bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese linearer und verzweigter perfluoralkylierter Carbonsäuren durch radikalische Addition von Perfluoralkyliodiden an ungesättigte Fettsäuren
Authors: Metzger Jürgen O. , Linker Ursula
Published: July 2007

Synthesis of Linear and Branched Perfluoroalkylated Carboxylic Acids by Radical Addition of Perfluoroalkyl Iodides to Unsaturated Fatty Acids

Linear and branched perfluoroalkylated carboxylic acids, i.e. 6a, 11a, 12a, 15a and 16a, are easily available by tin(II) chloride/silver(I) acetate‐initiated free radical additions of perfluoroalkyl iodides to unsaturated carboxylic acids 1a–3a followed by tributylstannan reduction of the respective addition products. The unsaturated perfluoroalkylated carboxylic acids 7a can be obtained by regioselective base‐catalyzed elimination of HI from the addition products.
Glycosyl Imidates, 52. Synthesis of Globotriaosylceramide (Gb3) and Isoglobotriaosylceramide (isoGb3)
Authors: Qiu Dongxu , Schmidt Richard R.
Published: July 2007

The synthesis of globotriaosylceramide (1) was based on O‐galactosyl trichloroacetimidate 5α as donor and 4b‐O‐unprotected lactose 7 as acceptor; 7 was readily accessible from lactose. Glycosylation by an “inverted procedure” afforded preferentially the α‐trisaccharide 8α. Its transformation into the O‐acetyl‐protected trichloroacetimidate 11α led to an efficient triaosyl donor for the β‐selective glycosylation of 3‐O‐benzoyl‐azidosphingosine 12. The obtained lysoglycosphingolipid derivative 13 was directly converted into the N‐palmitoyl derivative 14 which gave upon O‐deacylation the target molecule 1. For the synthesis of isoglobotriaosylceramide (2) essentially the same procedure was applied. Thus, by starting from 5α and 3b, 4b‐O‐unprotected lactose acceptor 15 the use of the inverted procedure for glycoside‐bond formation gave preferentially trisaccharide 16α, which was transformed into triaosyl donor 24α. Application of the azidosphingosine glycosylation procedure afforded lysosphingolipid 25 and subsequently glycosphingolipid 26; after deprotection the target molecule 2 was obtained.
Novel Concepts in Directed Biaryl Synthesis, IX. Synthesis and Structure of Benzonaphthopyranones, Useful Bridged Model Precursors for Stereoselective Biaryl Syntheses
Authors: Bringmann Gerhard , Hartung Thomas , Göbel Lothar , Schupp Olaf , Ewers Christian L. J. , Schöner Bernd , Zagst Rainer , Peters Karl , von Schnering Hans Georg , Burschka Christian
Published: July 2007

A practicable two‐step procedure for the preparation of a series of lactone‐type bridged biaryls 7 as favorable substrates for subsequent atropisomer‐selective ring‐opening reactions is described. Due to the efficiency of the coupling step, which tolerates even a tert‐butyl group next to the biaryl axis and avoids problems of regioselectivity, a variety of differently substituted representatives is prepared. These cover a broad range of steric hindrance and thus molecular distortion. The structures are investigated mainly by NMR spectroscopy and X‐ray diffraction, showing the lactones 7 to be helically distorted, depending on the size of the residues R.
Synthesis of Amines and Amino Alcohols by Electrophilic Amination and Highly Stereoselective Reduction
Authors: Gmeiner Peter , Bollinger Bernd
Published: July 2007

A practical and selective method for the synthesis of the β‐arylamines 5 and the cis‐ or trans‐amino alcohols 8 or 11 is reported. The reaction sequence starts from α‐tetralones 1 which readily react with dibenzyl azodicarboxylate to afford the protected α‐hydrazino ketones 2. Then, depending on the reduction conditions, the trans‐hydrazino alcohols 10 or the cis isomers 7 are formed predominantly. The stereoselectivities which range between 18:1 and 1:67 (trans/cis) are explained by stereoelectronic effects (σ,σ interactions) and steric hindrance. Depending on the workup procedure, we can control, whether the cis‐hydrazino alcohols 7 or the oxazolidinone derivatives 3 are isolated. Subsequent hydrogenolyses of 4, 7 and 10 lead to the target molecules 5, 8 and 11, respectively.
Unusual Rearrangement in the Dehydration of Aroylated Butanodihydrazides
Authors: Tashtoush Hasan , Al‐Talib Mahmoud , Odeh Nedal
Published: July 2007

Dehydration of N,N′‐diaroylbutanodihydrazides 3a–f with phosphoryl chloride gave, unexpectedly, 2,5‐diaryl‐1,3,4‐oxadiazoles 4a–f. However, dehydration of N,N′‐dialkanoylbutanodihydrazides 1a–c afforded 5,5′‐dialkyl‐2,2′‐(1,2‐ethandiyl)‐bis(1,3,4‐oxadiazoles) 2a–c.
A Bisnitroxyl Dipeptide
Authors: Dulog Lothar , Wang Wei
Published: July 2007

The dinitroxylamide 8 is synthesized from the monomer 4‐amino‐4‐carboxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (2). The benzyloxycarbonyl group as amino protective group and the methoxy group as carboxyl protective group have been introduced. The acylation of compound 3 with compound 4 is carried out in the presence of dicyclohexylcarbodiimide. After deprotection the dinitroxylamide 8 is obtained.
Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate
Authors: Mihailović Mihailo Lj. , Vukićević Rastko , Konstantinović Stanimir , Milosavljević Slobodan , Schroth Gerhard
Published: July 2007

Reactions of some primary and secondary Δ4‐, Δ5‐ and Δ6‐alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated. When terminally unsubstituted Δ4‐alkenols, such as 4‐penten‐1‐ol (5a) and 5‐hexen‐2‐ol (5b), are treated with TTA in benzene, β‐acetoxylated tetrahydrofurans 8a and 8b are obtained. However, when the reaction is carried in acetic acid the products are both regioisomers, i.e. five‐ and six‐membered cyclic ethers (8a, 8b, 7a and 7b). 4‐Methyl‐4‐penten‐1‐ol (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7c is predominant, and in acetic acid it is the sole cyclization product. Terminally dialkylated alkenols, such as 5‐methyl‐4‐hexen‐1‐ol (1b) and 6‐methyl‐5‐hepten‐2‐ol (1c), are converted into β‐acetoxylated (4b and 4c) and unsaturated cyclic ethers (9a and 9b), in both cases of the tetrahydrofuran type. 5‐Hexen‐1‐ol (10) and 6‐hepten‐1‐ol (11) cyclize to the corresponding six‐ (13) and seven‐membered cyclic ether (14), respectively. Organothallium intermediates have been isolated and identified in the cases of alcohols 5a, 5c and 10, proving that the TTA addition to the double bond has originally obeyed the Markovnikov rule.
Zur Synthese von (Z)‐ und (E)‐3‐(1H‐Imidazol‐4‐yl)‐2‐propenamin und einigen 3‐(1H‐Imidazol‐4‐yl)propanaminen
Authors: Sellier Christian , Buschauer Armin , Elz Sigurd , Schunack Walter
Published: July 2007

