bluuebunny/crossref_metadata_2025 huggingface dataset:
Festphasensynthese von O‐Glycopeptiden
Authors: Paulsen Hans , Merz Gunnar , Peters Stefan , Weichert Udo
Published: July 2007

Solid Phase Synthesis of O‐Glycopeptides

The solid phase synthesis of a number of O‐glycopeptides are described. A polystyrene resin containing p‐alkoxybenzyl alcohol groups was used as support. Glycosylamino acids of 2‐acetamido‐2‐deoxy‐D‐galactose and threonin or serin can be coupled with further amino acids and also with other glycosylated amino acids. The introduction of disaccharide‐containing amino acids gives uncomplete reaction. The final cleavage from the carrier and the deprotection present no difficulties. Partial structures of the ovine submaxillary mucin and of human and porcine glycophorin are prepared.
Lipidic peptides, I. Synthesis, resolution and structural elucidation of lipidic amino acids and their homo‐ and hetero‐oligomers
Authors: Gibbons William A. , Hughes Richard A. , Charalambous Mario , Christodoulou Marika , Szeto Alice , Aulabaugh Anne E. , Mascagni Paolo , Toth Istvan
Published: July 2007

The α‐amino acids with long alkyl side chains, the so‐called lipidic amino acids 1a–e, and their homo‐oligomers, the lipidic peptides 1p–aj, represent a class of compounds which combine the structural properties of peptides and proteins with the characteristics of lipids and membranes. The amino acids were synthesised from the appropriate alkyl bromide and diethyl acetamidomalonate. Resolution was made chemically, by forming diastereomers of the amino acid esters with an optically pure α‐pinene derivative. The protected homooligomers were synthesised in solution with the assistance of a water‐soluble carbodiimide coupling agent. In order to modify the physical and chemical properties of the peptides, a series of protected hetero‐oligomers were prepared, by similar methods, incorporating either other amino acids (3a – d, 7a – i) or side‐chain‐substituted lipidic amino acids (6a–d).
Structural variations of N‐acetylneuraminic acid, 18. Synthesis of the side chain stereo and deoxy analogs of 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐erythro‐L‐manno‐nononic acid
Authors: Bandgar Babasaheb P. , Hartmann Michael , Schmid Walther , Zbiral Erich
Published: July 2007

The synthesis of 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐ erythro‐L‐manno‐nonic acid (3b, 7,8‐epi2‐2‐d‐2‐HeqNeu5Ac) and sodium 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐L‐threo‐L‐manno‐nonate (6b, 8‐epi‐2‐d‐2‐Heq‐Neu5Ac) could be realized by transformation of 5‐acetamido‐3,5‐dideoxy‐L‐glycero‐L‐altro‐2‐nonulopyranosonic acid (2a, 7,8‐bis‐epi‐Neu5Ac) and 5‐acetamido‐3,5‐dideoxy‐3‐L‐glycero‐D‐galacto‐2‐nonulosonic acid (5a, 8‐epi‐Neu5Ac) into the corresponding peracetylated 2‐chloro derivatives and subsequent catalytic hydrogenation. As this procedure could not be applied to the synthesis of the 7‐epi, 7‐deoxy and 8‐deoxy derivatives a new strategy, which started with the methyl 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐erythro‐L‐manno‐nonoate (1e), was designed. For this purpose, a gram‐scale preparation of 1e was developed. Transformation of protecting groups and radical reduction of selectively introduced tolylthiocarbonate groups led to the corresponding 5‐acetamido‐2,6‐anhydro‐3,5,7‐trideoxy‐D‐glycero‐L‐manno‐nonoic acid (12b, 2,7‐d2‐2Heq‐Neu5Ac) and sodium 5‐acetamido‐2,6‐anhydro‐3,5,8‐trideoxy‐D‐glycero‐L‐manno‐nonate (11b, 2,8‐d2‐2Heq‐Neu5Ac). An oxidation — reduction sequence yielded 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐threo‐L‐manno‐nonoic acid (9c, 2d‐2Heq‐7‐epi‐Neu5Ac). Also the sialic acid analog 6b could be prepared according to this newly designed strategy.
De novo synthesis of carbohydrates and related natural products, 34. Synthesis of N‐acetyl‐β‐D‐neuraminic acid derivatives via inverse‐type hetero‐Diels‐Alder reaction
Authors: Haag‐Zeino Brigitte , Schmidt Richard R.
Published: July 2007

Inverse‐type hetero‐Diels‐Alder reaction‐based diastereoselective synthesis of 3‐deoxy‐2‐glyculosonates is performed with the help of chiral carbon substituents in the 2‐position of the 1‐oxa‐1,3‐diene required as heterodiene. This is demonstrated for the synthesis of the selectively O‐protected and the O‐unprotected N‐acetylneuraminic acid derivatives 21 and 22, respectively. Thus, the heterodiene 10, obtained from D‐mannose in high overall yield, affords with methyl α‐methoxy‐acrylate as heterodienophile preferentially the stereoisomer 11 with β‐D‐ribo configuration. Phenylthio group removal, diastereospecific 5‐hydroxy and 6‐hydrogen transfer, and then stereocontrolled introduction of the acetamino group into the 5‐position furnished compound 21 with the required D‐glycero‐D‐galacto configuration. Structural proof comes from the transformation into the known N‐acetylneuraminic acid derivative 22.
Lignanglucoside aus Wurzeln von Urtica dioica
Authors: Kraus Rupert , Spiteller Gerhard
Published: July 2007

Lignan Glucosides from Roots of Urtica dioica

Lignan glucosides isolated from stinging nettle roots (Urtica dioica) were separated by GC on short glass capillary columns (5–6 m) after appropriate derivatization. By use of mass spectrometry (GC/EI‐MS, EI‐MS, LSI‐MS) and NMR spectroscopy, 11 lignan glucosides were identified, 5 of which were previously unknown. Mixtures of isomeric lignan glucosides which could not be separated by GC were investigated by two‐dimensional NMR methods. The spectra allowed the identification of the single components. Mass spectra of the trimethylsilylated glucosides show typical fragments which enabled us to decide if the glucose was attached to an alcoholic or phenolic hydroxy group of the aglycone. The nature of the aglycones could be also deduced from the spectra.
Darstellung von 3‐Keto‐Derivaten des Frontalins, des endo‐und exo‐Brevicomins
Authors: Claßen Arnold , Scharf Hans‐Dieter
Published: July 2007

Preparation of 3‐Keto Derivatives of Frontalin, endo‐ and exo‐Brevicomin

The oxidative desulfonation of the phenylsulfonyl derivatives 1–4 of the title pheromones with MoO5 · Py · HMPT leads to the formation of the ketones 5–7 in yields which depend on the configuration of C‐7.
Stereoselective synthesis of alcohols, XXXVI. Stereoselective generation of homoallyl alcohols having quaternary stereogenic centers
Authors: Hoffmann Reinhard W. , Schlapbach Achim
Published: July 2007

