- Naphthyl 3,4,6-tri-O-methyl-β-D-glucopyranoside as a chiral auxiliary in an asymmetric 1,4-addition reaction
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Naphthyl 3,4,6-tri-O-methyl-β-D-glucopyranoside, easily synthesized from tri-O-acetyl-D-glucal, has been applied as a chiral auxiliary in an asymmetric Michael addition to the 2-O-crotonate. A very high facial diastereoselection (>95%) was obtained. No diastereoselection was observed when 1,3,4,6-tetra-O-methyl-β-D-glucopyranoside was used as the chiral auxiliary. A stereochemical model, taking into account steric shielding and π-stacking effects, is proposed on the basis of the observed results.
- Chiappe, Cinzia,Lo Moro, Giacomo,Munforte, Paola
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- Stereoselective synthesis of belactosin C and its derivatives using a catalytic proline catalyzed crossed-aldol reaction
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A highly practical and concise stereoselective total synthesis of belactosin C and synthetic variants was achieved using an S-proline catalyzed crossed-aldol reaction as the key step.
- Kumaraswamy,Markondaiah
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Read Online
- Effect of chiral substituents on the secondary structure of poly(N-alkynylamides)
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Optically active N-alkynylamides (S)-HC≡C(CH2) aNHCO(CH2)bCH(CH3)CH 2CH3 (1: a = 1, b = 0; 2: a = 1, b = 1; 3: a = 1, b = 2; 4: a = 1, b = 3; 5: a = 2, b = 0; 6: a = 2, b = 1; 7: a = 3, b = 0), having several numbers of methylene spacers between the ethynyl group and chiral carbon or amide group, and (S)-HC≡C(CH2)2OCOCH 2CH(CH3)CH2CH3 (8) were polymerized with (nbd)Rh+[η6-C6H5B --(C6H5)3] to afford the corresponding polymers with moderate molecular weights (Mn = 11 000-21 000) in 67-99% yields. The 1H NMR spectra demonstrated that the resulting polymers had stereoregular structures (cis content = 79-100%). CD, UV-vis, and IR spectroscopic studies revealed that the position of the amide group and chiral center strongly affects the pitch and stability of helical structure of the polymers, and intramolecular hydrogen bonding is formed between the amide groups in CHCl3. By comparison with the results of CD measurements and molecular orbital calculation, the sign of Cotton effect and the relationship between the screw sense of poly(N-propargylamides) was elucidated.
- Tabei, Junichi,Shiotsuki, Masashi,Sanda, Fumio,Masuda, Toshio
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Read Online
- Differential Effects of β3- versus β2-Amino Acid Residues on the Helicity and Recognition Properties of Bim BH3-Derived α/β-Peptides
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Oligomers containing α- and β-amino acid residues (α/β-peptides) have been shown to mimic the α-helical conformation of conventional peptides when the unnatural residues are derived from β3-amino acids or cyclic β-amino acids, but the impact of incorporating β2 residues has received little attention. The effects of β2 residues on the conformation and recognition behavior of α/β-peptides that mimic an isolated α-helix were investigated. This effort has focused on 26-mers based on the Bim BH3 domain; a set of isomers with identical α/β backbones that differ only in the placement of certain side chains along the backbone (β3 vs. β2 substitution) was compared. Circular dichroism data suggest that β2 residues can be helix-destabilizing relative to β3 residues, although the size of this effect seems to depend on side chain identity. Binding data show that β3→β2 substitution at sites that contact a partner protein, Bcl-xL, can influence affinity in a way that transcends effects on helicity.
- Eddinger, Geoffrey A.,Gellman, Samuel H.
