bluuebunny/crossref_metadata_2025_split huggingface dataset:
Konformation und Bromierung von Bicyclo[3.3.1]nonan‐2,6‐dion sowie Dehydrobromierung der Bromketone. – Verbesserte Synthese von Bicyclo[3.3.1]nona‐3,7‐dien‐2,6‐dion
Authors: Quast Helmut , Becker Christian , Geißler Evelyn , Knoll Katja , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg 
Published: July 2007

Conformation and Bromination of Bicyclo[3.3.1]nonane‐2,6‐dione and Dehydrobromination of the Bromo Ketones. – Improved Synthesis of Bicyclo[3.3.1]nona‐3,7‐diene‐2,6‐dioneBromination by copper(II) bromide of bicyclo[3.3.1]nonane‐2,6‐dione (1) affords the epimeric α‐bromo diketones exo‐and endo‐5 and, eventually, the α, α′‐dibromo diketones exo‐ and endo‐7 (3:7) in high yield. Dehydrobromination of the mixtures of bromo diketones by calcium carbonate in dimethylacetamide yields the unsaturated diketones 6 (30%) and 2 (72%), respectively. Bromination of 1 by molecular bromine is less selective and furnishes mixtures of brominated diketones consisting of exo‐ and endo‐7, 8 and the tetrabromo diketone 10. An excess of bromine yields pure 10. – The ethylene acetal 12 is brominated by pyridinium perbromide to produce the α,α′‐dibromo acetal 13 which is very reluctant towards 1,2‐dehydrobromination by potassium tert‐butoxide. Thus, with an excess of potassium tert‐butoxide in tetrahydrofuran, 1,2‐dehydrobromination is achieved only on one side to afford 14. In contrast, potassium tert‐butoxide in dimethyl sulphoxide induces a transannular dehydrobromination leading to the diacetal 15 of 3‐bromonoradamantane‐2,6‐dione. – The conformations of 1,10, and 13 in the solid state are determined by X‐ray diffraction analyses. From torsional angles, vicinal proton coupling constants are calculated with the aid of the Karplus equation and compared to those determined from solutions by high‐field NMR spectroscopy. The reasonable agreement provides the basis for the assessment of the configuration and conformation for exo‐ and endo‐7. magnified image
Regioselective aectylations of sialic acid α‐ketosides
Authors: Reinhard Bernd , Faillard Hans 
Published: July 2007

AbstractVarious partially acetylated sialic acid α‐ketosides were obtained without expensive protecting group techniques by using trimethyl orthoacetate or dimethylacetamide dimethyl acetal as acetylating agents or by performing a partial Zemplén de‐O‐acetylation. Using trimethyl orthoacetate as acetylating agents we synthesized 9‐O‐acetylated, 8‐O‐acetylated, and 8,9‐di‐O‐acetylated sialic acid α‐ketoside benzyl ester derivatives. The acetylation with dimethylacetamide dimethyl acetal yielded 9‐O‐acetylated, 8‐O‐acetylated, 4, 9‐di‐O‐acetylated, 8,9‐di‐O‐acetylated, and 4,8,9‐tri‐O‐acetylated sialic acid α‐ketoside benzyl ester derivatives. The partial Zemplén de‐O‐acetylation permitted the synthesis of 7,8,9‐tri‐O‐acetylated sialic acid α‐ketoside benzyl ester derivatives. After catalytic hydrogenation the 8‐O‐acetylated derivatives 2e and 3d were not stable and were completely converted into the 9‐O‐acetylated sialic acid α‐thioketoside 2k. The N‐acetyl‐8,9‐di‐O‐acetylneuraminic acid α‐aminophenylthioketoside 21 showed a migration of the acetyl group from position 8 to position 7 in polar solvents, yielding a mixture of the 8,9‐di‐O‐ and the 7, 9‐di‐O‐acetylated derivatives 21 and 2m in a molar ratio of approximately 1:1. The 7, 9‐di‐O‐acetylated derivative 2m could be separated and was completely stable in methanol. Using the isopropylidene protecting group we could also prepare the 4‐O‐acetylated sialic acid α‐thioketoside 2o. Treatment of the 9‐O‐acetylated derivative 2k with fluorescein isothiocyanate gave the fluorescent derivative 5. magnified image
Synthesis of 4‐nitro‐1‐(trialkylsilylalkyl)imidazoles
Authors: Földeák Sándor , Molnár Mária , Lǒkös Magdalena 
Published: July 2007