Synthesis of (Z)‐ and (E)‐3‐(1H‐imidazol‐4‐yl)‐2‐propenamine and Some 3‐(1H‐imidazol‐4‐yl)propanamines

3‐(1H‐Imidazol‐4‐yl)propanamine (6, homohistamine), an essential intermediate for the synthesis of potent impromidine‐type histamine H2 receptor agonists, is efficiently prepared from trans‐urocanic acid (1) by reduction of the methyl ester 2 and conversion to the saturated amide 4. Dehydration with thionyl chloride yields the nitrile 5 which is subsequently reduced to 6. Side‐chain methylated 3‐(1H‐imidazol‐4‐yl)propanamines 12 are available from 1H‐imidazole‐4‐carbaldehyde (7) and 1‐(1H‐imidazol‐4‐yl)ethanone (8), respectively, via unsaturated nitriles 10 and stepwise reduction. Cyclization of the appropriate 4‐bromo‐5‐oxohexanenitriles 14α with formamidine in liquid ammonia and reduction of the obtained nitriles 15 furnishes ring‐methylated amines 16. (E)‐3‐(1H‐Imidazol‐4‐yl)‐2‐propenamine [(E)‐23] is obtained in six steps from the trans‐ester 2 while (Z)‐23 is accessible by treating 7 with triphenyl(2‐phthalimidoethyl)phosphonium bromide (17) and final deprotection. These primary amines are valuable intermediates for the synthesis of impromidine analogues.
Spiroketal Synthesis. — A Case of Intramolecular Glycoside Bond Formation
Authors: Preuss Rainer , Jung Karl‐Heinz , Schmidt Richard R.
Published: July 2007

From 4‐O‐unsubstituted glucose derivatives 1a, b the 4‐hydroxymethyl‐substituted glucose derivatives 9a, b were obtained via oxidation to the ketone, Wittig reaction with methylenetriphenylphosphorane, borane addition, and subsequent oxidation to yield the diastereomeric galactose‐derived compounds 5a, b; the required inversion of configuration at C‐4 was accomplished through oxidation to the formyl derivatives, base‐catalyzed isomerisation, and then reduction. Transformation of hydroxymethyl derivatives 9a, b into the iodo derivatives 11a, b and reaction with n‐butyllithium generated the C‐lithiated species 11aA, bA which furnished with O‐benzyl‐protected gluconolactone 12 the ketose derivatives 13a, b. Treatment with Et2O–BF3 afforded under concomitant 6‐O‐debenzylation the spiroketals 15a, b. Hydrogenolytic O‐debenzylation and subsequent O‐acetylation led to compounds 16a and 16b, respectively. The anomeric ketoside configuration was derived from NOE experiments.
Studien zur Chemie von O,N‐ und S,N‐haltigen Heterocyclen, 13. Untersuchungen zur Ringverengung von 1,5‐Benzothiazepinen zu 1,4‐Benzothiazinen
Authors: Erker Thomas , Bartsch Herbert
Published: July 2007

Studies on the Chemistry of O,N‐ and S,N‐Containing Heterocycles, 13. — Investigations on the Ring Contraction of 1,5‐Benzothiazepines to 1,4‐Benzothiazines

Reaction of the (3R)‐1,5‐benzothiazepinon derivative 5 with NaNO2 in glacial acetic acid leads to the rac‐1,4‐benzothiazinone derivatives 6a and 7. Furthermore, reaction of 5 with NaNO2 in sulphuric acid/KBr yields the ring‐contracted compound rac‐6b. Compound 8, after heating with thionyl chloride, affords the E/Z isomeres 9 and 10.
Syntheses and Reactions of 2,2‐Disubstituted Cyclopentane‐1,3‐diones, 6. Conversion of 2‐Methylcyclopentane‐1,3‐dione into 5‐Methylcycloheptane‐1,4‐dione via 3‐(1‐Methyl‐2,5‐dioxocyclopentyl)propanal
Authors: Schick Hans , Roatsch Birgit , Schwarz Hartmut , Hauser André , Schwarz Sigfrid
Published: July 2007

In contrast to earlier reported unsuccessful experiments the Michael addition of prop‐2‐enal to 2‐methylcyclopentane‐1,3‐dione (1) affords 3‐(1‐methyl‐2,5‐dioxocyclopentyl)propanal (3) in 90% yield, if the reaction is carried out in water without a basic catalyst. This aldehyde is converted by an intramolecular aldol reaction to (±)‐endo‐2‐ and (±)‐exo‐2‐hydroxy‐5‐methylbicyclo[3.2.1]octane‐6,8‐dione (rac‐4 and rac‐6), both affording (±)‐5‐methylcycloheptane‐1,4‐dione (rac‐8) after oxidation to (±)‐5‐methylbicyclo[3.2.1]octane‐2,6,8‐trione (rac‐2), hydrolytic ring‐opening and decarboxylation. This reaction sequence allows the transformation of the 2‐alkylated cyclopentane‐1,3‐dione 1 into the 5‐alkylated cycloheptane‐1,4‐dione rac‐8 in a good overall yield. The pathway of the ringopening process has been determined by an investigation of the reaction intermediates.
Lewis Acid‐Catalysed Anomerisation and Rearrangement of Alkyl D‐Glycopyranosides During Acetalisation with Methyl Pyruvate: How to Utilise it for the Preparation of 1‐(Carboxyethylidene)glycopyranosyl Donors
Authors: Ziegler Thomas , Eckhardt Elisabeth , Herold Gerhard
Published: July 2007

The preparation of 4,6‐O‐(1‐methoxycarbonylethylidene)‐D‐glycopyranosides 5 starting from 2,3‐di‐O‐benzoyl‐D‐glycopyranosides 1 and their 4,6‐bis‐O‐trimethylsilyl ethers 2 using methyl 2,2‐bis(phenylthio)propionate (4) and methyl pyruvate (3), respectively, under Lewis acid catalysis conditions is described. In the D‐gluco series anomerisation of alkyl β‐D‐glucopyranosides is observed as a side reaction, giving complex mixtures and low yields of the title compounds whereas alkyl‐α‐D‐glucopyranosides and alkyl or phenyl 1‐thio‐β‐D‐glucopyranosides react without anomerisation. The reactions are accompanied by isomerisation of the initially formed diastereomer (R)‐5 having an equatorial methoxycarbonyl group to the thermodynamically favoured diastereomer (S)‐5 having the methoxycarbonyl group in an axial position. In the D‐galacto series similar side reactions are observed accompanied by rearrangement to furanosides 9 of alkyl and phenyl β‐D‐galactopyranosides. The results are used for efficient syntheses of two protected disaccharides 8 and 11 representing structural fragments of the polysaccharide repeating units of Mycobacteria and Rhizobia via pyruvate acetal‐containing glucosyl and galactosyl donors 7 and 10.
Enzymatic Synthesis of ß‐L‐Fucose‐1‐phosphate and GDP‐fucose
Authors: Stiller Regine , Thiem Joachim
Published: July 2007