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supporting information
p. 13829 - 13832
(2018/09/25)
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- Novel iridium complex of spirophosphine-carboxylic acid, preparation method and application thereof
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The invention relates to an iridium complex of spirophosphine-carboxylic acid, a preparation method and application thereof. The iridium complex of spirophosphine-carboxylic acid is a compound with a structure shown as formula (I), wherein n=0-3; and the values of R1, R2, R3, R4, R5, R6 and R7 are defined as claim 1. Substituted 7-carboxyl-7'-diarylphosphino-1, 1'-spirobiindane is taken as the ligand to from carboxylic acid anion under the action of alkali, and then complexation with an iridium precursor is carried out to obtain different iridium/spirophosphine-carboxylic acid complexes. The iridium complex of spirophosphine-carboxylic acid provided by the invention can catalyze the asymmetric hydrogenation reaction of a variety of unsaturated carboxylic acids, and show high activity and enantioselectivity, thus having good industrialization prospects. (formula (I)).
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Paragraph 0076; 0077; 0079
(2017/05/20)
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- Neutral iridium catalysts with chiral phosphine-carboxy ligands for asymmetric hydrogenation of unsaturated carboxylic acids
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We developed neutral iridium catalysts with chiral spiro phosphine-carboxy ligands (SpiroCAP) for asymmetric hydrogenation of unsaturated carboxylic acids. Different from the cationic Crabtree-type catalysts, the iridium catalysts with chiral spiro phosphine-carboxy ligands are neutral and do not require the use of a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF?) counterion, which is necessary for stabilizing cationic Crabtree-type catalysts. Another advantage of the neutral iridium catalysts is that they have high stability and have a long lifetime in air. The new iridium catalysts with chiral spiro phosphine-carboxy ligands exhibit unprecedented high enantioselectivity (up to 99.4% ee) in the asymmetric hydrogenations of various unsaturated carboxylic acids, particularly for 3-alkyl-3-methylenepropionic acids, which are challenging substrates for other chiral catalysts.
- Yang, Shuang,Che, Wen,Wu, Hui-Ling,Zhu, Shou-Fei,Zhou, Qi-Lin
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p. 1977 - 1980
(2017/03/09)
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- Synthesis of Polysubstituted γ-Butenolides via a Radical Pathway: Cyclization of α-Bromo Aluminium Acetals and Comparison with the Cyclization of α-Bromoesters at High Temperature
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Polysubstituted butenolides were obtained in good to high yields from α-bromoesters derived from propargyl alcohols by a one-pot reaction involving the radical cyclization of α-bromo aluminium acetals, followed by the oxidation of the resulting cyclic aluminium acetals in an Oppenauer-type process and migration of the exocyclic C-C bond into the α,β-position. Comparison with the direct cyclization of α-bromoesters at high temperature and under high dilution conditions is described. Deuterium-labelling experiments allowed us to uncover "invisible" 1,5-hydrogen atom transfers (1,5-HATs) that occur during these cyclization processes, together with the consequences of the latter in the epimerization of stereogenic centres. Compared to the classical approach, the cyclization of aluminium acetals proved to be highly chemoselective and its efficiency was illustrated by the short total syntheses of optically enriched γ-butenolides isolated from Plagiomnium undulatum and from Kyrtuhrix maculans.
- Bénéteau, Romain,Despiau, Carole F.,Rouaud, Jean-Christophe,Boussonnière, Anne,Silvestre, Virginie,Lebreton, Jacques,Dénès, Fabrice
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p. 11378 - 11386
(2015/08/03)
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- Design and synthesis of the stabilized analogs of belactosin A with the unnatural cis-cyclopropane structure
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The belactosin A analog 2a, having the unnatural cis-cyclopropane structure instead of the trans-cyclopropane structure in belactosin A, is a much more potent proteasome inhibitor than belactosin A. However, its cell growth inhibitory effect is rather lower than that expected from its remarkable proteasome inhibitory effect, probably due to its instability under cellular conditions. We hypothesized that the instability of 2a was due to chemical and enzymatic hydrolysis of the strained β-lactone moiety. Thus, to increase the stability of 2a by chemical modification, its analogs with a sterically more hindered β-lactone moiety and/or cyclopropylic strain-based conformational restriction were designed and synthesized, resulting in the identification of a stabilized analog 6a as a proteasome inhibitor with cell growth inhibitory effects. Our findings suggest that the chemical and biological stability of 2a is significantly affected by the steric hindrance around its β-lactone carbonyl moiety and the conformational flexibility of the molecule.