Abstract1‐(2‐Hydroxyethyl)‐2‐methyl‐5‐nitroimidazole (1) reacts with haloalkyltrialkylsilanes [Hal(CH2)nSiMe2R] to give 4‐nitroimidazole derivatives 3 and acetaldehyde. This process involves at least two reaction steps, N‐alkyl quaternization and elimination of the hydroxyethyl group. magnified image
Organofluorine compounds and fluorinating agents, 10. Unusual regio‐ and stereoselective 3,4‐acetalizations of selected pyranosides by hexafluoroacetone as a result of a new reaction pathway
Authors: Miethchen Ralf , Rentsch Daniel , Michalik Manfred 
Published: July 2007

AbstractRegio‐ and stereoselective direct acetalizations of chiral vicinal polyols with hexafluoroacetone (HFA) are described. Thus, the reaction of methyl α‐D‐mannopyranoside (1) and methyl a‐L‐rhamnopyranoside (5) with HFA affords cyclic 3, 4‐Acetals accompanied by simultaneous inversion of configuration at C‐3 when N, N′‐dicyclohexylcarbodiimide (DCC) is added as a coreagent. Methyl 2‐O‐(cyclohexylcarbamoyl)‐3, 4‐O‐(hexafluoroisopropylidene)‐a‐D‐altropyranoside (2) and methyl 6‐deoxy‐3, 4‐O‐(hexafluoroisopropylidene)‐a‐L‐altropyranoside (6), respectively, have been found to be the major products. The carbamoyl groups found in 2 and moreover in the byproduct 7 may be cleaved by methanolysis giving the Acetals 3 and 6, respectively. All of the products, 2, 3, 6, and 7 adopt a boat conformation as confirmed by NMR data and, additionally, ensured by X‐ray analysis in the case of 7. The incorrect structural formula for compound 6, reported as “methyl 2, 3‐O‐(hexafluoroisopropylidene)‐ct‐L‐rhamnopyranoside” in ref. [2], has to be corrected. The direct Acetalization described in this paper probably includes an intramolecular nucleophilic attack of a hemiacetal oxygen (4‐position) on C‐3 with substitution of an isourea function. magnified image
Unexpected triphenylphosphane‐promoted conversion of 2‐azido‐3‐vinyl‐l, 4‐naphthoquinones into 2‐amino‐3‐acyl‐l, 4‐naphthoquinones
Authors: Molina Pedro , Tárraga Alberto , Baño Maria Jose Del , Espinosa Arturo 
Published: July 2007

AbstractAn unusual behavior of several 2‐azido‐3‐vinyl‐l, 4‐naphtho‐quinones 1 towards triphenylphosphane leading both to azido group reduction and unsaturated carbon‐carbon side chain oxidation is described. magnified image
Lithium‐selektive Chromoionophore vom Arylazobutenoat‐Typ
Authors: Kirschke Klaus , Baumann Hendrik , Costisella Burkhard , Ramm Matthias 
Published: July 2007

Lithium‐Selective Chromoionophores of Arylazobutenoate TypeNew lithium‐selective chromoionophoric compounds with arylazobutenoic acid structure have been synthesized from dichlorodihydropyrazole 2. The (E,E) isomers of esters of the arylazobutenoic acid (3a, 4, 5) exhibit a remarkable color change in the presence of lithium ions and triethylamine from orange to purple. magnified image
Pheromone synthesis, CLX. A new synthesis of the oviposition‐deterring pheromone of the European cherry fruit fly Rhagoletis cerasi L.
Authors: Mori Kenji , Qian Zhao‐Hui 
Published: July 2007

