bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthese von Pakyonol, einem macrocyclischen Bis(bibenzylether) aus Mannia fragrans
Authors: Nógrádi Mihály , Vermes Borbála , Kajtár‐Peredy Mária , Novikov V. P. 
Published: July 2007

Synthesis of Pakyonol, a Macrocyclic Bis(bibenzyl ether) from Mannia fragransThe unambigous synthesis of pakyonol (1), a bis(bibenzyl ether) with a 20‐membered ring by Ullmann, Wittig, and modified Wurtz reaction is reported.
Diastereoselectivity in the halolactonization of 2‐alkoxy‐4‐alkenoic acids and‐4‐alkenamides
Authors: Maier Martin E. , Kandler Helmut , Haller Bernd U. , Hofmann Josef H. , Fischer Helmut 
Published: July 2007

AbstractIodolactonization of 2‐alkoxy‐ and 2‐hydroxy‐4‐alkenoic acids 3a–d under kinetic control gives mixtures of cis‐ and trans‐lactones 6a–d and 7a–d with cis‐selectivity up to 5.5:1.0. The bromolactonization of carboxamides 4 a, 4 c, and 5 c shows moderate 1,3‐asymmetric induction, favoring the trans‐lactones 9 with a selectivity of up to 2.5:1.0.
Synthesis of a new azapeptide with renin‐inhibiting properties
Authors: Gante Joachim , Weitzel Reinhard 
Published: July 2007

AbstractBoc‐hydrazine (1) was treated with 4‐nitrophenyl chloroformate (2) to give Boc‐Azagly 4‐nitrophenyl ester (3). Reaction of 3 with H‐ACHP‐Ile‐3‐pyridylmethylamide5) (4) provided Boc‐Azagly‐ACHP‐Ile‐3‐pyridylmethylamide (5). This was deprotected with HCl/dioxane to give H‐Azagly‐ACHP‐Ile‐3‐pyridylmethylamide dihydrochloride (6), which was coupled with Boc‐Phe‐OH (7) by the carbodiimide/HOBt method providing the final azapeptide Boc‐Phe‐Azagly‐ACHP‐3‐pyridyl‐methylamide (8). This compound was shown to be a renin inhibitor of high specificity.
Synthesis and structure of some thiazole derivatives
Authors: Badawy Mohamed A. , Abdel‐Hady Sayed A. , Ibrahim Yehia A. 
Published: July 2007

AbstractThe addition of thiosemicarbazones 1 to α‐halo acids 2 is shown to give 2‐hydrazino‐2‐thiazolin‐4‐ones 3 and not 3‐substituted 2‐imino‐3‐(methyleneimino)thiazolidin‐4‐ones 4. The independent synthesis of 2‐thiazolin‐4‐one derivatives 3 is also described.
Studien zur Synthese helicaler Naphthochinon‐Oligomerer, I. 2,2′;3′,2″‐Ter‐ und 2,2′;3′,2″;3″,2‴‐Quater(1,4‐naphthochinon)
Authors: Laatsch Hartmut 
Published: July 2007

Studies in the Synthesis of Helical Naphthoquinone Oligomers, I. — 2,2′;3′,2″‐Ter‐ and 2,2′;3′,2′;3′,2‴‐Quater(1,4‐naphthoquinone)2,2′;3′,2′‐Ter(1,4‐naphthoquinone) (6a) and 2,2′;3′,2″;3″,2‴‐quater(1,4‐naphthoquinone) (8a) are obtained by cooxidation of the phenolic precursors 16a and 2b. It is shown, that partially reduced 6a cyclizes under basic conditions yielding triphthaloylbenzene (7); therefore, it is also a possible intermediate of the synthesis of 7 by phenol/quinone addition of 2a to 1a. Spectroscopic data suggest that the tetrameric hydroquinonylquinone 8b is stabilized by hydrogen bonding, forming a helical quinhydron structure.
3a‐Azaazulenone mit einer Carbonylgruppe im Fünfring
Authors: Flitsch Wilhelm , Hohenhorst Manfred 
Published: July 2007

