N′‐ditosylhydrazines 12 were obtained by stepwise treating of N,N′‐ditosylhydrazine with alkyl halide and phenacyl bromide/potassium tert‐butoxide/DMF.
Synthesis of 1 ‐[2,3‐dideoxy‐3‐(3‐hydroxypropyl)‐D‐pentofuranosyl]thymines
Authors: Walczak Krzysztof , Pupek Krzysztof , Pedersen Erik B.
Published: July 2007

Free radicals generated by reaction of protected methyl 2,3‐ dideoxy‐3‐iodopentofuranosides 2, 3, and 9 with tributyltin hydride in the presence of a radical initiator (AIBN) were treated with acrolein to give methyl 2,3‐dideoxy‐3‐(3‐oxopropyl)pentofuranosides 4 and 5. Reduction of 5 with Sodium borohydride followed by protection of hydroxy groups by reaction with tert‐butyl chlorodiphenylsilane gave the carbohydrate derivative 11 which was condensed with silylated thymine to afford a separable mixture of α‐ and β‐nucleosides 13 and 14. These nucleosides were subsequently deprotected to give the 3′‐propyl‐extended thymidine 16 and its corresponding α‐isomer 15.
Synthese neuer optisch aktiver Kronenether
Authors: Dehmlow Eckehard V. , Knufinke Volker
Published: July 2007

Syntheses of New Optically Active Crown Ethers

Optically active crown ethers 1a–1l, 2, 3a, b, 4a, b, 5a, b and the analogue 6 are synthesized. The efficiency of these compounds as phase‐transfer catalysts for a series of enantioselective reactions will be tested. This will be described in a following publication.
Efficient one‐pot approach to sugar phosphates of potential biochemical interest
Authors: Fatima Ayjaz , Zaman Fakhar , Malik Abdul , Shekhani Mohammed Saleh , Voelter Wolfgang
Published: July 2007

Efficient one‐pot syntheses of sugar phosphates 4 – 8 are developed by way of displacement reactions of suitably protected monosaccharides with tetrabutylammonium dihydrogen phosphate and dibenzyl phosphates. This procedure is mild, convenient, and does not attack highly acid‐labile groups.
Unsymmetrically substituted furoxans, XIII. Phenylfuroxancarbaldehydes and related compounds
Authors: Gasco Andrea Marcello , Fruttero Roberta , Sorba Giovanni , Gasco Alberto
Published: July 2007

The synthesis and structure of the two isomeric phenylfuroxancarbaldehydes 7a and 7b, of the phenylfurazancarbaldehyde 6 and of the corresponding alcohols 3a, 3b and 5 are reported. Thermal equilibration of the furoxan derivatives and their oxidation to the corresponding carboxylic acids 8a and 8b are also discussed.
Ring Transformation Reactions, I. Conversion of 6‐Aryl‐4‐(methylthio)‐2‐oxo‐2H‐pyran‐3‐carbonitriles to pyrazoles
Authors: Ram Vishnu Ji , Verma Monika , Hussaini Falak Anwer , Shoeb Aboo
Published: July 2007

A new ring transformation reaction has been studied by treating 6‐ or 5,6‐disubstituted 4‐(methylthio)‐2‐oxo‐2H‐pyran‐3‐carbonitriles 2 with hydrazine and methylhydrazine leading to polysubstituted pyrazoles 4, 5, 6.
Terpenes and Terpene Derivatives, XXVII. Salsolene oxide – A sesquiterpene epoxide with a new carbon skeleton
Authors: Weyerstahl Peter , Marschall Helga , Wahlburg Hans‐Christian , Kaul Vijay K.
Published: July 2007

From the essential oil of Artemisia salsoloides a sesquiterpene epoxide with a new carbon skeleton, salsolene oxide (1), could be isolated. The structure and relative stereochemistry were deduced from extended NMR studies.
Addition von Nitromethan an Aldosen Untersuchung der Diastereoselektivität der Fischer‐Sowden‐Reaktion mit Hilfe der 13C‐NMR‐Spektroskopie
Authors: Köll Peter , Stenns Claudia , Seelhorst Willi , Brandenburg Heinz
Published: July 2007