- Kawamura, Shuhei,Unno, Yuka,Asai, Akira,Arisawa, Mitsuhiro,Shuto, Satoshi
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supporting information
p. 6615 - 6622
(2013/09/24)
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- Efficient synthesis of (2S,3S)-2-ethyl-3-methylvaleramide using (1S,2S)-pseudoephedrine as a chiral auxiliary
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An efficient and scaleable synthesis of (2S,3S)-2-ethyl-3-methylvaleramide (1) has been developed starting from inexpensive and readily available L-isoleucine. The key step in this process is an asymmetric alkylation using (1S,2S)-pseudoephedrine as a chiral auxiliary. A practical procedure was developed to remove the sterically hindered pseudoephedrine auxiliary from the amide. The process consists of eight chemical steps and five isolations without any chromatographic purification. It has been successfully implemented to prepare several multikilogram batches of the target compound 1 in 41% overall yield.
- Li, Bin-Feng,Hughes, Robert M.,Le, Jackie,McGee, Kevin,Gallagher, Donald J.,Gross, Raymond S.,Provencal, David,Reddy, Jayachandra P.,Wang, Peng,Zegelman, Lev,Zhao, Yuxin,Zook, Scott E.
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experimental part
p. 463 - 467
(2010/04/22)
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- Volatile lactones - (5S,S)-5-methyl-3-(methylalkyl)furan-2(5H)-ones - Identified in the submerged cultivation of Streptomyces avermitilis
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Six new compounds have been identified in the volatile fractions produced during the submerged cultivation of Streptomyces avermitilis. By recording the GC/MS, GC/FTIR, CD, 1H and 13C NMR data and by performing chemical degradation experiments, these compounds were determined to be (5S,S)-5-methyl-3-(methylalkyl)furan-2(5H)-ones. Herein, the existence of volatile lactones with an anteiso structure of the side-chain is thus documented for the first time. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Rezanka, Tomas,Sigler, Karel
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p. 4277 - 4284
(2007/10/03)
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- Diastereoselective synthesis of the acyl side-chain and amino acid (2S,3R)-3-hydroxy-3-methylproline fragments of polyoxypeptin A
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Synthesis of the acyl side-chain and amino acid (2S,3R)-3-hydroxy-3- methylproline units of the potent depsipeptide polyoxypeptin A, is described. Key intermediates were secured via diastereoselective addition involving a homoenolate ion and allylation of
- Chen, Zhiyong,Ye, Tao
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p. 2781 - 2785
(2007/10/03)
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- Enantioselective total syntheses of belactosin A, belactosin C, and its homoanalogue
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Enantioselective total syntheses of belactosin A, belactosin C, and its homoanalogue have been accomplished in high overall yields (32% for belactosin A from the amino acid 10, and 35 and 36% for belactosin C and its homoanalogue, respectively). This conc
- Larionov, Oleg V.,De Meijere, Armin
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p. 2153 - 2156
(2007/10/03)
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- Total synthesis of (+)-belactosin A.
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A concise first total synthesis of the antitumour antibiotic belactosin A is reported, involving coupling of beta-lactone carboxylic acid 3 with N-Ala-aminocyclopropyl alanine 11.
- Armstrong, Alan,Scutt, James N
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p. 510 - 511
(2007/10/03)
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- Cu-catalyzed enantioselective conjugate additions of alkyl zinc reagents to unsaturated N-acyloxazolidinones promoted by a chiral triamide phosphane
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A chiral triamide phosphane promotes highly efficient and enantioselective Cu-catalyzed conjugate additions of alkyl zinc compounds to unsaturated oxazolidinones (see scheme). The resulting β-alkyl chiral oxazolidinones are readily converted into synthetically useful carbonyl compounds not accessible by alternative catalytic methods.