3a‐Azaazulenones with a Carbonyl Group in the 5‐Membered RingSyntheses and properties of unstable 3a‐aza‐3‐azulenones 1 are described. Attempts of a synthesis of 3a‐aza‐1‐azulenones 2 resulted in a formation of rearranged pyridones 10 and a dimer 11 indicating the unstable intermediates 2.
Reaktionen der Trialkylsilyl‐trifluormethansulfonate, X. N‐(Trifluoracetyl)‐α,β‐didehydro‐α‐aminosäureester durch Trimethylsilanol‐Eliminierung aus 2‐[(Trifluoracetyl)amino]‐3‐(trimethylsiloxy)carbonsäureestern
Authors: Seethaler Toni , Simchen Gerhard 
Published: July 2007

Reactions of Trialkylsilyl Trifluoromethanesulfonates, X. – N‐(Trifluoroacetyl)‐α,β‐didehydro‐α‐amino Carboxylic Acid Esters from 2‐(Trifluoroacetyl)amino]‐3‐(trimethylsiloxy)carboxylic Acid Esters by Elimination of Trimethylsilanolα‐Amino‐β‐(trimethylsiloxy)carboxylates 4 are obtained by trimethylsiloxy alkylation of the ketene acetal 1 with aldehydes 2 in the presence of trimethylsilyl triflate (3). β‐Elimination of trimethylsilanol from the esters 4 by means of trifluoroacetic acid anhydride (8) or methanesulfonic acid anhydride (15) yields (Z)‐didehydro amino acid esters 7. The course of the elimination reaction is studied.
Struktur und Geruch, XIII. Synthese und olfaktorische Eigenschaften von Megastigmatrienon‐Analoga
Authors: Weyerstahl Peter , Meisel Thomas , Mewes Klaus , Negahdari Shoreh 
Published: July 2007

Structure–Odor Correlation, XIII1). – Synthesis and Olfactive Properties of Megastigmatrienone AnaloguesThe key compound 9 was readily prepared in larger quantities by an improvement of a known procedure. Addition of carbanions to the unprotected ketone 9 gives the hydroxy ketones 16–21 via the acetals 10–15. Dehydration of 16–20 furnishes the dienones 2–6 while 7 is available in fair yield via the acetoacetate 21. Through intramolecular cyclization also the ester 26 is formed which affords with NaOH the keto ester 29 by a retro‐Michael reaction. The diketone 28 (obtained from 29) can be reduced selectively to give 30, dehydration of which leads to 31/32. – The odor of 2 (camphor, sweet, wood, plum) is the olfactive link between the odor of isophorone and megastigmatrienone (A). Elongation of the alkyl group (→ 3–5) leads first to a herbaceous, then to a leathery note. The one‐diene‐one 7 smells unexpectedly weak. For the very strong odor (tobacco, wood, plum) of A obviously the total osmophor is responsible including the unsaturated side chain.
[2.2]γ‐Pyronopyridinophane: Synthese und Untersuchungen zur konformativen Beweglichkeit
Authors: Flitsch Wilhelm , Niedenbrück Matthias 
Published: July 2007

[2.2](2,6)γ‐Pyronopyridinophanes: Synthesis and Investigation of the Conformational FlexibilityThe [2.2](2,6)γ‐pyronopyridinophane 1 has been obtained via the bis(thio ether) 3 by oxidation with m‐chloroperbenzoic acid and subsequent pyrolysis. Bromination of the bis(sulfone) 6 and Ramberg‐Bäklund reaction gave the olefinic sulfone 9 which was transformed into the [2.2](2,6)γ‐pyronopyridinophan‐1‐ene 2 by heating. The ring inversion of the heterophanes 1 and 2 was studied using dynamic NMR spectroscopy.
Synthese der Markierungssubstanz der Kirschenfruchtfliege Rhagoletis cerasi L.
Authors: Küchler Birgit , Voß Gundula , Gerlach Hans 
Published: July 2007