AbstractA new synthesis of the ammonium salt 1c of (8RS,15R)‐N‐[(β‐D‐glucopyranosyloxy)‐8‐hydroxypalmitoyl]taurine, the oviposition‐deterring pheromone of the European cherry fruit fly Rhagoletis cerasi L., was achieved by starting from 2,3,4,6‐tetra‐O‐pivaloyl‐α‐D‐glucopyranosyl bromide (2), taurine (4), ethyl (R)‐3‐hydroxybutanoate (5), propargyl alcohol (6), methyl acetoacetate (7), and 1,6‐hexanediol (8). magnified image
Naturstoffchemie, 180. Synthese von Acronycinepoxid
Authors: Reisch Johannes , Schiwek Katrin 
Published: July 2007

Natural Product Chemistry, 180. – Synthesis of Acronycine EpoxideTreatment of acronycine (1) with dimethyldioxirane in the presence of potassium carbonate resulted in acronycine epoxide (2), 1,2‐dihydro‐1,2‐dihydroxyacronycine and 5‐hydroxyacronycine (3). magnified image
Glycosyl Phosphites as Glycosyl Donors – A Comparative Study
Authors: Müller Thomas , Hummel Gerd , Schmidt Richard R. 
Published: July 2007

AbstractTri‐O‐benzyl‐L‐fucose (3) was transformed into the bis(trichloroethyl) phosphite derivative 4 which was allowed to react with 3‐O‐unprotected azidoglucose 7 as fucosyl acceptor in the presence of TMSOTf as catalyst to furnish disaccharide building block 1, useful in Lewis antigen X (LeX) synthesis, in 75% yield. Similarly, 2,3,4,6‐tetra‐O‐acetyl‐D‐galactose (8) was transformed into the bis(trichloroethyl) phosphite derivative 9 which afforded by treatment with acceptor 7 disaccharide 10 in 64% yield. The reaction of the derived acceptor 11 with donor 4 furnished trisaccharide building block 12, useful in Lewis antigen A (Lea) synthesis, in 88% yield. Transformation into the less reactive donor 14 and reaction with lactose acceptor 15 gave pentasaccharide 2 only in modest yield, thus exhibiting the scope and limitations of phosphite leaving groups in glycosylation reactions. magnified image
Synthesis of Garugamblin‐2, a Macrocyclic Diarylheptanoid Constituent of Garuga gamblei
Authors: Keserü György M. , Nógrádi Mihály , Kajtár‐Peredy Mária 
Published: July 2007

AbstractThe macrocyclic diarylheptanoid garugamblin‐2 (1) and its constitutional and sterical isomers 17–19 were synthesized using the isoxazole derivative 8 for the introduction of the β‐methoxyenone function. Ring closure was accomplished by an intramolecular Wittig reaction. magnified image
Anwendung des Azid‐Glycopeptidsynthese‐ Verfahrens in der multiplen Festphasensynthese zur Gewinnung von O‐Glycopeptiden des Mucin‐Typs
Authors: Paulsen Hans , Bielfeldt Tim , Peters Stefan , Meldal Morten , Bock Klaus 
Published: July 2007

Application of the Azido Glycopeptide Synthesis Strategy for the Multiple Column Solid Phase Synthesis of Mucin O‐GlycopeptidesFollowing the strategy via azido glycopeptides the 34 O‐glycopeptides 4, 7–23 and 27–42 were synthesized in a multiple column solid phase peptide synthesis. 4, 7–23 and 27–42 are part of the repeating unit of a human intestinal mucin. The amino acids Pro and Thr in the +1 and ‐1 positions relative to the glycosylation site in 4 were exchanged by all usual amino acids. Furthermore the penta‐glycosylated octapeptide 47 was synthesized containing five vicinal 2‐acetamido‐2‐deoxy‐D‐galactosyl residues each α‐linked to Thr. magnified image
Synthese von DD‐Heptosephosphaten als Substrate oder potentielle Inhibitoren für die Heptose‐Synthetase
Authors: Paulsen Hans , Pries Meike , Lorentzen Jens Peter 
Published: July 2007