- Hird, Alexander W.,Hoveyda, Amir H.
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p. 1276 - 1279
(2007/10/03)
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- Amelioration of neurological disorders by the administration of (2R),(3S), and/or (2S),3(S) stereoisomers of valnoctamide
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The present invention generally relates to the individual stereoisomers of the drug valnoctamide (a mixture of four stereoisomer kinds, VCD-valmethamide or 2-ethyl-3-methyl pentanamide) useful in treatment of neurological and psychotic disorders such as d
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- Silylformylation of chiral 1-alkynes, catalysed by solvated rhodium atoms
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Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R1R2CH(CH2)nC≡CH, with catalytic activities comparable with and even higher than more common species such as Rh4(CO)12. Z-Silylalkenals are exclusively formed in high yields (60-95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the α-position of the unsaturated moiety, to afford enantiomerically enriched β-silylalkenals.
- Aronica, Laura Antonella,Terreni, Silvia,Caporusso, Anna Maria,Salvadori, Piero
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p. 4321 - 4329
(2007/10/03)
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- Highly diastereoselective 1,4-addition of an organocuprate to methyl α-D-gluco-, α-D-manno-, or α-D-galactopyranosides tethering an α,β-unsaturated ester. Novel asymmetric access to β-C-substituted butanoic acids
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The 1,4-addition of magnesium divinylcuprate prepared from vinylmagnesium bromide and cuprous bromide to some 4-O-crotonyl derivatives of methyl α-D-glucopyranoside proceeds with a high level of diastereochemical induction, providing the adduct in good-to
- Totani,Nagatsuka,Yamaguchi,Takao,Ohba,Tadano
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p. 5965 - 5975
(2007/10/03)
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- Optically active compound, liquid crystal composition containing the same, and liquid crystal electro-optic element using the same
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An optically active compound represented by formula (I): wherein A represents wherein R2 represents an alkyl group having from 8 to 12 carbon atoms; R1 represents a straight chain alkyl group having from 2 to 5 carbon atoms; X represents a fluorine atom or a methyl group; n represents 1 or 2; m represents an integer of from 0 to 3; and C* represents an asymmetric carbon atom, and a liquid crystal composition containing the same are disclosed. The compound exhibits large spontaneous polarization and low viscosity and, when added to an achiral base liquid crystal composition, induces a chiral nematic phase in which the helical pitch has small temperature dependence.
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- Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia
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The partial configurations of C25 isoprenoid alkenes isolated from the diatom Haslea ostrearia Gaillon (Simonsen) have been established. A combination of NMR spectroscopy studies of the alkenes with chiral shift reagents in conjunction with soluble silver β-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed between different laboratory cultures of the alga. (C) 2000 Elsevier Science Ltd.
- Johns, Lesley,Belt, Simon,Lewis, C. Anthony,Rowland, Steven,Masse, Guillaume,Robert, Jean-Michel,Koenig, Wilfried A.
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p. 607 - 611
(2007/10/03)
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- Absolute configuration of the four stereoisomers of valnoctamide (2- ethyl-3-methyl valeramide), a potentially new stereospecific antiepileptic and CNS drug
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Valnoctamide (2-ethyl-3-methyl valeramide, Nirvanil, VCD), a mild tranquilizer endowed with anticonvulsant properties, exhibits diastereoselective and enantioselective pharmacokinetics in healthy subjects and epileptic patients. The purpose of this paper
- Roeder, Michael,Spiegelstein, Ofer,Schurig, Volker,Bialer, Meir,Yagen, Boris
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p. 841 - 853
(2007/10/03)
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- Enatiomeric separation of branched fatty acids after conversion with trans-2-(2,3-Anthracenedicarboximido)cyclohexanol, a highly sensitive chiral fluorescent conversion reagent
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(1R,2R)-2-(2,3-Anthracenedicarboximido)cyclohexanol was synthesized as a highly sensitive chiral fluorescent conversion reagent. The diastereomeric derivatives of chiral branched fatty acids that had methyl ethyl chirality from the 2 to 12 position were separated into 2 peaks by reversed-phase HPLC and detected at the 10-15 mole level by fluorometry.