Addition of Nitromethane to Aldoses. – A Comprehensive Study of the Diastereoselectivity of the Fischer‐Sowden Reaction by the Help of 13C‐NMR Spectroscopy1)

The addition of nitromethane to aldoses, commonly referred to as „Fischer‐Sowden reaction”︁, is not as stereoselective as can be concluded from the literature. This is the outcome of a comprehensive study which covered besides glyceraldehyde all aldotetroses, ‐pentoses and ‐hexoses. The ratio of the pair of diastereomeric nitroalditols has been determined in each case by 13C‐NMR spectroscopy. Thus, incidentially, a whole set of spectral data for all tetritols, pentitols, hexitols and heptitols with a terminal nitro group has been obtained, which can be correlated systematically to the respective data for the parent alditols. From these results follows that at least under conditions which give high yields of products, the reaction is thermodynamically controlled; thus, the product ratio is determined by the different energy content of the product nitroalditols (or their nitronates), which is a result of different patterns of steric interactions between substituents.
Hochsubstituierte Cyclopentadiene mit Arylthio‐ und Arylsulfonyl‐Gruppen
Authors: Hartke Klaus , Lee Kyung‐Hee , Massa Werner , Schwarz Birgit
Published: July 2007

Highly Substituted Cyclopentadienes with Arylthio and Arylsulfonyl Groups

Cyclopentadienes 1 react with diaryl disulfides 2 to form the tetrakis(arylthio)cyclopentadienides 3, which have been oxidized with m‐chloroperbenzoic acid to give the tetrakis(arylsulfonyl)cyclopentadienides 5. Protonation of 5 yields the tetrakis(arylsulfonyl)cyclopentadienes 7 by migration of arylsulfonyl groups. Oxidation of 3 by iodine leads to the dihydropentafulvalenes 11. By reaction of 3 with arylthiosulfonates 14 the pentakis(arylthio)cyclopentadienes 15 have been obtained. Their salts 16 may be oxidized to form the pentakis(arylsulfonyl)cyclopentadienides 17, or condensed with sulfenyl chlorides to give the hexakis(arylthio)cyclopentadienes 19. The structure of the phenylthio compound 19a was confirmed by an X‐ray structure analysis.
Pheromone synthesis, CXXIX. Synthesis of the (5S,9S)‐isomers of 5,9‐Dimethylheptadecane and 5,9‐dimethyloctadecane, the major and the minor components of the sex pheromone of Leucoptera malifoliella costa
Authors: Mori Kenji , Wu Jiang
Published: July 2007

The synthesis of (5S,9S)‐5,9‐dimethylheptadecane (1) as well as that of (5S,9S)‐5,9‐dimethyloctadecane (2) has been achieved by starting from methyl (R)‐3‐hydroxy‐2‐methylpropanoate (3a) and (S)‐citronellal (7).
Sulfoborierung cyclischer Ether — ein präparativer Weg zu Mercaptoalkanolen und Bis(hydroxyalkyl)sulfiden
Authors: Köster Roland , Kucznierz Ralf
Published: July 2007

Sulfoboration of Cyclic Ethers — A Preparative Route to Mercaptoalkanols and Bis(hydroxyalkyl) Sulfides