Synthesis of DD‐Heptose Phosphates as Substrates or Potential Inhibitors for the Heptose SynthetaseA synthesis of D‐glycero‐D‐manno‐heptose (DD‐Hep) via an inversion of L‐glycero‐D‐manno‐heptose (LD‐Hep) is described. Starting from DD‐Hep the α‐1‐phosphate 3 and the α‐1‐methylphosphonate 30 were synthesized. Furthermore, the α‐1‐dialkyldithiophosphate esters from DD‐Hep were prepared. The 2,3,4,6, 7‐penta‐O‐benzyl‐D‐glycero‐α‐D‐ manno‐heptosyl trichloroacetimidate (22) turned out to be a very successful glycosyl donor in the reaction with the phosphate esters. The amidophosphates 41 and 42 of DD‐Hep have been synthesized according to the Staudinger reaction using glycosyl azides of DD‐Hep and tribenzyl or tributyl phosphite. The modified phosphates represent potential inhibitors for the heptose synthetase, an enzyme of the biosynthesis of the inner core region of lipopolysaccharides. Reaction of the phosphate 3 with AMP morpholidate afforded ADP‐DD‐Hep 4 which represents the product of the heptose synthetase enzyme reaction. magnified image
Synthesis of N‐Acetylneuraminic Acid Derivatives and Structural Analogues
Authors: Bodenmüller Arthur , Schmidt Richard R. 
Published: July 2007

AbstractThe cis‐selective Wittig reaction of D‐lyxo‐pentodialdose derivative 2 with C4 building block 3 in the presence of NaN(TMS)2 as a base furnished C9 species 4 which was transformed into ring‐opened derivative 7; diastereoselective epoxidation of the CC double bond with MCPBA afforded the required epoxide 8. Regioselective epoxide opening via trichloroacetimino derivative 9 and cleavage of the derived oxazoline 10 led to 5‐trichloroacetylamido‐substituted compound 11 having from C‐4 to C‐9 the functions and stereochemistry found for neuraminic acid. Regioselective oxidation of the 2‐hydroxy group of 1,2,4,6‐tetra‐O‐unprotected 11 with (Bu3Sn)2O/Br2 afforded directly 2‐nonulose derivative 13 which adopts the pyranose form. Compound 13 could be readily transformed into the known methyl 5‐acetylamido‐3,5‐dideoxy‐D‐glycero‐D‐galacto‐2‐nonulopyranoside (19). Regioselective Cbz protection of the 1‐hydroxy group of 13 and then treatment with MeOH/HCl furnished methyl pyranoside 22. Per‐O‐acetylation and subsequent hydrogenation liberated the primary hydroxy group at C‐1, thus providing after oxidation and esterification of the carboxylic acid moiety N‐dichloroacetylneuraminic acid derivative 25. Treatment with Bu3SnH/AIBN afforded O‐acyl protected Neu5Ac derivative 26. The structure of 26 was confirmed by an independent synthesis from Neu5Ac. magnified image
Preparation of the N‐Acetylglucosaminidase Inhibitor 1‐Acetamido‐1,2,5‐trideoxy‐2,5‐imino‐D‐glucitol from Methyl α‐D‐Mannopyranoside
Authors: Schumacher‐Wandersleb Michael H. M. G. , Petersen Stefan , Peter Martin G. 
Published: July 2007

