bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bacterial Constituents, XXXVII. Pyoverdin‐Type Siderophores from Pseudomonas aeruginosa
Authors: Briskot Gernot , Taraz Kambiz , Budzikiewicz Herbert 
Published: July 2007

AbstractThe structures of pyoverdin C, D, and E isolated from the culture medium of Pseudomonas aeruginosa (which are identical with the pyoverdins PaB, PaA, and Pa6–8)) have been elucidated by spectroscopic methods and degradation studies. The pyoverdins consist of a chromophore which could be identified as (1S)‐5‐amino‐2,3‐dihydro‐8,9‐dihydroxy‐1H‐pyrimido[1,2‐a]quinoline‐1‐carboxylic acid substituted at the amino group with a 4‐carboxy‐4‐oxobutanoyl (C), a 3‐carboxypropanoyl (D) or a succinamoyl residue (E) and at the carboxy group with the N‐terminus of D‐Ser‐L‐Arg‐D‐Ser‐L‐Orn(N5‐OH‐N5‐CHO)‐L‐Lys‐L‐Orn(N5‐OH‐N5‐CHO)‐L‐Thr‐L‐Thr]. In an appendix a tentative nomenclature for pyoverdin‐type compounds is proposed.
Intramolekulare Cycloadditionen mit Isobenzofuranen, V. Synthese von rac‐Thiamarmelerin, einem Thiophenanalogon eines natürlich vorkommenden Furanosesquiterpens
Authors: Schöning Axel , Friedrichsen Willy 
Published: July 2007

Intramolecular Cycloaddition Reactions with Isobenzofurans, V1). ‐ Synthesis of rac‐Thiamarmelerin, a Thiophene Analogue of a Naturally Occurring Furanosesquiterpenerac‐Thiamarmelerin (7b) is prepared by an intramolecular Diels‐Alder reaction of a thieno[2,3‐c]furan.
3,6‐Epoxyalkansäuren (Tetrahydrofuran‐2‐essigsäuren) ‐ neue Bestandteile des Humanplasmas
Authors: Scheinkönig Josef , Puchta Volker , Spiteller Gerhard 
Published: July 2007

AbstractHumanplasma enthält die cis,trans‐isomeren 3,6‐Epoxyalkansäuren (2,5‐substituierte Tetrahydrofuranmonocarbonsäuren) 2a–i. Diese bisher unbekannte Naturstoffklasse liegt im Humanplasma hauptsächlich als freie Säuren vor.
Makrocyclen aus Alanin und Phenoxathiin, Synthese und Konformation in Lösung
Authors: Feigel Martin 
Published: July 2007

AbstractDie Synthese von dimeren und monomeren Cyclopeptiden 2 bzw. 3 aus Alanin und der Pseudoaminosäure 6‐(Aminomethyl)‐2,8‐dimethyl‐4‐phenoxathiinessigsäure‐10,10‐dioxid (1) wird beschrieben. Phthalimid‐ oder Boc‐geschützte Derivate von 1 erhält man in vier bzw. fünf Stufen ausgehend von 2,8‐Dimethylphenoxathiin. Lineare Zwischenstufen aus 1 und Alanin werden durch Standardpeptidreaktionen gebildet; Azid‐Cyclisierung führt in geringer Ausbeute dann zu den Cyclen 2 und 3, deren Konformation durch ein‐ und zweidimensionale NMR‐Methoden bestimmt wird. Die Verbindung 3 ist in Lösung ein Gemisch zweier Konformerer, die jeweils eine cis‐ und eine trans‐Amidbindung im Ring enthalten. 2 liegt in Dimethylsulfoxid in einer gestreckten Konformation vor, jedoch sind permanente, intramolekulare Wasserstoffbrücken nicht nachzuweisen. Zusätzlich werden in Chloroform bei tiefen Temperaturen Konformationsgleichgewichte beobachtet.
Synthese und Reaktionen des 6,11‐Dihydro‐5H‐pyrido[3,2‐c]‐[1] benzazepin‐5‐ons
Authors: Firl Joachim , Maier Walter , Daake Heinz 
Published: July 2007