Bis(1,5‐cyclooctanediylboryl) sulfide (1) reacts slowly with the cyclic ethers A–D to give the O,S‐bis(9‐BBN)mercaptoalkanols 2a–d in excellent yields. From oxetane (E) and 1, however, 2e is obtained rapidly, which further reacts with E to yield the bis(9‐BBN‐oxypropyl) sulfide 3ee. 2a and c react with E to form mixed thioethers 3ae and 3ce, respectively. The methanolysis of 2a–e leads to the O‐(9‐BBN)mercaptoalkanols 4a–e. The compounds 2 and 3 react with acetylacetone or with 2‐aminoethanol to yield the mercaptoalkanols 7a–c, e and the bis(hydroxyalkyl) sulfides 8ae, 8ce and 8ee, resp., in high yields beside the 9‐BBN‐chelates 5 or 6.
Isolation of 4‐Hydroxy‐5‐methoxycanthin‐6‐one from Picrasma quassioides and Revision of a Previously Reported Structure
Authors: Liu Jian , Davidson R. Stephen , Heijden Robert Van Der , Verpoorte Robert , Howarth Oliver W.
Published: July 2007

A new alkaloid, 4‐hydroxy‐5‐methoxycanthin‐6‐one (1), has been isolated from Picrasma quassioides (Simaroubaceae), and its structure has been determined by high‐field 1H‐ and 13C‐NMR, 13C,1H‐HETCOR, 1H,1H‐2D‐COSY, and NOE‐difference spectra. Previous data, interpreted by other workers as being from this compound, is instead tentatively reassigned to another new alkaloid structure, 4‐hydroxy‐3‐methylcanthine‐5,6‐dione (2).
Untersuchungen zur Charge‐Transfer‐Wechselwirkung von Phenolen mit Tetracyanethylen (TCNE)
Authors: Spange Stefan , Maenz Karsten , Stadermann Dietmar
Published: July 2007

Investigations on the Charge‐Transfer Interaction of Phenols with Tetracyanoethylene (TCNE)

The donor properties of some phenol derivatives were determined by measuring the UV/Vis spectra of their CT complexes with tetracyanoethylene in 1,2‐dichloroethane and acetonitrile at room temperature. The ionization potentials of the phenolic compounds have been calculated by using the longest visible charge‐transfer absorption of the donor‐acceptor complex by linear correlation analysis. The charge‐transfer spectra are discussed in dependence on the ring substituents in terms of electronic and steric factors. Increasing donor strength of the substituents decreases the ionization potential of the phenols as demonstrated by an LFE relationship using the Hammett constants. However, ortho donor substituents enhance the donor strength of the aromatic ring as well.
Oxidation of 8‐Methoxypsoralen (8‐MOP) by Dimethyldioxirane. Evidence for the Formation of a Furocoumarin Epoxide by Methanol Trapping, a Potential Mutagenic Agent
Authors: Adam Waldemar , Sauter Markus
Published: July 2007

The reaction of 8‐methoxypsoralen (1) with dimethyldioxirane in methanol at 25°C yields the methanol adduct 3, namely the 2,3‐dihydro‐2‐hydroxy‐3,9‐dimethoxy‐7H‐furo[3,2‐g][1]benzopyran‐7‐one, whose structure was unequivocally assigned by means of spectroscopic data. Methanol adduct 3 is produced by dioxirane epoxidation of the furan double bond of 1 to 2 followed by nucleophilic attack by methanol at the benzylically activated C‐3. The direct observation of the 8‐methoxypsoralen epoxide (2) was not possible, because at low temperature (below 0°C) dimethyldioxirane does not epoxidize 1, while at 25°C this labile epoxide decomposes. On the basis of these results, a rational explanation is offered as to the origin of the regioisomeric methanol adduct 5, namely 2,3‐dihydro‐3‐hydroxy‐2,9‐dimethoxy‐7H‐furo[3,2‐g][1]benzopyran‐7‐one, observed in traces (ca. 0.2%), when 1 is treated with sodium hypochlorite and hydrogen peroxide in aqueous methanol.
Zur Struktur cyclotrimerer 1,4‐Chinone
Authors: Laatsch Hartmut , Beck Holger , Egert Ernst
Published: July 2007

