bluuebunny/crossref_metadata_2025 huggingface dataset:
Aromatic and Azaaromatic Diselenides, Benzisoselenazolones and Related Compounds as Immunomodulators Active in Humans: Synthesis and Properties
Authors: Młochowski Jacek , Kloc Krystian , Syper Ludwik , Inglot Anna D. , Piasecki Egbert
Published: July 2007

Convenient syntheses of aryl diselenides 2, 1,2‐benzisoselenazol‐3(2H)‐ones 4 and their 1‐oxides 7 are reported. Reductive conversions of these compounds to bis(2‐carbamoyl)‐phenyl diselenides 5 and oxidative cyclization of 5 to 1,2‐benzisoselenazol‐3(2H)‐one 1‐oxides 7 as the methods for the synthesis of these compounds are reported. Their ability to induce cytokines, such as TNF and IFN‐γ, in human peripheral blood leucocyte cultures is described.
Epoxidierung von Kohlenstoff‐Kohlenstoff‐Doppelbindungen in Terpenen durch Linolsäurehydroperoxide
Authors: Meyer Werner , Spiteller Gerhard
Published: July 2007

Epoxidation of Carbon‐Carbon Double Bonds in Terpenes by Linoleic Acid Hydroperoxides

Epoxidation of CC double bonds in terpenes is achieved by reaction with linoleic acid hydroperoxides (LOOH) exemplified with caryophyllene (3), methyl farnesoate (5) and squalene (8). Linoleic acid (9S)‐hydroperoxide was obtained by reaction of linoleic acid (1) with lipoxygenase present in tomato homogenisate. When 18O2‐labeled (9S)‐LOOH (2) was used 18O was found in the terpene epoxide. While 3 is converted under physiological conditions regioselectively in high yiled into its 4,5‐epoxide 4, the yield of epoxidized products from long‐chain molecules, e.g. squalene (8), decreases strongly and no regioselectivity was observed.
Regioselektive Reaktionen an der 17‐Oxogruppe von Androsta‐1,4‐dien‐3,17‐dion nach in‐situ‐Schutz mit Titantetrakis(dimethylamid)
Authors: Müller Andreas , Beckert Rainer , Schönecker Bruno , Weiß Dieter
Published: July 2007

Regioselective Reactions at the 17‐Oxo Group of Androsta‐1,4‐dine‐3,17‐dione after in situ Protection with Titaniumtetrakis(dimethylamide)

After in situ protection of androsta‐1,4‐diene‐3,17‐dione (1) with titaniumtetrakis(dimethylamide) (10) at −20°C to −30°C, the lithium enolates of methyl methoxyacetate (2a) and ethyl acetate (2b) react regio‐ and stereoselectively at the 17‐position to give the 17‐hydroxy‐17α‐pregnanes 12 and 6. Dehydration of 12 and 6 furnishes the 17(20)‐olefins 13 and 14, intermediates for the synthesis of corticoids and gestagens. The reaction of 1 with 10 and 2a at −60°C gives byproducts of a dienone‐benzene rearrangement of the A‐ring. The reactions of 1 with 2a and 2b without titaniumtetrakis‐(dimethylamide) (10) proceed regioselectively at the 3‐position or nonregioselectively at the 3‐ and 17‐positions, respectively.
Aminosäuren, 16. Darstellung von N‐Acyl‐2,3‐didehydro‐2‐aminocarbonsäureestern
Authors: Effenberger Franz , Kühlwein Jürgen , Drauz Karlheinz
Published: July 2007

Amino Acids, 16. – Synthesis of N‐Acyl‐2,3‐didehydro‐2‐amino Acid Esters[2]

N‐Acyl‐2,3‐didehydro‐2‐amino acid esters 3, 5, 7–12, with a great variety of N‐substituents, are obtained in good yields by the perrhenate‐catalyzed decomposition of methyl 2‐azido carboxylates 1 in organic solvents in the presence of the corresponding acyl chlorides 2. By using methyl 2‐azidoisovalerate (1a), the conditions (catalyst, solvent, temperature) for the reaction to give 3a were optimized. The reactivity of acyl chlorides can be strongly enhanced with equimolar amounts of dimethyl formamide, which allows a lowering of the decomposition temperature for this reaction. Under these mild reaction conditions also the unstable N‐acyldehydroalanine derivative 5f can be obtained in good yield.
Etheranaloge der Thio‐ und Dithiophospholipide mit CSP‐Bindung
Authors: Markowska Anna , Młotkowska Barbara , Olejnik Jadwiga , Sażała Małgorzata
Published: July 2007

Ether Analogues of Thio‐ and Dithiophospholipids with C–S–P Bond

The efficient synthesis of 1‐O‐hexadecyl‐2‐O‐methyl‐3‐thioglycero‐3‐phosphocholine (5a) and 1‐S‐hexadecyl‐2‐O‐methyl‐1,3‐dithioglycero‐3‐phosphocholine (5b) based on phosphorylation of 1‐O‐hexadecyl‐2‐O‐methyl‐3‐thioglycerol (3a) and 1‐S‐hexadecyl‐2‐O‐methyl‐1,3‐dithioglycerol (3b) with 2‐chloro‐2‐oxo‐1,3,2‐dioxaphospholane (6) followed by ring opening of the resulting intermediates 4a and 4b is described.
The Synthesis of the Principal Dihydroisocoumarins of Ononis natrix
Authors: Rama Nasim H. , Saeed Aamer , Bird Clive W.
Published: July 2007

(±)‐6,8‐Dihydroxy‐3‐undecyl‐3,4‐dihydroisocoumarin (7) and its 6‐O‐methyl and 6,8‐di‐O‐methyl derivatives 6 and 5, isolated as the (−)‐enantiomers from the plant Ononis natrix by other authors, were synthesized starting with (3,5‐dimethoxyphenyl)acetic acid via (±)‐1‐(3,5‐dimethoxyphenyl)tridecan‐2‐yl acetate (2) and its corresponding 2‐formyl and 2‐carboxy derivatives 3 and 4, respectively.
Synthesis of Enantiomerically Pure Tetrahydro‐2‐methylharman
Authors: Shiqi Peng , Min Guo , Winterfeldt Ekkehard
Published: July 2007

L‐Tryptophan methyl ester reacts with acetaldehyde in a Pictet‐Spengler condensation to give a 2.5:1 mixture of the stereoisomers (1S,3S)‐2 and (1R,3S)‐2. These were converted by ammonolysis into the corresponding amides (1S,3S)‐3 or (1R,3S)‐3. On methylation of (1S,3S)‐3 or (1R,3S)‐3 the corresponding 2‐methylcarbolineamide (1S,3S)‐4 or (1R,3S)‐4 were obtained. Dehydration of (1S,3S)‐4 or (1R,3S)‐4 affords 2‐methylcarbolinenitrile (1S,3S)‐5 or (1R,3S)‐5. After reduction with NaBH4 (1S,3S)‐5 or (1R,3S)‐5 was decyanated and the title compound (1S)‐6 or (1R)‐6 was obtained. With NOE experiments their stereochemistry were determined and their optical purities were confirmed by measurements using a chiral shift reagent.
Eine einfache, selektive Synthese von (Z)‐tert‐Butylketen‐O,N‐acetalen durch Phenol/Azol‐Austauschreaktion
Authors: Reuther Wolfgang , Ruland Alfred , Gangkofner Stefan , Baus Ulf
Published: July 2007