AbstractWir berichten über eine dreistufige Synthese für das neue 6,11‐Dihydro‐5H‐pyrido[3,2‐c][1]benzazepin‐5‐on (6a) und dessen Derivate 6b–d. Das reaktive Verhalten des Tricyclus wird durch Darstellung der Derivate 7–15 aus der Stammverbindung 6a umrissen. Die Produkte werden durch 1H‐ und 13C‐NMR‐Daten charakterisiert.
Pyridazines, XLIV. Novel Heteroaromatic Analogues of o‐Aminobenzophenones ‐ Preparation and Cyclization to Diazaacridone Derivatives
Authors: Grabenwöger Monika , Haider Norbert , Heinisch Gottfried 
Published: July 2007

AbstractA variety of 2‐(alkylamino)phenyl 4‐pyridazinyl ketones (3a–e) was prepared. The novel compounds were found to cyclize with remarkable regioselectivity upon treatment either with acetic anhydride or aqueous sodium hydroxide, giving 5‐alkylpyridazino‐[4,5‐b]quinolin‐10(5H)‐ones (5a–e).
Neue heterocyclische Phane aus 2,3‐Bis(5‐tetrazolyl)pyrazinen und α,ω‐Dibromalkanen
Authors: Ried Walter , Lee Chiu‐Huei , Bats Jan W. 
Published: July 2007

New Heterocyclic Phanes from 2,3‐Bis(5‐tetrazolyl)pyrazines and α,ω‐DibromoalkanesThe symmetric or asymmetric 2,3‐bis(5‐tetrazolyl)pyrazines 2a–f react with α,ω‐dibromoalkanes in the presence of triethylamine to give the new heterocyclic phanes 3–4, the constitutions of which were confirmed by spectroscopical data and elementary analyses. The structure of 3f3 was determined by X‐ray analysis.
Azole, 26. Stellvertretende nucleophile Substitution von Wasserstoff in Nitropyrazolderivaten
Authors: Bernard Marek K. , Szafran Barbara , Wrzeciono Urszula , Mąkosza Mieczyslaw 
Published: July 2007

Abstract4‐Nitropyrazolderivate 1a–1c und 1g–1j reagieren mit dem Carbanion von Chlormethyl‐p‐tolylsulfon (2) unter stellvertretender nucleophiler Substitution von Wasserstoff in Position 5. Die Anwesenheit einer zweiten Nitrogruppe in Stellung 3 (1c) oder 2′ (1h) setzt die Ausbeute der Reaktion bedeutend herab. Aus 1d und 1e wurden keine Substitutionsprodukte erhalten. Bei 1f erfolgt die Substitution in Position 4. Bei der Einwirkung von 2 auf 1h und 1j entstehen die Nebenprodukte 3h1 und 4/4a bzw. 3j1, 3j2 und 5.
Reductive Transformations of Polyfunctional Nitro Compounds: Synthesis of Methyl 7‐Aminoalkanoates and Five‐Membered Cyclic Nitrones ‐ Inter‐ and Intramolecular 1,3‐Dipolar Cycloadditions
Authors: Zschiesche Ruth , Reißig Hans‐Ulrich 
Published: July 2007

AbstractUsing ammonium formate and Pd/C, acetals 1 and 3 are converted into the amines 2 and 4, respectively, whereas unprotected nitro ketones as 5, 7, 9, and 11 furnish five‐membered nitrones in good yields. With these nitrones 1,3‐dipolar cycloadditions to acrylonitrile and trimethyl(vinyl)silane are described. The regio‐chemistry of these reactions, giving mixtures of 5‐substituted and 4‐substituted isoxazolidines in most cases, can be explained by the frontier‐orbital model. One example of an intramolecular nitrone cycloaddition (27 → 28) demonstrates the potential of this approach for construction of polycyclic compounds.
A New Synthesis of (‐)‐Biopterin Employing 5‐Deoxy‐L‐ribose as a Key Intermediate
Authors: Mori Kenji , Kikuchi Haruhiko 
Published: July 2007