Synthesis of the Oviposition‐Deterring Pheromone of Rhagoletis cerasi L.The oviposition‐deterring pheromone of Rhagoletis cerasi L. (−)‐(8R,15R)‐1 and a mixture of the two compounds (−)‐(8R and 8S,15R)‐1 have been synthesized. In the presence of the 1,5‐cyclooctadiene–CuCl complex as catalyst the Grignard reagent of (−)‐(R)‐4 reacts with the epoxides (−)‐(S)‐5 and (±)‐5 to give (−)‐(7R,14R)‐6 and (−)‐(7R and 7S,14R)‐6. The optically active reagent (−)‐(R)‐4 has been prepared from ( + )‐(R)‐1,2‐epoxypropane. (−)‐(S)‐5 has been prepared from L‐malic acid dimethyl ester. – After converting the 7‐hydroxy groups of (7R,14R)‐6 and (7R and 7S,14R)‐6 into benzyl ethers 7, treatment with methanolic HCl solvolyzed the silyl ether and tricyclic orthoester groups to give the methyl esters (8R,15R)‐20 and (8R and 8S,15R)‐20. Next, these compounds were transformed into the benzyl ether–benzyl esters (8R,15R)‐21 and (8R and 8S,15R)‐21 that could be β‐glucosylated in high yields with tetrapivaloyl‐α‐D‐bromoglucose to give (8R,15R)‐22 and (8R and 8S,15R)‐22. Hydrogenolysis of the benzyl groups in 22 gave the corresponding 8‐hydroxy acids that could be activated as mixed anhydrides and reacted with 2‐aminoethanesulfonic acid to give the taurinamides (8R,15R)‐23 and (8R and 8S,15R)‐23. In the last step the pivaloyl groups of the glucose moiety of the molecules were removed by alkaline hydrolysis. Treatment of the hydrolysis products with an Amberlyst 15 (H+ form) ion exchanger and then with ammonia gave (8R,15R)‐1 and (8R and 8S,15R)‐1 as ammonium salts. The tetraacetyl‐β‐glucosides (13R)‐2 and (13S)‐3 have been synthesized and allow to deduce the (15R) configuration for the pentaacetyl derivative of the natural compound 1 by comparing their 1H‐NMR spectra.
Nachweis maskierter, langkettiger α‐Hydroxyaldehyde in Säugetiergewebe‐Lipiden
Authors: Lutz Arnulf , Spiteller Gerhard 
Published: July 2007

Evidence for the Occurrence of Masked α‐Hydroxy Aldehydes in Mammalian Tissue LipidsIf samples of mammalian tissue lipids are treated with dithioethyleneglycol, Et2O ‐ BF3, and acetic acid, bound α‐hydroxy aldehydes are converted into dithiolane derivatives. After reduction, they are separated from large amounts of accompanying lipid derivatives by TLC. The trimethylsilylated samples have been investigated by GLC and GLC/MS.
Enantioselective total synthesis of harmonine, a defence alkaloid of ladybugs (Coleoptera: Coccinellidae)
Authors: Enders Dieter , Bartzen Dominika 
Published: July 2007

AbstractAn efficient and highly enantioselective (ee > 97%) total synthesis of the ladybug defence alkaloid (17R,9Z)‐1,17‐diaminooctadec‐9‐ene [(R,Z)‐1, harmonine] in good overall yield is described. As the key step for the generation of the stereogenic center, asymmetric CC bond formation by nucleophilic addition of methyllithium to an aldehyde SAMP hydrazone is used.
Secondary metabolites by chemical screening, 18. Narbosines, new carbohydrate metabolites from Streptomyces
Authors: Henkel Thomas , Breiding‐Mack Sabine , Zeeck Axel , Grabley Susanne , Hammann Peter E. , Hütter Klaus , Till Gudrun , Thiericke Ralf , Wink Joachim 
Published: July 2007