- Akasaka, Kazuaki,Ohrui, Hiroshi
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p. 1209 - 1215
(2007/10/03)
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- Enantiomeric separation of carboxylic acids having chiral centers remote from the carboxyl group by labelling with a chiral fluorescent derivatization reagent
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Enantiomeric separations of 2-, 3-, 4-, 5- and 6-methyl fatty acids and 3-, 4- and 5-hydroxy fatty acids derivatized with (S) -(+)-2-(anthracene-2,3-dicarboximido)-1 propyl trifluoromethanesulfonate are described. Although there are 4-8 bond distances between the chiral centers of these diastereomeric derivatives, they are separated on HPLC and detected at fmol levels.
- Akasaka, Kazuaki,Meguro, Hiroshi,Ohrui, Hiroshi
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p. 6853 - 6856
(2007/10/03)
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- Complete structures of the sphingosine analog mycotoxins fumonisin B1 and AAL toxin T(A): Absolute configuration of the side chains
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Fumonisin B1 and AAL toxin T(A) are sphingosine-analog mycotoxins characterized by propane-1,2,3-tricarboxylic acid side chains esterified to alkylamine backbones. The absolute configuration of all stereogenic centers in the backbones is known. Using chiral gas chromatography methodology we have determined the absolute configuration at C-3' in the side chains to the S, thereby completing structure determination of both toxins.
- Shier,Abbas,Badria
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p. 1571 - 1574
(2007/10/02)
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- SYNTHESIS OF ENANTIOMERICALLY PURE (5S)-4-AZA-2-OXA-6,6-DIMETHYL-7,10-METHYLENE-5-SPIRODECAN-3-ONE, A NOVEL CHIRAL OXAZOLIDIN-2-ONE FROM (-)-CAMPHENE FOR USE AS A RECYCLABLE CHIRAL AUXILIARY IN ASYMMETRIC TRANSFORMATIONS
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By an intramolecular nitreno-mediated route (-)-camphene is transformed into a novel spiro-oxazolidin-2-one whose efficiency as a chiral auxiliary is highlighted by the excellent levels of chiral induction attained in an array of asymmetric transformations such as the Diels-Alder, conjugate addition, aldol condensation, alkylation and acylation reactions.
- Banks, Malcolm R.,Cadogan, J. I. G.,Gosney, Ian,Grant, Keith J.,Hodgson, Philip K. G.,Thorburn, Paul
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p. 199 - 206
(2007/10/02)
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- Asymmetric hydrogenation of prochiral carboxylic acids catalyzed by the five-coordinate ruthenium(II)-hydride complex PF6 (binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)
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The five-coordinate complex PF6 (1, binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) has been found to have sufficient catalytic activity for asymmetric hydrogenation of itaconic acid and other prochiral carboxylic acids under mild conditions.The catalytic hydrogenation of itaconic acid by I was examined under a variety of conditions, and the addition of triethylamine was found to effect high enantioselectivities (above 90percent ee). 1H and 31 P NMR examinations of reaction mixtures of I and itaconic acid under conditions similar to the hydrogenation suggested the formation of ruthenium species containing one binap chelate.
- Saburi, Masahiko,Takeuchi, Hiroshi,Ogasawara, Masamichi,Tsukahara, Touru,Ishii, Youichi,et al.
