bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mimicking the Vancomycin Carboxylate Binding Site: Synthetic receptors for sulfonates, carboxylates, and N‐protected α‐amino acids in water
Authors: Hinzen Berthold , Seiler Paul , Diederich François 
Published: December 2004

AbstractThe novel H2O‐soluble cyclophanes 1 and 2 incorporating different anion‐recognition sites were prepared in short synthetic routes (Schemes 1 and 2) as first‐generation mimics of the natural, D‐Ala‐D‐Ala binding antibiotic vancomycin. The X‐ray crystal structure of 1, a tris(hydrochloride)salt, revealed an open, preorganized cavity of sufficient size for the incorporation of small aliphatic residues (Fig. 3). In the crystal, molecules of 1 are arranged in parallel stacks, generating two types of channels, an ‘intra‐stack’ channel passing through the cyclophane cavities and an ‘inter‐stack’ channel located between cyclophane stacks (Fig. 4). The strongest intermolecular interactions between macrocycles in the crystal are CO…︁HN H‐bonds between the carboxamide residues of adjacent cyclophanes in neighboring stacks (Fig. 5). The ‘intra‐’ and ‘inter‐stack’ channels incorporate the three ordered Cl− counterions and several, partially ordered solvent molecules (4 MeOH, 1 H2O) (Fig. 6). Counterion Cl(2) is located within the ‘intra‐stack’ channel and interacts with a protonated piperazinium N‐atom and both ‘intra‐stack’ MeOH molecules. The two other counterions, Cl(1) and Cl(3), are located within the ‘inter‐stack’ channel. They are connected to two MeOH and one H2O molecules and also interact both with the NH group of the protonated spiropiperidinium ring in 1, forming an infinite, chain‐like H‐bonding network …︁Cl(1)…︁HOH…︁MeOH…︁Cl(3)…︁HNH…︁Cl(1′)…︁. Both ‘intra‐’ and ‘inter‐stack’ MeOH molecules undergo weak CH…︁π interactions with neighboring aromatic rings. Cyclophane 1 complexed aromatic sulfonates in 0.5M KCl/DCl buffer in D2O, whereas the tetrakis(quaternary ammonium) receptor 2 bound the sodium salts of aliphatic and aromatic carboxylates and sulfonates, of N‐acylated α‐amino acids as well as of N‐acetyl‐D‐alanyl‐D‐alanine (Ac‐D‐Ala‐D‐Ala), a substrate of vancomycin, in pure H2O. In all of these complexes, ion pairing between the cationic recognition site in the periphery of the cyclophane receptor and the anionic substrates represents the major driving force for host‐guest association. The 1H‐NMR analysis of complexation‐induced changes in chemical shift clearly demonstrated that, in solution, this ion pairing exclusively takes place outside the cavity. Nevertheless, the macrocyclic bridges are essential for the efficiency of the anion‐recognition sites in the two cyclophane receptors 1 and 2. Control compounds 3 and 4 possess nearly the same anion‐recognition sites than 1 and 2, but lack their macrocyclic preorganization; as a consequence, they do not form stable ion‐pairing complexes with mono‐anionic substrates in the considered concentration ranges ( < 50 mM) in D2O.
Analogs of Cinchona Alkaloids Incorporating a 9,9′‐Spirobifluorene Moiety
Authors: Winter‐Werner Barbara , Diederich François , Gramlich Volker 
Published: December 2004

