bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel diaza‐crown ether and cryptands from glucopyranose and their complex‐forming properties
Authors: Bakó Péter , Fenichel László , Tőke László 
Published: July 2007

AbstractChiral diaza‐crown ether 6 and cryptands of type [2.2.2] (9), containing one glucopyranoside unit, have been prepared. Two methods are described for the synthesis of 9. The new cryptand 12 containing two glucopyranoside units has also been prepared. The association constants (Ka) of these compounds with Li, Na, K and NH4 cations have been measured.
Festphasensynthese von O‐Glycopeptiden
Authors: Paulsen Hans , Merz Gunnar , Peters Stefan , Weichert Udo 
Published: July 2007

Solid Phase Synthesis of O‐GlycopeptidesThe 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

AbstractThe 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

AbstractThe 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

AbstractInverse‐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 dioicaLignan 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‐BrevicominThe 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

AbstractE‐ 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‐HexosaminidaseUsing 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

AbstractAcetylated 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

AbstractA 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

AbstractStimulation 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

AbstractThe 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

AbstractHydroxylation, 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 SynthesisThe 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 BenzenehexamineCondensation 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

AbstractA 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‐DithiolesThe 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

AbstractThe 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

AbstractChlorophenylcarbene 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 DichloridesDiacyl 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

AbstractCarboline 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

AbstractAcylation 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

AbstractThe 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

AbstractAn 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

AbstractA 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.
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 DerivativesOn 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

AbstractApproaches 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 TetrafluoroborateAn 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.