AbstractIn the culture broth of two new Strepomyces strains several novel 2,3,6‐trideoxy‐L‐threo‐hexose (rhodinose) metabolites, narbosines A to E (2–6, 8, 9), were detected besides α‐N‐acetylanhydro‐L‐ornithine (11) by using the chemical screening method. Their structures were deduced from spectroscopical data as well as from chemical transformations. Narbosine A (2/3) was shown to be a 1:1 anomeric mixture of α‐L‐rhodinopyranosyl‐(1→4) ‐α/β‐L‐rhodinopyranose, the others are partially oxidatively and reductively transformed derivatives of 2/3. A destinct antiviral activity was observed for the described metabolites.
Formation of quinolines from 2‐phenylbenzopyrylium chloride
Authors: Sonnenschein Helmut , Schmitz Ernst , Hiller Wolf 
Published: July 2007

AbstractThe quinolines 5a–e are prepared by thermal treatment of 2‐phenylbenzopyrylium chloride (4) with aromatic amines. The substitution pattern of the products shows that an unusual Skraup synthesis has taken place.
An efficient synthesis of cis‐ and trans‐2‐aminocyclohexanecarboxamides and their N‐substituted derivatives
Authors: Göndös György , Szécsényi István , Dombi György 
Published: July 2007

AbstractIn this paper we describe a new approach to cis‐ and trans‐2‐aminocyclohexanecarboxamides and their N‐substituted derivatives. Which proceeds much faster and in higher yields than the methods described in the literature and usually employed in peptide chemistry. This method opens a route to the production of many previously unknown cis‐ and trans‐2‐aminocyclohexanecarboxylic acid derivatives.
Studies on N‐Acetylation of 3‐Aryl‐5‐ethyl‐4,5‐dihydro‐1,2,4‐oxadiazoles
Authors: Srivastava R. M. , Carpenter G. B. 
Published: July 2007

AbstractA facile synthesis of 2‐acetyl‐3‐aryl‐5‐ethyl‐2,5‐dihydro‐1,2,4‐oxadiazoles 2 is described.
Reactions of organic anions, 182. Vicarious nucleophilic substitution of a hydrogen atom in 1‐fluoro‐2,4‐dinitrobenzene (Sanger's Reagent)
Authors: Mąkosza Mieczyslaw , Stalewski Jacek 
Published: July 2007

AbstractReactions of carbanions of aryl chloromethyl and dichloromethyl sulfones 3 and 4 and tert‐butyl chloro‐ and dichloroacetates (5 and 6) with 1‐halo‐2,4‐dinitrobenzenes 1 and 2 proceed by nucleophilic replacement of a hydrogen atom. The SNAr of the halogen atom occurs to a negligible extent.
Tumor‐associated antigen synthesis synthesis of the gal‐α‐(1→3)‐gal‐β‐(1→4)‐GlcNAc epitope a specific determinant for metastatic progression?
Authors: Schaubach Regine , Hemberger Jürgen , Kinzy Willy 
Published: July 2007

AbstractA versatile synthesis of the Gal‐α‐(1→3)‐Gal‐β‐(1→4)‐GlcNAc epitope coupled to an alkyl spacer molecule could be developed. The important building block 3′‐allyl‐D‐lactal 6 was prepared in high yield by the action of dibutyltin oxide and allyl bromide on D‐lactal and converted in several steps into the lactosamine derivative 13 with free 3′‐OH group. Stereoselective glycosidation with the β‐trichloroacetimidate of benzylated D‐galactose 18 led to the trisaccharide in high yield. Activation of the protected Gal‐α‐(1→3)‐Gal‐β‐(1→4)‐GlcNAc derivative 21 by desilylation and trichloroacetimidate formation followed by glycosidation with ethyl 9‐hydroxynonanoate furnished the spacer‐bound trisaccharide hapten 24 in excellent yield after simple two‐step deprotection. The trisaccharide hapten 24 can easily be used as immunogen after coupling to an immunogenic carrier.
Derivate natürlicher Tetrapyrrole, Synthese einiger Modellverbindungen für die Photodynamische Therapie
Authors: Mackenbrock Ursula , Risch Nikolaus 
Published: July 2007