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p. 155 - 167
(2007/10/02)
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- Synthesis of the Three Stereoisomers of Auxin-Glutaric Acid to Confirm the Non-Existence of Koegl's Auxin-a and -b
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All of the three possible stereoisomers of (5S,1'S)-4-carboxy-5-methyl-1-(1'-methylpropyl)heptanoic acid were synthesized and their stereostructures assigned unambiguously by 13C-NMR and X-ray analyses.The melting points and the specific rotations of the
- Mori, Kenji,Kamada, Atsushi,Kido, Masaru
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p. 775 - 781
(2007/10/02)
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- Photosynthetic Electron Transport Inhibition by Phlorophenone Derivatives
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The structure/activity relationships of phlorophenone derivatives including grandinol and homograndinol, which are potent inhibitors of photosynthetic electron transport (PET) in Eucalyptus grandis, were examined.The results indicate that at least one acy
- Yoneyama, Koichi,Asami, Tadao,Crow, Wilfrid D.,Takahashi, Nobutaka,Yoshida, Shigeo
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p. 471 - 476
(2007/10/02)
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- Asymmetric Conjugate Addition to Unsaturated Chiral Amido Alcohols Using Grignard Reagents Co-ordinated with Tertiary Amines or DBU. Preparation of Optically Active 3-Substituted Carboxylic Acids and (S)-(-)-Citronellol
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Optically active 3-substituted carboxylic acids and (S)-(-)-citronellol have been obtained by diastereoselective conjugate addition of Grignard reagents co-ordinated with 1,8-diazabicyclo-undec-7-ene (DBU) to chiral amidoalcohols derived from (S)-proline.
- Soai, Kenso,Machida, Hideaki,Yokota, Noriko
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p. 1909 - 1914
(2007/10/02)
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- EFFICIENT ASYMMETRIC HYDROGENATIONS OF CAMPHOR-SULTAM-IMIDE-CONJUGATED ALKENES.
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The trisubstituted olefinic bond of sultam-imides 2 was hydrogenated in the presence of Pd/C with >90percent diastereoface discrimination to give after saponification recovered auxiliary 7 and the β-substituted carboxylic acids 5 or 6 in high e.e..
- Oppolzer, Wolfgang,Mills, Robert J.,Reglier, Marius
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p. 183 - 186
(2007/10/02)
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- Tobacco Chemistry 64. A New Sucrose Ester from Greek Tobacco
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A new sucrose ester has been isolated from Greek tobacco and shown to be 6-O-acetyl-2,3,4-tri-O--sucrose (1) by spectral methods and chemical correlation.
- Wahlberg, Inger,Walsh, E. Brian,Forsblom, Ingrid,Oscarson, Stefan,Enzell, Curt R.,et al.
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p. 724 - 730
(2007/10/02)
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- ASYMMETRIC CONJUGATE ADDITION REACTION BY THE USE OF (S)-γ-TRITYLOXYMETHYL-γ-BUTYROLACTAM AS A CHIRAL AUXILIARY
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(S)-γ-Trityloxymethyl-γ-butyrolactam (2) serves as a chiral auxiliary in the conjugate addition reaction of the corresponding imide (3) of α,β-unsaturated carboxylic acids with Grignard reagents in the presence of CuBr-SMe2 in THF to give, after hydrolysis, the β,β-disubstituted carboxylic acids (5) with predictable absolute configuration and high enantiomeric excess.
- Tomioka, Kiyoshi,Suenaga, Toshiro,Koga, Kenji
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p. 369 - 372
(2007/10/02)
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- New Synthesis of (4R,8R)-4,8-Dimethyldecanal, the Aggregation Pheromone of Tribolium castaneum, and its (4R,8S)-Isomer
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Die Synthese der Titelverbindungen (4R,8R)-1 und (4R,8S)-1 aus (R)-Citronellsaeure wird beschrieben.Die Anwendung der Kolbe-Elektrolyse ist der Schluesselschritt der Synthese.