Fucose is an important component of complex heterooligosaccharides. Here we describe the preparative enzymatic synthesis of ß‐L‐fucose‐1‐phosphate as well as its enzymatic conversion into GDP‐fucose. Fucose (1) was converted into ß‐L‐fucose‐1‐phosphate (2) with fucose kinase (EC 2.7.1.52) obtained from porcine submaxillary glands by consumption of ATP. Syntheses carried out with the enzymes enclosed in a dialysis bag gave 19% yield of ß‐L‐fucose‐1‐phosphate. Application of the enzymes in a batch procedure using an ultrafiltration cell gave 40% yield of the fucose‐1‐phosphate. The yield could be increased to 80% if the inhibitor ADP was removed by cofactor regeneration with phosphoenolpyruvate. ß‐L‐Fucose‐1‐phosphate was isolated as various salts and analyzed by NMR spectroscopy. In a second enzymatic reaction ß‐L‐fucose‐1‐phosphate was converted into GDP‐fucose (3) by the action of GDP‐fucose pyrophosphorylase (EC 2.7.7.30) obtained from porcine submaxillary glands. In a 50‐μmolar scale reaction, yields around 20% were obtained.
Concave Reagents, 11. Concave Benzoates, Sterically Extremely Shielded Esters
Authors: Lüning Ulrich , Wangnick Carsten
Published: July 2007

The synthesis and the properties of concave methyl benzoates 4 are described. The difficulties encountered in their saponification and 1H‐NMR data show that these esters 4 are severely shielded. Saponification is possible via nucleophilic substitution at the methyl groups by lithium iodide in pyridines. The products are the new concave benzoic acids 5d and 5e.
Preparative Bioorganic Chemistry, XVI. Synthesis of 3,4′‐Dihydroxypropiophenone 3‐ß‐D‐Glucopyranoside, a Constituent of Betula platyphylla var. japonica, by Enzymatic Transglucosylation
Authors: Mori Kenji , Qian Zhao‐Hui , Watanabe Sadamoto
Published: July 2007

3,4′‐Dihydroxypropiophenone 3‐ß‐D‐glucopyranoside (1a) has been synthesized, without having recourse to any protective group technology, by transglucosylation catalyzed by lactase from Kluyveromyces lactis.
Asymmetric Synthesis via Heterocyclic Intermediates, XLVIII. Asymmetric Synthesis of Diastereomerically and Enantiomerically Pure, 3‐Substituted (2S,3R)‐N‐Methylserine Esters
Authors: Beulshausen Tessa , Groth Ulrich , Schöllkopf Ulrich
Published: July 2007

A novel method for the synthesis of N‐methylserines has been developed. The oxazolidines 4 are formed by condensation of the serine methyl esters 1 with formaldehyde. These intermediates are subsequently reduced to the N‐methylserine methyl esters 9 by an acid‐catalyzed ring opening via their iminium ions 2 with triethylsilane/trifluoroacetic acid.
Synthesis of Some Deoxymannosyl Phosphates
Authors: Niggemann Jutta , Thiem Joachim
Published: July 2007

3‐Deoxy‐α‐D‐arabino‐hexopyranosyl‐, 4‐deoxy‐α‐D‐lyxo‐hexopyranosyl‐ and 6‐deoxy‐α‐D‐mannopyranosyl phosphates 6, 12 and 21 were synthesized by phosphorylation of the deoxygenated glycosyl chlorides 3, 9 and 18 with silver dibenzyl phosphate and subsequent deprotection of the obtained α‐dibenzyl phosphates 4, 10 and 19.
Total Synthesis of (+)‐Myomontanone and (+)‐10,11‐Didehydromyomontanone
Authors: Roussis Vassilios , Hubert Terrance D.
Published: July 2007

The sesquiterpenoid (+)‐myomontanone (2), a toxic component of the Australian plant Myoporum montanum, has been synthesized through a short efficient sequence. An electrochemical oxyselenation‐deselenation sequence allows oxidation of an intermediate olefin, in the presence of the furan ring, ultimatively providing the requisite enone of the natural product. This approach also allowed synthesis of (+)‐10,11‐didehydromyomontanone (13) and several other natural products of this family of furanosesquiterpenoids.
Präparative Enantiomerentrennung einer Chroman‐2‐carbonsäure durch Chromatographie von Glucose‐Derivaten
Authors: Netscher Thomas , Gautschi Iwan
Published: July 2007

Preparative Separation of the Enantiomers of a Chroman‐2‐carboxylic Acid via Chromatography of Glucose Derivatives

Starting from the commercially available racemic carboxylic acid 2a, b (S)‐Trolox methyl ether (1a), useful as a chiral reagent for capillary gas chromatography and supercritical fluid chromatography, was obtained in enantiomerically pure form (e.e. >99.9%) by the separation of esters derived from diacetone D‐glucose and subsequent saponification.
Some Reductive Transformations in the Furazano[3,4‐d]pyridazine System. — Formation of 1,2‐Dipyridazinyldiazene Derivatives
Authors: Lange Jerzy , Karolak‐Wojciechowska Janina , Tondys Hanna
Published: July 2007

Hydrogenation of 4,7‐diarylfurazano[3,4‐d]pyridazine 1‐oxides 1 on palladized carbon or platinum oxide yielded 4,5‐diamino‐3,6‐diarylpyridazines 2 and trans‐1,2‐bis(5‐amino‐3,6‐diaryl‐pyridazin‐4‐yl)diazene 1‐oxides 3, readily converted by stannous chloride into trans‐1,2‐bis(5‐amino‐3,6‐diarylpyridazin‐4‐yl)diazenes 6. Reduction of 1 with sodium tetrahydroborate gave 4,7‐diarylfurazano[3,4‐d]pyridazines 5 and 4,7‐diaryl‐4,5‐dihydrofurazano[3,4‐d]pyridazine 1‐oxides 4. The crystal structures of 3a and 4a were solved by X‐ray analysis.
Biosynthese von Naturstoffen mit einer PC‐Bindung, IX. Synthese und Einbau von (S)‐ und (R)‐2‐Hydroxy‐[2‐2H1]ethylphosphonsäure in Fosfomycin durch Streptomyces fradiae
Authors: Hammerschmidt Friedrich
Published: July 2007

Biosynthesis of Natural Products with a P—C Bond, IX.— Synthesis and Incorporation of (S)‐ and (R)‐2‐Hydroxy‐[2‐2H1]ethylphosphonic Acid into Fosfomycin by Streptomyces fradiae