E‐ and Z‐γ,γ‐disubstituted allylboronates 12 have been generated by the carbocupration of alkynes and subsequent homologation. These allylboronates add to aldehydes, forming the homoallyl alcohols 13 and 14 with 88–99% simple diastereoselectivity. The highest diastereoselectivity was obtained with α‐branched aldehydes.
Synthese von 4‐Acetamido‐3,7‐anhydro‐2‐azi‐1,2,4‐tridesoxy‐D‐glycero‐D‐gulo‐octitol, einem potentiellen Photoaffinitätsreagens mit guter Affinität zu menschlicher β‐Hexosaminidase
Authors: Áts Sándor‐Csaba , Lausberg Elke , Lehmann Jochen , Sandhoff Konrad
Published: July 2007

Synthesis of 4‐Acetamido‐3,7‐anhydro‐2‐azi‐1,2,4‐trideoxy‐D‐glycero‐D‐gulo‐octitol a Good Competitive Inhibitor and Potential Photoaffinity Reagent for Human β‐Hexosaminidase

Using the known 3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranosyl cyanide 2 the corresponding heptonic acid was prepared via its amide by NO2 treatment. Chain extension to yield 5,6,8‐tri‐O‐acetyl‐3,7‐anhydro‐1,4‐dideoxy‐4‐phthal‐imido‐D‐glycero‐D‐gulo‐oct‐2‐ulose (6) was carried out by condensing the heptonic acid chloride 5 with Meldrum's acid. Compound 6 was finally converted into 4‐acetamido‐3,7‐anhydro‐2‐azi‐1,2,4‐trideoxy‐D‐glycero‐D‐gulo‐octitol (8) by conventional methods. This compound, being an enzyme resistant analog of a glucosaminide, was shown to be a good competitive inhibitor for lysosomal β‐hexosaminidase (2‐acet‐amido‐2‐deoxy‐β‐D‐hexoside acetamidodeoxyhexohydrolase, E.C. 3.2.1.52) and a potential photoaffinity reagent.
Preparation of 2,6‐anhydro‐3‐deoxyhept‐(or hex‐)2‐enononitriles (1‐cyanoglycals) from 1‐bromo‐D‐glycosyl cyanides with zinc under aprotic conditions
Authors: Somsák László , Bajza István , Batta Gyula
Published: July 2007

Acetylated 1‐bromo‐D‐glycosyl cyanides 1–5 react with zinc dust in acetic acid, acetic acid/water, or 2‐propanol to give mixtures of acetylated 1‐cyanoglycals 6–9 and anomeric pairs of glycosyl cyanides 10–14. Reaction of 1–5 in refluxing benzene in the presence of one equivalent of triethylamine or especially pyridine predominantly leads to the formation of 1‐cyanoglycals.
Novel 8‐hydroxy‐3‐phenoxazinone derivatives related to the actinomycin D chromophore
Authors: Sehgal Raj K.
Published: July 2007

A reexamination of the reaction of the model actinomycin D chromophore (1a) with DDQ revealed the presence of hitherto unknown 8‐hydroxy‐substituted phenoxazinone derivative 1c as a minor product along with the 7‐hydroxy derivative 1b as the major product. Further, the isomeric hydroxy derivatives can be conveniently converted by reaction with suitable alkyl halides to afford the corresponding alkylated products with suitable alkylating species for interaction of the actinomycin D chromophore with DNA of the cell.
Glycosidation, 13; anticancer agents, 10. Novel stable bioactivated cyclophosphamide derivatives for selective cancer chemotherapy, synthesis of aldophosphamide acetal‐glycosides and their glycoconjugates
Authors: Tietze Lutz F. , Fischer Roland , Beller Matthias , Seele Rainer
Published: July 2007

Stimulation of tumor cell glycolysis in vivo leads to an increase of lactic acid formation and thus a decrease of pH in malignant tissue compared with a normal cell population. The difference in pH may be used to cleave a nontoxic prodrug selectively in a tumor to give a highly cytotoxic compound. In this respect, acetal‐glycosides of aldophosphamide (3), a biological active metabolite of the anticancer agent cyclophosphamide (1) with α‐D‐ and β‐D‐glucose as well as α‐D‐mannose have been synthesized. Reaction of the trimethylsilyl glycosides 8a, 8b, and 8c with the acetals 9a, 9b, and 9c in the presence of TMS–OTf at −78°C gave selectively according to the anomeric center the acetal‐glycosides 10a–e in 68–88% yield. Debenzylation, reaction with the phosphorous acid amide dichloride 12 and ammonia, led to the aldophosphamide derivatives 15a–e. For coupling with biopolymers, the ester moiety in 15d and 15e was hydrolyzed to give 16a and 16b. As a model study, coupling of 16a and 16b with the lysine derivative 17 using 1‐hydroxybenzotriazol (18) and an excess of diisopropyl carbodiimide (19) was accomplished to afford 16c and 16d which were acetylated to give 16e and 16f.
New porphyrinoids, 9. Synthesis of a bisvinylogous porphyrin with a [22] annulene system
Authors: Gosmann Martin , Vogt Andreas , Franck Burchard
Published: July 2007

The twofold vinylogously enlarged porphyrin with a 22‐π‐electron system 3 was prepared by vinylogous bisformylation of the dipyrrylmethane 7 to give 8 and subsequent acid‐catalyzed condensation of 8 with 7. The [22]porphyrin 3 is characterized by a Soret band at 469 nm, which on protonation of the porphyrinoid becomes very narrow with the highest extinction coefficient so far observed for an organic pigment (ϵ = 1090000). In the 1H‐NMR spectrum 3 reveals a strong diamagnetic ring‐current effect with a shift difference between inner and outer protons of Δδ = 20.1 ppm, thereby proving itself a pronounced aromatic system.
Electrochemical hydroxylation, methoxylation, and hydroxymethylation of active methine compounds
Authors: Kawabata Jin‐Ichi , Nozawa Koohei , Kawai Ken‐Ichi , Nakajima Shoichi
Published: July 2007

Hydroxylation, methoxylation, or hydroxymethylation at the active methine group of phenylmalonate, benzylmalonate and diphenylacetate were achieved by anodic oxidation.
Nucleophile Ringöffnung von 1‐Nitro‐1‐cyclopropancarbonsäure‐arylestern mit sterisch geschützter, aber elektronisch wirksamer Carbonyl‐ und Nitrogruppe. Ein neues Prinzip der Aminosäuresynthese
Authors: Vettiger Thomas , Seebach Dieter
Published: July 2007

Nucleophilic Ring Opening of Aryl 1‐Nitro‐1‐cyclopropanecarboxylate with Sterically Protected, but Electronically Effective Carbonyl and Nitro Group. A New Principle of Amino Acid Synthesis