AbstractThe Cinchona alkaloid analogs (+)‐ and (−)‐5 with a quinuclidine‐2‐methanol residue attached to C(2) of a 9,9′‐spirobifluorene moiety were prepared as a racemic mixture by reacting lithiated 2‐bromo‐9,9′‐spirobifluorene 7 with (2‐ethoxycarbonyl)quinuclidine (±)‐6 to give ketone (±)‐8, followed by diastereoselective reduction with diisobutylaluminum hydride (DIBAL‐H). The absolute configuration at C(9) and C(8), i.e., at the methanol bridge and the adjacent quinuclidine C‐atom, in the two enantiomers of 5 is identical to the configuration at the corresponding centers in (−)‐quinine (1) and (+)‐quinidine (2), respectively. For the optical resolution of (±)‐5, a chiral stationary phase for HPLC was prepared by covalently bonding quinine via a thiol spacer to a silica‐gel surface. The enantiomer separation was accomplished at an α value of 1.61 with (±)‐5 being eluted last, in agreement with 1H‐NMR studies in CDCl3 which showed that (+)‐5 underwent a more stable host‐guest association with quinine than (−)‐5. 1H{1H} Nuclear Overhauser effect (NOE) difference spectroscopical analysis of the host‐guest associations with quinine in CDCl3, combined with computer‐model examinations, allowed the assignment of the absolute configurations as (+)‐(8R,9S)‐5 and (−)‐(8S,9R)‐5. A detailed conformational analysis displayed excellent agreement between the results of computational methods (Monte Carlo multiple minimum simulations, analyses of the total energy as a function of the flexible dihedral angles in the molecule) and 1H{1H}‐NOE difference spectroscopical data. It was found that (−)‐5 and (+)‐5 differ significantly in their conformational preference from their natural counterparts quinine (1) and quinidine (2). Whereas the natural alkaloids prefer the ‘open’ conformation, with the quinuclidine N‐atom pointing away from the quinoline ring, analog (±)‐5 adopts preferentially (by ca. 4 kcal mol−1) a ‘closed’ conformation, in which the quinuclidine N‐atom points into the cleft of the 9,9′‐spirobifluorene moiety. Since the basic quinuclidine N‐atom in the ‘closed’ conformation is sterically shielded from forming strong H‐bonds, the new Cinchona alkaloid analogs form less stable host‐guest associations via H‐bonding than quinine or quinidine.
The Diels‐Alder Reactivity of 2,2′‐Ethylidenebis[3,5‐dimethylfuran] and Exploratory Chemistry of the Mono‐adducts
Authors: Ancerewicz Jacek , Vogel Pierre , Schenk Kurt 
Published: December 2004

AbstractIn the presence of Me3Al, 1‐cyanovinyl acetate added to 2,2′‐ethylidenebis[3,5‐dimethylfuran] (1) to give a 20:10:1:1 mixture of mono‐adducts 4,5,6, and 7 resulting from the same regiocontrol (‘para’ orienting effect of the 5‐methyl substituent in 1). The additions of a second equiv. of dienophile to 4–7 were very slow reactions. The major mono‐adducts 4 (solid) and 5 (liquid) have 2‐exo‐carbonitrile groups. The molecular structure of 4(1RS,1′RS,2SR,4SR)‐2‐exo‐cyano‐4‐[1‐(3,5‐dimethylfuran‐2‐yl)ethyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl acetate) was determined by X‐ray single‐crystal radiocrystallography. Mono‐adducts 4 and 5 were saponified into the corresponding 7‐oxanorbornenones 8 and 9 which were converted with high stereoselectivity into (1RS,1′SR,4RS,5RS,6RS)‐4‐[1‐(3,5‐dimethyl furan‐2‐yl)ethyl]‐6‐exo‐methoxy‐1,5‐endo‐dimethyl‐7‐oxabicyclo [2.2.1]heptan‐2‐one dimethyl acetal (12) and its (1′RS‐stereoisomer 12a, respectively. Acetal hydrolysis of 12a followed by treatment with (t‐Bu)Me2SiOSO2CF3 led to silylation and pinacol rearrangement with the formation of (1RS,1′RS,5RS,6RS)‐4‐[(tert‐butyl)dimethy lsilyloxy]‐1‐(3,5‐dimethylfuran‐2‐yl)ethyl]‐5‐methoxy‐6‐methyl‐3‐methylidene‐ 2‐oxabicyclo[2.2.1]heptane (16). In the presence of Me3Al, dimethyl acetylenedicarboxylate added to 12 giving a major adduct 19 which was hydroborated and oxidized into (1RS,1′RS,2″RS,3″RS,4SR,4″RS,5 SR,6SR)‐dimethyl 5‐exo‐hydroxy‐4,6‐endo‐dimethyl‐1‐[1‐(3‐exo,5,5‐trimeth oxy‐2‐endo,4‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐2‐yl)ethyl]‐7‐oxabicyclo [2.2.1]hept‐2‐ene‐2,3‐dicarboxylate (20). Acetylation of alcohol 20 followed by CC bond cleavage afforded (1′RS,1″SR,2RS,2′″SR,3RS, 3″SR,4RS,4″SR,5RS)‐dimethyl {3‐acetoxy‐2,3,4,5‐tetrahydro‐2,4‐dimethyl‐5‐[1‐(3‐exo,5,5‐trimethoxy −2‐endo,4‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐1‐yl)‐ethyl]furan‐2,5‐diyl} bis[glyoxylate] (24).
Biosynthesis of Dodecano‐4‐lactone in Ripening Fruits: Crucial Role of an Epoxide‐Hydrolase in Enantioselective Generation of Aroma Components of the Nectarine (Prunus persica var. nucipersica) and the Strawberry (Fragaria ananassa)
Authors: Schöttler Michael , Boland Wilhelm 
Published: December 2004