(S)‐ and (R)‐2‐(benzyloxy)‐[1‐2H1]ethanol (8) were transformed into (S)‐ and (R)‐2‐hydroxy‐[2‐2H1]ethylphosphonic acid (13). These were fed to cultures of Streptomyces fradiae. The fosfomycin produced was isolated as aminopropylphosphonic acid and contained 32% Deuterium, when (S)‐13 was added to the growth medium, and no deuterium, when the antipode (R)‐13 was added as substrate. The dehydrogenase‐accepting 2‐ hydroxyethylphosphonic acid is stereospecifically removing its pro‐R hydrogen from C‐2.
Amination of 3,5‐Dinitropyridines with Liquid Ammonia/Potassium Permanganate
Authors: Woźniak Marian , Bańskira Andrzej , Szpakiewicz Barbara
Published: July 2007

3,5‐Dinitropyridine and some of its derivatives are aminated with a liquid ammonia solution of potassium permanganate to the corresponding 2‐, 4‐ and 6‐ mono‐ and (or) di‐ and (or) triamino‐substituted compounds. The intermediate amino σ‐adducts of 3,5‐dinitropyridines are detected by 1H‐NMR spectroscopy. Quantum‐mechanical calculations for a few 3,5‐dinitropyridines suggest that the experimentally observed regioselectivity of the amination is a charge‐controlled process.
Zur Regioselektivität SH‐haltiger Nucleophile gegenüber Androsta‐1,4‐dien‐3,17‐dion, einem Vorläufer für biologisch aktive Steroide
Authors: Müller Anreas , Weiß Dieter , Beckert Rainer
Published: July 2007

On the Regioselectivity of SH‐Containing Nucleophiles towards Androsta‐1,4‐diene‐3,17‐dione, a Precursor for Biologically Active Steroids

Thioketals have been prepared from androsta‐1,4‐diene‐3,17‐dione (1) and SH‐containing compounds in the presence of different catalysts. The thioketals 4 are obtained by using the aromatic thiols 3d, 3e, and 3g, whereas the aliphatic thiols 3a and 3c yield a mixture of regioisomeric products 4–6. A higher selectivity with regard to the 17‐oxo group was observed by using the thiol 3b leading to 5b. With the araliphatic thiol 3f compound 5f is selectively formed. In contrast to the described thioketal formation, the thiol 3d yields in addition to 4d a double Michael addition product 7, which was predominantly obtained by using other catalysts and/or a higher reaction temperature.
Structure Elucidation of the Gallium–Ornibactin Complex by 2D‐NMR Spectroscopy
Authors: Stephan Holger , Freund Stefan , Meyer Jean‐Marie , Winkelmann Günther , Jung Günther
Published: July 2007

From a Pseudomonas strain novel hydroxamate/carboxylate siderophores were isolated which were named ornibactins representing the modified tetrapeptide L‐Orn1(Nδ‐OH,Nδ‐acyl)‐D‐threo‐Asp(β‐OH)‐L‐Ser‐L‐Orn4(Nδ‐OH,N δ‐formyl)‐1,4‐diaminobutane. The side‐chain amino function of Orn1(Nδ‐OH,Nδ‐acyl) is acylated by 3‐hydroxyoctanoic acid in the most lipophilic component of the microheterogeneous siderophore mixture. The structure elucidation was based on GC amino acid analysis, GC‐MS and electrospray mass spectrometry of the iron complex. The 3‐hydroxyoctanoic acid and the primary sequence were established on the basis of 1H and inverse detected 13C two‐dimensional NMR spectra (COSY, TOCSY, NOESY, HMQC, HMBC) of the gallium‐ornibactin‐F complex which allowed the complete assignment of all 1H and 13C signals.
Biologically Active Glycosides from Asteroidea, XXX. – Synthesis of an Optically Active Ceramide of GM1‐Type Ganglioside from (+)‐diethyl L‐Tartrate
Authors: Metz Katrin , Honda Masanori , Komori Tetsuya
Published: July 2007

A short total synthesis of the ceramide (2S,3R,4E)‐2‐(octadecanoylamino)‐4‐octadecene‐1,3‐diol (1) is reported, using (+)‐diethyl L‐tartrate (2) as the optically active starting material.
Studies on Heterocyclic Enaminonitriles, XIII. Reactions of Ethyl N‐2‐(3‐Cyano‐4,5‐dihydro‐2‐furyl)carbamates with Sodium Iodide
Authors: Maruoka Hiroshi , Yamagata Kenji , Yamazaki Motoyoshi
Published: July 2007

The reaction of ethyl N‐2‐(3‐cyano‐4,5‐dihydro‐2‐furyl)carbamate (1), 1‐cyano‐N‐(ethoxycarbonyl)cyclopropanecarboxamide (2), and ethyl 3‐cyano‐2‐oxo‐1‐pyrrolidinecarboxylate (3) with sodium iodide gave 3‐ethyl‐2‐oxo‐3‐pyrrolidinecarbonitrile (5). Similarly, the reaction of ethyl N‐2‐[3‐cyano‐4,5‐dihydro‐4‐(or ‐5‐)phenyl‐2‐furyl]carbamate (7 or 8) and trans‐1‐cyano‐N‐(ethoxycarbonyl)‐2‐phenylcyclopropane‐carboxamide (9) afforded 3‐ethyl‐2‐oxo‐5‐phenyl‐3‐pyrrolidinecarbonitrile (10).
Pheromone Synthesis, CLII. Synthesis of Blattellastanosides A and B, Chlorinated Steroid Glucosides Isolated as the Aggregation Pheromone of the German Cockroach, Blattella germanica L.
Authors: Mori Kenji , Fukamatsu Kunio , Kido Masaru
Published: July 2007

β‐Sitosterol (3) was converted to blattellastanosides A (1, 6α‐chloro‐4β,5‐epoxy‐5β‐stigmastan‐3β‐yl β‐D‐glucopyranoside) and B (2, 6α‐chloro‐5‐hydroxy‐5β‐stigmastan‐3β‐yl β‐D‐glucopyranoside), the arrestant components of the aggregation pheromone of the German cockroach, Blattella germanica L.
Synthese von 1,3,5‐Triamino‐2,4,6‐triphenylbenzol und dessen Reaktion mit Pikrylhalogeniden
Authors: Zierer Dirk , Dulog Lothar
Published: July 2007

Synthesis of 1,3,5‐Triamino‐2,4,6‐triphenylbenzene and Its Reaction with Picryl Halides

′,4′,6′‐Trinitro‐5′‐phenyl‐1,1′:3′,1″‐terphenyl (5) was synthesized by Ullmann reaction of 1,3,5‐trichloro‐2,4,6‐trinitrobenzene (3) with iodobenzene and copper powder in the presence of N,N‐dimethylformamide. Reduction of 5 with tin/tin(II) chloride in a mixture of hydrochloric and acetic acid yields 2′,4′,6′‐triamino‐5′‐phenyl‐1,1′:3′,1″‐terphenyl (6). By reaction of this symmetric benzenetriamine with picryl chloride and fluoride in different media, but utmost two of the three amino groups were converted into picrylamide groups to 7 and 8.
Antibiotics from Gliding Bacteria, LII. Thiangazole, a New Tris(thiazoline) Derivative From Polyangium spec.: Absolute Configuration
Authors: Jansen Rolf , Schomburg Dietmar , Höfle Gerhard
Published: July 2007