On the Structure of Cyclotrimeric 1,4‐Quinones

According to a crystal structure analysis the quinone units of the anthraheptaphene derivative 1b are heavily deformed, due to steric interference. The central ring, however, is plain and shows only slightly alternating bond lengths. So in 2a, which is easier accessible, the central double bonds have retained in part their quinonoid properties: When boiling with piperidine, 2a reacts to 5a, which gives 8a and 9 on reductive acetylation. With sodium hydroxide, 2a forms the pentaphenediquinone 7a and further unidentified products.
Diastereoselective Michael Additions of Chiral Imidazolidines to Trityl Enones
Authors: Seebach Dieter , Pfammatter Elmar , Gramlich Volker , Bremi Tobias , Kühnle Florian , Portmann Stefan , Tironi Ilario
Published: July 2007

The enolatesAandCoft‐butyl (R)‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate (1, Boc‐BMI) and of 1‐t‐butyl 5‐methyl (2R,5S)‐2‐t‐butyl‐3‐methyl‐1,5‐imidazolidinedicarboxylate (3) andt‐butyl (R)‐2‐t‐butyl‐5‐lithio‐3‐methyl‐1‐imidazolidinecarboxylate (B, from2) add in a Michael‐type reaction to trityl enones (E, 4, 5). With one exception (product8) a single diastereoisomer is formed (≫98% ds). — In two cases (6, 10), the crystal structures of the products are determined by X‐ray diffraction. The steric course of the reactions (the relative topicity isunlikewith the enolates) is discussed and compared with that of other conversions of the same reagents. — The trityl groups of two adducts (8and9) are cleaved off by treatment with LiBH4/cat. LiBHEt3to give diaminopentanol derivatives (12and13).
Donorsubstituierte Benzenderivate als Dienophile in der [4 + 2]‐Cycloaddition mit inversem Elektronenbedarf
Authors: Hoferichter Reinhard , Seitz Gunther
Published: July 2007

Donor‐Substituted Benzenes as Dienophiles in the [4 + 2] Cycloaddition with Inverse Electron Demand

[4 + 2] Cycloadditions of various donor‐substituted benzenes (2a, 2b, 12, 15, 21 and 24) with 3,6‐bis(trifluoromethyl)‐1,2,4,5‐tetrazine (1), are described. 1 exhibits the highest diene reactivity so far observed in Diels‐Alder reactions with inverse electron demand. The unusual reactivity is in accord with frontier orbital theory; for instance with 2a, 2b and 24 [4 + 2] cycloaddition takes place with high site selectivity in 3,4‐ and 1,2‐position of the donor‐substituted benzenes, resulting in preferential formation of the 6‐substituted phthalazines 5a, 5b and 28, respectively. Main side products are in each case the (E)‐4.4′‐Ethylenebis[3,6‐bis(trifluoromethyl)pyridazine] (9) and the phthalazine 11. In addition, with 24 as dienophile the azine 32 is formed in 24% yield. Its formation proceeds presumably via the reaction sequence 29→31→30→32.
Chemie und Stereochemie der Iridoide, XVIII. Enantiomerenreines (+)‐Cyclosarkomycin aus Catalpol
Authors: Weinges Klaus , Ziegler Hans Jürgen , Schick Hartmut
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XVIII. — Enantiomerically Pure (+)‐Cyclosarkomycin from Catalpol

The reaction of hexaacetylcatalpol (2) with peroxyformic acid results in hexaacetyl‐3‐formyloxy‐4‐hydroxycatalpol (3), which is cleaved to4and sorbit (4a) by reduction with LiAlH4. The mixture of4/4awas acetylated and the resulting acetates5/5aseparated by column chromatography. The following reactions from5to9(reactions e—i of Scheme 1) are each nearly quantitative. Therefore, the isolation of the intermediates6–8was not necessary. The constitutions of6–8were proven by13C‐NMR spectroscopy. The (1S,2RS,5R)‐2‐hydroxy‐3‐oxabicyclo[3.3.0]octan‐6‐one (9) was purified by column chromatography and its oxidation by pyridinium chlorochromate (PCC) in dichloromethane leads to crystalline (+)‐cyclosarkomycin (10) [yield 85%, based on5].
Hydrazidine, V. Synthese und Reaktionen aromatischer und aliphatischer Hydrazidine und deren N1‐substituierter Derivate
Authors: Neunhoeffer Hans , Karafiat Ute , Köhler Gernot , Sowa Birgit
Published: July 2007