Abstract(‐)‐Biopterin (1) was synthesized from 5‐deoxy‐L‐ribose (6) which was derived from commercially available D‐ribose (2) employing the highly stereoselective Grignard reaction of 2,3‐O‐cyclohexylidene‐D‐ribose (3) with methylmagnesium iodide.
Ein α‐Methylanthrachinon aus Streptomyceten
Authors: Krupa Johann , Lessmann Holger , Lackner Helmut 
Published: July 2007

An α‐Methylanthraquinone from StreptomycetesFrom cultures of several streptomycete strains producing isochromanquinone antibiotics (4, 5), 3,8‐dihydroxy‐1‐methylanthraquinone‐2‐carboxylic acid (2b), one of the rare naturally occurring α‐methylanthraquinones, was isolated. Native compounds of this group became known only as insect pigments (e.g. 1d) and later on as constituents of a few plants. A common biosynthesis of benzoisochromanquinones and α‐methylanthraquinones is discussed.
Die Synthese des Octacidomycins
Authors: Kerber Karl‐Heinz , Lackner Helmut 
Published: July 2007

AbstractDie Totalsynthese von Octacidomycin (1), einem neuartigen Oligocarbonsäure‐Antibioticum, und einigen kürzerkettigen, neuen Modellcarbonsäuren (19, 21, 24) wird beschrieben. Schlüsselverbindungen in einer Folge von Fragmentkondensationen von C19‐, C5‐ und C2‐Einheiten (Abb. 1) sind α,α′‐bis(brompentyl)substituierte Azelainsäure‐ (6) und 3‐(Benzyloxypropyl)malonsäureester (7). In einer sechsstufigen Synthese entsteht bakteriostatisch voll aktives Octacidomycin (14 = 1). 14 und dessen Octamethylester 15 sind mit den nativen Produkten chemisch und spektroskopisch identisch. Weitere Kombinationen von Fragmenten liefern Tri‐, Tetra‐ und Pentacarbonsäuren. Sie zeigen die Flexibilität dieses weiträumig variierbaren, zu neuen Carbonsäuren und Kohlenwasserstoffen führenden Syntheseweges.
Synthese des Sesquiterpens (±)‐Lemnal‐5a‐en‐2‐on
Authors: Dischmann Michael , Ernst Ludger , Wolf Herbert 
Published: July 2007

AbstractSchlüsselreaktion für die Synthese von Lemnal‐5a‐en‐2‐on [(±)‐1] ist die SnCl4‐katalysierte stereoselektive Cyclisierung der Carbonsäure 4 zum Tricyclus 5. Als Modellverbindung wurde die Carbonsäure 2 zu 3 cyclisiert. 2 wie 4 wurden aus dem leicht zugänglichen Enolether 13 dargestellt über reduktive Spaltung des Allylethers 17 und nachfolgende Oxidation von 19 zu 2 bzw. durch Oxidation des Homoallylethers 23 zu 4. Aus dem Cyclisierungsprodukt 5 wurde in drei Schritten (±)‐1 erhalten. – Die 1H‐ und 13C‐NMR‐Spektren von 1, 3 und 5 wurden mit zweidimensionalen Techniken (H,H‐ und C,H‐COSY) zugeordnet. Die Stereochemie von 5 ergab sich aus NOE‐Differenz‐Spektren.
Photoaddition of 2‐Pyridones and 2‐Quinolones to Conjugated Dienes
Authors: Sato Eisuke , Ikeda Yoshiya , Kanaoka Yuichi 
Published: July 2007

AbstractIrradiation of 2‐pyridones 1 in the presence of excess cyclic conjugated dienes 2 gave [4 + 4] cycloaddition products. Some of the photoproducts were thermally unstable and underwent rearrangement at room temperature to give [2 + 2] adducts. Irradiation of 2‐pyridones and 2‐quinolones with noncyclic conjugated dienes afforded [2 + 2] cycloaddition products and 2‐substituted derivatives, the latter being derived probably from an oxetane intermediate.
Studies on Amino Acids and Peptides, 13 Improved Synthesis of 5‐Thioxo‐L‐proline and of Some N‐Acyl and S‐Alkyl Derivatives as Building Blocks in Peptide Synthesis
Authors: Larsen Claus , Kragh Henrik , Rasmussen Preben B. , Andersen Torben P. , Senning Alexander 
Published: July 2007