AbstractEarly steps in the biosynthesis of dedecano‐4‐lactone in ripening nectarines (Prunus persica var. nucipersica) and strawberries (Fragaria ananassa) were studied using cis‐9,10‐([18O]epoxy)heptadecanoic acid (5), instead of the natural C18‐precursor epoxystearic acid 1. In nectarines, an epoxide hydrolase catalyzed, in a highly regio‐ and enantioselective reaction, the attack of H2O at C(9) of epoxy acid 5 yielding preferentially (9R,10R)‐dihydroxyheptadecanoic acid 6a as an early intermediate and, after further metabolization, undecano‐4‐lactone 7a. In strawberries, the same transformation exhibited only a moderate regio‐ and enantioselectivity. Besides the previously established function of phytogenic epoxide hydrolases involved in generating oxygenated fatty‐acid derivatives, which are used in cutin monomer production and plant defence, a new rǒle for these enzymes now emerges in the enantioselective production of aroma components of ripening fruits. The cis‐9,10‐([18O]epoxy)heptadecanoic acid (≥ 98% 18O; 5) was obtained in good overall yield (68%) from isopropyl (9Z)‐heptadec‐9‐enoate using 18O2 gas in a free‐radical chain reaction in the presence of 2‐methylbutanal.
Stereoselektive Synthese des Nitrit‐reduzierenden Cofaktors Häm d1 ausgehend von Hämatoporphyrin
Authors: Romanowski Frank , Mai Gerhard , Kusch Dirk , Montforts Franz‐Peter , Bats Jan W. 
Published: December 2004

Steroselective Synthesis of the Nitrite‐Reducing Cofactor Heme d1 from HematoporphyrinThe nitrite‐reducing cofactor heme d1 has been synthesized in a few synthetic steps, starting from readily accessible hematoporphrin dimethyl ester (rac‐4a). A single‐crystal structure analysis of the synthesized target molecule rac‐10a unequivocally established the constitution and the relative configuration of heme d1 (3).
Säurekatalysierte Umlagerung von 9‐Hydroxyfuranoeremophilanen zu Eremophilanlactonen
Authors: Siegenthaler Peter , Neuenschwander Markus 
Published: December 2004