The readily available [2,6‐di‐(tert‐butyl)‐4‐methoxyphenyl] 1‐nitro‐1‐cyclopropanecarboxylate (4) is ring‐opened by nucleophilic attack of the amino groups of (S)‐α‐amino acid esters (products 20–26). Reduction of the nitro group gives rise to derivatives 27–30 of 2,4‐diaminobutanoic acid which are connected with a second amino acid through the nitrogen in position 4 (2‐substituted 6‐amino‐3‐azaheptanedioic acids). In two cases, these were converted into enantiomerically and diastereomerically pure Freidinger's γ‐lactam dipeptides (31, 32), which have previously been shown to mimic a peptide β‐turn.
Benzotris[1,2,5]thiadiazol in einer Eintopfreaktion aus Benzolhexamin
Authors: Praefcke Klaus , Kohne Bernd , Korinth Frank
Published: July 2007

Benzotris[1,2,5]thiadiazole in a One‐Pot Reaction from Benzenehexamine

Condensation of benzenehexamine (1) with thionyl chloride in the presence of pyridine gave the title compound 2 (69% yield) in a one‐pot reaction. A similar reaction of 1 with seleninyl chloride or an alternative condensation of 1 with selenium dioxide led to the analogous selenium heterocycle 3 in traces only.
Synthesis of 4‐substituted 2‐aminopyrrolo[2,3‐d]pyrimidine 2′,3′‐dideoxyribonucleosides
Authors: Seela Frank , Muth Heinz‐Peter
Published: July 2007

A number of new 2‐aminopyrrolo[2,3‐d]pyrimidine N‐7‐(2′,3′‐dideoxyribonucleosides) (11–13 and 15) were synthesized. These are related to 7‐deaza‐2′,3′‐dideoxyguanosine (14), but carry various substituents at C‐4. 2‐Amino‐4‐chloro‐7‐(2′,3′‐dideoxy‐β‐D‐glycero‐pentofuranosyl)‐7H‐pyrrolo[2,3‐d]‐pyrimidine (3) was used as a common intermediate, and was obtained from the corresponding 2′‐deoxyribonucleoside 4 by selective silylation of 5′‐OH and Barton deoxygenation of 3′‐OH.
Neue Synthesen von 1,3‐Oxazinen, Thiazolen und 1,2‐Dithiolen
Authors: Capuano Lilly , Bolz Gerda , Burger Robert , Burkhardt Volker , Huch Volker
Published: July 2007

New Syntheses of 1,3‐Oxazines, Thiazoles, and 1,2‐Dithioles

The 2‐diazo‐1,3‐diketones 1 react with thioamides 4 via the acyl ketenes 3, resulting from Wolff rearrangement, to give the 1,3‐oxazine‐4‐ones 10; however, by increasing the electro‐philicity of the diazo compounds or the nucleophilicity of the thioamides, the 5‐acylthiazoles 9 are obtained. These are derived from the diketocarbene intermediates 2. The structure of 9g was confirmed by X‐ray diffraction analysis. — The best preparative method for 1,3‐oxazinones consists in the dehydratation of the 2,N‐diacylacetamides 8, which are readily available from the reaction of diazodiketones with carboxamides. — The thionation of 8 or 10 with P4S10 proceeds with spontaneous dehydrogenation, affording high yields of 3‐(thiobenzoylimido)‐1,2‐dithioles 15. The structure of 15a was established by X‐ray diffraction analysis.
Solution synthesis of a biologically active fragment (33–41) of thymosin β9
Authors: Kalbacher Hubert , Jahan Meeno , Mihelić Mirna , Zaman Fakhar , Voelter Wolfgang
Published: July 2007

The C‐terminal fragment 33–41 of thymosin β9 is synthesized by solution synthesis, using the strategy of maximum side‐chain protection with acid‐labile tert‐butyl groups and temporary Nα‐benzyloxycarbonyl protection during the elongation steps. Part of this peptide is deprotected, coupled to KLH and the conjugate used for the production of antibodies. The biological activities of two fragments and of the nonapeptide are tested in our α‐amanitin‐inhibited E‐rosette assay.
Formation of a benzopyrylium ion and a quinoline from benzofuran
Authors: Sonnenschein Helmut , Schmitz Ernst , Pritzkow Wolfgang
Published: July 2007

Chlorophenylcarbene reacts with benzofuran to give the cyclopropane derivative 3, which undergoes thermal opening of the three‐membered ring to give the benzopyrylium cation 5. With aniline, 3 forms the quinoline 11 containing two C atoms of the starting compound 1 in positions 2 and 4.
Reaktionen von Methylthiocyanat mit Dicarbonsäuredichloriden
Authors: Herrmann Dieter , Jungheim Axel , Weikämper Johannes
Published: July 2007

Reactions of Methyl Thiocyanate with Diacyl Dichlorides

Diacyl dichlorides react with methyl thiocyanate in the presence of SbCl5 to give dicationic bis(1,3,5‐oxadiazinium) salts 1. Hydrolysis of 1 yields derivatives of N,N′‐bis[(methyl‐thiocarbonyl)carbamoyl] diamides 2.
Enantiomerically pure Indoloquinolizines from tryptophane
Authors: Peng Shiqi , Winterfeldt Ekkehard
Published: July 2007

Carboline derivatives 8 and 11, obtained from L‐tryptophane methyl ester in a Pictet‐Spengler reaction with the corresponding acetals 6 and 10, add methyl vinyl ketone to form the diastereomeric mixtures 9 and 12. Under phase‐transfer conditions only 12 can be converted into a mixture of the title compounds 2a and 2b. With potassium carbonate as catalyst, however, 2b can be converted into 2c, the enantiomer of 2a.
The stereoselectivity of michael additions leading to enantiomerically pure indoloquinolizidones
Authors: Peng Shiqi , Winterfeldt Ekkehard
Published: July 2007

Acylation of the carboline derivatives 6 and 9 with diketene affords the corresponding N‐(acetoacetyl)carbolines 7 and 10, respectively. While 10 can be converted into a 1:2.1 mixture of the title compounds 11 a and 11 b on treatment with oxalic acid, the cyclic acetal 7 can only be cyclized to yield the pyridone derivative 8. Michael addition of methyl malonate to the unsaturated ketone 11 b proceeds with excellent stereoselectivity to generate the keto diester 12 a which, on treatment with a base is transformed into its diastereoisomer 12 b. In contrast to 11 b, its stereoisomer 11 a does not react with methyl malonate.
The synthesis of 1‐aminoalkylphosphonic acids. A revised mechanism of the reaction of phosphorus trichloride, amides and aldehydes or ketones in acetic acid (Oleksyszyn reaction)
Authors: Soroka Miroslaw
Published: July 2007

The mechanism of the amidoalkylation of trivalent phosphorus compounds in acetic acid has been reinvestigated. Evidence is presented that 1‐(acylamino)alkyl acetates 5 and not N,N′‐alkylidenebisamides 2 are the intermediates in this reaction. Supporting literature analogies are discussed. This paper also describes a convenient procedure for the preparation of crude (acylamino)alkyl alkanoates 5, which are excellent amidoalkylating agents. The usefulness of these reagents is demonstrated by a simple two‐step “one pot” synthesis of 1‐aminoalkylphosphonic acids 1.
Hydroazulene derivatives, II. Enantioselective synthesis of the cyclopentanoid moiety
Authors: Schäfer Hans‐Jürgen , Baringhaus Karl‐Heinz
Published: July 2007