Natural Tetrapyrrol Derivatives, Synthesis of Some Model Compounds for the Photodynamic TherapyIn photodynamic therapy, di‐ and polymeric porphyrins with ether, ester or direct CC linkages are the active components of hematoporphyrin derivative. Here we describe the synthesis of some new model compounds for such ether/ester dimers.
Stereoselektive Umsetzungen von rac‐, (R), oder (S)‐5‐Alkyliden‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidincarbonsäure‐t‐butylestern (chirale 2,3‐Dehydroaminosäure‐Derivate) und Herstellung einiger nichtproteinogener Aminosäuren
Authors: Seebach Dieter , Bürger H. Michael , Schickli Christof P. 
Published: July 2007

Stereoselective Conversions of t‐Butyl rac‐, (R)‐, or (S)‐5‐Alkylidene‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylates (Chiral 2,3‐Dehydroamino Acid Derivatives) and Preparation of Some Nonproteinogenic Amino AcidsThe reacivity of the alkylidene derivatives 1–11 specified in the title and prepared in two operational steps from commercially available Boc‐BMI and aldehydes is investigated. – According to high‐field 1H‐NMR analysis of the crude products, additions of HH and DD (catalytic hydrogenation, products 12–20, of RH (BF3‐activated R2CuLi/LiI and protonation, products 21–29), and of Cl2C (CHCl3/NaOH, products 33, 34) occur with complete selectivity from the face opposite to the t‐butyl group. The doubly unsaturated carbonyl derivative 11 reacts with dibutyl cuprate in the δ position, again with formation of a single diastereomer 32, while trifluoroethylidene‐Boc‐BMI 3a is reduced to the difluoro analogue 30 by this cuprate. – Li dienolates are generated by deprotonation with LDA of the ethylidene (2a) and butylidene compound 4a; subsequent alkylations (with primary and secondary halides, products 35–41) and hydroxyalkylations (with aldehydes, products 42–44) lead to single products of electrophilic attack in the a carbonyl position (C‐5 of the imidazolidinone ring) under kinetic control. On the other hand, reaction of the 2a‐derived dienolate with benzaldehyde under equilibrating conditions furnishes the four possible (E/R, E/S, Z/R, and Z/S) γ adducts 45–48. – A combination of methods – 1H‐ and 13C‐NMR spectroscopy, NOE measurements, spectroscopic analogies, chemical correlation (with authentic samples or by spectroscopic or optical comparison), and X‐ray analysis (Table 1, Figure 1, Schemes 1 and 2) – is used to assign the product configurations and thus the stereochemical course of the reactions. Some unusual amino acids (50–52, 54, 55) are prepared by hydrolysis of the corresponding imidazolidinones.
Natural product chemisrty, 143. Convenient synthesis of isoacronycine and some other new acridone derivatives
Authors: Reisch Johannes , Herath H. M. T. Bandara , Kumar N. Savitri 
Published: July 2007

AbstractThe iodination of 1,3‐dihydroxy‐9‐acridone (1), 1‐hydroxy‐3‐methoxy‐10‐methyl‐9‐acridone (2) and 1,3‐dihydroxy‐10‐methyl‐9‐acridone (3) yields 1,3‐dihydroxy‐2,4‐diiodo‐9‐acridone (4), 1‐hydroxy‐2‐iodo‐3‐methoxy‐10‐methyl‐9‐acridone (5) and 1,3‐dihydroxy‐2‐iodo‐10‐methyl‐9‐acridone (6), respectively. The methylation of 4 and 5 gives 2,4‐diiodo‐1,3‐dimethoxy‐10‐methyl‐9‐acridone (7) and 2‐iodo‐1,3‐dimethoxy‐10‐methyl‐9‐acridone (9), respectively. The direct CC coupling of 2‐methyl‐3‐buten‐2‐ol to the compounds 5, 7 and 9 by palladium catalysed Heck condensation method gives three new acridone derivatives 1‐hydroxy‐2‐(3‐hydroxy‐3‐methyl‐1‐butenyl)‐3‐methoxy‐10‐methyl‐9‐acridone (10), 2,4‐bis(3‐hydroxy‐3‐methyl‐1‐butenyl)‐1,3‐dimethoxy‐10‐methyl‐9‐acridone (12) and 2‐(3‐hydroxy‐3‐methyl‐1‐butenyl)‐1,3‐dimethoxy‐10‐methyl‐9‐acridone (13) while compound 6 is converted into isonoracronycine (11). The methylation of 11 yields isoacronycine (14).
Zur stereoselektiven Synthese von 1‐O‐Alkyl‐3‐O‐benzyl‐sn‐glycerolen und 1‐O‐Alkyl‐2‐O‐methyl‐3‐O‐β‐D‐glycosyl‐sn‐glycerolen
Authors: Bauer Friederike , Rueß Klaus‐Peter , Liefländer Manfred 
Published: July 2007