Hydrazidines, V. — Synthesis and Reactions of Aromatic and Aliphatic Hydrazidines and Their N1‐Substituted Derivatives

Aromatic hydrazidines 3 have been synthetized by reaction of aromatic orthocarboxylates 4 with tert‐butyl carbazate (5) and reaction of the protected hydrazidines 7 with HCl/methanol or HBr/acetic acid. Aliphatic N1‐methylhydrazidines 8 have been prepared by methylation of bis (tert‐butoxycarbonyl)‐hydrazidines 7 and deprotection with HBr/acetic acid. Aromatic N1‐methylhydrazidines 8 have been obtained by methylation of N1‐methyl(thiohydrazides) 11, reaction of 12 with tert‐butyl carbazate (5) and deprotection of 13 with HCl/methanol. — Attempts to remove both protecting groups in N1‐alkyl‐N2,N4‐bis
Photooxygenation of α‐Ionone and Oxygen Transfer Reactions of the Resulting Allylic Hydroperoxides
Authors: Adam Waldemar , Griesbeck Axel G. , Wang Xiaoheng
Published: July 2007

The photooxygenation of α‐ionone (4) in different solvents leads, with higher than 90% regioselectivity, to a mixture of two diastereomeric allylic hydroperoxides 5a and 5b (diastereomeric ratio 77:23). These compounds are transformed in the presence of Ti(OiPr)4 into the corresponding epoxy alcohols 8a and 8b (cis selectivity) and the allylic alcohols 7a and 7b with high diastereoselectivity. In these cases the substrate configuration exhibits a pronounced control of type selectivity: the cis allylic hydroperoxide 5a is preferentially reduced to the allylic alcohol 7a, whereas the diastereomeric trans compound 5b is preferentially (syn selectivity) converted to the epoxy alcohol 8b. Epoxidation of the allylic alcohol 7a with meta‐chloroperbenzoic acid leads, in contrast to the Ti(IV)‐catalyzed reaction, to a mixture of diastereomeric epoxy alcohols 8a and 8c, with the anti product 8c as major diastereomer (diastereomeric ratio 28:72). These reactions serve as a route to three of the four possible diastereomeric epoxides of 3‐hydroxy‐γ‐ionone.
Über die radikalische Desoxygenierung sekundärer Alkohole
Authors: Weinges Klaus , Schick Hartmut , Zöllner Peter
Published: July 2007

On the Radical Deoxygenation of Secondary Alcohols

The derivatives 1c–1f were prepared from tetramethyl‐(+)‐catechin (1b). Their radical reduction with tri‐n‐butyltin hydride or tris(trimethylsilyl)silane in the presence of azobis‐(isobutyronitrile) as initiator led to (2R)‐(—)‐3′,4′,5,7‐tetramethoxyflavan (1g). The best yield of 1g (about 75% from 1b) was achieved via the N‐(imidazolyl)thiocarbonyl derivative 1c. Analogously the enantiomeric (2S)‐(+)‐3′,4′,5,7‐tetramethoxyflavan (2g) was obtained from tetramethyl‐(+)‐epicatechin (2b) via 2c. Experimental evidence is given which shows that in aqueous solution, with a catalytic amount of potassium hydrogen carbonate, (+)‐catechin (1a) epimerises at the C‐2 position of the flavan skeleton to give (+)‐epicatechin (2a).
Dithiocarboxylierung von CH‐aciden Sulfoxiden und Thioethern
Authors: Rudorf Wolf‐Dieter , Uhlig Gabriele , Dargatz Manfred
Published: July 2007