A Facile and Selective Synthesis of (Z)‐tert‐Butylketene O,N‐Acetals

Melting the ketene O,O‐acetals 1 with azoles in the presence of a catalytic amount of a proton acid yields the ketene O,N‐acetals 2. The products of this phenol‐azol substitution reaction are obtained as their (E/Z)‐mixtures with the (Z)‐isomers highly predominating. The (E)‐isomers are easily converted into the (Z)‐isomers by a proton acid catalysed isomerisation reaction.
Klassische Synthese eines selektiven Peptid‐Substrates für die Messung der Proteinkinase C
Authors: Spencker Torsten , Goppelt‐Struebe Margarete , Keese Wolfgang , Resch Klaus , Rimpler Manfred
Published: July 2007

Conventional Synthesis of a Selective Peptide Substrate for Measurements of Protein Kinase C

Protein kinase C (PKC), a family of serin/threonin kinases, plays a key role in signal transduction. We have prepared the PKC‐selective peptide substrate H‐Phe‐Lys‐Lys‐Ser‐Phe‐Lys‐Leu‐NH2 (7) by classical solution synthesis. 7 allows PKC‐measurements in crude extracts or permeabilized cells. The protection of the N‐terminal amino acid and the side chains by Boc resp. tert‐butyl groups enables a one‐step liberation of the desired heptapeptide amide 7.
Secondary Metabolites by Chemical Screening, 22. Gabosines, New Carba‐sugars From Streptomyces
Authors: Bach Gabriela , Breiding‐Mack Sabine , Grabley Susanne , Hammann Peter , Hütter Klaus , Thiericke Ralf , Uhr Hermann , Wink Joachim , Zeeck Axel
Published: July 2007

Chemical screening of different Streptomycetes strains resulted in the detection, isolation, and structure elucidation of a number of novel carba‐sugars. The constitution of these secondary metabolites, named gabosines A to K (1 to 11), was deduced from spectroscopic data as well as chemical transformation reactions. The gabosines exhibit a basic C7 skeleton and can be characterized as hydroxylated branched cyclohexanone derivatives, which show structural similarities to carbohydrates deriving from secondary metabolism. The configuration fo the gabosines (absolute stereochemistry for 1, 4, 5, and 6; relative configuration for the remaining metabolites) was determined by derivatization with chiral acids (Helmchen's method), NMR spectral analysis, as well as by a comparison of optical rotation values with those of the already known gabosines B (2) and C (3). The new term “ketocarbasugars” is used to characterize a typical ketone containing subgroup of carba‐sugars originating from microbial sources. The well available natural gabosines can be used as suitable chiral building blocks.
Chemistry of the Ginkgolides, V. On the Preparation of the Ginkgolide Skeleton
Authors: Weinges Klaus , Rümmler Matthias , Schick Hartmut , Schilling Gerhard
Published: July 2007

3,14‐Didehydro‐10‐hydroxyginkgolide

On the nomenclature: The skeleton of the ginkgolides A, B, C, M and J with the natural configuration is called “ginkgolide” since the systematic IUPAC nomenclature is too complicated. According to our nomenclature ginkgolide “A” is 3,10‐dihydroxyginkgolide, ginkgolide “B” is 1,3,10‐trihydroxyginkgolide etc. The numbering of the C atoms (formula 1) and the indexing of the H atoms (formula 2) are those proposed by Nakanishi[2].

(1) was prepared by reaction of 3,10‐dihydroxyginkgolide (3) (ginkgolide “A”) by reaction with phosphoryl chloride in pyridine. Catalytic hydrogenation of 1 leads to 10‐hydroxy‐14‐epiginkgolide (2a), which was epimerized with 4‐(dimethylamino)pyridine (DMAP) in acetonitrile to give 10‐hydroxyginkgolide (3a). 14‐Epiginkgolide (2d) and ginkgolide (3d) were obtained from 2a and 3a via the 10‐O‐phenylthiocarbonyl derivatives 2c and 3c by means of a free‐radical reduction with tri‐n‐butyltin hydride/α,α′‐azobis(isobutyronitrile) (AIBN). By heating the 14‐epiginkgolides 2a and 2b and the ginkgolides 3a and 3b in acetonitrile with DMAP an equilibrium on the side of the ginkgolides was established. The constitution and configuration of the compounds were proven by their 1H‐ and 13C‐NMR spectra.
Synthesis of 6‐Deoxy and 3,6‐Dideoxy Derivatives from Unprotected Glycosides Employing the Mitsunobu Reaction
Authors: Dancy Isabelle , Laupichler Lothar , Rollin Patrick , Thiem Joachim
Published: July 2007

Starting with unprotected hexopyranoside derivatives, an efficient synthesis of 6‐deoxy‐ and 3,6‐dideoxyhexopyranosides was achieved in two consecutive steps involving a highly regioselective Mitsunobu reaction and subsequent desulfurization.
Reactions of Phosphites with 1,4‐Benzoquinone Monoimines
Authors: Boulos Leila Sadek , Hennawy Ibtisam Tadros , Arsanious Mona Hazkial Nasr
Published: July 2007

Trimethyl phosphite (2a) reacts with N‐(phenylsulfonyl)‐1,4‐benzoquinone monoimine (1a) to give the respective phosphonate 3c, phosphates 3d, 3e and the alkylated products 3a and 3b. The reaction of triethyl phosphite (2b) with the same quinone imine 1a yields only the phosphate adduct 3f and the amide 3g. Triisopropyl phosphite (2c) reacts with 1a to form the alkylated product 3h. Trimethyl phosphite (2a) gives the phosphate 4a on reaction with N‐(methylsulfonyl)‐ 1,4‐benzoquinone monoimine (1b). In case of the reaction of triethyl and triisopropyl phosphites (2b, c) with 1b only the respective alkylated products 4b–d are obtained. A mechanism is proposed to explain the formation of the new adducts.
Reactions of Organic Anions, 194. Reactions of Carbanions Generated from 2‐(Dialkylamino)‐2‐phenylacetonitriles with Disubstituted Acetylenes
Authors: Zdrojewski Tadeusz , Jończyk Andrzej
Published: July 2007

Reactions of aminonitriles 1a–e with disubstituted acetylenes 2, 3, carried out in DMSO in the presence of powdered sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst, afford either 4 and 5 or a mixture of 4 and 6; unmasking of the carbonyl group in 5a and 6a gives ketones 7 and 8, respectively.
Unsymmetrically Substituted Furoxans, XIV. Synthesis and Structure of a Trimer of the Furoxan System with High Vasodilator and Platelet Antiaggregatory Activity
Authors: Gasco Andrea Marcello , Di Stilo Antonella , Fruttero Roberta , Sorba Giovanni , Gasco Alberto , Sabatino Piera
Published: July 2007