The absolute configuration of thiangazole (1), which was previously derived by chemical degradation, was confirmed by X‐ray structure analysis. Energy minimization with MO and MM2 methods indicate, that the conformation of 1 in the crystal is controlled by crystal forces while various equally preferred conformations may be present in solution.
Bausteine von Oligosacchariden, CVII – Synthese von modifizierten Oligosacchariden der N‐Glycoproteine zur Untersuchung der Substratspezifität der N‐Acetylglucosaminyltransferase II
Authors: Paulsen Hans , Meinjohanns Ernst , Reck Folkert , Brockhausen Inka
Published: July 2007

Building Units of Oligosaccharides, CVII. – Synthesis of Modified Oligosaccharides of N‐Glycoproteins for Substrate Specificity Studies of N‐Acetylglucosaminyltransferase II

Several modified derivatives of the tetrasaccharide β‐D‐GlcNAc‐(1→2)‐α‐D‐Man‐(1→3)‐[α‐D‐Man‐(1→6)]‐β‐D‐Man‐octyl (1) were synthesized for substrate specifity studies of N‐acetylglucosaminyltransferase II (GlcNAcT II). The hydroxyl groups at C‐3, C‐4 or C‐6 of the α(1→6)‐linked Man residue and the hydroxyl groups at C‐3 and C‐6 of the α(1→3)‐linked Man were replaced by deoxy groups. All five tetrasaccharides were synthesized by a block synthesis by using deoxy saccharide residues. The trichloroacetimidate method was particulary successful for synthesizing the glycosidic linkages. The modified compounds have been tested as substrates for N‐acetylglucosaminyltransferase II (GlcNAcT II) from rat liver. The substrate specificity of GlcNAcT II will be discussed.
Bausteine von Oligosacchariden, CVIII. Synthese von modifizierten Oligosacchariden der N‐Glycoproteine zur Untersuchung der Substratspezifitäten der N‐Acetylglucosaminyltransferasen III bis VI
Authors: Paulsen Hans , Meinjohanns Ernst , Reck Folkert , Brockhausen Inka
Published: July 2007

Building Units of Oligosaccharides, CVIII. – Synthesis of Modified Oligosaccharides of N‐Glycoproteins for Substrate Specificity Studies of N‐Acetylglucosaminyltransferase III to VI

The pentasaccharide β‐D‐GlcNAc‐(1→2)‐α‐D‐Man‐(1→3)‐[β‐D‐GlcNAc‐(1→2)‐α‐D‐Man‐(1→6)]‐β‐D‐Man‐octyl (3) and a series of modified derivatives of this compound were synthesized. The 4‐OH group of the β‐Man residue, the 3‐OH or 4‐OH group of the α‐(1→3)‐linked Man residue or the 6‐OH group of the α(1→6)‐linked Man residue were replaced by deoxy groups. The modified pentasaccharides were synthesized by a block synthesis using functionalized deoxy saccharide residues. Glycosylation reactions were achieved by the trichloroacetimidate method. These pentasaccharides are useful for substrate specificity studies of N‐acetylglucosaminyltransferases III to VI (GlcNAcT III to VI). The substrate specificity of GlcNAcT V will be discussed since this activity has been found to be increased in malignancies.
Synthese und Struktur Phenyl‐substituierter Bicyclo[3.3.1]nonene
Authors: Quast Helmut , Knoll Katja , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg
Published: July 2007

Synthesis and Structure of Phenyl‐Substituted Bicyclo[3.3.1]nonenes

Addition of one mole of phenyllithium to bicyclo[3.3.1]nonane‐2,6‐dione (5) affords the hydroxy ketone6besides small amounts of the known diol7. Dehydration of this mixture by sulfuric acid in acetic acid yields the unsaturated ketone8and the diene1which are separated by chromatography. Wolff‐Kishner reduction of8furnished the hydrocarbon2. In the same way, the known ketonesexo‐ andendo‐10are converted into4. The preferential formation of the less stableendo‐10is interpreted in terms of the relative stability of the conformations required in the intramolecular aldol reaction of diketone9. The conformations of4, 8,exo‐ andendo‐10are determined by X‐ray diffraction analyses. Vicinal proton coupling constants are calculated from torsional angles and compared to those determined in solutions by high‐field NMR spectroscopy.
Herstellung von α‐verzweigten Phenylalaninen und von 1,1‐disubstituierten Ethylendiaminen über chirale Imidazolidinone und Oxazolidinone aus Glycin – präparative und mechanistische Aspekte
Authors: Seebach Dieter , Gees Thomas , Schuler Franz
Published: July 2007

Preparation of α‐Branched Phenylalanines and of 1,1‐Disubstituted Ethylenediamines via Chiral Imidazolidinones and Oxazolidinones of Glycine – Preparative and Mechanistic Aspects

To test the structural prerequisites for a new carbanionoid rearrangement of 3‐methyl‐2‐pivaloyl‐1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid to N‐(t‐butoxycarbonyl)‐1‐amino‐2‐methylindan‐2‐carboxylic acid (A → B), various α‐branched phenylalanines (C) were required. Geminal dialkylation of the chiral glycine building block Boc‐BMI (1) occurs in excellent yields and selectivities and can be carried out in a one‐pot procedure (products 2–10). However, phenylalanines with methoxy groups on the benzene ring and α‐branching by substituents larger than methyl cannot be set free by hydrolysis of the corresponding imidazolidinones, which, on the other hand can be reduced through N‐methyl amino acid amides (13–15) to geminally disubstituted N‐methyl‐ethylenediamines (16–18). A series of 2‐t‐butyl‐5‐oxo‐1,3‐oxazolidin‐3‐carboxylates (19–27) was prepared and could be resolved on ChiraSphere, Chiralcel OD, and Pirkle columns (Table 1). Alkylation (Me, Et, Bu), allylation, and benzylation of the rac‐oxazolidinones lead to trans‐disubstituted products (29–43) which were alkylated a second time (products 44–51); yields and selectivities are satisfactory (Table 2). Hydrolysis of 4,4‐dibenzyl‐substituted oxazolidinones to the amino acid derivatives is possible (examples 52–54). – Comparison of the methylation selectivities of seven 2‐t‐butyl‐1,3‐oxazolidin‐5‐one Li‐enolates bearing different N‐acyl groups (Figure 1) and an X‐ray crystal structure analysis of a phenol carbamate (26, Figure 2 and Table 3) show that our previous mechanistic model obtains: t‐butyl in the COR group gives the poorest selectivity (3:1), O‐phenyl the highest (>50:1). This is compatible with the view that the acylgroups (on pyramidalized nitrogens!) in these heterocyclic acetals occupy one face of the average plane of the rings, and the substituents on the acetal center (here t‐Bu) the other one (Figure 1).
Michael Addition of Malononitrile to α‐Acetylcinnamamides
Authors: Martín Nazario , Martínez‐Grau Angeles , Seoane Carlos , Marco José L. , Albert Armando , Cano Félix H.
Published: July 2007