An enantioselective route to functionalized 3‐oxabicyclo‐[3.3.0]octane derivatives which can be used in hydroazulene synthesis is described. The configuration and conformation of the ketone 10 has been determined by 1H‐NMR spectroscopy and force‐field calculations.
Hydroazulene derivatives, III. Enantioselective synthesis of a highly functionalized perhydroazulene
Authors: Schäfer Hans‐Jürgen , Baringhaus Karl‐Heinz
Published: July 2007

A synthesis of the enantiomerically pure perhydroazulene 19 is reported. 19 gives rise to homochiral guaianolides. Lactone 3 serves as starting material and is first converted into the diol 12 by two different consecutive alkylations. Subsequent functional group transformations generate the aldehyde 17, and Lewis acid catalyzed intramolecular cyclization produces 19. Configuration and stereochemistry of 19 have been determined by spectroscopic means in combination with force‐field calculations.
Triterpenoid total synthesis, I. Synthesis of ambrein and Ambrox®
Authors: Mori Kenji , Tamura Hiroshi
Published: July 2007

The first total synthesis of (+)‐ambrein (1), a triterpene alcohol isolated from ambergris, was achieved. Both the enantiomers of ambrox® (2) were also synthesized.
Triterpenoide, 5. Synthese und Strukturaufklärung einiger neuer 18α‐Oleanolsäurederivate
Authors: Zaprutko Lucjusz , Gzella Andrzej , Wrzeciono Urszula
Published: July 2007

Triterpenoids, 5. — Synthesis and Structure Elucidation of Some New 18α‐Oleanolic Acid Derivatives

On treatment with hydrogen bromide, 3β‐acetoxy‐11‐oxoolean‐12‐en‐28‐oic acid methyl ester (1) affords the expected 18α‐diastereomer 2 and the unknown 3‐isopropyl‐11‐oxo‐4‐nor‐18α‐oleana‐3(5),12‐dien‐28‐oic acid methyl ester (3) as product of a Wagner‐Meerwein rearrangement accompanied by the migration of the new introduced exocyclic double bond. Alkaline hydrolysis of 2 gives the known methyl ester 5 together with the new 3β,11‐dihydroxy‐12‐oxooleana‐9(11),13(18)‐dien‐28‐oic acid methyl ester (4). The byproducts 3 and 4 can also be obtained by treatment of 5 with acetic anhydride (3) or KOH/ethanol (4), respectively. The structure elucidation of 3 and 4 is described. The structure of 4 was confirmed by X‐ray analysis.
Enantioselektive Verseifungen substituierter, achiraler 3‐Acyloxy‐propylester mit Lipasen: Herstellung chiraler Derivate von „Tris(hydroxymethyl)methan”︁
Authors: Ehrler Jürg , Seebach Dieter
Published: July 2007

Enantioselective Saponification of Substituted, Achiral 3‐Acyloxy‐propionates with Lipases: Synthesis of Chiral Derivatives of „Tris(hydroxymethyl)methane”︁

Ethyl 3‐hydroxy‐2‐(hydroxymethyl)propionate (11) was synthesized with an overall yield of 40% starting from the pentaerythritol derivative 5,5‐bis(hydroxymethyl)‐1,3‐dioxane (7). Both OH groups of 11 were acylated (ethanoyl‐, propanoyl‐, butanoyl, hexanoyl, and octanoyl derivatives 6a—e), and the formed triesters were partially hydrolyzed by lipases. According to 19F‐NMR analysis of the corresponding Mosher ersters, the monocapronate 12d formed by PPL (porcine pancreas lipase) showed an enantiomeric ratio of 93.5:6.5 (87% ee). Using standard reactions, it was converted into chiral non‐racemic derivatives 16 (O‐benzyl‐O′‐silyl) and 21 (O‐benzyl‐O′‐methoxymethyl) of the C3v‐symmetric title compound. Possible applications of these derivatives are discussed. A “model” for the enantioselectivity of PPL hydrolysis is formulated.
Synthesis of cyclopropanated and branched‐chain pyranosides via carbohydrate triflates
Authors: Fatima Ayjaz , Zaman Fakhar , Shekhani Mohammed Saleh , Malik Abdul , Voelter Wolfgang
Published: July 2007

Approaches to the cyclopropanated pyranosides benzyl 3,4‐(“exo”‐cyano)methano‐3,4‐dideoxy‐β‐(L‐arabinopyranoside (5) and benzyl 3,4‐(“exo”‐cyano)methano‐3,4‐dideoxy‐α‐D‐arabinopyranoside (6) and the branched‐chain epoxy sugars benzyl 2,3‐anhydro‐4‐(tert‐butoxycarbonyl)methyl‐4‐deoxy‐β‐L‐lyxopyranoside (7) and benzyl 2,3‐anhydro‐4‐(tert‐butoxycarbonyl)‐methyl‐4‐deoxy‐α‐D‐lyxopyranoside (8) by displacement of the triflate group with carbanions are described. Preparation of biologically important sugars bearing peptides has been demonstrated by reduction of 5 and 6 to benzyl 3,4‐(“exo”‐aminomethyl)methano‐3,4‐dideoxy‐α‐L‐arabinopyanoside (9) and benzyl 3,4‐(“exo”‐aminomethyl)methano‐3,4‐dideoxy‐α‐D‐arabinopyranoside (10) and the coupling of the resulting amines with protected L‐alanine.
Versuche zur Herstellung von 2,6‐Bis(2‐furyl)‐4‐phenylpyrylium‐tetrafluoroborat
Authors: Reichardt Christian , Milart Piotr
Published: July 2007

Attempts toward the Synthesis of 2,6‐Bis(2‐furyl)‐4‐phenylpyrylium Tetrafluoroborate

An improved synthesis of the 1,5‐diketone 3 is reported. Ring closure of 3 with triphenylcarbenium tetrafluoroborate leads only to a mixture of the pyrylium salts 4 and 5.
Steroids, XLII. Configurational analysis of 3‐methoxy‐16‐methylestra‐1,3,5(10)‐trien‐17‐ol derivatives
Authors: Meskó Eszter , Schneider Gyula , Dombi György , Zeigan Dieter
Published: July 2007

The four possible isomers of 16‐hydroxymethyl‐3‐methoxyestra‐1,3,5(10)‐trien‐17‐ol 5a, 6a, 7a, 8a were converted into the corresponding 16‐methyl analogues 4a, 11a, 12a, 13a, which were characterized from their 1H‐ and 13C‐NMR spectra. The results permit a configurational correlation with 16‐methyl derivatives reported in the literature.
Marine Bakterien, II. Synthese cyclischer und sterisch gehinderter Pseudiline
Authors: Pudleiner Heinz , Laatsch Hartmut
Published: July 2007