AbstractFragmentation of methyl 3‐O‐benzyl‐6‐bromo‐2‐O‐(tert‐butyldimethylsilyl)‐6‐deoxy‐4‐O‐(4‐methoxybenzyl)‐α‐D‐mannopyranoside (2) and in situ reductive amination give (3R,4S,5R)‐6‐benzylamino‐4‐benzyloxy‐5‐(tert‐butyldimethylsilyloxy)‐3‐(4‐methoxybenzyloxy)hexene (3) which is converted by intramolecular aminomercuration into an epimeric mixture of the bromomercuriopiperidine derivatives 4 and 5. The minor D‐manno epimer 4 is transformed into mesylate 10 which, upon reaction with LiN3 in DMF, suffers a piperidine‐pyrrolidine ring contraction to give azidomethylpyrrolidine 11. Reductive acetylation by means of thioacetic acid affords the fully protected pyrrolidine aza sugar derivative 12. The major L‐gulo epimer 5 is transformed into the mesylate 15 which, again, upon reaction with LiN3 in DMF undergoes piperidine‐pyrrolidine ring contraction to give the 1‐azido‐3‐O‐benzyl‐2,5‐benzylimino‐6‐bromomercurio‐1,2,5,6‐tetradeoxy‐4‐O‐(4‐methoxybenzyl)‐L‐iditol (16). Eliminative dehalomercuration by means of Zn powder is accompanied by in situ reduction of the azido group to give amino alkene 17. Intramolecular aminomercuration of 17 followed by N‐acetylation yields the protected 1,2,5,6‐tetradeoxy‐2,5‐imino‐D‐glucitol derivative 20 as the major epimer. Reductive oxygenation of 20 leads to pyrrolidine 22 which is deprotected to give title compound 1. Selective cleavage of the PMB group of 22 leads to 24. Benzylation of 22 affords again 12 from which the OH group at C‐4 is liberated by selective cleavage of the PMB ether to give pyrrolidine 13. Compound 1 inhibits NAGase from bovine kidney. magnified image
Conformation of Deoxy Oligosaccharides: Solution Conformation and Flexibility of the Antibiotic Kijanimicin Studied by NMR Spectroscopy and MMC Calculations
Authors: Köpper Sabine 
Published: July 2007

AbstractThe solution conformation of the macrolide antibiotic kijanimicin (1) was deduced by a combination of NMR spectroscopy and potential energy calculations of the carbohydrate parts using the HSEA force field. The study was based on temperature dependent NMR spectroscopic shift data, 1D nuclear Overhauser enhancements (NOE) of selected protons and 2D rotating frame NOE of the complete antibiotic. NOEs in the oligosaccharide part of the antibiotic indicated some unusual short distances between the α‐linked digitoxose residues A and B, as well as between not directly linked residues A and C. Calculation of preferred conformations revealed a global minimum with ΦA,B/ΨA,B ≈ 70°/50°, ΦB,C/ΨB,C ≈ 60°/30°, and ΦB,D/ΨB,D ≈ −60°/5° for the oligosaccharide moiety. MMC simulations of the conformational flexibility indicated a high rigidity of the carbohydrate. The range of the glycosidic angles covered during MMC simulations was 50°–70° for the α‐linkages of the oligosaccharide. The ß‐glycosidic linkages of residue D and E showed slightly more flexibility, covering a range of 120° – 270°. Minimum energy calculations of the oligosaccharide part revealed a second minimum with different orientation of sugar residues A‐B and an energy difference of 2 kcal/mol to the global minimum. This energy difference increased to 12 kcal/mol when the complete antibiotic was calculated and MMC simulations did not show any transitions between the two minima. The experimental NOE in the oligosaccharide moiety and the enhancements between carbohydrate and lactone part agree well with theoretical NOEs that were obtained by sampling the global minimum in MMC simulations. The conformation of the macrolide moiety was evaluated by comparing experimental NOEs with the crystal structure of the isolated aglycon. The conformation found in solution is slightly altered around the sites of attachment of the carbohydrate parts. Constancy of the proton chemical shifts over a temperature range of 70°C indicated the high degree of rigidity of the carbohydrate moiety and most of the macrolide structure. Flexibility was observed for the C‐13/C‐20 part of the lactone ring. The antibiotic has a fairly unpolar surface and adopts a well defined and quite rigid conformation. magnified image
Chirale Lactole, XII. Untersuchungen zur basenkatalysierten Glycolaldehydaldolisierung
Authors: Noe Christian R. , Knollmüller Max , Ettmayer Peter , Freissmuth Jerome 
Published: July 2007