The reaction of α‐acetylcinnamamides 7a–e with malononitrile using piperidine as the catalyst is described. When one or two equivalents of malononitrile are used, the 2‐amino‐4H‐pyran 6a or the polyfunctionalized carbocycles 9b–e, respectively, can be isolated as major products, depending on the experimental conditions. Compounds 9b–e apparently arise from a sequential Michael plus Knoevenagel addition of two molecules of malononitrile followed by Thorpe cyclization. The structure of 9b was determined by an X‐ray crystallographic analysis, which revealed a twisted cyclohexadiene ring with a characteristic crystal packing.
Carotenoids and Degraded Carotenoids, VIII – Synthesis of (+)‐Dihydroactinidiolide, (+)‐ and (−)‐Actinidiolide, (+)‐ and (−)‐Loliolide as well as (+)‐ and (−)‐Epiloliolide
Authors: Mori Kenji , Khlebnikov Vladimir
Published: July 2007

Enantiomerically pure (S)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐ol (1) was efficiently converted into four degraded lactonic carotenoids: (S)‐dihydroactinidiolide (5), (S)‐actinidiolide (9), (6S,7aR)‐loliolide (11) and (6S,7aS)‐epiloliolide (12). (R)‐Actinidiolide (9), (6R,7aS)‐loliolide (11) and (6R,7aR)‐epiloliolide (12) were also prepared from (R)‐1.
1‐[1,7‐dicarba‐closo‐dodecaboran(12)‐1‐yl]aldoses: Novel Boron Neutron Capture Candidates
Authors: Dahlhoff Wilhelm V. , Bruckmann Joachim , Angermund Klaus , Krüger Carl
Published: July 2007

Monolithiated 1,7‐dicarba‐closo‐dodecaborane(12) reacts withO‐isopropylidene derivatives ofD‐erythrono‐1,4‐lactone (1),L‐mannono‐1,4‐lactone (3) and with tetra‐O‐trimethylsilylatedD‐glucono‐1,5‐lactone (2) andD‐gulono‐1,4‐lactone (4) to give the title compounds after deprotection. An X‐ray structure analysis of the protectedL‐mannofuranose carborane derivative9reveals that the more stable anomer has the β‐Lconfiguration.
Synthese halogenierter Benzyl‐ und Benzoylpyrrole
Authors: Renneberg Bernd , Kellner Michael , Laatsch Hartmut
Published: July 2007

Synthesis of Halogenated Benzyl‐ and Benzoylpyrroles

Several halogenated aroyl‐1H‐pyrroles of type 2, 14 and 19 are synthesized by reaction of aroylchlorides with pyrrolylmagnesium bromide, bromination or iodination of the pyrrole ring and demethylation with boron tribromide. Furthermore, the synthesis of the naphthylpyrrole 19b was performed by analogy with the synthesis of 1. Their antibiotic and cytotoxic activity is compared with 1, an antibacterial, enzyme‐inhibitory and cytotoxic compound, isolated from the marine bacterium Alteromonas luteoviolaceus.
Steroids, LII. Configurational Analysis of 16‐Methyl‐19‐nortestosterone Derivatives
Authors: Meskó Eszter , Dombi György , Lukács Ferenc , Schneider Gyula
Published: July 2007

The four possible stereoisomers of 3‐methoxy‐16‐methyloestra‐1,3,5(10)‐trien‐17‐ol (1, 2, 3, 4) were converted into the corresponding 16‐methyl‐19‐nortestosterone analogs (5, 6, 7, 8), which were characterized by their 1H‐ and 13C‐NMR spectra. The coupling constants J16,17 and the characteristic 13C signals (C‐12, C‐17, C‐18, 16‐CH3) clearly confirmed the configurations at C‐16 and C‐17.
Synthesen von α‐Aminophosphonsäuren aus N‐Ethoxyiminium‐Salzen, II
Authors: Shatzmiller Shimon , Neidlein Richard , Weik Christian
Published: July 2007

Syntheses of α‐Aminophosphonic Acids from N‐Ethoxyiminium Salts, II

Nitrones 2 obtained from aldehydes 1 are used for the synthesis of N‐ethoxyiminium salts 3. These react with several esters of hydrogen phosphite 4 to give the N‐methyl α‐amino phosphonic esters 5 to 13. The N‐benzyl α‐amino phosphonic esters 24 and 25 can be obtained by the same procedure. Hydrogenolysis and ester hydrolysis afford the α‐amino phosphonic acids 14 as well as 26 and 27, respectively.
Multidimensional NMR Techniques for the Elucidation of Oligosaccharide Structures: Verbascosaponin and a Further Saponin from Wool Flower
Authors: Schröder Harald , Haslinger Ernst
Published: July 2007

The application of 1D selective, 2D and 3D NMR techniques to the structure elucidation of verbascosaponin (1) is demonstrated. Combinations of ROESY and TOCSY are powerful tools. Each of these multidimensional ROESY‐TOCSY and TOCSY‐ROESY experiments provides detailed information about the sequence of oligosaccharide structures and the positions of glycosidation. The structure of a further saponin 2 from the officinal drug Flores Verbasci is determined as 3β‐O‐{α‐L‐rhamnopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→2)‐]‐β‐D‐fucopyranosyl}‐13β,28‐epoxyolea‐11‐ene‐16α,23α‐diol.
Ein Porphyrinogen mit 1,8‐Diphenylanthracen‐Brücke
Authors: Marx Thomas , Breitmaier Eberhard
Published: July 2007

A Porphyrinogen with 1,8‐Diphenylanthracene Bridge

The title compound 3 was prepared in good yield by cyclization of 1,8‐Bis(4‐formylphenyl)anthracene (2) with the 2,2′ – Dipyrrylmethane 1.
Photochemical Reactions of Caffeine with Aliphatic Aldehydes
Authors: Erndt Aleksander , Fiedorowicz Maciej , Kostuch Andrzej , Para Andrzej
Published: July 2007

Photochemical reactions of caffeine with several aliphatic aldehydes are performed. In the reactions with ethanal, propanal and butanal stable 8‐acyl‐8,9‐dihydrocaffeines 2 and 3 together with unreduced 8‐acylcaffeines 4 and 8‐(α‐hydroxyalkyl)caffeines 6 are produced. Under similar conditions, the reactions of 2‐methylpropanal, 2‐methylbutanal and 2,2‐dimethylbutanal resulted in the formation of the corresponding 8‐alkylcaffeines 7.
Vier neue Pregnanglycoside aus Gongronema latifolium (Asclepiadaceae)
Authors: Schneider Christiane , Rotscheidt Klaus , Breitmaier Eberhard
Published: July 2007

Four New Pregnane Glycosides from Gongronema latifolium (Asclepiadaceae)