The synthesis and structure of a trimer 5 of the furoxan system are reported. The probable origin of this derivative is the dimerization of the intermediate 4‐phenyl‐3‐furoxancarbonitrile oxide (4) obtained by decomposition of the corresponding nitrolic acid 3. The title compound shows a high level of activity as vasodilator and inhibitor of platelet aggregation.
Diastereoselektive Synthese von Anthracyclinon‐Vorläufern
Authors: Flock Markus , Nieger Martin , Breitmaier Eberhard
Published: July 2007

Diastereoselective Synthesis of Anthracyclinone Precursors

[4 + 2] Cycloaddition of various dienes such as 1‐acetoxy‐1,3‐butadienes 4a, b or 1‐phenylethyloxy‐1,3‐butadienes 4c–g with 1,4‐anthraquinones 3 affords tetracyclic precursors of anthracyclinone. Using the chiral substituted 1,3‐butadienes 4 cycloadducts with d.e. > 98% are obtained. The high stereoselectivity is explained by π stacking.
Hetarylsulfoniumsalze durch Cyclisierung
Authors: Gewald Karl , Rehwald Matthias , Gruner Margit
Published: July 2007

Hetarylsulfonium Salts by Cyclization

Reaction of tetrahydrothiophene with the N‐(iodoacetyl)anthranilic acid derivatives 1a, b and 2‐(iodoacetylamino)acetophenone (1c) yields the 1‐(2‐oxoquinolin‐3‐yl)tetrahydrothiophenium salts 3a–c in two steps. Analogously the heterocondensed 1‐(2‐oxopyridin‐3‐yl)tetrahydrothiophenium salts 6 and 7 can be prepared. The 1‐(3‐oxopyridazin‐4‐yl)‐ and 1‐(2‐oxopyridin‐3‐yl)tetrahydrothiophenium salts 10, 13, 16, 18 are synthesized on the same way. From the tetrahydrothiophenium salt 3a the 3‐(alkylthio)‐4‐aminoquinolin‐2(1H)‐ ones 19 arise.
Total Synthesis of rac‐Silyhermin and Its 2‐Diastereomers of Potential Antihepatotoxic Activity
Authors: Antus Sándor , Baitz‐Gács Eszter , Gottsegen Ágnes , Seligmann Otto , Wagner Hildebert
Published: July 2007

The first synthesis of racemic silyhermin (rac‐1a) and its 2‐diastereomers 1b (as a ca. 1:1 mixture) was accomplished by starting from caffeic acid ethyl ester and coniferyl alcohol.
Synthesis of 2′‐Azido‐2′,3′‐didehydro‐2′,3′‐dideoxythymidine
Authors: Mikhailopulo Igor A. , Zaitseva Galina V. , Vaaks Elena V. , Balzarini Jan , De Clercq Eric , Rosemeyer Helmut , Seela Frank
Published: July 2007

Compound 15 – the 2′‐azido analog of the anti‐HIV compound 2′,3′‐didehydro‐2′,3′‐dideoxythymidine – was synthesized. Treatment of 5′‐O‐trityl‐β‐D‐ribofuranosylthymine (1) with DAST or MSTF gave the 2,2′‐anhydro derivative 2. The latter and its 3′‐O‐benzoate 3 were used for the synthesis of the 2′‐azido‐2′‐deoxy derivatives 4 and 5. Two routes to the synthesis of 15 from 5 were investigated. (i) Treatment of 5 with DAST gave a mixture of the 5′‐O‐trityl derivatives 12 and 13 as well as 1‐(2‐azido‐2,3‐dideoxy‐3‐fluoro‐β‐D‐xylofuranosyl)thymine (16) along with 2,3′‐anhydro derivative 14 (2%). Detritylation of the mixture yielded 15 (39%) and 16 (12%). (ii) Mesylation of 5 gave 17 which yielded 15 upon saponification and detritylation. Compound 15 showed moderate inhibitory activity against HIV‐1 and HIV‐2 in MT‐4 cells.
Bausteine von Oligosacchariden, CVI. Darstellung synthetischer Antigene von LD‐Heptose‐haltigen Trisacchariden der Core‐Region von Lipopolysacchariden durch Copolymerisation mit Acrylamid
Authors: Paulsen Hans , Höffgen Elisabeth C.
Published: July 2007

Building Units of Oligosaccharides, CVI. – Preparation of Synthetic Antigens Composed of LD‐Heptose‐Containing Trisaccharides of the Core Region of Lipopolysaccharides by Copolymerization with Acrylamide

The allyl glycosides of the trisaccharide L‐α‐D‐Hep‐(1→3)‐α‐D‐Hep‐(1→5)‐Kdo in the α form 3 and β form 6 and furthermore of L‐α‐D‐Hep‐(1→7)‐L‐α‐D‐Hep‐(1→3)‐L‐α‐D‐Hep in the α form 20 were synthesized. The allyl glycosides were coupled with a cysteamin spacer in a radical‐addition reaction followed by an acylation with acryloyl chloride. The products could be copolymerized with acrylamide to afford the polymers 21, 22 and 23 with the trisaccharide structure as an immunological determinant.
Secondary Metabolites by Chemical Screening, 24. Oasomycins, New Macrolactones of the Desertomycin Family
Authors: Grabley Susanne , Kretzschmar Gerhard , Mayer Marion , Philipps Siegrid , Thiericke Ralf , Wink Joachim , Zeeck Axel
Published: July 2007

New macrolactones, named oasomycin A to D (1 to 4), were discovered by a chemical screening in the culture broth of Streptoverticillium baldacii subsp. netropse (strain FH‐S 1625). The structures were established by detailed spectroscopic analysis. The fundamental 42‐membered lactone moiety of oasomycin A and B (1 and 2) is analogous to that of desertomycin A (5), while the oasomycins C and D (3 and 4) are the first representatives of macrolactones bearing a 44‐membered skeleton. These metabolites can be distinguished by side chain modifications at C‐41 or C‐43 as well as the presence of an α‐linked D‐mannose moiety attached to 22‐OH. Due to the structural similarities the oasomycins are integrated into the desertomycin family. In vitro testing by using the HEP‐G2 cell assay showed oasomycin A (1) to be an inhibitor of de novo cholesterol biosynthesis.
Chemistry of 1,2,4‐triazines, XV. First metalation of 1,2,4‐triazine derivatives
Authors: Plé Nelly , Turck Alain , Quéguiner Guy , Glassl Bernd , Neunhoeffer Hans
Published: July 2007

5‐Methoxy‐1,2,4‐triazines 2 were lithiated with lithium 2,2,6,6‐tetramethylpiperidide and the formed 6‐lithio‐5‐methoxy‐1,2,4‐triazines 4 trapped with aldehydes or iodine.
Zur Differenzierung der antennenspezifischen enzymatischen Galaktosylierung durch kernmagnetische Resonanzspektroskopie
Authors: Áts Sándor‐Csaba , Hunkler Dieter , Lehmann Jochen
Published: July 2007

Differentiation of the Branch‐Specific Enzymic Galactosylation by Nuclear‐Magnetic Resonance Spectroscopy