Dithiocarboxylation of CH‐Acidic Sulfoxides and Thioethers

Reaction of (arylsulfinyl)acetonitriles or (arylthio)acetonitriles 1 (X = SO, S) with carbon disulfide in the presence of sodium hydride and subsequent alkylation yield the open‐chain or cyclic ketene S,S‐acetals 3 or 4, respectively. Using two equivalents of an α‐CH‐acidic halo compound as alkylating agent, thiophenes 5 are formed. Treatment of 3a with 2‐mercaptoethanol affords the 1,3‐oxathiolane 6. The 1H‐NMR spectra of phenylsulfinyl‐substituted compounds 3b, 4a, 4b, 5a and 6 show a typical AB system for the methylene group caused by the chiral sulfoxide group.
Ring Transformation of 2,4,6‐Tris(aminoalkenyl)‐1,3,5‐triazines to 4‐Aminopyrimidines
Authors: Schulz Hans‐Joachim , Liebscher Jürgen , Maas Gerhard
Published: July 2007

Acid hydrolysis of 2,4,6‐Tris(aminoalkenyl)‐1,3,5‐triazines 1 gives 4‐amino‐5‐aryl‐2‐benzylpyrimidines 3 by ring transformation including elimination of amine, formic acid, and carboxylic acid.
Hochsubstituierte Cyclopentadiene mit Methylthio‐ und Methylsulfonyl‐Gruppen
Authors: Hartke Klaus , Lee Kyung‐Hee
Published: July 2007

Highly Substituted Cyclopentadienes with Methylthio and Methylsulfonyl Groups

Sodium cyclopentadiene (1) reacts with S‐methyl methane‐thiosulfonate (2) to yield the hexakis(methylthio)cyclopentadiene (3), which is transformed into the pentakis(methylthio)‐cyclopentadienides 4 by S‐nucleophiles. Oxidation of 4 gives rise to pentakis(methylsulfonyl)cyclopentadienide, isolated as tetraphenylarsonium salt 7.
Pyridinium N‐Phenoxide Betaines and Their Application to the Characterization of Solvent Polarities, XX. – Synthesis, Solvatochromism, and Halochromism of Chromoionophoric Crown Ether‐substituted Pyridinium N‐Phenolate Betaine Dyes
Authors: Reichardt Christian , Asharin‐Fard Siamak , Schäfer Gerhard
Published: July 2007

Synthesis, negative solvatochromism (Table 1, Figure 1), and negative halochromism (Tables 2–3, Figures 2–3) of the new crown ether‐substituted pyridinium N‐phenolate betaine dyes 3–6 are described. In contrast to other known chromoionophores, 3–5 exhibit a cation‐selective negative halochromism, which manifests itself as a hypsochromic shift of the longwavelength intramolecular charge‐transfer (CT) absorption band of the betaine chromophore on addition of salts. As this CT absorption band lies within the visible spectral region, the cation‐induced colour change can be followed easily by eye, which suggests an application of these new chromoionophoric betaine dyes as cation indicators. The halochromism of 3–6 constitutes a new type of true halochromism, in contrast to the trivial halochromism first defined by Baeyer and Villiger in 1902.
Alkylaluminium Dichloride Induced Friedel‐Crafts Acylation of Unsaturated Carboxylic Acids and Alcohols
Authors: Metzger Jürgen O. , Biermann Ursula
Published: July 2007