- Mori, Kenji,Kato, Minoru,Kuwahara, Shigefumi
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p. 861 - 865
(2007/10/02)
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- Asymmetric Conjugate Addition of Grignard Reagents in the Presence of Tertiary Amines to α,β-Unsaturated Amides Derived from (S)-2-(1-Hydroxy-1-methylethyl)pyrrolidine or (S)-Prolinol
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In the presence of tertiary amines, diastereoselective conjugate addition of Grignard reagents to α,β-unsaturated amides affords 3-substituted carboxylic acids of high enantiomeric excess (up to 89percent e.e.).
- Soai, Kenso,Machida, Hideaki,Ookawa, Atsuhiro
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p. 469 - 470
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF β-SUBSTITUTED ALCANOIC ACIDS VIA HIGHLY STEREOSELECTIVE CONJUGATE ADDITIONS OF ORGANOCOPPER COMPOUNDS TO CHIRAL ENOATES
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Conjugate additions of organocopper compounds RCu*BF3 to enoates of sulfonamide-shielded alcohols 1x and 1n quite generally proceed with >99percent ee and >90percent yield.
- Helmchen, Guenter,Wegner, Guenter
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p. 6051 - 6054
(2007/10/02)
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- TRANSFER OF ASSYMETRY BY THE PALLADIUM-CATALYZED ALKYLATION OF CHIRAL ALLYLIC SULFINATES
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The pallladium-catalyzed substitution of chiral allylic sulfinates was performed by the initial transformation of the sulfinates into allyl sulfones and the subsequent alkylation of the sulfones with retention of configuration.Reaction of trans- and cis-2-butenyl (S)-(-)-p-toluenesulfinate with the sodium salt of dimethyl malonate was undertaken in the presence of tetrakis(triphenylphosphine)palladium and triphenylphosphine to produce dimethyl (S)-(+)- and (R)-(-)-1-buten-3-ylmalonate, respectively, with the α-alkylated product, dimethyl 2-butenylmalonate.
- Hiroi, Kunio,Kitayama, Ryuichi,Sato, Shuko
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p. 929 - 932
(2007/10/02)
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- A FACILE ASYMMETRIC SYNTHESIS OF β-SUBSTITUTED ALKANOIC ACID. THE HIGHLY STEREOSELECTIVE MICHAEL ADDITION OF GRIGNARD REAGENTS TO α,β-UNSATURATED CARBOXYLIC AMIDES DERIVED FROM L-EPHEDRINE
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The Michael addition of Grignard reagents to chiral α,β-unsaturated carboxylic amides derived from l-ephedrine affords highly optically active β-substituted alkanoic acids after acid hydrolysis.This high stereoselectivity is explained by considering the formation of rigid internal chelate complexes.
- Mukaiyama, Teruaki,Iwasawa, Nobuharu
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p. 913 - 916
(2007/10/02)
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- Synthese chiraler Azobenzole und Untersuchung der in nematischen Fluessigkristallen durch sie induzierten cholesterischen Phasen
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The chiral cis- and trans-azo compounds 8a - d and 9a - d with para- or ortho-standing chiral side chains as well as the trans-azoxy derivatives 17a - d and 18a - d are synthesized.The influence of the molecular structure and the distance of the chiral centre from the aromatic nucleus on screw sense and pitch of induced cholesteric phases is investigated.The cis-azo compounds 9c and d show atropisomerism.
- Heppke, Gerd,Marschall, Helga,Nuernberg, Peter,Oestreicher, Feodor,Scherowsky, Guenter
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p. 2501 - 2518
(2007/10/02)
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- Synthesis of (S)-2-(2-Methylbutyl)thiophene (1)
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Optically active (S)-2-(2-methylbutyl)thiophene was obtained by different procedures.Among them, the cross-coupling reaction between 2-methylbutylmagnesium chloride and 2-chlorothiophene proved to be the most efficient one.Compound 1 was thus obtained in satisfactory yield and rather high optical purity (82percent).
- Menicagli, R.,Botteghi, C.,Marchetti, M.
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