A spacer‐modified biantennary trisaccharide glycoside (2) carrying two GlcNAc end groups was galactosylated by UDP‐Gal and β‐(1→4)‐D‐galactosyltransferase to yield compounds 3a, 3b and 4. The non‐separable monogalactosylated compounds 3a and 3b were investigated by NMR spectroscopy (COSY, COLOC, RELAY) to determine a potential branch‐specific transgalactosylation found for native acceptor‐oligosaccharides (1). Since the “3‐branch” is galactosylated at the same rate as the “6‐branch” the presence not only of the center‐mannosyl unit but also of the flanking mannosyl residues replaced by spacers in compound 2 are necessary for site specificity. magnified image
Solvent‐dependent reversible rearrangement of 4‐(hydroxyimino)hexahydro‐pyrimidines to 4‐aminotetrahydropyrimidine 3‐oxides
Authors: Korbonits Dezső , Tóbiás‐Héja Erzsébet , Simon Kálmán , Kolonits Pál
Published: July 2007

1,2‐Disubstituted 4‐hydroxyiminohexahydropyrimidines (8) isomerize in alcohols to yield 1,2‐disubstituted 4‐aminotetra‐hydropyrimidine 3‐oxides (9). In aprotic solvents the opposite transformation (9→8) takes place, presumably by a different mechanism. The structure of the N‐oxide 9a was confirmed by an X‐ray crystallographic analysis. magnified image
Beschleunigung von Substitutionsreaktionen eines Phosphorsäurediesters durch Bis(guanidinium)‐Verbindungen
Authors: Gross Ralf , Dürner Gerd , Göbel Michael W.
Published: July 2007

Acceleration of Substitution Reactions of a Phosphoric Acid Diester by Bis(guanidinium) Compounds

Ion‐pair coordination of phosphoric acid diesters with positively charged guanidines may cause large rate accelerations in substitution reactions. Here we present a comparative study on the catalytical influence of several mono‐ bis‐ and tris(guanidines) and of other cationic compounds. Large rate effects occur if 1,3‐bis(aminomethyl)benzene or 1,2‐ethylenediamine are used as spacers. Further acceleration can be achieved by exchanging guanidinium groups by 2‐aminoimidazolines. The 4800‐fold rate enhancement seen in the best case demonstrates the importance of the bis(guanidinium) moiety of staphylococcal nuclease and gives good perspectives towards future uses of guanidinium compounds as RNA cleaving agents. magnified image
Synthese von Retinoiden mit Aryltetrahydroanthracenstruktur
Authors: Hanefeld Wolfgang , Jung Manfred
Published: July 2007

Synthesis of Retinoids with Aryltetrahydroanthracene Structure

We describe the synthesis of analogues of the retinoid Temarotene (Ro 15‐0778) (1a), which shows due to its lack of a polar end group no signs of hypervitaminosis A. A variety of substituted tetrahydroanthracenes 6, 8, 11, 13 is prepared starting from 2‐methoxynaphthalene (5b) using palladiumcatalyzed coupling techniques. magnified image
Marine Bakterien, VII. Enzymatische Bromierung von Pseudilinen und verwandten Heteroarylphenolen mit der Chlorperoxidase aus Streptomyces aureofacens Tü 24
Authors: Laatsch Hartmut , Pudleiner Heinz , Pelizaeus Birgit , van Pée Karl‐Heinz
Published: July 2007

Marine Bacteria, VII. – Enzymatic Bromination of Pseudilins and Related Heteroarylphenols with a Chloroperoxidase from Streptomyces aureofaciens Tü 24

During the bromination of various substituted synthetic phenyl pyrroles with a chloroperoxidase from Streptomyces aureofaciens Tü 24, mixtures of bromopyrroles are obtained which are not easily accessible by chemical methods. According to the structure of the pyrroles and the kinetics of their transformation, the reaction centre of the enzyme is situated in a slitlike cavity of about 4 × 7 × 8 Ä. magnified image
Constituents of holothuroideae, IV. Isolation and structure of three new cerebrosides, CE‐2b, CE‐2c and CE‐2d, from the sea cucumber Cucumaria echinata
Authors: Higuchi Ryuichi , Inagaki Masanori , Togawa Kenichi , Miyamoto Tomofumi , Komori Tetsuya
Published: July 2007

Three new sphingosine‐type glucocerebrosides, CE‐2b (1), CE‐2c (2) and CE‐2d (3), were isolated by means of highperformance liquid chromatography (HPLC) from a cerebroside molecular species (CE‐2) which was obtained from the less polar fraction of the methanol extract of the sea cucumber Cucumaria echinata. The structures of these cerebrosides were determined on the basis of chemical and spectroscopic evidences. magnified image
Novel concepts in directed biaryl synthesis, XXXIV. Synthesis, optical resolution, and helimerization of dinaphtho[2,1‐b:1′,2′‐d]‐pyran‐4‐one
Authors: Bringmann Gerhard , Schöner Bernd , Schupp Olaf , Peters Karl , Peters Eva‐Maria , von Schnering Hans Georg
Published: July 2007

A rational synthesis of the biaryl lactone 3 is described. This bridged biaryl, which gradually helimerizes at room temperature, could be synthesized in a non‐racemic form, chemically by atropo‐selective ring opening with a chiral O‐nucleophile and subsequent ring closure, and chromatographically by HPLC on a chiral phase. For the enantiomerization process (M)‐3 ⇄ (P)‐3, the activation parameters were determined. magnified image
Reduktone von Tetron‐, Thiotetron‐ und Tetramsäuren, II. Reduktone durch Rhodium‐katalysierte Zersetzung von Diazoverbindungen
Authors: Stachel Hans‐Dietrich , Poschenrieder Hermann , Redlin Jutta , Schachtner Josef , Zeitler Klaus
Published: July 2007

Reductones of Tetronic, Thiotetronic and Tetramic Acids, II. – Reductones by Rhodium‐Catalyzed Decomposition of Diazo Compounds

The diazoketones 2 have been synthesized by diazo transfer reaction with 2‐azido‐3‐ethylbenzthiazolium tetrafluoroborate. The rhodium‐catalyzed decomposition of compounds 2 in tert‐butyl alcohol at 130°C furnishes the reductone monoethers 3 and after deprotection the aci‐reductones 4. Methylation of compounds 4 with diazomethane proceeds stepwise leading first to the monoethers 5 and then to the diethers 6. The thiolactone 4b and even more the lactams 4c and 4d are stronger reducing agents than the lactone 4a. magnified image
Synthesis of doubly labeled enantiomerically pure (R)‐mevalonolactone from lactic and malic acid
Authors: Krohn Karsten , Meyer Annegrete
Published: July 2007

Enantiomerically pure 13C‐ and 1H‐labeled (R)‐mevalonolactones are prepared from (S)‐malic and/or (S)‐lactic acid by Seebachs methodology of self‐reproduction of chirality. The two reaction pathways are complementary in the possibilities of multiple isotopic labeling. The labeling potential is exemplified by the synthesis of a doubly 13C, 1H‐labeled, one 13C‐, and one 1H‐labeled mevalonolactone. magnified image
1,3‐Dithiole mit anelliertem Cyclopentadienring
Authors: Hartke Klaus , Timpe Carsten
Published: July 2007