Marine Bacteria, II. — Synthesis of Cyclic and Steric Hindered Pseudilines

For structure‐activity studies, various derivatives of pentabromopseudiline (1) were synthesized with distorted (3a) or hetero‐cis‐arranged rings (30c). The pyrrole 30c was accessible by Paal‐Knorr cyclization of the 4‐keto aldehyde 25d, which was obtained in a 5‐step synthesis starting from 18.
Synthesis of 2‐alkyl‐3‐vinyloxaziridines as potential antitumor agents
Authors: Said Samy B. , Młochowski Jacek , Skarżewski Jacek
Published: July 2007

A convenient method for the synthesis of previously unknown oxaziridines having unsaturated substituents at the 3‐position (3a–k) is based on the selective oxidation of the imino group of α,β‐unsaturated aldimines 2 with m‐chloroperbenzoic acid. The title compounds and 2‐tert‐butyl‐3‐(phenylethynyl)oxaziridine (3k) exhibit potent activity against experimental tumor cells in vitro.
Ein 1,5‐Diazabicyclo[3.3.0]octa‐2,7‐dien aus Acetylendicarbonsäure‐dimethylester und einem 3,5‐Dihydro‐4H‐1,2,3‐triazol‐4‐on
Authors: Quast Helmut , Meichsner Georg , Regnat Dieter , Banert Klaus , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg
Published: July 2007

A 1,5‐Diazabicyclo[3.3.0]octa‐2,7‐diene is Formed from Dimethyl Acetylenedicarboxylate and a 3,5‐Dihydro‐4H‐1,2,3‐triazol‐4‐one

The 3,5,5‐trialkyl‐3,5‐dihydro‐4H‐1,2,3‐triazol‐4‐one 1 and dimethyl acetylenedicarboxylate (2) react slowly at 50°C in a 1 : 1 ratio to afford a 40% yield of a deep red crystalline product C18H24N2O8. 1H‐, 13C‐ and 15N‐NMR spectra and an X‐ray diffraction analysis prove the structure 6 for the red product.
Functionally substituted vinyl carbanions, 40. Synthesis of the basic structure of ezomycin A
Authors: Maier Sibylle , Preuss Rainer , Schmidt Richard R.
Published: July 2007

Direct 1‐C‐lithiation of the readily available 2‐phenylsulfinyl‐D‐galactals 3h, 1 leads to reactive intermediates, which on reaction with glyoxal monodiethyl acetal as electrophile yield compounds 7. Subsequent O‐benzylation of the unprotected hydroxy group, removal of the phenylsulfinyl group with Raney nickel, and diastereospecific 3‐hydrogen and 4‐hydroxy transfer provide a convenient entry into functionalized C‐β‐D‐galactopyranosides or 3,7‐anhydrooctoses 11, respectively. Acid‐catalyzed deacetalization and furanose formation with acetic anhydride/pyridine affords 3,7‐anhydrooctofuranoses‐(1,4) 14. The O‐acetylated D‐erythro‐L‐talo isomer (R)‐17 reacts with the cytidine derivative 18, leading to the ezomycin A basic structure 4.
Synthesis of gibberellin A29 β‐D‐glucosides and β‐D‐glucosyl derivatives of [17‐13C,T2]gibberellin A5, A20, and A29
Authors: Schneider Gernot , Schreiber Klaus , Jensen Einar , Phinney Bernard O.
Published: July 2007

2‐O‐GA29β‐D‐glucopyranoside (1e) and 13‐O‐GA29, β‐D‐glucopyr‐anoside (1h) were synthesized from GA29 methyl ester (1b). Their structures were confirmed by 1H NMR and GC‐MS. Likewise, [17‐13C,T2]‐labelled 1e and 1h could be obtained. From [17‐13C,T2]GA20 (2a) and [17‐13C,T2]GA5 (3a) the 13‐O‐GA β‐D‐[6‐D2]glucopyranosides [17‐13C,T2;6′‐D2]‐2d and [17‐13C,T2;6′‐D2]‐3d, and the β‐D‐glucopyranosyl esters [17‐13C,T2;6′‐D2]‐2f and [17‐13C,T2;6′‐D2]‐3f were synthesized. The labelled compounds were characterized by HPLC and GC‐MS.
Synthesis and reactions of biginelli compounds, 3. Unexpected formation of nitriles from reactions of 6‐(dibromomethyl)‐1,2,3,4‐tetrahydro‐2‐oxo‐5‐pyrimidinecarboxylates with sodium azide
Authors: Kappe C. Oliver
Published: July 2007

The action of sodium azide on (dibromomethyl)pyrimidines 2a and 8a leads to the nitriles 3a and 9, whereas the 1‐methyl derivatives 2b and 8b afford the geminal diazides 7 and 10. The nitriles 3a, b add another mole of azide to give the tetrazoles 4a, b. The palladium‐catalyzed decomposition of azide 5, obtained from bromide 6 by treatment with sodium azide, yields nitrile 3a.
Neopentylierung von Phenolen und Hydrochinonen
Authors: Quast Helmut , Schulze Johannes
Published: July 2007

Neopentylation of phenol, the hydroquinones 6 as well as the hydroquinone diacetates 8 by means of neopentyl iodide in diethylene glycol dimethyl ether in the presence of cesium carbonate affords high yields of the neopentyl ethers 2a and 7, respectively. Even sterically hindered hydroquinones and hydroquinone diacetates, e.g. 6e and 8c, d, are smoothly converted to the neopentyl ethers 7c–e.
Photochemische Bildung von Heteromethylencyclopropanen, 20. Diastereomere 3,3,5,5‐Tetraalkyl‐3,5‐dihydro‐4H‐pyrazol‐4‐one
Authors: Quast Helmut , Jakobi Harald , Seiferling Bernhard
Published: July 2007

Photochemical Formation of Heteromethylenecyclopropanes, 201)). – Diastereomeric 3,3,5,5‐Tetraalkyl‐3,5‐dihydro‐4H‐pyrazol‐4‐ones

The dibromo ketones (u/1)‐8b react with sodium azide to afford the α,α′‐diazido ketones (u/1)‐9b, which are reduced to the diastereomeric α,α′‐diamino ketones (u/1)‐11b. The hydrochlorides of the latter are separated through fractionating crystallization yielding pure (1)‐11b · 2 HCl (d.e. >99%) and (u)‐11b · 2 HCl having d.e. of 60%. Oxidation of (u)‐11b and (1)‐11b with sodium hypobromite produces the 4‐pyrazolones cis‐6b (d.e. = 60%) and trans‐6b (d.e. >99%), respectively. The mixture of cis‐and trans‐6b is reduced with sodium tetrahydridoborate to the diastereomeric alcohols cis,cis‐, cis,trans‐, and trans,trans‐5, which exhibit separation factors of α = 1.08 and α = 1.15, respectively, in the HPLC on silica gel. The diastereomeric alcohols are separated on large scale (d.e.'s >99%) by means of cyclic medium‐pressure chromatography (silica gel/ petroleum ether/ethyl acetate). Swern oxidation of cis,cis‐5 and trans,trans‐5 produces high yields of cis‐6b, while cis,trans‐5 affords trans‐6b. Both ketones possess d.e.'s >99%.
2,6‐Epoxy‐3‐benzoxocin‐4‐ol‐Derivate durch zweifache intramolekulare Halbacetalbildung
Authors: Wünsch Bernhard , Bauschke Gerd
Published: July 2007