Acid‐Catalyzed Rearrangement of 9‐Hydroxyfuranoeremophilanes to Eremophilanlactones9‐Hydroxyfuranoeremophilanes 1–3 are the main components of freshly harvested rhizomes of P. hybridus (furanopetasin chemovar, Table, Fig. 1). They easily and quantitatively rearrange in the presence of traces of acid to give an epimeric mixture of 8‐H‐eremophilanlactones 4–6 (eremophilenolides, Table, Figs. 4 and 5). Besides subsequent oxidation (see 4 → 7), this is the most important reaction occuring during drying and storage of rhizomes of P. hybridus (Figs. 1 and 3). A reasonable mechanism of the rearrangement is presented, and spectroscopic structure elucidation of 8‐H‐eremophilanlactones is discussed.
Asymmetric Synthesis of 3‐Hydroxyprolines by Photocyclization of C(1′)‐Substituted N‐(2‐Benzoylethyl)glycine Esters
Authors: Steiner Andrê , Wessig Pablo , Polborn Kurt 
Published: December 2004

AbstractThe chiral N‐(2‐benzoylethyl)‐N‐tosylglycine esters 5a–h and the α‐amino‐γ‐keto ester 6 were prepared from γ‐(tosylamino) alcohols 7a–h. Irradiation of compounds 5a–c, e gave cis‐3‐hydroxyproline esters 20–23 (Scheme 6), partly with complete asymmetric induction by the C(1′)‐substituent, whereas 6 gave enantiomerically pure 4‐hydroxy‐4‐phenyl‐L‐proline esters 24 in good yield but low de (Scheme 6). The de of the photocyclization depended on the nature and/or size of the C(1′)‐substituents. Irradiation of ketones 5d and 5f, bearing H‐atoms at C(γ) with respect to the keto function, gave cyclobutanols (Scheme 9) in low yields besides the preferred Norrish‐type‐II cleavage product. Cyclopentanol 25 was a by‐product of the photocyclization of 5c as a result of HC(δ) abstraction from the t‐Bu group. The structure of products 20, 22, and 24a, b was established by NMR or X‐ray analyses.
Synthesis and Odor of Chiral Partial Structures of Khusimone. Part 1
Authors: Sprdizer Helmut , Pichler Andrea , Holzer Wolfgang , Toth Irene , Zuchart Bettina 
Published: December 2004

AbstractKhusimone (1), one of the main odor‐donating compounds of vetiver oil is subject of the following study on structure/odor relationship. The omittance of the ethano bridge of the tricyclic khusimone leads to a bicyclic system. The stereoselective approach to this degraded structure is described, and the olfactory properties are studied. The key step of the synthesis of the hydrindane nucleus is based on a highly diastereoselective conjugate addition to a chiral oxo‐cyclopentene‐2‐carboxylate.
Ringöffnungen von sterisch gehinderten spirocyclischen 2, 5‐Dihydro‐1, 3, 4‐thiadiazolen mit cycloaliphatischen, sekundären Aminen
Authors: Miostoń Grzegorz , Romańsld Jaroslaw , Linden Anthony , Heimgartner Heinz 
Published: December 2004

Ring Opening of Sterically Crowded Spirocyclic 2, 5‐Dihydro‐l, 3, 4‐thiadiazoles by Cycloaliphatic Secondary AminesAt room temperature, the spirocyclic 2, 5‐dihydro‐l, 3, 4‐thiadiazole 3 reacted with cyclic secondary amines 6 via ring opening to give N‐alkylidene‐hydrazones of type 7 (Scheme 2). A reaction mechanism via a base‐catalyzed transformation of the dihydrothiadiazole ring to the corresponding thiolate 19 and the intermediate thioaldehyde 21 is proposed in Scheme 6. An analogous reaction occurred with the mixture of the dispiro compounds 4/5 and morpholine (6a) or azetidine (6d), leading to a mixture of isomeric dihydrazones 8 and 9 (Scheme 3). The structure of the symmetrical isomer 8a was established by X‐ray crystallography. In addition to 8a and 9a, the thiirane lOa (Scheme 3) was isolated as a minor product.
3′‐(β‐D‐Glycopyranosyloxy)flavylium Ions: Synthesis and investigation of their properties in aqueous solution. Hydrogen bonding as a mean of colour variation
Authors: Hajji Hakima El , Dangles Olivier , Figueiredo Paulo , Brouillard Raymond 
Published: December 2004