1,3‐Dithiols with an Annulated Cyclopentadiene Ring

5‐Chloro‐2‐cyclopenten‐1‐ones 4 react with sodium N, N‐di‐alkyldithiocarbamates to form the dithiocarbamic esters 5. These are cyclized by strong acids to yield either in a Michael addition the iminium salts 6 or in a condensation reaction the iminium salts 7. Sulfhydrolysis of 7 gives rise to the 4H‐cyclopenta‐1,3‐dithiol‐2‐thione 8. By cleavage of dithiuram disulfides 10 with sodium cyclopentadienide the [(dial‐kylamino)thiocarbonylthio]cyclopentadienes 12 and 13 are formed. They condense with acetone/pyrrolidine to give either the pentafulyenes 16 or the dihydropentalenes 17. magnified image
Eine einfache Synthese der enantiomeren (E)‐9‐Hydroxy‐2‐decensäuren
Authors: Schweitzer Stefan , Voß Gundula , Gerlach Hans
Published: July 2007

Simple Synthesis of the Enantiomeric (E)‐9‐Hydroxy‐2‐decenoic Acids

The enantiomeric (E)‐9‐Hydroxy‐2‐decenoic acids (1), components of the swarm settling pheromone in Apis mellifica L. (honey bee) have been synthesized. The lithium derivative of 1‐hexyne was treated with (R)‐(+)‐methyloxirane (2), (S)‐(−)‐2 or (±)‐2 to give the alkynols (R)‐(−)‐3, (S)‐(+)‐3 or (±)‐3, which could be isomerized with the sodium salt of 1,3‐propanediamine to give (R)‐(−)‐8‐nonyn‐2‐ol (4) and (±)‐4. These were methoxycarbonylated to produce the esters (R)‐(−)‐5, (S)‐(+)‐5 or (±)‐5. Selective hydrogenation in pyridine with Pd/BaSO4 as catalyst gave the (Z)‐esters (R)‐(−)‐6, (S)‐(+)‐6 or (±)‐6 which could be isomerized with photochemically generated phenylthio radicals to produce the (E)‐esters (R)‐(–)‐7, (S)‐(+)‐7 or (±)‐7. The acids present in the pheromone (R)‐(−)‐1, (S)‐(+)‐1 and (±)‐1 could be obtained by basic hydrolysis of the esters. The minor but important component 8 of the swarm settling pheromone has been synthesized by treating the Grignard reagent obtained from 5‐bromo‐guaiacol benzyl ether with ethylene oxide to give 9 in high yield. Hydrogenolytic removal of the benzyl group in 9 produced 8 directly. magnified image
Enzymes in organic synthesis, 19. The enzyme‐catalyzed sequential esterification of (±)‐anti‐2,4‐dimethylglutaric anhydride. – An efficient route to enantiomerically enriched mono‐ and diesters of anti‐2,4‐dimethylglutaric acid
Authors: Ozegowski Rüdiger , Kunath Annamarie , Schick Hans
Published: July 2007

(±)‐anti‐2,4‐Dimethylpentanedioic anhydride (rac‐1) was converted in good yields and with high enantiomeric excess by an enzyme‐catalyzed sequential esterification into the (2R,4R)‐monoester 2 and the (2S,4S)‐diester ent‐3. Best results were obtained with Novozym 435, a lipase from Candida antarctica. magnified image
Electroorganic synthesis, 56. Synthesis of advanced prostaglandin precursors by Kolbe electrolysis, I. – Preparation of (1′R,4′S,3RS)‐3‐(cis‐4‐acetoxycyclopent‐2‐enyloxy)‐3‐ethoxypropionic acid
Authors: Weiguny Jens , Schäfer Hans J.
Published: July 2007

The key intermediate of a novel synthesis of prostaglandin precursors, (1′R,4′S,3R/S)‐3‐(cis‐4‐acetoxycyclopent‐2‐enyl oxy)‐3‐ethoxypropionic acid (3), is prepared by two different synthetic sequences: In a first strategy transacetalization of ethyl 3,3‐diethoxypropionate (6) with (1R, 4S)‐4‐acetoxy‐1‐hydroxy‐2‐cyclopentene (7) leads to the formation of the mixed acetal 8. By subsequent hydrolysis and acylation 8 could be converted into acid 3 in six steps in 6% overall yield. However, the generation of acid 3 by bromoalkoxidation of 3‐ethoxyacrylates 13d, e and subsequent electrochemical reduction proved to be more efficient. In this reduction it is possible to debrominate the α‐bromo esters 14d, e and to remove the 2‐haloethyl ester group in one step. Using this reaction sequence, we could synthesize acid 3 in five steps in 38% overall yield. magnified image
Synthese isomerer ϵ‐hydroxycarbonsäure‐methylester
Authors: Arth Christoph , Clemens Martina , Meise Werner
Published: July 2007

Synthesis of Isomeric Methyl ϵ‐Hydroxycarboxylates

The synthesis of the three isomeric methyl ϵ‐hydroxycarboxylates 3, 6 and 10a in good overall yields is described. magnified image
Synthesis of 1‐Azabicyclo[3.3.1]nona‐3,6‐diene Derivatives by a Modified Prins Reaction
Authors: Csuzdi Emese , Ling István , Ábrahám Gizella , Pallagi István , Sólyom Sándor
Published: July 2007

Intramolecular electrophilic cyclization reactions were performed with 1‐(3‐oxo‐3‐phenylpropyl)‐1,2,5,6‐tetrahydropyridine derivatives 1a–p in strong acids to give 4,6‐diphenylsubstituted 1‐azabicyclo[3.3.1]nonadienes 2a–p. Some qualitative observations were made on substituents and reaction conditions influencing the ring closure reaction. Naphthylsubstituted starting compounds 3a, b were converted into pentacyclic compounds 4a, b which represent a new ring system, suggesting the occurrence of a carbenium ion intermediate in the ring closure reaction. Some of the compounds 2a–p show remarkable antifungal and antibacterial effects. magnified image
Fluorogenic Substrates Containing 7‐Amino‐4‐methyl‐2‐quinolinone for Aminopeptidase M, Chymotrypsin, Elastase and Trypsin, Determination of Enzyme Activity
Authors: Tzougraki Chryssa , Noula Catherine , Geiger Reinhard , Kokotos George
Published: July 2007

Several new fluorogenic substrates for four proteases were synthesized by coupling the highly fluorescent 7‐amino‐4‐methyl‐2‐quinolinone (AMeq) with appropriate amino acids and peptides. Compounds HCl · H‐Ala‐NH‐Meq (1) and HCl · H‐Leu‐NH‐Meq (2) are substrates for aminopeptidase M, Glt‐Tyr‐NH‐Meq (3) and Glt‐Leu‐Tyr‐NH‐Meq (4) for chymotrypsin, Boc‐(Ala)4‐NH‐Meq (5) for elastase and Z‐Arg‐NH‐Meq (6) for trypsin. The kinetic parameters for the hydrolysis of the new substrates were determined and showed that each new substrate is suitable for a convenient fluorometric assay of the corresponding enzyme. magnified image
Novel Concepts in Directed Biaryl Synthesis, XXXVIII. Synthesis and Structure of a Protected Lactolate‐Bridged Biaryl with Relevance to the Atropisomer‐Selective Ring Opening of Biaryl Lactones
Authors: Bringmann Gerhard , Schöner Bernd , Peters Karl , Peters Eva‐Maria , von Schnering Hans Georg
Published: July 2007