Stereoselective Synthesis of 1‐O‐Alkyl‐3‐O‐benzyl‐sn‐glycerols and 1‐O‐Alkyl‐2‐O‐methyl‐3‐O‐β‐D‐glycosyl‐sn‐glycerolsStarting with D‐mannitol, the yield of the synthesis of 3‐O‐benzyl‐sn‐glycerol (1) could be improved. The regioselective alkylation of 1 at the primary hydroxy group to the 1‐O‐alkyl‐3‐O‐benzyl‐sn‐glycerols 3 was achieved by using the dibutylstannylene protecting group. The 1‐O‐alkyl‐2‐O‐methyl‐sn‐glycerols 4, readily obtainable from 3, were successfully glycosylated under the conditions of the Koenigs‐Knorr reaction to give 1‐O‐alkyl‐2‐O‐methyl‐3‐O‐β‐D‐glycosyl‐sn‐glycerols.
Pheromone synthesis, CXXXI. Synthesis of the four stereoisomers of 6,10,13‐trimethyl‐1‐tetradecanol, the aggregation pheromone of predatory stink bug, Stiretrus anchorago
Authors: Mori Kenji , Wu Jiang 
Published: July 2007

AbstractThe synthesis of the four stereoisomers of 6,10,13‐trimethyl‐1‐tetradecanol (1a), the male‐produced aggregation pheromone of the predatory stink bug Stiretrus anchorago, was achieved by starting from (R)‐citronellol (2a), methyl (R)‐ or (S)‐3‐hydroxy‐2‐methylpropanoate (10) and 4‐chloro‐1‐butanol (12a).
A novel one‐step synthesis of 4H‐furo[3,4‐b]pyrans and a transformation into a difuro[3,4‐b: 3′,4′‐e]pyridine
Authors: Martín Nazario , Segura José L. , Seoane Carlos , Soto José L. , Morales Margarita , Suarez Margarita 
Published: July 2007

AbstractA simple one‐step synthesis of 2‐amino‐4‐aryl‐5‐oxo‐4H‐furo[3,4‐b]pyran‐3‐carbonitriles 7 is described. It involves reaction of 2,4(3H,5H)‐furandione (β‐tetronic acid) (5) with arylmethylenemalononitriles 4 in basic medium. Some substituent effects are noted and the assignments of 13C‐NMR spectra are discussed. Ring transformation of the furo[3,4‐b]pyran 7a leads to the difuro[3,4‐b:3′,4′‐e]pyridine 9.
Herkunft des Sauerstoffatoms im Furanring von F‐Säuren
Authors: Batna Andreas , Spiteller Gerhard 
Published: July 2007

Origin of the Oxygen Atom in the Furan Ring of F AcidsIncubation experiments with 18O2 gas on suspension cultures of Saccharum spec. demonstrate that the oxygen atom in the furan ring of F acids 1 is derived from the air. This result points to the participation of lipoxygenase systems in the biosynthesis of these compounds. Specific incorporation into the furan ring, using an apparatus with 18O2 influx in portions, was confirmed by GC/MS analysis of the tetrahydofuran derivatives 2, obtained by esterification and hydrogenation of the corresponding furan derivatives 1.
Preparation and crystal structure of methyl [12‐acetyl‐8‐ethyl]‐bacteriopheophorbide d. – A new bacteriochlorophyll derivative
Authors: Senge Mathias O. , Bobe Frank W. , Huster Michael S. , Smith Kevin M. 
Published: July 2007