AbstractThis work describes a straightforward synthesis of two 3′‐(β‐D‐glycopyranosyloxy)flavylium ions thought to be good models of natural anthocyanins (pigments). For both pigments and for the non‐glycosylated flavylium ion taken as a reference, H2O addition and proton‐transfer reactions as well as formation of molecular complexes with chlorogenic acid and caffeine (copigmentation) are quantitatively investigated in mildly acidic aqueous solution. A remarkable affinity of caffeine for the trans‐chalcone form of the pigments is demonstrated. Moreover, the differences in the flavylium pKa values are interpreted in terms of possible intramolecular H‐bonding between the glycosyl residue and the chromophore. The discussion is then extended to a series of malonylated anthocyanins recently reported for their unusual pigmentation properties. A possible role for the malonyl group (frequently encountered in the structure of naturally occurring anthocyanins) in plant colour expression is outlined for the first time.
Wechselwirkungen in Kristallen. 106. Mitteilung. Die Klaviatur der Na⊕‐Koordinationszahlen in ihren Carbazolanion‐Salzen
Authors: Bock Hans , Arad Claudia , Nather Christian , Havlas Zdenek 
Published: December 2004

Interaction in Crystals: The Keyboard of Na⊕ Coordination Numbers in Its Carbazole Anion SaltsSome local minima in the shallow potential of the system carbazole anion, sodium cation, and the ethers tetrahydrofuran, 1,2‐dimethoxyethane, diglyme, triglyme, tetraglyme, 15‐crown‐5 as well as 2.2.1‐cryptand are explored experimentally and by quantum‐chemical calculations. Three prototype contact‐ion multiples of Na⊕‐solvated carbazole anion M⊖ salts have been crystallized and structurally characterized: polyether‐solvated monomers [M⊖Na⊕solv]1, solvent‐shared dimers [M⊖Na⊕solv]2, and solvent‐separated polyions [(M⊖)nNa⊖solv](n−1)− [Na⊕solv](n−1). The Na⊕ coordination numbers stretch from 3 to 7 as illustrated by the compounds [(M−)3Na+]⊖⊖[Na+(2.2.1‐crytand)]2 for 3 and 7, [(M−)2Na+(THF)2]⊖ [Na⊕(2.2.1‐cryptand)] for 4 and 7, [M− Na+(diglyme)]2 for 5, or [M− Na+(l 5‐crown‐5)] for 6. Structural comparison is based on literature analogies as well as on results of MNDO calculations concerning charge distribution and enthalpies of formation. Taken together, the results demonstrate the delicate energy balance, by which cation solvation can influence the formation of organic salts.
Synthesis of Modified Tripeptides and Tetrapeptides as potential bisubstrate inhibitors of the epidermal growth factor receptor protein tyrosine kinase
Authors: Rossé Gérard , Séquin Urs , Mett Helmut , Furet Pascal , Traxler Peter , Fretz Heinz 
Published: December 2004

AbstractThe synthesis of a series of bisubstrate inhibitors of the epidermal growth factor receptor protein kinase (EGF‐R PTK) consisting of small pep tides linked covalently to adenosine via appropriate triphosphate substitutes is described. Boc‐Glu(OtBu)‐Tyr‐Leu‐OBzl (5) and Ac‐Glu(OtBu)‐Tyr‐Leu‐Arg(Pmc)‐NH2 (8; Pmc = 2,2,5,7,8‐pentamethylchroman‐6‐sulfonyl) were prepared by standard peptide chemistry, (Scheme 1), then modified at the OH group of tyrosine either with adipic anhydride or with 4‐(chlorosulfonyl)benzoic acid, 4‐(chlorosulfonyl)‐2‐hydroxybenzoic acid, or benzene‐1,4‐disulfonyldichloride (Scheme 2), and finally coupled with the 5′‐OH group of 2′,3′‐O‐isopropylideneadenosine (Scheme 3). In addition, N6‐[(benzyloxy)carbonyl]‐2′,3′‐O‐isopropylidene‐adenosine 5′‐(hydrogenhexanedioate) (26), an ATP substitute, was coupled with the morpholide of 5 (Scheme 4). Removal of the protecting groups gave the bisubstrate analogs 23, 24, and 28. The compounds synthesized were tested as inhibitors of the EGF‐R PTK. The most active bisubstrate‐type inhibitor was 24, composed of the tripeptide sequence H‐Glu‐Tyr‐Leu‐OBzl, the 2‐hydroxy‐4‐sulfonylbenzoyl moiety, and adenosine; it showed an IC50 value of 33 μM.
Synthèse de (3‐aminopropyl)arylsilanes, comportant un ou deux motifs hétérocycliques, fongicides potentials
Authors: Garandeau Par Jean‐Marc , Chollet Jean‐FrançOis , Miginiac Léone 
Published: December 2004