The preparation and crystal structure of the O‐methyl‐protected analog 5 of a lactolate‐type intermediate 3 in the atropisomer‐selective ring opening of configuratively unstable lactone‐bridged biaryls 1 is described. Thus, 5a could be prepared by oxidation of the cyclic ether 7a to give the substituted pyrylium salt 6a and subsequent reaction with methanolate. Attempts to similarly prepare the more strained higher homologous 5, i.e. with a higher steric hindrance next to the biaryl axis, failed. Structural information on 5a could be obtained through X‐ray crystallography, but no decoalescence was observed in the low‐temperature NMR spectrum. magnified image
Total Syntheses, Optical Rotations and Fragrance Properties of Sandalwood Constituents: (−)‐(Z)‐ and (−)‐(E)‐β‐Santalol and Their Enantiomers, ent‐β‐Santalene
Authors: Krotz Achim , Helmchen Günter
Published: July 2007

Enantiomerically pure 5‐norbornene‐2‐carboxylic acids 4, obtained by asymmetric Diels‐Alder additions, were oxidatively degraded to (+)‐ and (−)‐2‐norbornanone [(+)‐, (−)‐21] and (+)‐ and (−)‐3‐methyl‐2‐norbornanone [(+)‐, (‐)‐11] which were converted into the title compounds by stereoselective alkylations, subsequent cis‐ and trans‐selective Wittig reactions and reductions. Precise optical rotations were determined for (Z)‐ and (E)‐β‐santalol (1 and 2) and β‐santalene (3a) which were obtained by total synthesis and, in addition, by isolation from East Indian sandalwood oil. magnified image
Synthesis of Uridine with Methylene‐2‐thiohydantoin as 5‐Substituent
Authors: El‐Barbary Ahmed A. , Khodair Ahmed I. , Pedersen Erik B. , Nielsen Claus
Published: July 2007

5‐Formyl‐1‐(2,3,5‐tri‐O‐acetyl‐β‐D‐ribofuranosyl)uracil (4) was synthesized from 5‐formyluracil (2) and 1,2,3,5‐tetra‐O‐acetyl‐β‐D‐ribofuranose (3) and condensed with 2‐thiohydantoin derivatives 5 by using piperidine as the catalyst to give 5‐(uridin‐5‐ylmethylene)‐2‐thiohydantoin (8a) and 3‐phenyl‐5‐(uridin‐5‐ylmethylene)‐2‐thiohydantoin (8b) after deprotection with sodium methoxide in methanol. Compound 8a was also obtained in an inversed reaction sequence from 5‐formyluracil starting with condensation with 2‐thiohydantoin and then with 3. The compounds 8a and 8b did not show any activity against HSV‐1 or HIV‐1. magnified image
A Stereoselective Synthesis of threo‐3‐Hydroxyglutamic Acid
Authors: Dell'Uomo Natalina , Di Giovanni Maria C. , Misiti Domenico , Zappia Giovanni , Monache Giuliano Delle
Published: July 2007

The highly stereoselective iodocyclocarbamation of the chiral Z olefins 6 and 12, derived from the corresponding α‐amino acid, yields threo‐3‐hydroxy‐D‐ and ‐L‐glutamic acid (1 and 2). magnified image
Glycosyl Imidates, 66. Synthesis of the Tetrasaccharide Moiety of Plant Growth Regulator Calonyctin A
Authors: Jiang Zi‐Hua , Schmidt Richard R.
Published: July 2007

3‐O‐Benzyl‐protected quinovose 6 was transformed into 1,2‐O‐unprotected derivative 9 which on treatment with TBS‐Cl in the presence of a base gave selectively 2‐O‐unprotected glycosyl acceptor 10. Similarly, 3‐O‐allyl‐protected quinovose 11 was transformed into 1,2‐O‐unprotected derivative 14. 1,2‐O‐Acetylation of 14, selective removal of the 1‐O‐acetyl group with hydrazinium acetate, and subsequent treatment with trichloroacetonitrile in the presence of DBU furnished the versatile 2‐O‐acetyl‐3‐O‐allyl‐protected quinovosyl donor 17. Reaction of donor 17 with acceptor 10 in the presence of TMSOTf as the catalyst gave disaccharide 19. Treatment of 19 with NaOMe/MeOH provided 2b‐O‐unprotected derivative 20 which gave with rhamnosyl donor 18 in the presence of TMSOTf as the catalyst trisaccharide 21. 3b‐O‐Deallylation of 21 and subsequent reaction with donor 17, again in the presence of TMSOTf as the catalyst, gave target tetrasaccharide 2. Removal of all O‐protective groups furnished D‐Quiß(1→3)[L‐Rhaα(1→2)]D‐Quiß(1→2)D‐Qui (3), the tetrasaccharide moiety of calonyctin A. magnified image
Thioalkylation of Enolates, III. Stereoselective Synthesis of Steroids and Related Compounds, II α‐Thioalkylation of Zinc Dienolates to 4‐Substituted 1‐tert‐Butoxy‐7a‐methyl‐hexahydroinden‐5‐ones
Authors: Groth Ulrich , Köhler Thomas , Taapken Thomas
Published: July 2007

α‐Alkylation of the α,β‐unsaturated ketone 1 at C‐4 has been achieved by thioalkylation of the corresponding zinc dienolate with α‐chlorosulfides of type 2. The desulfurization of the β‐(phenylthio) ketones 4 leads directly to the 4‐substituted hexahydroinden‐5‐ones 5. magnified image
Synthesis of Quaternary Indoxyl Derivatives by Intramolecular Cyclization of Some Substituted Acetophenones
Authors: Ruiz José R. , Arán Vicente J. , Asensio Juan L. , Flores María , Stud Manfred
Published: July 2007

The intramolecular cyclization of N,N‐disubstituted 2′‐halogenophenacylamine hydrobromides 1a–h to 1,1‐disubstituted 3‐oxoindolinium bromides 3a–f has been studied. Some 3‐oxoindolinium salts have also been prepared according to a different pattern by intramolecular cyclization of the phenacyl halides resulting from the bromination of 2′‐(dialkylamino)acetophenones 4 or from the treatment of 2′‐(dialkylamino)‐2‐diazoacetophenones 6a, b with hydrogen halides. Removal of hydrogen halide in salts 3a–g gives indolylio oxides 2a–g; these compounds have been shown to be unstable and decompose easily giving in general complex mixtures; only in the case of tetrahydroisoquinoline‐derived ylides 2e, g we have observed clear‐cut reactions leading, via a Stevens rearrangement followed by oxidation, to the 6,7‐dihydro‐13H‐indolo[2,1‐b][3]benzazepin‐13‐ones 8a, b. magnified image
Dioxirane Oxidation of Furocoumarins and Naphthofurans Preparation of the Psoralen Epoxides
Authors: Adam Waldemar , Sauter Markus
Published: July 2007