Four so far unknown pregnane biosides have been isolated from the chloroform extract of the leaves of Gongronema latifolium Benth. et Hook. (Asclepiadaceae). From one‐ and twodimensional NMR experiments (NOE difference spectroscopy, ROESY, H,H‐COSY, C,H‐COSY, HMBC) their structures have been established as 3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1a), 3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐oleandropyranosyl]‐17β‐marsdenin (1b), 12‐O‐acetyl‐3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1c) and 11‐O‐acetyl‐3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1d).
Novel Porphyrinoids, 13. – Synthesis and Electrophilic Substitution of New Partially β‐Unsubstituted [18]Porphyrins
Authors: Franck Burchard , Krautstrunk Gerhard
Published: July 2007

Three porphyrins2, 3, and4, related to Hans Fischer's octaethylporphyrin1, but with unsubstituted pyrrole β‐positions were synthesized via the biladiene pathway. The ring‐closing reaction to form the porphyrin reveals a conformational control, calledhelical effect. These new porphyrins made possible an investigation of the regioselectivity of electrophilic aromatic substitutions at the porphyrin perimeter.
Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
Authors: Franck Burchard , Timmermann Ralf , Sirges Wolfram
Published: July 2007

Six N,N′‐alkylene‐bridged bispyrroles 9a–9e and one N,N′‐oxaalkylene‐bridged bispyrrole 16 with a reactive group at C‐1 of each pyrrole unit were synthesized in 53–78% yields. Acid‐catalyzed “biomimetic” condensations of the bispyrroles with N,N′‐C3 to N,N′‐C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′‐alkylene chain of 9e to reduce the Prelog strain, the condensation yield was significantly increased. The N,N′‐C1‐and the N,N′‐C2‐bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′‐C1‐bridged dipyrrylmethane 12 instead.
Dithio‐ und Thionester, 59. Zur Reaktion von aliphatischen Dithiosäure‐dianionen mit Schwefelkohlenstoff
Authors: Hartke Klaus , Rettberg Norbert , Dutta Dinah , Gerber Hans‐Dieter
Published: July 2007

Dithio and Thiono Esters, 59. – Reactions of Aliphatic Dithio Acid Dianions with Carbon Disulfide

Dianions 2 of dithioacids 1 and carbon disulfide yield in a kinetically controlled reaction at – 78°C S‐adducts (e.g. 3, 13) or in a thermodynamically controlled reaction at room temperatur C‐adducts [the tetrahthiomalonic acid trianions 10 or the 2,2‐dimethyltetrathiomalonic acid dianion 15]. Acidification of 10 and subsequent reactions give rise to the tetrathiomalonic acids 18 and its derivatives 19 with 2,6,9,10‐tetrathiaadamantane structure. Deprotonation of 10a leads to the tetrathiomalonic acid tetraanion (20) which may be alkylated to yield the tetrakis(alkylthio)allenes 21. By condensation of the dithioacid dianions 2, the tetrathiomalonic acid trianions 10 and the tetrathiomalonic acid tetraanion (20) with 2,3‐dichloro‐1,4‐naphthoquinone (32) a number of naphtho[2,3‐d]‐1,3‐dithiole‐4,9‐diones [e.g. 33, 35, 37] are obtained.
Enzymes in Organic Synthesis, 15. – Synthesis of Methyl (S)‐(−)‐2,3‐O‐Isopropylideneglycerate by Enantioselective Enzyme‐catalyzed Hydrolysis of Methyl (±)‐2,3‐O‐Isopropylideneglycerate
Authors: Schick Hans , Schrötter Eberhard , Szymanowski Matthias , Knoll Alexander
Published: July 2007

In contrast to porcine pancreatic lipase (PPL), the serine proteases aP 41 and thermitase are suited as catalysts for the enantioselective ester hydrolysis of methyl (π)‐2,3‐O‐isopropyl‐ideneglycerate (rac‐1). These enzymes allow the preparation of methyl (S)‐(−)‐2,3‐O‐isopropylideneglycerate (1) with an enantiomeric excess of 84–87% in a yield of 19–27% related to the starting racemate.
Reductive Transformations of 6H‐1,2‐Oxazines with Hydride Reagents: Formation of Aziridines and 3‐Hydroxyalkylated 1,2‐oxazines
Authors: Zimmer Reinhold , Homann Kai , Reißig Hans‐Ulrich
Published: July 2007

6H‐1,2‐Oxazines 1 and 3 are converted into aziridines 2 and 4, respectively, by reduction with LiAlH4. Reduction of 1,2‐oxazine 5 lacking the 6‐alkoxy substituent leads to phenyl ketone 6, 6‐Alkoxy‐substituted 1,2‐oxazine‐3‐carboxylates 7, 9, and 11 are reduced with NaBH4 to give the corresponding 3‐hydroxymethylated compounds 8, 10, and 12 in good yields.
Total Synthesis of Thymosin β4 by Fragment Condensation
Authors: Kapurniotu Afroditi , Link Peter , Voelter W.
Published: July 2007

The total synthesis of thymosin β4 by means of classical methods using three protected fragments is described. For their syntheses the Z/tBu strategy and temporary phenyl ester protection of the C‐terminal carboxyl were used. Various coupling procedures were applied in order to optimize the yields of the synthesis. The BOP/HOBt method proved to be very efficient for the coupling of larger fragments. The fragment condensation for the synthesis of protected thymosin β4 was performed by two different strategies. The deprotected thymosin β4 was purified by prep. HPLC on a RP‐18 column. Applying the first synthetic strategy the 43‐peptide was obtained in 12% overall yield for the final steps of the synthesis, including two fragment condensations, two hydrogenations, deprotection, and purification. The second synthetic strategy afforded thymosin β4 in 4% overall yield (based on the final synthetic steps: two fragment condensations, two hydrogenations, deprotection, and purification). The purified products of both synthetic pathways were shown to be identical with the natural thymosin β4, isolated from calf thymus tissue, according to HPLC, capillary zone electrophoresis, SDS‐PAGE, ion‐spray mass spectrometry, and amino acid analysis.
1,3‐Dipolar Cycloaddition of Benzonitrile Oxide to Substituted 4,5‐Dihydro‐3‐methylene‐2(3H)‐furanones
Authors: Štverková Slávka , Žák Zdirad , Jonas Jaroslav
Published: July 2007