Synthesis of (3‐Aminopropyl)arylsilanes, Including One or Two Heterocyclic Patterns, Potential FungicidesFlusilazole is an effective silylated fungicide used on a large scale for plant protection. We synthesized several flusilazole analogs and also copied the tebuconazole design, an other very efficient fungicide, which has four atoms between the aromatic group and the heterocyclic moiety. In contrast to flusilazole, we obtained dissymetric structures around the Si‐atom by using successively two different Grignard reagents. In another way, the 1H‐1,2,4‐triazole moiety was exchanged in several cases by other N‐heterocycles such as 1H‐imidazole, piperidine, and 2,6‐dimethylmorpholine, already present in other fungicidal compounds. Finally, several compounds having two N‐heterocycles of the same or different nature were prepared.
Synthesis of Cyclic Depsipeptides and Peptides via Direct Amide Cyclization
Authors: Villalgordo José M. , Heimgartner Heinz 
Published: December 2004

AbstractThe 2,2‐disubstituted 2H‐azirin‐3‐amines 7 (2,2‐disubstituted 3‐amino‐2H‐azirines) were used as amino‐acid synthons in the preparation of medium‐sized cyclic depsipeptides and peptides derived from salicylic acids 6 and anthranilic acid 19, respectively (Schemes 2‐‐4 and 5, resp.). The combination of the ‘azirine/oxazolone method’ for the synthesis of linear peptides containing α,α‐disubstituted α‐amino acids and the acid‐catalyzed amide cyclization in DMF at 60° proved to be an excellent preparative route to ten‐membered cyclic depsipeptides and peptides. In the case of the anthranilic‐acid derivative, a transannular ring‐closure reaction was observed (24 → 25). Larger rings proved to be extremely sensitive to hydrolysis.
Quantitative Analysis of Enzyme‐Mediated Hydrolytic Processes and Their Products Using HPLC and NMR Techniques
Authors: Wimmer Zdenêk , Zarevúcka Marie , Rejzek Martin , Šaman David , Zhao Qiu‐Yu , Legoy Marie‐Dominique 
Published: December 2004

AbstractSecond derivatives of the UV spectra of 2‐(4‐alkoxybenzyl)cyclopentan‐1‐ols and their acetates were used for the quantitative analysis of reaction kinetics of enzyme‐mediated hydrolytic process. To determine the enantiomeric purity of the products using non‐chiral HPLC columns, their diastereoisomeric esters of 3,3,3‐trifluoro‐2‐methoxy‐2‐phenylpropanoic acid(MTPA) were prepared. The absolute configuration of the products was established using a combination of the results of a HPLC analysis and 1H/19F‐NMR measurements of the diastereoisomeric MTP esters. The analytical method described consists of an easy routine HPLC analysis which can sometimes be used as a quick on‐line analysis of the reaction kinetics and as a quick stepwise analysis of the optical purity and the absolute configuration of the products.
Diazoaldehyde Chemistry. Part 4vilsmeier‐haack formylation of diazo compounds: A re‐investigation
Authors: Sezer Özhan , Dabak Kadir , Anaç Olcay , Akar Ahmet 
Published: December 2004

