- Asymmetric reduction of α-keto aldoxime o -ethers
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The catalytic asymmetric reduction of -keto aldoxime O-methyl, O-benzyl, and O-trityl ethers, derived from substituted acetophenones, with borane/oxazaborolidines, by transfer hydrogenation, and with yeast, was studied. The reduction with borane/oxazaborolidines produced the corresponding -hydroxy oxime ethers, -hydroxy hydroxylamine ethers, and -amino alcohols in 39-78% yields and up to 77% ee. The carbonyl group was selectively reduced by transfer hydrogenation with formic acid-triethylamine catalyzed by RhCl[(R,R)-TsDPEN](Ce, and also with yeast, producing -hydroxy oxime ethers, up to 75% ee and 93% ee, respectively. Georg Thieme Verlag Stuttgart New York.
- Bosiak, Mariusz J.,Pakulski, Marcin M.
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experimental part
p. 316 - 324
(2011/03/18)
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- Catalytic enantioselective Steglich rearrangements using chiral N-heterocyclic carbenes
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The evaluation of a range of enantiomerically pure NHCs, prepared in situ from imidazolinium or triazolium salt precatalysts, to promote the catalytic enantioselective Steglich rearrangement of oxazolyl carbonates to their C-carboxyazlactones, is reported. Modest levels of enantioselectivity (up to 66% ee) are observed using oxazolidinone derived NHCs.
- Campbell, Craig D.,Concellon, Carmen,Smith, Andrew D.
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experimental part
p. 797 - 811
(2011/08/06)
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- The practical synthesis of a uterine relaxant, Bis( 2-{[(2S)-2-({(2R)-2-hydroxy-2-[4-hydroxy-3-(2-hydroxyethyl) -phenyl]ethyl}amino) -1,2,3,4-tetrahydronaphthalen-7-yl]oxy}-N,N-dimethylacetamide) sulfate (KUR-1246)
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The synthetic route for a uterine relaxant, bis(2-{[ (2S)-2-({(2R)-2-hydroxy-2-[4-hydroxy-3- (2-hydroxyethyl)-phenyl]ethyl}amino) -1,2,3,4-tetrahydronaphthalen-7-y1]oxy}-N,N-dimethylacetamide) sulfate (KUR-1246), was established by the coupling of optically active components, the bromohydrin 14 and the amine 24. We now describe the practical synthesis of these two optically active components. Bromohydrin 14 was obtained by the asymmetric borane reduction of the prochiral phenacyl bromide 13 using a catalyst prepared from aluminum triethoxide and a chiral amino alcohol. The other optically active component 24 was prepared from (S)-AMT.
- Yanagi, Takashi,Kikuchi, Ken,Takeuchi, Hideki,Ishikawa, Takehiro,Nishimura, Toshihiro,Yamamoto, Iwao
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p. 1018 - 1023
(2007/10/03)
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- CREATION OF CHIRALITY IN THE REACTION OF THE CHIRAL ESTER ENOLATE-IMINE CONDENSATION LEADING TO THE STEREODIVERGENT SYNTHESIS OF β-LACTAMS
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Stereocontrol at C-4 of the β-lactams possessing substituents at 3- and 4-positions in the ester enolate-imine condensation is studied using different metal enolates of the chiral esters possessing amino alcohols derived all from (+)-camphor as an auxiliary, and 4R- or 4S-β-lactam is obtained in a highly stereoselective manner, respectively.The effects of the structure of the chiral auxiliary and the coordination ability of the heteroatoms in the ester part are also dicussed.
- Shimizu, Makoto,Teramoto, Yoshihiro,Fujisawa, Tamotsu
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p. 729 - 732
(2007/10/02)
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- Preparative scale synthesis of (+) endo-2-hydroxy-endo-3-aminobornane
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A convenient preparation of the enantiomerically pure title compound is proposed from (+) camphor in 5 steps with an overall yield between 42 and 62percent.The benzoylation of this compound leads to the expected products 6 and 8 and to the oxazoline 10 formed from 6 with retention of configuration.Key Words: chiral 2-hydroxy-3-aminobornanes / benzoylation / acidic hydrolysis
- M'Boungou-M'Passi, A.,Henin, F.,Muzart, J.,Pete, J. P.
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p. 214 - 217
(2007/10/02)
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- Asymmetric Synthesis of (R)-(-)- and (S)-(+)-Muscone by Enantioselective Conjugate Addition of Chiral Dimethylcuprate to (E)-Cyclopentadec-2-en-1-one
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A variety of optically active secondary amino alcohols have been prepared from camphor and screened as chiral non-transferable cuprate ligands in conjugate addition reactions.The reactions of (E)-cyclopentadec-2-en-1-one with chiral dimethylcuprates derived from the ligand in toluene afforded muscone in enantiomeric excesses as high as 26 - 89 percent.The stereochemistry of the product correlates with the configuration of the chiral ligand used.Thus the conjugate addition using the ligand prepared from exo-3-monosubstituted-amino-exo-2-hydroxybornane gave (S)-(+)-muscone, while with endo-ligand, (R)-(-)-muscone was obtained in higher enantioselectivity.Muscone of essentially 100percent optical purity was obtained by the addition of small amounts of THF (tetrahydrofuran) (2 - 10 equiv.) to the toluene solution of the chiral cuprate reagent prepared from (1R,2R,3S,4S)-3--1,7,7-trimethylbicycloheptan-2-ol 23 (endo-MPATH).The effect of the stoichiometry of the chiral ligand and the cuprate reagent on the chemical yield and enantioselectivity was briefly investigated.
- Tanaka, Kazuhiko,Ushio, Hideki,Kawabata, Yasuyuki,Suzuki, Hitomi
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p. 1445 - 1452
(2007/10/02)
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- Stereoselective Reactions. XI. Asymmetric Alkylation of Cyclohexanone via Chiral Chelated Lithioenamines Derived from D-Camphor Derivatives
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Metalation and alkylation of the chiral imines prepared from cyclohexanone and methoxy amines (2b, 4c, 6d and 7d) derived from D-camphor derivatives provided, after hydrolysis, optically active 2-alkylcyclohexanones (9) in high enantiomeric purities of up to 99.5percent.Keywords - asymmetric synthesis; asymmetric alkylation; D-camphor; chiral methoxy amine; 2-alkylcyclohexanone; chelated lithioenamine.
- Ikota, Nobuo,Sakai, Hiroshi,Shibata, Hisanari,Koga, Kenji
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p. 1050 - 1055
(2007/10/02)
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