Methyl(trifluoromethyl)dioxirane oxidation of natural psoralen (1a) and 8‐methoxypsoralen (8‐MOP, 1b) and dimethyldioxirane oxidation of some related 2,3‐substituted furocoumarins 1c–e at subambient temperature afforded the corresponding labile epoxides 2a–e. The reaction of acetylated 2,3‐dimethylnaphthofurans 1f,g with dimethyldioxirane afforded the corresponding quinone methides 3f, g, derived from the valence‐isomeric epoxides 2f,g. Cycloaddition of ethyl vinyl ether to the quinone methides 3b, c led to the benzopyrans 5b, c. In methanol at −50°C, the 8‐MOP epoxide (2a) was converted by nucleophilic attack into the corresponding adduct 4b. The latter result demonstrates that the psoralen epoxides may serve as powerful alkylating agents and provides a possible chemical basis for their observed genotoxicity due to adduct formation by nucleophilic attack of DNA. magnified image
Pheromone Synthesis, CLXIII. Synthesis of (9Z,25S,26R,43Z)‐25,26‐Epoxy‐9,43‐henpentacontadiene and Its Antipode, Components of the Nymph Recognition Pheromone Produced by Nymphs of the Cockroach Nauphoeta cinerea
Authors: Mori Kenji , Argade Narshinha P.
Published: July 2007

(9Z,25S,26R,43Z)‐25,26‐Epoxy‐9,43‐henpentacontadiene (1) and its antipode, the nymph recognition pheromone of Nauphoeta cinerea, were synthesized by extending the carbon chain of (2S,3R)‐4‐Acetoxy‐2,3‐epoxy‐1‐butanol (25). The Grignard coupling was the key reaction. magnified image
Total Synthesis of Myxovirescins, 2 Assembly of the “Northwestern” Part [C(15)–C(28)]
Authors: Sefkow Michael , Neidlein Axel , Sommerfeld Thimo , Sternfeld Francine , Maestro Miguel A. , Seebach Dieter
Published: July 2007

The part of the target molecules myxovirescins A and M containing the atoms C(15)–C(28) is described in this paper (for retrosynthetic analysis see Scheme 1). There are three stereogenic centers which are incorporated by using (S)‐2‐hydroxymethyl‐butanoic acid and the appropriate enantiopure diastereoisomeric 2,4‐dimethyl‐glutaric acids as building blocks (Schemes 2–4). These are joined by the achiral unit 4‐oxo‐hex‐5‐enoic acid. The key steps of the assembly are a cuprate Michael addition (Scheme 5) and a nucleophilic addition of a Li derivative to an aldehyde (Scheme 6). In both cases the organometallic reagents are generated by I/Li exchange using two equiv. of tBuLi. The chiral building blocks are prepared by yeast reduction of ethyl 2‐formyl‐butanoate and by resolution of the 2,4‐dimethyl‐pentanedioic acid monomethyl ester with phenethylamine; both enantiomers derived from the meso‐2, 4‐dimethyl‐glutaric acid are converted to the same aldehyde (5a; “meso‐trick”, Schemes 3 and 4). The “northwestern” parts for the final synthesis are actually hydroxy sulfones (2 in Scheme 6), the termini of which are ready for Julia coupling and oxidation to a carboxylic acid group. The preparation of the intermediates on gram scales is described and all new compounds are fully characterized by their physical properties, by spectroscopy (IR, 1H‐ and 13C‐NMR spectra) and by elemental analysis. magnified image
Iminophosphorane‐Mediated Synthesis of Fused Perimidines: Preparation of Quinazolino[3,4‐a]perimidine Derivatives
Authors: Molina Pedro , Alías Asunción , Balado Ana , Arques Antonio
Published: July 2007

An aza‐Wittig‐type reaction of iminophosphoranes 2 and 3, derived from 2‐(2‐azidophenyl)‐1,2‐dihydroperimidine and 2‐(2‐azidophenyl)perimidine, respectively, with isocyanates, carbon dioxide, carbon disulfide and acyl chlorides provides 6‐substituted quinazolino[3,4‐α]perimidines 4–10. magnified image
D‐Erythronolactone and 2,3‐O‐Isopropylidene‐L‐erythrose as C4 Building Units: An Efficient Synthesis of both Enantiomers of endo‐Brevicomin and its 7‐Vinyl Analogues
Authors: Gypser Andreas , Flasche Michael , Scharf Hans‐Dieter
Published: July 2007

Both enantiomers of endo‐brevicomin (+)‐ and (−)‐3a were synthesized from D‐erythronolactone (1) and 2,3‐O‐isopropylidene‐L‐erythrose (2), respectively. In the course of the synthesis also the 7‐vinyl analogues (+)‐ and (−)‐3b of endo‐brevicomin are available. The key step of the synthesis is the diastereoselective acetalization of the diols 1 and 10 with 4‐(phenylsulfonyl)‐2‐butanone (4) and boron trifluoride‐diethyl ether complex as a catalyst. The described procedure yields the key compounds 5a and ent‐7b in good yields and with high diastereomeric purity. magnified image
Cyclische Guanidinium‐Ionen als Glycosylkation‐Analoga sind kompetitive und nichtkompetitive Inhibitoren für Glycosidhydrolasen
Authors: Lehmann Jochen , Rob Beatrice
Published: July 2007

Cyclic Guanidinium Ions as Analogues of Glycosyl Cations are Competitive and Noncompetitive Inhibitors of Glycoside Hydrolases

Four cyclic guanidinium compounds 8–11 were synthesised and found to be competitive and noncompetitive inhibitors of β‐D‐galactosidase (E. coli), α‐D‐glucosidase (yeast) and β‐D‐glucosidase (emulsin). The compounds were ineffective against α‐D‐mannosidase from jack beans. For the effect of compounds 8–11, resembling hypothetical glucosyl and galactosyl cations, a flattened conformation as well as a permanent positive charge is made responsible. magnified image
Synthesis and Antifungal Activity of 3‐Deoxy‐DL‐prumycin Analogues
Authors: Constantinou‐Kokotou Violetta , Kokotos George , Chrysayi‐Tokousbalides Maria , Couladouros Elias A. , Georgiadis Minas P.
Published: July 2007

A number of 3‐deoxy‐DL‐prumycin analogues containing one or more amino acid moieties were synthesized. Key intermediate 2 afforded ester analogues by coupling with H‐D‐ or L‐Ala‐OH, while intermediates 6 and 9 afforded amide analogues by coupling with H‐D‐Ala‐D‐Ala‐OH, H‐D‐Ala‐OH, 2‐amino‐4,4‐dichlorobutanoic acid and acetic acid. The antifungal activity of the analogues against various phytopathogenic fungi was measured. magnified image
1,3,5‐Triphenyl‐5‐(4‐phenyl‐2‐piperidinothiazol‐5‐yl)penta‐2,4‐dien‐1‐on. – Ein Beispiel für die Fixierung von N‐Invertomeren durch unterschiedliche Kristallstrukturen
Authors: Zimmermann Thomas , Teller Joachim , Kopf Jürgen , Abeln Dirk
Published: July 2007

1,3,5‐Triphenyl‐5‐(4‐phenyl‐2‐piperidinothiazol‐5‐yl)penta‐2, 4‐dien‐1‐one. – An Example of the Fixation of N‐Invertomers by Different Crystal Structures

