- Improved robust method for preparing optically active 3-alkyl-3-phenyl-1,4- dioxane-2,5-diones; A promising new chiral template
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A robust method for preparing (3S)-3-alkyl-3-phenyl-1,4-dioxane-2,5-diones was developed using an improved cyclocondensation reaction between (S)-α-alkylmandelic acids and 2-bromocarbonyl halides. Subtle differences in the reaction conditions, including separate additions of triethylamine, significantly increased the yield compared with Schollkopf s original method. Georg Thieme Verlag Stuttgart · New York.
- Nagase, Ryohei,Iida, Yuuki,Sugi, Mikiko,Misaki, Tomonori,Tanabe, Yoo
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experimental part
p. 3670 - 3674
(2009/07/25)
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- Construction of enantiomerically enriched tertiary α- hydroxycarboxylic acid derivatives by phase-transfer-catalyzed asymmetric alkylation of diaryloxazolidin-2,4-diones
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(Chemical Equation Presented) Center of attention: The chiral ammonium bromide 1 has been used as a catalyst for the highly enantioselective alkylation of diaryloxazolidindiones 2 under mild phase-transfer conditions (TBME = tert-butyl methyl ether). This
- Ooi, Takashi,Fukumoto, Kazuhiro,Maruoka, Keiji
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p. 3839 - 3842
(2007/10/03)
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- Process for preparing optically active α-hydroxy acids and derivatives thereof
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The present invention provides a process for preparing optically active α-hydroxy acids and derivatives thereof by subjecting the alkylated 1,3-dioxolanones of formula (IV) wherein R1and R2are the same or different and are each independently H or C1-6alkyl; R5is H, C1-16alkyl, or unsubstituted or substituted phenyl; and R6is C1-8alkyl, C2-7alkenyl or unsubstituted or substituted benzyl, to either alcoholysis or hydrolysis, in which the alkylated 1,3-dioxolanones are obtained by using 10-camphorsulfonamide as a chiral auxiliary.
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Page/Page column 20
(2008/06/13)
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- Isomannide and isosorbide as new chiral auxiliaries for the stereoselective synthesis of tertiary α-hydroxy acids
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Isomannide and isosorbide are selectively protected to provide new chiral auxiliaries suitable for the preparation of enantiopure tertiary α-hydroxy acids. Diastereoselective additions of organozinc reagents on the derived phenylglyoxylates afford the desired α-hydroxy acids with 60-99% ee after saponification. Both absolute configurations of the α-hydroxy acids can be accessed, by adapted choice of either the starting diol or the protecting group.
- Loupy, André,Monteux, Daphné A
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p. 1541 - 1549
(2007/10/03)
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- Enantioselective synthesis of α-hydroxy acids employing (1S)-(+)-N,N-diisopropyl-10-camphorsulfonamide as chiral auxiliary
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matrix presented I R1=H, Me, Ph II (>98 de.) III Lewis acid (BF3·-OEt2) catalyzed condensation of dimethoxy acetal 2 with α-hydroxy acids produces chiral 1,3-dioxolanones I. The enolates derived from these compounds underg
- Chang, Jia-Wen,Jang, Der-Pin,Uang, Biing-Jiun,Liao, Fen-Ling,Wang, Sue-Lein
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p. 2061 - 2063
(2008/02/09)
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- Asymmetric synthesis of tetrahydrofurans by diastereoselective [3+2] cycloaddition of allylsilanes with α-keto esters bearing an optically active cyclitol as a chiral auxiliary
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Tin (IV) chloride mediated [3+2] cycloadditions of allylsilanes with optically active α-keto esters derived from L-quebrachitol afforded tetrahydrofuran derivatives via 1,2-silyl migration with high level of diastereoselectivity. Removal of the chiral aux
- Akiyama, Takahiko,Yasusa, Takuya,Ishikawa, Keiichiro,Ozaki, Shoichiro
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p. 8401 - 8404
(2007/10/02)
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- Pig Liver Esterase Catalyzed Hydrolyses of Racemic α-Substituted α-Hydroxy Esters
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Pig liver esterase catalyzed hydrolyses of some α-substituted α-hydroxy esters give product acids and recovered esters in 9-94percent enantiomeric excess.The observed enantiomeric selectivity could be rationalized using a recently proposed active site mod
- Moorlag, Henk,Kellogg, Richard M.,Kloosterman, Marcel,Kaptein, Bernard,Kamphuis, Johan,Schoemaker, Hans E.
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p. 5878 - 5881
(2007/10/02)
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- SYNTHESIS OF ENANTIOMERICALLY ENRICHED ATROLACTIC ACID AND OTHER α-HYDROXY ACIDS
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The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lattic acid (2a, 2b; 3a; 10a, 10b) were alkylated with high stereoselectivity, The products formed were hydrolysed to α-hydroxy acids with 65-85percent e.e. ((S)(+)-5,7,9, (R)(-)-13).
- Frater, Gy.,Mueller, U.,Guenther, W.
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p. 4221 - 4224
(2007/10/02)
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