2,6‐Epoxy‐3‐benzoxocin‐4‐ol Derivatives by Double Intramolecular Formation of Hemiacetals

With dilute HCl the hydroxydialdehyde derivatives 10a‐c are cyclised to give the tricyclic hemiaccetals 6a–c. This double intramolecular formation of hemiacetals succeeds well, if R in 10 is not hydrogen; if R = H an equilibrium betwen 5a and 6a is observed. The 1H‐NMR data of 6 and 17 support the chair conformation of the 1,3‐dioxane ring bearing an equatorial substituent (OH, OAc) in position 4.
Tartraldehydes, 4. Synthesis of D‐ and L‐rhodinose
Authors: Herczegh Pál , Kovács Imre , László Attila , Dinya Zoltán , Sztaricskai Ferenc J.
Published: July 2007

Starting from tartraldehyde derivatives 1 and 2, we prepared the title compounds 6 and 7 via a Wittig‐type chain elongation, protection of the formyl group, simultaneous reduction of the double bond and reductive desulfurization of the dithioacetal function as well as hydrolytic removal of the acetal‐type protective groups.
Konsequenzen einer Einschränkung des Porphyrin‐π‐Systems: Versuche zur Synthese des Bakteriophins und Chlorophins
Authors: Bohusch Michael , Flitsch Wilhelm , Kneip Heinz‐Gerd
Published: July 2007

Consequences of a Diminution of the Porphyrin π‐System: Attempted Syntheses of Bacteriophin and Chlorophin

A report is given on a synthesis of bacteriophin (1) from 2,5‐disubstituted pyrrole derivatives. Spectroscopic properties of 1 resemble those of octaethylbacteriochlorin. Starting from 2,2‐dipyrrylmethane and 2‐(2‐aminoethyl)pyrrole the chlorophin derivative 6 has been obtained.
The mechanism of formation of 3H,9H‐Pyrano[3,4‐b]indol‐3‐ones from 3‐indolalkanoic acids
Authors: Medio‐Simon Mercedes , Erfanian‐Abdoust Houshang , Pindur Ulf
Published: July 2007

The mechanism of the formation of 1‐methyl‐3H,9H‐pyrano[3,4‐b]indol‐3‐one (4) from the corresponding 3‐indolacetic acid 1 is discussed. The suggested mechanism is substantiated by the isolation of a stable intermediate 2 and its transformations in the presence of acetic anhydride and/or Lewis acids.
Totalsynthese von (±)‐Bonellin‐dimethylester
Authors: Montforts Franz‐Peter , Schwartz Ulrich Manfred
Published: July 2007

Total Synthesis of (±)‐Bonellin Dimethyl Ester

Bonellin (1) is the green sex‐differentiating pigment ofBonellia viridis, a marine animal widely distributed in the Mediterranean Sea. Bonellin dimethyl ester (rac‐2), has been synthesized from the four monocyclic building blocks6, 7, 8b, 10and the selectively cleavable malonic ester9by an highly convergent synthetic concept.
Diterpenoid total synthesis, XXIX. Synthesis of (±)‐14‐deoxystypoldione, an analogue of the marine natural product stypoldione
Authors: Mori Kenji , Koga Yasuo
Published: July 2007

(±)‐14‐Deoxystypoldione (2) has been synthesized by starting from geranylacetone. The key step was the construction of the spirobenzofuran moiety by an intramolecular Michael addition (15 → 16). (−)‐Stypoldione is the ichthyotoxic and cytotoxic metabolite of the tropical brown alga Stypopodium zonale (Lamouroux) Papenfuss.
Structural variations of N‐acetylneuraminic acid, 23. Synthesis of 2‐deoxy‐2Heq‐sialic Acid analogues structurally varied at C‐4
Authors: Hartmann Michael , Zbiral Erich
Published: July 2007

2‐Deoxy‐2‐Heq‐N‐acetylneuraminic acid (1a) has been shown to be a versatile mimic for sialosyl 2‐α‐glycosides to study the hemagglutinin‐sialic acid interaction. Starting with a 4‐oxo derivative of 2‐deoxy‐2‐Heq‐sialic acid, we obtained the 4‐C‐methylax and 4‐C‐methyleq derivatives 4 and 5 as a separable mixture. The derivative 4 was formed as a single product by using tributoxymethylzirconium. The 4‐C‐methylene derivative 10 was formed by treatment of the ketone with Cp2ZrCl2/Zn/CH2I2. Catalytic hydrogenation of the exo‐methylene compound 10 yielded the two 4‐deoxy‐4‐C‐methyl diastereomers 13 and 14. All above‐mentioned derivatives could be transformed into the unprotected 4‐branched 2‐deoxy‐2‐Heq‐sialic acids 7, 9, 12, 16, and 18. 2‐Deoxy‐2Heq‐4‐oxosialic acid (21) was synthesized by a different pathway.
Acetogenic isoquinoline alkaloids, XXI. An atropisomer‐differentiating reaction for the chemical analysis of axial chirality and its computational investigation: Proof of the stereostructure of dioncophylline A
Authors: Bringmann Gerhard , Jansen Johannes R. , Busse Holger
Published: July 2007

A chemical method for the unambiguous elucidation of axial chirality in naphthylisoquinoline alkaloids such as dioncophylline A (1a) is described. It involves synthetic connection of the stereogenic axis to be investigated with the stereocenters present in the same molecule. The resulting macrocyclic ansa compound 7c is formed in high yield, yet exclusively for only one of the two atropodiastereomers (4c), the other isomer (4b) does not cyclize at all. This cyclization behavior fully confirms the stereostructure 1a of dioncophylline A, as postulated by us earlier. For an interpretation of the striking atropisomer specificity of this ring closure reaction, computer‐assisted theoretical investigations on the molecular geometries and thus thermodynamical properties of both of the imaginable cyclization products 7b/c have been performed by using force‐field (MM2, MMX) and semiempirical methods (AM1). The optimized structures show the obtained macrocycle 7c to be a nonstrained, stable compound, whereas the other possible product 7b (which definitely is not formed) should be severely distorted.
Preparation of enantiomerically pure pyrazolines by an enantioconvergent process
Authors: Bosum‐Dybus Annegrit , Neh Harribert
Published: July 2007