The ethylaluminium dichloride induced Friedel‐Crafts acylation of unsaturated carboxylic acids, for example 10‐undecenoic acid (1a) and oleic acid (5a), and of the respective alcohols 1b and 5b with acyl chlorides and cyclic acyl anhydrides gave the corresponding long‐chain β,γ‐unsaturated ketones 3, 6/7, 11 and 13/14 with ω‐carboxy and ω‐hydroxy functions, respectively. The intramolecular cyclization of petroselinic acid chloride (17) yielded (E)‐2‐dodecylidenecyclohexanone (18). Catalytic hydrogenation gave the respective saturated ketones 4, 8/9, 12, 15/16 and 19.
Anomeric O‐alkylation, 11. Anomeric O‐Alkylation of O‐Unprotected Hexoses and Pentoses – Convenient Synthesis of Decyl, Benzyl, and Allyl Glycosides
Authors: Klotz Wolfgang , Schmidt Richard R.
Published: July 2007

The base‐promoted reaction of O‐unprotected aldoses 1–6 with didecyl sulfate in DMPU affords decyl glycosides 1aα–6aα and 1aβ, 3aβ–6aβ in good overall yields. Similarly, the treatment of O‐unprotected hexoses 1–4 and pentoses 5 and 6 with benzyl bromide and allyl bromide yields after subsequent O‐acetylation monosaccharides 1cα–6cα, 1cβ, 3cβ–6cβ and 1dα–6dα, 1dβ, 3dβ–6dβ, respectively. The regio‐ and stereoselectivity in these reactions was determined by 1H‐NMR spectroscopic data of the O‐acetylated derivatives.
Synthesis of Tetramethyl 2,6‐Dihydroxybicyclo[3.3.1]nona‐2,6‐diene‐1,3,5,7‐tetracarboxylate (Meerwein Ester). – Use of tert‐Butyl Methyl Ether Instead of Benzene in Azeotropic Distillation
Authors: Quast Helmut , Witzel Martina
Published: July 2007

In the condensation of dimethyl malonate with formaldehyde, leading eventually to the title compound 5, water is formed which is removed by azeotropic distillation with benzene in the original procedure. It is shown that benzene may be replaced by tert‐butyl methyl ether without any loss in the yield.
Sequential Analysis of Oligosaccharide Structures by Selective NMR Techniques. – 1D Multistep‐relayed COSY‐ROESY
Authors: Schröder Harald , Haslinger Ernst
Published: July 2007

Sequential analysis of oligosaccharide structures by 1D multistep‐relayed COSY‐ROESY experiments is described. Selective excitation is performed by Gaussian‐shaped soft pulses. The application to saponins and flavonoids is demonstrated.
Secondary Metabolites by Chemical Screening, 25. New Cyclic Polysulfides from Hyperthermophilic Archaea of the Genus Thermococcus
Authors: Ritzau Michael , Keller Martin , Wessels Peter , Stetter Karl O. , Zeeck Axel
Published: July 2007

From the intact cells of the sulfur‐metabolizing hyperthermophilic archea Thermococcus tadjuricus (strain Ob9) and Thermococcus acidaminovorans (strain Vc6bk) 23 predominantly new cyclic polysulfides could be isolated by using chemical screening methods. The structures of nine preparatively separated compounds were determined by spectroscopic methods, whereas those of 14 compounds were established by GC‐MS only. Most of the polysulfides are derivatives of 1,2,4‐trithiolane, 1,2,4,5‐tetrathiane and 1,2,3,5,6‐pentathiepane. They differ from each other by aliphatic or aromatic side chains, derived from predominantly metabolized proteinogenic amino acids. The building mechanism and the relevance of the polysulfides are discussed.
Combretastatin Analogs via Hydration of Stilbene Derivatives
Authors: Mannila Erkki , Talvitie Antti
Published: July 2007

Hydration of the double bond of some stilbene congeners of Picea abies bark by TiCl4·NaBH4 reagent is described. Five racemic 1,2‐diphenylethanol derivatives (9–13), structurally related to (R)‐(·)‐combretastatin [(R)‐1], have been obtained and characterized mainly by 13C‐ and 1H‐NMR as well as mass spectrometry. The antileukemic activity of each compound has preliminarily been tested by the mouse leukemia L1210 system. Compound 10 has been synthesized by Friedel‐Crafts acylation.