AbstractWe herein report an improved synthetic pathway to 5‐thioxo‐L‐proline (2) (using R,S nomenclature, the L form here possesses the S configuration). Compound 2 is synthesized from naturally occurring 5‐oxo‐L‐proline (1) at room temperature with 2,4‐bis(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane 2,4‐disulfide (3) (Lawesson′s reagent, LR). The synthesis is an improved version of our previously published method. The optical purity of 2 has been proven by thin‐layer chromatography based on chiral ligand exchange. The synthesis of N‐acyl and S‐alkyl derivatives of 5‐thioxo‐L‐proline (Top‐OH), 5‐thioxo‐L‐proline methyl ester (Top‐OCH3), and the pseudodipeptide Boc‐L‐Phe‐Top‐OCH3 is also described.
Assignment of All Proton, Carbon, and Nitrogen NMR Signals of Antamanide in Chloroform Solution
Authors: Kessler Horst , Müller Arndt , Pook Karl‐Heinz 
Published: July 2007

AbstractHomo‐ and heteronuclear one‐ and two‐dimensional techniques have been used to assign the 1H, 13C, and 15N NMR spectra of the cyclic decapeptide antamanide (1) in CDCl3. The assignment includes the aromatic resonances of phenylalanine and the non‐protonated nitrogen atoms of proline by means of heteronuclear two‐dimensional NMR spectroscopy. Sequence analysis of the four phenylalanine and four proline amino acid residues was performed by heteronuclear proton – carbon long‐range couplings using the COLOC sequence. Three new thiazolidine analogues of antamanide confirm the sequence analysis of prolines and open the possibility for the extraction of extended spectral parameters. The interpretation of NOE data, obtained from one‐ and two‐dimensional spectra at high field and low temperatures, demonstrate possible misinterpretations of this effect respecting sequence assignment, if only NOEs between NH protons and α‐protons are considered.
Studies on Cinnamonitriles: The Reaction of Cinnamonitriles with Cyclopentanone
Authors: Sofan Mamdouh A. , El‐Taweel Fathy M. , Elagamey Abdel Ghani A. , Elnagdi Mohamed H. 
Published: July 2007

AbstractCyclopentanone reacts with arylidenemalononitriles 1a–c to give dihydro‐4,6‐indenedicarbonitriles 5a–c. Similarly, the diethyl dihydro‐4,6‐indenedicarboxylate derivative 6 is formed when treating ethyl α‐cyanocinnamate (1d) with cyclopentanone. Cyclopenta[b]pyrans 5a–c are obtained from the reaction of diarylidene derivatives of cyclopentanone with malononitrile.
Palladiumacetat‐vermittelte Cyclisierung von di‐ und tri‐funktionellen Triarylaminen, Diarylethern und Diarylketonen
Authors: Hellwinkel Dieter , Kistenmacher Thomas 
Published: July 2007

AbstractTriphenylamin und seine 4,(4′,4″)‐substituierten Nitro‐ bzw. Ester‐und Methylderivate lassen sich mit Pd(OAc)2 in Eisessig zu den entsprechenden Carbazolderivaten 4a–d cyclodehydrieren. Weitergehende Cyclisierungen werden hier nicht beobachtet. Mehrfache Cyclisierungen dieser Art lassen sich jedoch bei Verbindungen vom Typ des 1,4‐Diphenoxybenzols (6a), 1,4‐Dibenzoylbenzols (6b) und 2,8‐Diphenoxydibenzofurans (10) realisieren, wobei in sehr einfacher Weise die Benzobisbenzofurane 8a, 9a sowie Indeno[3,2‐b]fluoren‐6,12‐dion (8b), 11H‐Fluoreno[3,2‐b]benzofuran‐11‐on (8c) und Bisbenzofuro[3,2‐a: 3′,2′‐i]dibenzofuran (12) zugänglich werden.
Preparative Bioorganic Chemistry, XI Preparation of the Enantiomers of Paraconic Acid Employing Lipase‐Mediated Asymmetric Hydrolysis of Prochiral Diacetates as the Key Step
Authors: Mori Kenji , Chiba Naoki 
Published: July 2007