Derivatization of insecticidally active rac‐pyrazoline 2 with (1S)‐(−)‐camphanic acid chloride led to the separable diastereomers 3a and 3b. Regioselective cleavage to the enantiomerically pure pyrazolines 2a and 2b was achieved under mild conditions. Diastereomer 3b was transformed into diastereomer 3a by crystallization under equilibrating conditions making the overall process enantioconvergent.
Secondary metabolites by chemical screening, 10. Glycerinopyrin, a novel metabolite from Streptomyces violaceus
Authors: Schönewolf Monika , Grabley Susanne , Hütter Klaus , Machinek Reinhard , Wink Joachim , Zeeck Axel , Rohr Jürgen
Published: July 2007

Glycerinopyrin (1) was detected by chemical screening as a new metabolite from Streptomyces violaceus. Its structure was elucidated by chemical and spectroscopical methods as (2S)‐ 2,3‐dihydroxypropyl 1‐hydroxy‐4‐methyl‐2‐pyrrolecarboxylate.
Synthese des Thiophosphatidylcholins und seiner Analogen
Authors: Młotkowska Barbara , Markowska Anna
Published: July 2007

Synthesis of Thiophophatidylcholine and Its Analogues

Synthesis of thiophatidylcholine 5, its phosphonothionate 7 and phosphonate 9 analogues are described. A novel facile rearrangement of 2‐(2,3‐distearoyloxypropylthio)‐1,3,2‐dioxaphospholane (3) into 2‐(2,3‐distearoyloxypropyl)‐1,3,2‐dioxaphospholane 2‐sulfide (6) was observed by 13P‐NMR spectroscopy.
Synthese des Morphan‐Gerüstes aus 4‐Acetamidocyclohexanon
Authors: Teuber Hans‐Joachim , Tsaklakidis Christos
Published: July 2007

Synthesis of the Morphane Skeleton from 4‐Acetamidocyclohexanone

4‐Acetamidocyclohexanone (1) was substituted via the enamine 2 to yield the estermaids 3a and 4. By means of sodium hydride the cis isomer of the acetal 3b could be cyclized to give the 2‐azabicyclo[3.3.1]nonane (morphane) 5.
Studies on isocyanides and related compounds. – Synthesis and cyclization of N‐substituted 1‐isocyano‐1‐cycloalkanecarboxamides
Authors: Bossio Ricardo , Marcaccini Stefano , Paoli Paola , Papaleo Sandro , Pepino Roberto , Polo Cecilia
Published: July 2007

The Ugi four‐component condensation between cycloalkanones, isocyanides, and ammonium formate affords N‐substituted 1‐formylamino‐1‐cycloalkanecarboxamides 1 which are dehydrated to give the corresponding isocyanides 2. Compounds 2 are cyclized with arylsulfenyl thiocyanates to 1,3‐diazaspiro‐2‐thiones 4 and 5. A series of 1,3‐diazaspiro[4,5]dec‐1‐en‐4‐ones 7 is prepared by cyclizing 2c–j with butyllithium. The structures of these compounds are confirmed by means of IR, 1H‐NMR, and X‐ray analysis.
Regioselectivity of the amination of some 3‐nitropyridines by liquid ammonia/potassium permanganate
Authors: Woźniak Marian , Barański Andrzej , Szpakiewicz Barbara
Published: July 2007

3‐Nitropyridine and some of its derivatives are aminated in a liquid ammonia solution of potassium permanganate to the corresponding 2‐ and (or) 4‐ and (or) 6‐amino compounds. Quantumchemical calculations for a few 3‐nitropyridines suggest that the experimentally observed regioselectivity of the amination is controlled by Coulombic interaction.
Gezielte Funktionalisierung des Pimarangerüstes, I. – Oxidationsreaktionen
Authors: John Michael , Rudolph Sabine , Haslinger Ernst
Published: July 2007

Directed Functionalization of the Pimarane Skeleton, I. – Oxidation Reactions

Selective oxidation of dextropimaric acid (2) using different reagents, e.g. H2SeO3, pyridine–SO3, air etc., is described. The structures of the products have been determined by spectroscopic methods. The 1H‐ and 13C‐NMR resonances of all compounds have been assigned.
Chemie und Stereochemie der Iridoide, XVI. EPC‐Synthese von (−)‐Hypnophilin
Authors: Weinges Klaus , Iatridou Helene , Dietz Uwe
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XVI. – EPC‐Synthesis of (−)‐Hypnophilin

The synthesis of enantiomerically pure (−)‐hypnophilin (27) from (6R,7R)‐(−)‐7‐hydroxy‐3‐oxabicyclo[4.3.0]non‐1‐en‐9‐one (1) is described. 1 was obtained in 93% yield from catalpol, which is readily available from the aqueous sodium carbonate extract of Picrorhiza kurrooa (Scrophulariaceae). The specific rotation, MS, 1H‐ and 13C‐NMR data of synthetic (−)‐hypnophilin were identical with those of the natural product.
Stereoelectronically controlled cyclization reactions on the way to peri‐fused tetrahydropyrazolo[1,5‐a]pyridines as aza analogs of ergoline partial structures
Authors: Gmeiner Peter , Sommer Josef
Published: July 2007

The synthesis of the 3‐substitued tetrahydropyrazolopyridin‐4‐ylalkyl iodides 7a, 7b, 8a and 8b as well as their behavior towards anionic cyclization conditions have been investigated. An (enol endo)‐exo‐tet‐type ring closure only proceeds when a seven‐membered ring is annulated (9b, 10b). Otherwise, treatment of the β‐keto ester 7a with NaH results in O‐alkylation to yield the stereoelectronically favored (Z)‐enol ether 13a, which can be isomerized to the thermodynamically more stable (E) isomer 13b. Various attemps to achieve ring closure of the methyl ketone 8a failed; instead, β‐elimination is observed. Annulation of a six‐membered carbocycle is acchieved when the triester 17 is treated by a Dieckmann condensation to give the tricyclic products 18 and 19.
New umbelliferone sesquiterpene ethers from roots of Ligularia persica
Authors: Marco Juan Alberto , Sanz Juan Francisco , Yuste Alberto , Rustaiyan Abdolhossein
Published: July 2007

An extract of roots of Ligularia persica yielded thirteen umbelliferone sesquiterpene ethers, among them the new ones ligupersin A (11) and ligupersin B (13).
Synthese von N‐Acetyl‐D‐ und ‐L‐glucosamin, cis‐3,5‐Cyclohexadien‐1,2‐diol als Baustein für die Gewinnung modifizierter Hexosen
Authors: Lehmann Jochen , Moritz Andreas
Published: July 2007

Synthesis of N‐Acetyl‐D‐ and ‐L‐glucosamine, cis‐3,5‐Cyclohexadiene‐1,2‐diol as Building Block for the Preparation of Modified Hexoses