Benzonitrile oxide cycloadds to the CC bond of substituted 4,5‐dihydro‐3‐methylene‐2(3H)‐furanones 1a–1g. Thus, (E)‐1a and (E)‐1b are converted into the corresponding isoxazolinespirodihydrofuranones (4RS,5RS)‐2a and (4RS,5RS)‐2b, and (E)‐1c is converted into a mixture of isomers (4RS,5RS)‐2c and (4RS,5RS)‐3c. The reactions of (E)‐1d–1g yield mixtures of the corresponding diastereomeric isoxazolinespirodihydrofuranones (4RS,5RS,8RS)‐2d and (4RS,5RS,8SR)‐2d, (4RS,5RS)‐3e and (4RS,5SR)‐3e, (4RS,5RS)‐3f and (4RS,5SR)‐3f, (4RS,5RS)‐3g and (4RS,5SR)‐3g. The addition of benzonitrile oxide to (Z)‐1a gives (4RS,5SR)‐2a and 4a. In the cycloaddition with (E)‐1a the p‐tolylsulfonyloxy group in the intermediate (4RS,5RS)‐2a is partially replaced by chlorine to give (4RS,5RS)‐2h. – The structures of (4RS,5RS)‐2h, (4RS,5RS)‐3e, (4RS,5SR)‐3e, and 4a are determined by X‐ray analysis. The 1H‐ and 13C‐NMR spectra of the products are discussed and the reaction course is rationalized on the basis of HOMO‐LUMO energy gaps.
Glycosyl Imidates, 63. – Synthesis of the Sulfated Steroidal Glycosides Forbeside E3 and E1
Authors: Jiang Zi‐Hua , Han Xiao‐Bing , Schmidt Richard R.
Published: July 2007

Reaction of 6α‐hydroxy‐substituted steroids 7 and 8 with the 2‐O‐benzyl‐protected quinovosyl donors 4a, b afforded α,β‐mixtures of the glycosides 9a, b; with O‐acetyl‐protected donor 4c, due to neighboring group participation, exclusively β‐glycoside 9cβ was obtained. Similarly, reaction of donor 4c with 3β‐O‐silyl‐protected 6α‐hydroxy‐steroid 12 furnished β‐connected 6O‐quinovosyl derivative 14 in high yield. 3‐O‐Desilylation of 14 with TBAF and ensuing 3‐O‐sulfation with pyridine/sulfur trioxide complex yielded pyridinium sulfate derivative 17, which turned out to be rather unstable. Treatment of 17 with sodium methoxide in methanol gave in high yield forbeside E 3 (1) the physical data of which were in good agreement with literature reports. Diastereoselective reduction of the keto group in 18 with NaBH4 led preferentially to 19 which was deacetylated to afford forbeside E 1 (2).
Basenhydrierte Phosphonsäure‐Derivate von Pyrimidinnucleosiden, Nebenprodukte bei der Desoxygenierung von 2′‐O‐Phenoxythiocarbonyl‐Vorstufen
Authors: Morr Michael , Ernst Ludger
Published: July 2007

Base‐Hydrogenated Phosphonic Acid Derivatives of Pyrimidine Nucleosides, Side Products in the Deoxygenation of 2′‐O‐Phenoxythiocarbonyl Precursors

Persilylation of N4‐anisoyl‐1‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphorylmethyl‐2‐O‐phenoxythiocarbonyl‐β‐D‐ribofuranosyl)cytosine (1) with iodotrimethylsilane followed by a Barton‐McCombie reaction with Bu3SnH/azobis(isobutyronitrile) and hydrolysis with Et3NH+ buffer furnishes, in a side reaction, the N4‐anisoyl‐O5′‐benzoyl‐3′‐deoxy‐3′‐phosphonomethyl‐3,4,5,6‐tetrahydro‐cytosine lactones 4a and 4b, which are epimers at C‐4 and can be separated by chromatography. Two‐step hydrolysis of 4a and/or 4b yields an epimeric mixture of 1‐(3‐deoxy‐3‐phosphonomethyl‐β‐D‐ribofuranosyl)‐3,4,5,6‐tetrahydro‐uracil (6a/6b). A possible mechanism of the formation of 4a/4b from 1 via persilylated 2,2′‐anhydro‐N4‐anisoyl‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphoryl‐β‐D‐arabinofuranosyl)cytosine (9) as well as the reactivity of 9 and the behaviour of methyl 5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphoryl‐2‐O‐phenoxythiocarbonyl‐β‐D‐erythro‐pentofuranoside (17) under the same reaction conditions are discussed. The structures of all new compounds are confirmed by their 1H‐, 13C‐, 31P‐NMR and FAB mass spectra.
Synthesis and Reductive Elimination Reactions of Aryl Thioglycosides
Authors: Fürstner Alois
Published: July 2007

Treatment of the sugar hemiacetals 1, 5, 7, 10, 12 and 14 with ArSSAr (Ar = phenyl, 2‐pyridyl, 2‐benzothiazolyl) and trialkylphosphanes affords in an SN2 process the corresponding aryl thioglycosides 3, 6, 8, 9, 11, 13, 15 and 16 in good to excellent yields. The reaction can be performed in a variety of solvents of greatly different polarity and avoids the use of free thiols and Lewis acid catalysts. The promoting phosphane has to carry at least two alkyl groups, with R3P (R = short, unbranched alkyl group) being best suited in terms of yield and reaction rate. In contrast, triphenylphosphane and phosphites are inactive. The reaction is compatible with a variety of functional groups and distinguishes between the anomeric center and other free hydroxyl groups in the substrates. Thus, thioglycosides from partially protected or unprotected sugars can be readily obtained. Treatment of phenyl thioglycosides 13a and 3a with potassium‐graphite laminate (C8K) in THF affords the corresponding pyranoid or furanoid glycals 17 and 18 by reductive elimination.
Conversion of Fatty Acids and Derivatives, IV. Conversion of Fatty Acid Methyl Esters into Dialkylated Succinic Esters by Oxidative Coupling of their Enolates
Authors: Quermann Rolf , Maletz Reinhard , Schäfer Hans J.
Published: July 2007

The enolates of fatty acid methyl esters 1a–g are dimerized in good yields (56 to 73%) by means of oxidative coupling with copper(II) bromide to dialkylated succinic esters 2a–g. The configuration of meso‐2a was established by independent synthesis. On treatment with ozone the unsaturated dimer 2c is converted to the tetracarboxyl compound 6. Epoxidation of 2g leads to the corresponding bisepoxy diester 7.
Antibiotika aus Gleitenden Bakterien, LV – Myxochromid A: Ein hochungesättigtes Lipopeptidlacton aus Myxococcus virescens
Authors: Trowitzsch‐Kienast Wolfram , Gerth Klaus , Wray Victor , Reichenbach Hans , Höfle Gerhard
Published: July 2007

Antibiotics From Gliding Bacteria, LV. – Myxochromide A: A Highly Unsaturated Lipopetide from Myxococcus virescens

The isolation and structure elucidation of a new family of pigments, the myxochromides, are described. Myxochromide A was determined as a hexapeptide lactone out of: L‐Methyl‐Thr, D‐ or L‐Ala, L‐Leu, L‐Pro, D‐ or L‐Ala and L‐Glu, respectively. Its lactone formation was observed between the γ‐carboxyl of Glu and the OH group of the Me‐Thr residue. The chromophore, a heptaenoic acid, was found to bind as an amide to the N‐atom of the Thr moiety. Myxococcus flavescens produces the same pigments with myxochromide B as the main compounds.