Abstract(S)‐(‐)‐Paraconic acid (1) was prepared from 2‐(acetoxymethyl)‐3‐phenylpropyl acetate (4) by its asymmetric hydrolysis with pig pancreatic lipase as the key step. Similarly, (R)‐(+)‐1 was prepared from 2‐(acetoxymethyl)‐4‐pentenyl acetate (2) by its asymmetric hydrolysis with lipase MY.
Structure of Two Oxidation Products of β‐Lumicolchicine: A Remarkable Reaction with Active Manganese Dioxide
Authors: Buddrus Joachim , Defoin Albert , Krüger Carl , Tsay Yi‐Hung , Kuhn Hans Jochen 
Published: July 2007

AbstractTwo unusual reaction types of MnO2 and of m‐chloroperbenzoic acid with the tetrasubstituted CC bond of β‐lumicolchicine (1‐β) are presented. Active MnO2 oxidizes the 7a,10b cyclobutene double bond by adding a hydroxy group to the position 10b while the acetamido side chain is used to close a 2‐oxazoline ring in position 7a (2). m‐Chloroperoxybenzoic acid splits the cyclobutene ring of 1‐β and forms a ketonic 1:1 adduct (3) instead of an epoxide. X‐ray structure analysis of 2 reveals intermolecular interaction between the hydroxy groups and the nitrogen atoms. 2D‐INADEQUATE 13C‐NMR spectroscopy establishes structure 2 in solution, proves the structure of 3, and allows also to assign the 13C‐NMR signals of the tetracyclic skeleton of the stereoisomeric lumicolchicines 1‐β and 1‐γ. Furthermore, 13C,13C coupling constants were determined for 2 and 3.
Konformation von Anthranilsäurepeptiden, 2 Anthranilsäure‐Glycin‐Sequenzen als Bauteil „schalenförmiger”︁ Cyclopeptide
Authors: Feigel Martin , Lugert Gerhard 
Published: July 2007

AbstractDie vierstufige Synthese der Cyclopeptide 1 und 2 aus N‐(tert‐Butoxycarbonyl)(Boc)anthranilsäure und Glycin‐methylester‐hydrochlorid wird beschrieben. Die Ringverbindungen werden durch ein‐ und zweidimensionale NMR‐Methoden auf Vorzugskonformationen untersucht. Aus den Temperaturgradienten der chemischen Verschiebung der Amidprotonen und den NOE‐Ergebnissen lassen sich Hinweise auf intramolekulare Wasserstoffbrücken ableiten, die in 2 mit einem schalenförmigen, peptidischen Makrocyclus vereinbar sind. Für beide beschriebenen Peptide 1 und 2 wird jedoch eine in der NMR‐Zeitskala schnelle Ringinversion beobachtet. Kraftfeldmethoden (MMP2/H) und quantenmechanische Rechnungen (AM 1) dienen zur Unterstützung der Konformationsvorschläge.
Regioselective Synthesis of 2‐and 3‐Aryl‐1,4‐benzodioxanes
Authors: Antus Sándor , Gottsegen ágnes , Baitz‐Gács Eszter , Bauer Rudolf , Seligmann Otto , Wagner Hildebert 
Published: July 2007

Abstract3‐Aryl‐ and 2‐aryl‐1,4‐benzodioxane derivatives of type 4d and 5d are excellent starting compounds for the synthesis of natural flavano‐ and neolignans. The syntheses of 4d and 5d were achieved with high regioselectivity by oxidative coupling of caffeic acid ethyl ester (2h) and coniferyl alcohol (1c) in the presence of a silver salt (oxide, carbonate) and potassium hexacyanoferrate(III), respectively.
Synthesis of fluorinated α‐amino ketones, III. Preparation of fluorinated ketone analogues of phenylalanine, lysine, and p‐(Guanidino)phenylalanine
Authors: Kolb Michael , Neises Bernhard , Gerhart Fritz 
Published: July 2007