AbstractReaction of methyl bacteriopheophorbide d 2 in tetrahydrofuran with sodium methoxide led to oxidation of the ethyl side chain at position 12 to afford an acetyl group. Experiments with 18O2 suggest a mechanism via abstraction of a proton and reaction of the secondary radical formed with molecular oxygen. The implications of this mechanism for the biosynthesis of the bacteriochlorophylls are discussed. The 12‐acetyl compound 3 was investigated by X‐ray crystallography.
Synthesis of 6‐dimethylaminopurine 2′,3′‐dideoxynucleosides
Authors: Motawia Mohammed S. , El‐Torgoman Abdel Moneim , Pedersen Erik B. 
Published: July 2007

AbstractThe trimethylsilyated 6‐dimethylaminopurine 1 was coupled with the 2′,3′‐dideoxyribose derivatives 2a, b and 7 by using trimethylsilyl triflate as catalyst to yield the corresponding nucleosides 3a, b, 4a, b and 8, which were appropriately deprotected to give the desired nucleosides 5a, b and 9 as well as the related α‐isomers 6a, b and 10. The 2‐deoxyribose derivative 12 was mesylated at the 3′‐O‐position to give 13 which was coupled similarly with 1 to yield compound 14 and its α‐anomer 15. Compounds 14 and 15 were treated with tetrabutylammonium fluoride to give the desired 2′,3′‐didehydro‐2′,3′‐dideoxynucleoside analogue 16 and its α‐anomer 17.
Unexpectedly formed amino ketones, stereochemistry and conformation
Authors: Neszmélyi András , Lotter Hermann , Kiss Arpád , Pelczer István , Oszbach György 
Published: July 2007

AbstractBenzaldehyde adds to pyrrolidine enamines of cyclohexanone and 4‐tert‐butylcyclohexanone to form 1 and 4, respectively. The unstable ketones were reduced to afford stable alcohols 2 and 5. The stereochemistry of 2 was verified by X‐ray diffraction. Unambiguous structure elucidation of 5 was achieved by two‐dimensional NMR spectroscopy and by considering the system of vicinal and long‐range proton‐proton coupling constants determined at 400 MHz and analyzed by spin simulation. 13C‐T1 relaxation times proved the anisotropic motion of the subunits of 5. An intramolecular hydrogen bridge is observed both in the 1H‐NMR and in the IR spectrum. The relative stereochemistry of the chiral centers of 5 was determined by inter‐subunit nuclear Overhauser enhancements. The conformation in solution was predicted by NOE restrained nonbonded energy calculation and molecular modeling. The enhancements computed with the refined geometry are in good agreement with the observed NOE values.
Synthese von rac‐Norartemeseol
Authors: Kirschning Andreas , Narjes Frank , Schaumann Ernst 
Published: July 2007

Synthesis of rac‐NorartemeseolThe synthesis of the terpenoid rac‐norartemesol (1b) is accomplished using epoxide ring‐opening reactions as key steps. Thus, addition of the thio‐substituted allyl anion 2b to ethylene oxide followed by proton‐induced cyclisation provides the tetrahydrofuran 4a. The oxirane 6, which is formed by simple functional group interconversion, is opened by the diethylaluminium salt 10 of a propargylsilane. After catalytic hydrogenation and tosylation, fluoride‐induced cyclisation of the allylsilane 13 gives the target molecule 1b.
Enantiospecific synthesis of (2S,3S,5S)‐2‐acetamido‐2,4‐dideoxyhexopyranose (N‐acetyl‐4‐deoxy‐D‐mannosamine) from D‐glucose
Authors: Mulzer Johann , Seilz Carsten , Reutter Werner 
Published: July 2007

AbstractA 14‐step enantiospecific total synthesis (overall yield 6%) of the title compound 1 from the known furanose 4 (derived from D‐glucose) is described.