Chiral Lactols, XII. – Studies on the Aldolization of Glycolaldehyde Catalyzed by BasesBase‐catalyzed aldolization of the glycolaldehyde derivative 1 is studied under various reaction conditions. The resulting products, tetrose and hexose derivatives 2–11, are reduced to the corresponding sugar alcohols and analyzed by HPL chromatography. All experiments leading to a trimerization of 1 give threose 3 as major product among the tetroses and allose 4 among the hexoses. An exception is the reaction catalyzed by LiOH, in which trimerization of 1 to the corresponding hexose derivatives proceeds much slower and as products galactose 10 together with glucose 6 are favored above the other hexoses. magnified image
Synthesis and Transformation of 3‐Coumarinyl Methyl Ketone (Thio)Acylhydrazones and 5‐Substituted 3‐Acetyl‐2‐(3‐coumarinyl)‐2‐methyl‐1,3,4‐oxadiazolines under Acetylating Conditions
Authors: Somogyi László 
Published: July 2007

AbstractThe synthesis of 3‐acetylcoumarin (thio)acylhydrazones 1a–e and their transformation to 5‐substituted 3‐acetyl‐2‐(3‐coumarinyl)‐2‐methyl‐1,3,4‐oxa(thia)diazolines 2a–f (cyclic isomers of the alternatively accessible diacylhydrazones, e.g. 1f–h) under acetylating conditions are described. Treatment of the acetylation products 2c–f with the acetylating agent Ac2O/ZnCl2 resulted in the unexpected formation of acylhydrazones 1c, d, i with cleavage of the oxadiazoline ring and simultaneous loss of the acetyl group. magnified image
Reaction of Benzoyl(thioacetanilides) with α,β‐Unsaturated Nitriles; Synthesis of Functionalyzed Pyridines and Thiazoles
Authors: Bogdanowicz‐Szwed Krystyna , Ciechanowicz‐Rutkowska Maria , Czarny Agnieszka , Filippini Giuseppe , Pilati Tulio , Rys Barbara 
Published: July 2007

AbstractThe synthesis of spirofused 2‐thioxopyridines 3 from benzoyl(thioacetanilides) 1 and cyclohexylidenemalononitrile (2) is described. Cyclopentylidene‐ and cycloheptylidenemalononitrile do not react with 1. Heating of 1 in the presence of piperidine yields thiazoles 4. The structure of 4a has been established by an X‐ray analysis. magnified image
Stereoselective Synthesis of Steroids and Related Compounds, IV. Addition of Cerium Reagents Derived from (Trimethylsilyl)propargyl Bromide to Aldehydes
Authors: Eckenberg Peter , Groth Ulrich , Köhler Thomas 
Published: July 2007

AbstractThe addition of (trimethylsilyl)propargylmagnesium bromide (9) to aldehydes afforded predominantly the allenylic alcohols rac‐10. The regioselectivity of this addition changes dramatically when organocerium reagents were used for the addition. In this case nearly exclusive formation of the homopropargylic alcohols rac‐8 was observed. Highest selectivity for this process was obtained when cerium(III) isopropoxide (13) was used as a precursor for the formation of the organocerium reagent. magnified image
Total Synthesis of Myxovirescins, 3 Coupling of the Two Key Fragments and Last Steps to Myxovirescins A1 and M2
Authors: Maestro Miguel A. , Sefkow Michael , Seebach Dieter 
Published: July 2007