Six‐membered, unsaturated carbocycles are versatile starting materials for the preparation of a large variety of modified hexoses. This is exemplified by the synthesis of N‐acetylglucosamine 12 as a racemate from cis‐3,5‐cyclohexadiene‐1,2‐diol (1), which can be obtained by microbial oxidation of benzene. In this special case D‐ and L‐N‐acetylglucosamine could be differentiated by enzymatic D‐galactosylation of the former.
Darstellung und Untersuchung eines neuen Diacetylens mit Nitroxylradikal‐Endgruppen
Authors: Dulog Lothar , Lutz Sabine
Published: July 2007

Synthesis and Characterization of a New Diacetylene with Terminal Nitroxyl Radical Groups

The new diacetylene 4 was prepared from 4‐isocyanato‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (2) and 2,4‐hexadiyne‐1,6‐diol (3). The diacetylene 4 could not be polymerized by irradiation or thermal treatment, but decomposition and loss of paramagnetic properties was observed. A new synthesis of isocyanate 2 is also described.
Synthesis of bicyclic imidazole, 1,2,4‐triazole and 1,3,5‐triazine derivatives from N‐cyanolactam 2‐imines
Authors: Pätzel Michael , Bohrisch Jörg , Liebscher Jürgen
Published: July 2007

N‐Cyanolactam 2‐imines 1 are versatile NCNC building blocks for the synthesis of partially saturated bicyclic compounds. Reactions with acidic methyl halides, hydroxylamine O‐sulfonic acid, and phenyl isocyanate afford bicyclic imidazole (4), 1,2,4‐triazole (6), and 1,3,5‐triazine (8) derivatives, respectively.
Mehrstufige Redoxsysteme, LVII. Quartärsalze pyridinsubstituierter 1,3,5‐Triazine – eine neue Klasse zwei‐ bis vierstufiger, reversibler Redoxsysteme
Authors: Gries Willi‐Kurt , Günther Erhard , Hünig Siegfried
Published: July 2007

Multi‐Step Redox Systems, LVII. – Quaternary Salts of Pyridyl‐Substituted 1,3,5‐Triazines – A New Class of Two‐ to Four‐Step Reversible Redox Systems

The synthesis of 1,3,5‐triazines 3–5a–e substituted by one to three 4‐pyridinium rings [N‐substituents Me, Et, Benzyl, CH2C(O)NMe2, CH2CO2C(O)OEt] is described. According to voltammetric data 3–5 constitute a new type of redox systems with reversible electron transfer in two to four separate steps. Reduction by zinc or sodium amalgam in acetonitrile produces coloured stable solutions of radicals (SEM).
Asymmetric synthesis of bicyclic amino acid derivatives by Aza‐Diels‐Alder reactions in aqueous solution
Authors: Waldmann Herbert , Braun Matthias
Published: July 2007

Derivatives 7–10 and 13–16 of methyl and ethyl 2‐azabicyclo[2.2.1]heptane‐3‐carboxylates are synthesized by Aza‐Diels‐Alder reactions of chiral iminium ions, formed in situ from glyoxylic acid and chiral amines, with cyclopentadiene. Whereas the heterodienophiles derived from phenylglycinol and esters of sterically more demanding amino acids fail to undergo asymmetric cycloadditions, with alanine methyl ester and (R)‐1‐phenylethylamine hydrochoride the cycloadducts are formed in yields of 15 and 52%, respectively, reaching de values of up to 90:10 for the exo isomers.
Synthesis of polymerizable xylitol derivatives
Authors: Koßmehl Gerhard , Volkheimer Jürgen
Published: July 2007

Polymerizable esters of methacrylic acid, acrylic acid and crotonic acid with di‐O‐isopropylidenexylitol as the alcohol component have been synthesized and characterized.
Synthese von disubstituierten Cyclopropa[c]pyranosiden aus 2,3‐Epoxy‐4‐triflat‐pyranosiden
Authors: Zaman Fakhar , Fatima Ayjaz , Voelter Wolfgang
Published: July 2007

Synthesis of Disubstituted Cyclopropa[c]pyranosides from 2,3‐Epoxy‐4‐triflate‐pyranosides

Reaction of benzyl 2,3‐anhydro‐4‐O‐trifluoromethylsulfonyl‐β‐L‐ribopyranoside (1) and benzyl 2,3‐anhydro‐4‐O‐trifluoromethylsulfonyl‐α‐D‐ribopyranoside (4) with malonic acid derivatives yields, via the carbanions, the cyclopropa‐monosaccharides 3 and 6. The ester residues attached to the cyclopropane moiety can be saponified to give the corresponding acids which can be coupled to new carbohydrate amino acid derivatives of type 9 which are of biological interest in different immunological assays.
Photochemische Studien, 61. Photoisomerisierung von Digitoxin in kristallinem Zustand
Authors: Ekiz‐Gücer Nurten , Reisch Johannes
Published: July 2007

Photochemical Studies 61. – Photoisomerization of Digitoxin in Crystalline State

UV irradiation of digitoxin (1) in the crystalline state yields as major photoisomerization product 3β‐[O‐β‐D‐digitoxopyranosyl‐(1→4)‐O‐β‐D‐digitoxopyranosyl‐(1→4)‐O‐β‐D‐digitoxopyranosyloxy]‐14,20ξ‐epoxy‐5β‐cardanolide (2).
Chemie und Stereochemie der Iridoide, XVII. Palladium‐katalysierte Substitution an Hexaacetylaucubin
Authors: Weinges Klaus , Ziegler Hans Jürgen
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XVII. – Palladium‐Catalysed Substitution of Hexaacetylacubin

Acetoxy groups, in allylic position, can be replaced by nucleophiles in a palladium‐catalysed reaction. The reaction of hexaacetylaucubin (2) with piperidine or benzylamine regioselectively gives the crystalline, N‐containing iridoidglucosides 3 and 4. With the anion of diemethyl malonate, 5 was obtained along with the byproduct 7. Adding triethylammonium formate as a hydride donor, then the reaction gives 6; a reaction mechanism is discussed.
Produkte des reduktiven Abbaus von α‐(Acyloxy)plasmalogenen aus Rindergewebe‐Lipiden mit LiAlH4
Authors: Lutz Arnulf , Knörr Walter , Spiteller Gerhard
Published: July 2007

Products of Reductive Degradation of α‐(Acyloxy)plasmalogens from Bovine Tissue Lipids

If bovine tissue lipids are treated with LiAlH4, two types of unexpected products are detectable: 1‐Acetylglycerols (homologs of compound 2) and α‐hydroxylated glycerol acetals (homologs of compounds 7 and 8). This fact was assumed to indicate the presence of α‐(acyloxy)plasmalogens 1, an up to now unknown class of mammalian tissue lipids. To confirm this assumption, the model compound 6 possessing an enol ether‐enol acetate structure was synthesized and teated with LiAlH4. Corresponding derivatives of 1‐acylglycerols 2 as well as α‐hydroxylated glycerol acetals 7 and 8 were produced, thus confirming the existence of α‐(acyloxy) plasmalogens 1 in tissue of natural origin. They are detectable by GC and GC/MS after conversion of free hydroxy groups with diazomethane/silica gel into the corresponding methyl ether derivatives.