AbstractThe synthesis of α‐amino mono‐, di‐, and trifluoromethyl and difluoromethylene ketones and their derivatives is described. A one‐pot sequence related to the Dakin‐West reaction starts from amino acids and gives the corresponding fluorinated ketone analogues in good yields. The compounds are of interest as potential inhibitors of serine proteases.
Über Pyridinium‐N‐phenolat‐Betaine und ihre Verwendung zur Charakterisierung der Polarität von Lösungsmitteln, XIII. Erweiterung der empirischen Polaritätsskala ET(30) um 44 organische Lösungsmittel
Authors: Reichardt Christian , Eschner Michael , Schäfer Gerhard 
Published: July 2007

Pyridinium N‐Phenoxide Betaines and Their Application for the Characterization of Solvent Polarities, XIII. — Extension of the ET(30) Polarity Scale by 44 Organic SolventsEmpirical solvent polarity parameters ET(30), determined by means of the negatively solvatochromic betaine dye 1, are given for 44 organic solvents of current interest (Table 1).
A revision of the generally accepted pathway for the biosynthesis of the benzyltetrahydroisoquinoline alkaloid reticuline
Authors: Stadler Richard , Zenk Meinhart H. 
Published: July 2007

AbstractThe label from (S)‐[1‐13C]norcoclaurine and (S)‐[1‐13C]co‐claurine was highly and nonrandomly incorporated into (S)‐reticuline in benzyltetrahydroisoquinoline‐producing plant cell cultures of Berberis stolonifera, Eschscholtzia californica and Peumus boldus. From the intermediates observed in vivo we conclude that (S)‐norcoclaurine is stereoselectively metabolized to (S)‐reticuline via (S)‐coclaurine, (S)‐N‐methylcoclaurine and (S)‐3′‐hydroxy‐N‐methylcoclaurine. These results confirm a revised pathway to the benzylisoquinoline alkaloids.
Structural variations on N‐acetylneuraminic acid, 16. A convenient approach to 3‐deoxy‐D‐glycero‐D‐galacto‐nonulosonic acid (KDN), 5‐azido‐5‐deoxy‐KDN and 5‐deoxy‐KDN, and their 4‐methylumbelliferyl 2α‐glycosides
Authors: Schreiner Erwin , Zbiral Erich 
Published: July 2007

AbstractThe reaction of peracetylated N‐acetylneuraminic acid methyl ester 1 with nitrosyl acetate affords a mixture of anti/syn‐N‐nitroso derivatives 2a and 2a′, which can be transformed with sodium trifluoroethanolate into the 5‐diazo compound 3. The reaction of 3 with tetrabutylammonium acetate/acetic acid yields methyl 2,4,5,7,8,9‐hexa‐O‐acetyl‐3‐deoxy‐D‐clycero‐β‐D‐galacto‐2‐nonulopyranosidonate (KDN) (4a). On the other hand, 5‐azido‐5‐deoxy‐KDN (5a) is formed by treating 3 with hydrazoic acid in toluene. Heating of 2a/2a′ in toluene furnishes a mixture of the peracetylated deaminated furanoid sialic acid derivative 10 with probably changed configuration at C‐5 and C‐6 and the deaminated 5,6‐ and 4,5‐didehydrosialic acid derivatives 6 and 7. Catalytic hydrogenation of 6 and 7 yields the 5‐deoxy‐KDN derivative 9a and ‐ after hydrogen‐olysis of the 4‐acetoxy group ‐ a minor amount of compound 8. The compounds 4a, 5a, and 9a have been converted into the free deaminated sialic acids 4e, 5e, and 9e via the 4‐me‐thylumbelliferyl 2α‐glycosides 4c, d, 5c, d, and 9c, d.
Glycosidation, 15. — Anticancer agents, 11. Development of selective anticancer agents synthesis of acetal‐β‐glucosides from cytotoxic alcohols
Authors: Tietze Lutz F. , Beller Matthias 
Published: July 2007