AbstractThe last steps of a chiral building‐block approach to the synthesis of myxovirescins A1, A2 and M2 are described. The “northwestern” parts, hydroxy sulfones (see preceding paper), and the “southeastern” parts, hydroxy aldehyde derivatives (first paper in this series), of the target molecules (Scheme 1) are first coupled by a Julia olefination (60–70% yield); the resulting linear intermediates are oxidized (CH2OH → CO2H) and deprotected for the final Yamaguchi macrolactonization (85–90% yield, Scheme 2). Deprotection by hydrolysis of three different acetal moieties and chromatographic purification gave 20‐mg amounts of synthetic myxovirescins M2 and A1 (Scheme 3) which were identical in all respects with authentic samples isolated and supplied to us by the team at the Gesellschaft für Biotechnologische Forschung in Braunschweig. – The total syntheses of the macrocyclic antibiotics consist of 62 and 66 steps, and the longest linear sequence of 25 steps was carried out in an overall yield of 2.5 and 0.85% (over 85 and 80% each step), respectively. magnified image
Iridoids from Verbascum nigrum
Authors: Vesper Thorsten , Seifert Karlheinz 
Published: July 2007

AbstractIn addition to the known 6‐O‐{3‐O‐[(E)‐p‐coumaroyl]‐α‐L‐rhamnopyranosyl}aucubin (2) three novel acyl iridoid diglycosides 3–5 have been isolated from the aerial parts of Verbascum nigrum. On the basis of their spectral data the structures of these iridoids have been elucidated as 6‐O‐{2‐O‐[(E)‐p‐coumaroyl]‐α‐L‐rhamnopyranosyl}aucubin (3, nigroside III), 6‐O‐{3‐O‐[(E)‐isoferuloyl]‐α‐L‐rhamnopyranosyl‐} aucubin (4, nigroside IV) and 6‐O‐{2‐O‐[(E)‐isoferuloyl]‐α‐L‐rhamnopyranosyl}aucubin (5, nigroside V). magnified image
Antibiotics from Gliding Bacteria, LIX. Disorazoles, Highly Cytotoxic Metabolites from the Sorangicin‐Producing Bacterium Sorangium Cellulosum, Strain So ce12
Authors: Jansen Rolf , Irschik Herbert , Reichenbach Hans , Wray Victor , Höfle Gerhard 
Published: July 2007

AbstractTwenty‐nine disorazoles A–H (1–29) were isolated by solvent partitions and chromatographic separations from Sorangium cellulosum, strain So ce12, the producer of the sorangicin antibiotics. The disorazoles proved to be highly cytotoxic and active against fungi. The structures of the main component disorazole A1 (1) and 28 variants were elucidated by 2D‐NMR and mass spectroscopy. The disorazoles are macrocyclic dilactones of two 2‐pentadecyloxazol‐4‐carboxylic acids, which are modified in their carbon chain by variation of the position and configuration of double bonds and oxygen substituents like epoxide, hydroxyl, or methyl ether groups. In addition to these, three disorazoles are ring‐enlarged by lactonization to a more distant hydroxyl group. By feeding of 13C‐enriched precursors the biosynthetic origin of the carbons in disorazole A (1) was investigated. C‐2 of the oxazole and the attached pentadecyl chain arise from acetate. The geminal methyl groups and the methoxyl group are derived from the methyl group of methionine. magnified image
Synthesis of Sugar‐Amino Acid Conjugates via 2,3‐Dideoxy‐hex‐2‐enopyranos‐4‐uloses
Authors: Apostolopoulos Costas D. , Couladouros Elias A. , Georgiadis Minas P. 
Published: July 2007

AbstractMichael addition of amino acids to 5‐substituted 2,3‐dideoxy‐hex‐2‐enopyranos‐4‐uloses 1a–c afforded stereoselectively several sugar‐amino acid conjugates in good yield. magnified image