From an ethanol/acetone solution of 1,3,5‐triphenyl‐5‐(4‐phenyl‐2‐piperidinothiazol‐5‐yl)penta‐2,4‐dien‐1‐one 3 (Ar = Ar′ = Ar″ = Ph, NR2 = piperidino) yellow‐orange and red crystals are obtained simultaneously. X‐ray structure determinations show that the N‐invertomers of the dienone, easily convertible in solution, are fixed in the solid state by different crystal structures. magnified image
A Porphyrinogen Bridged with and a Porphyrin Substituted by 1,8‐Diethynylanthracene
Authors: Marx Thomas , Breitmaier Eberhard
Published: July 2007

Treatment of 1,8‐diethynylanthracene with n‐butyllithium and N‐formylpiperidine at −5°C gives a mixture of the monoaldehyde 4 and the dialdehyde 2. Further reaction of these aldehydes with the 2,2′‐dipyrrylmethane 1 affords the bridged porphyrinogen 3 and the meso‐substituted porphyrin 5, respectively. magnified image
Chemie von Aziridincarbonsäuren, IV. Enantioselektive Hydratisierung von Aziridin‐2‐carbonitril
Authors: Jähnisch Klaus , Gründemann Egon , Kunath Annamarie , Ramm Matthias
Published: July 2007

Chemistry of Aziridinecarboxylic Acids, IV. – Enantioselective Hydration of Aziridine‐2‐carbonitrile

Aziridine‐2‐carbonitrile rac‐1 was hydrated enantioselectively in aqueous medium by using (2R,3R,5R)‐(−)‐5‐(1‐hydroxy‐1‐methylethyl)‐2‐methyl‐3‐oxocyclohexanecarbonitrile (2) as chiral catalyst. The ee value of the unreacted (S)‐(−)‐aziridine‐2‐carbonitrile 1 depends on the conversion and reaches ≥99%.
Thioalkylation of Enolates, IV. α‐Alkylidenecyclopentanones by α‐Alkylidation of Methyl 2‐Oxocyclopentanecarboxylate
Authors: Arnecke Ralf , Groth Ulrich , Köhler Thomas
Published: July 2007

An α‐alkylidation of cyclopentanone was achieved in two reaction steps in an overall yield of 20 to 79% via a zinc chloride‐catalyzed thioalkylation of the zinc enolate of methyl 2‐oxocyclopentanecarboxylate (3) and subsequent saponification/desulfurization of the β‐(phenylthio) ketone intermediates 5. For the saponification/desulfurization step DABCO proved to be the reagent of choice and superior to the use of alkali or magnesium halides.
Stereoselective Cyclization of 4‐Substituted 5‐Hexen‐1‐ols and Related Compounds by Benzeneselenenyl Triflate
Authors: Inoue Hirohumi , Murata Shizuaki , Suzuki Toshiyasu
Published: July 2007

Oxyselenylation of 4‐substituted 5‐hexen‐1‐ols 1 with benzeneselenenyl trifluoromethanesulfonate proceeds by intramolecular exo cyclization stereoselectively to give 3‐substituted trans‐ or cis‐2‐(phenylselenenylmethyl)tetrahydropyrans 3. Formation of the trans isomers is favored when the substituents contain alkyl or phenyl substituents in the 4‐position, whereas the cis isomers predominate when the substituents are alkoxyalkyl, alkoxyl, acyl, and hydroxyl. The mechanism of the trans and cis stereoselectivity is explained by steric and electronic effects in the phenylseleniranium intermediates, 7 and 8.
Structure‐Odor Correlation, XX. Synthesis and Olfactory Properties of the “Irone‐Type Homolog” of Megastigmatrien‐3‐one
Authors: Weyerstahl Peter , Licha Kai , Marschall Helga
Published: July 2007

rac‐2‐Methylmegastigma‐4,6,8‐trien‐3‐one (11), the ironetype homolog of the important aroma component megastigmatrien‐3‐one (1), was synthesized starting from 4‐oxoisophorone (2) via 2‐methyl‐4‐oxoisophorone (7) and the ynediol 10 and additionally by methylation of 1. The odor of 11 (tobacco‐like, woody, leathery, plum‐like) is not very different from that of 1.
Synthesis of Fluorinated (±)‐Phoracantholide and Related Compounds: Regioselective Access to a Novel Class of Monofluorinated Fatty Acid Derivatives
Authors: Sattler Andreas , Haufe Günter
Published: July 2007

10‐Fluorodecan‐9‐olide (1a), a monofluorinated analogue of (±)‐phoracantholide, is synthesised in 20% overall yield by a five‐step sequence starting with 9‐decenoic acid (3a). 10‐Undecenoic acid (3b) is transformed in 28% overall yield into the next higher homologue, 11‐fluoroundecan‐10‐olide (1b). Their regioisomers, 9‐fluorodecan‐10‐olide (2a) and 10‐fluoroundecan‐11‐olide (2b), are obtained analogously in 20% or 29% yield. Key step of these syntheses is the regioselective opening of the epoxides of unsaturated fatty acid esters 5a and 5b.
Sterically Congested Molecules, 13. Note on the Substituent Effect of the Orthogonally Fixed Imino Function Connected by its Nitrogen Atom
Authors: Knorr Rudolf , Ferchland Kathrin
Published: July 2007

Determination of the pKa′ value for the carboxylic function of 3,5‐dimethyl‐4‐[(2,2,5,5‐tetramethylcyclopentylidene)amino]‐benzoic acid (2) in aqueous alcohols leads to the Hammett substituent parameter σp = +0.07 (±0.07) for the imino group whose π‐electron system is orthogonal to that of the mediating aromatic ring.
Glycosides of Heterocycles: A Direct Route to 1‐(β‐D‐Glycopyranosyl)pyridinethione Nucleosides
Authors: Elgemeie Galal E. H. , Attia Adel M. E. , Fathy Nahed M.
Published: July 2007

A novel synthesis of 1‐(β‐D‐glycopyranosyl)pyridinethione nucleosides 6 utilizing pyridine‐2(1H)‐thiones 3 and α‐halogeno sugars 4 as starting components is reported.
Reactions with and in Anydrous Hydrogen Fluoride, 13. A Convenient One‐Pot Synthesis of Glucofurano[2,1‐d]oxazolines with an Additional 3,5,6‐Orthoester Function
Authors: Miethchen Ralf , Klein Holger , Pedersen Christian
Published: July 2007

The reactions of dioxolanylium and oxazolinium ions, formed in anhydrous HF from N‐acylated 2‐amino‐2‐deoxy‐D‐glucoses and one equivalent of carboxylic acid anhydride or chloride, were investigated by treatment of their HF solutions with triethylamine/alkane or triethylamine/ether systems. Thus, the 2‐acylamido‐2‐deoxy‐D‐glucoses 1 and 2 react with acetic anhydride, dodecanoic anhydride or pivaloyl chloride in anhydrous HF at −30°C to give 5,6‐dioxolanylium ions. On treatment with formic acid at room temperature they undergo further reaction to yield the thermodynamically favored 3,6‐anhydro derivatives. The glucofurano‐oxazolines 3–5, containing an orthoester substructure, as well as the 3,6‐anhydro‐D‐glucofuranose derivatives 6 and 7 can be isolated after treatment of the HF solutions with triethylamine. The oxazoline derivative 4 was used as glycosyl donor for methanol giving the methyl glycoside 8 without cleavage of the orthoester moiety.