AbstractThe reaction of trimethylsilyl 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranoside 7 with hexanal and the trimethylsilyl ethers 9a–c of cytotoxic alcohols 4a–c in the presence of catalytic amounts of TMS triflate yields the acetal‐β‐glucosides 10a–c. In a similar way, the acetal‐α‐glucosides 12a, b are obtained from 8, hexanal, and 9a, b. In addition, the highly acid‐sensitive acetal‐β‐glucoside 13 is synthesized from 7, acetone, and 9a. Deacetylation of 10a, 10b, and 13 by solvolysis affords the deprotected acetal‐β‐glucosides 11a, 11b, and 14, respectively, which will be tested as selective anticancer agents.
Tetrahydrofurane und γ‐Lactone, III. γ‐Lactone mit funktionalisierten γ‐ständigen Seitenketten aus Cyclooctin nnd Furan
Authors: Scholz Gerhard , Konusch Joachim , Tochtermann Werner 
Published: July 2007

Tetrahydrofurans and γ‐Lactones, III. — γ‐Lactones with Functionalized γ‐Side Chains from Cyclooctyne and FuranThe oxanorbornadiene 1, easily available from cyclooctyne and furan, is converted in three simple steps (hydrogenation, ozonolysis, and oxidation by air) to the γ‐substituted γ‐lactone 4a with a carbonyl and a carboxyl group in the side chain. The corresponding methyl ester 4b gives by diastereoselective reduction the esters (±)‐syn‐ and anti‐5, which are fully characterized as pure crystalline compounds. Reduction of 4a with borane and subsequent oxidation with pyridinium chlorochromate leads to the aldehyde 4d via hydroxylated derivatives.
2,3‐Dihydro‐1H‐pyrrolizine aus Prolin und 3‐Alkoxyacroleinen
Authors: Walizei Gul Hassan , Breitmaier Eberhard 
Published: July 2007

2,3‐Dihydro‐1H‐pyrrolizines from Proline and 3‐Alkoxyacroleins6‐Alkyl‐2,3‐dihydro‐1H‐pyrrolizines 5 have been obtained in moderate yields in a one‐pot synthesis from substituted 3‐alkoxyacroleins 2 and proline methyl ester (1) in the presence of sodium methoxide as base.
Zur Chemie der 1,2,4‐Triazine, XIV. Synthese und Reaktionen von 5‐Chlor‐1,2,4‐triazinen
Authors: Neunhoeffer Hans , Reichel Diethard , Cullmann Birgit , Rehn Ingrid 
Published: July 2007

The Chemistry of 1,2,4‐Triazines, XIV. — Synthesis and Reactions of 5‐Chloro‐1,2,4‐triazines5‐Chloro‐1,2,4‐triazines 4 are prepared from 1,2,4‐triazin‐5(2H)‐ones 3 and transfered into 5‐amino‐ (7), 5‐cyano (8), and 5‐(ω‐alkinyloxy)‐1,2,4‐triazines (9). 7a–d are cyclized to imidazo[4,5‐e]1,2,4‐triazines (10a–d).
Aminosäureester als chirale Hilfsgruppen in Lewis‐Säure‐katalysierten Diels‐Alder‐Reaktionen
Authors: Waldmann Herbert 
Published: July 2007

Amino Acid Esters as Chiral Auxiliaries in Lewis Acid Catalyzed Diels‐Alder ReactionsCyclopentadiene, cyclohexadiene and alkyl‐substituted butadienes react with N‐acryloyl‐, N‐crotonoyl‐ and N‐(4‐nitro‐cinnamoyl)‐(S)‐proline benzyl and allyl ester in the presence of Lewis acids to give the cycloadducts in high yields and with stereoselectivities of up to 97:3 for the endo isomers. The sense of the asymmetric induction in these reactions can be directed by the use of differently coordinating catalysts (e.g. TiCl4: (2R):(2S) = 96:4; EtAlCl2: (2R):(2S) = 10:90 at 0°C). In the TiCl4‐catalyzed reactions with the fumaric acid derivatives the ratio of the diastereomers reaches values of up to 112:1 in the presence of 0.5–1 equivalent of the Lewis acid, thus indicating an efficient cooperation between the chiral auxiliaries. Higher catalyst/substrate ratios induce a reversal in the sense of the asymmetric induction. From the cycloadducts the chiral auxiliaries are removed by hydrogenolysis and subsequent hydrolysis of the proline amides. Alternatively, the cleavage of the amide bonds can be carried out by O‐alkylation with oxonium salts and subsequent hydrolysis of the iminium salts formed or by the application of an iodolactonization reaction.