AbstractDiazomethyl ketones (2‐diazoethanones) were reacted with the Vilsmeier reagent ((chloromethylidene)dimethylammonium chloride) to yield α‐diazo‐β‐oxoaldehydes and chloromethyl ketones. 2′,4′‐Dimethoxy‐α‐diazoacetophenone gave 2‐chloro‐1‐(2,4‐dimethoxyphenyl)‐3‐(dimethylamino)prop‐2‐en‐1‐one (5) in addition to the expected products. Phenyldiazomethanes gave the corresponding benzyl chlorides but not the (phenyl)diazoacetaldehydes even at temperatures as low as −60°. The diazo‐transfer reactions of phenylacetaldehydes and 2‐azido‐1‐ethylpyridin‐1‐ium tetrafluoroborate also did not yield the expected(phenyl)diazoacetaldehydes.
Chiral 2‐Aryl‐2‐methyl‐2H‐1‐benzopyrans: Synthesis, characterization of enantiomers, and barriers to thermal racemization
Authors: Harié Guenäelle , Samat André , Guglielmetti Robert , van Parys Inge , Saeyens Wim , de Keukeleire Denis , Lorenz Klaus , Mannschreck Albrecht 
Published: December 2004

AbstractThe ease of thermal breaking of the C(sp3)O bond of the 2‐aryl‐2‐methyl‐2H‐1‐benzopyrans 1–9 was evaluated by measuring the free energy (ΔG) of the racemization reaction of optically active compounds. The variation of ΔG of the thermal ring opening in terms of structural modifications is discussed. The synthesis of the studied compounds, the preparative separation of enantiomers by liquid chromatography, the determination of enantiomeric purity, the circular dichroism of enriched enantiomers, and the measurement of rate constants of enantiomerization by monitoring the decrease of the polarimetric angle of rotation at suitable temperatures are described.
Synthesis and Evaluation of 2‐{[(2‐Oxo‐1H‐quinolin‐8‐yl)oxy]methyl}‐Substituted α‐Methylidene‐γ‐butyrolactones
Authors: Tzeng Cherng‐Chyi , Chen Yeh‐Long , Wang Chyi‐Jia , Wang Tai‐Chi , Chang Ya‐Ling , Teng Che‐Ming 
Published: December 2004

AbstractO‐Alkylation of 8‐hydroxy‐1H‐quinolin‐2‐one (1) afforded 8‐(2‐oxopropoxy)‐1H‐quinolin‐2‐one (2) which was immediately cyclized to form the tricyclic 2,3‐dihydro‐3‐hydroxy‐3‐methyl‐5H‐pyrido[1,2,3‐de][1,4]benzoxazine,‐5‐one (3). The Reformatsky‐type condensation of 3 furnished antiplatelet 8‐[(2,3,4,5‐tetrahydro‐2‐methyl‐4‐methylidene‐5‐oxofuran‐2‐yl)melhoxy]‐1H‐quinolin‐2‐one (4). Its counterparts 7a–f, Ph‐substituted at C(2) of the furan ring, were obtained from 1 via alkylation and the Reformatsky‐type condensation. Although compound 4 was less active against platelet aggregation than 7a–f, it was the only compound which exhibited significant inhibitory activity on high‐K+ medium, Ca2+‐induced vasoconstriction and was more active than most of its Ph‐substituted counterparts against norepinephrine‐induced vasoconstrictions.
Reformulating the Kinetic Approach of Column Chromatography for a Single Component
Authors: Kuznetsov Alexander M. , Giraultb Hubert H. 
Published: December 2004

AbstractThe kinetic model of column chromatography is revisited to explicitly show that this approach yields, when neglecting axial dispersion, a rather simple analytical expression depending only on two dimensionless parameters, namely a dimensionless kinetic retention parameter and a dimensionless time parameter. An expression for the time corresponding to the maximum of the peak is also proposed.