- Enzymatic Resolution by a d-Lactate Oxidase Catalyzed Reaction for (S)-2-Hydroxycarboxylic Acids
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Oxidase-catalyzed kinetic resolution is important for the production of enantiopure 2-hydroxycarboxylic acids (2-HAs), which are versatile building blocks for the synthesis of many significant compounds. However, in contrast to that of (R)-2-HAs, the production of (S)-2-HA is challenging because of the lack of related oxidases. Herein, suitable enzymes were screened systematically through the analysis of numerous putative d-lactate oxidase sequences and identification of several required properties. Finally, a d-lactate oxidase from Gluconobacter oxydans 621H with advantageous characteristics, such as good solubility, broad substrate spectrum, and high stereoselectivity, was selected to resolve 2-HAs into (S)-2-HAs. A variety of (S)-2-HAs was produced successfully using this d-lactate oxidase with excellent enantiomeric excess values (>99 %). The presented screening criteria and approach for target biocatalysis suggested a guideline for the production of optically active chemicals such as (S)-2-HAs.
- Sheng, Binbin,Xu, Jing,Ge, Yongsheng,Zhang, Shuo,Wang, Danqi,Gao, Chao,Ma, Cuiqing,Xu, Ping
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p. 2630 - 2633
(2016/08/30)
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- Selective reductions. 59. Effective intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane and intermolecular asymmetric reductions of the corresponding esters with B-chlorodiisopinocampheylborane
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A comparison of the stereochemistry of the products obtained from the intramolecular asymmetric reduction of a series of keto acids with (-)-diisopinocampheylborane and intermolecular asymmetric reduction of the corresponding series of keto esters with (-)-B-chlorodiisopinocampheylborane ((-)-DIP-Chloride) has been made. The stereochemistry of the hydroxy acids from the reduction of keto acids is dependent only on the enantiomer of the reagent used. The stereochemistry of the products from the reduction of keto esters is also consistent, except those of aliphatic α-keto esters. α-, β-, and γ-keto acids provide the corresponding hydroxy acids in 77-98% ee, and the α- and γ-keto esters afford the hydroxy esters in 82-≥99% ee. β-Keto esters do not undergo reduction. Although the reduction of δ-keto acids does not proceed under the same reaction conditions, the reduction of δ-keto esters is facile. All of the products from the reduction of γ-keto acids and esters and δ-keto esters were converted to the corresponding lactones. This study revealed that DIP-Chloride is an efficient reagent for the reduction of α-keto esters at low temperatures.
- Ramachandran, P. Veeraraghavan,Pitre, Sangeeta,Brown, Herbert C.
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p. 5315 - 5319
(2007/10/03)
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- Efficient intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane1
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(equation presented) α-, β-, and γ-Keto acids are reduced with diisopinocampheylborane at room temperature to the corresponding hydroxy acids with predictable stereochemistry in very high ee. The γ-hydroxy acids produced were conveniently cyclized to the corresponding lactones. This provides a simple synthesis of 4-hexanolide, a component of the pheromone secreted by the female dermestid beetle Trogoderma glabrum.
- Veeraraghavan Ramachandran,Brown, Herbert C.,Pitre, Sangeeta
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- Asymmetric reactions of α-ketoacid-derived hemiacetals: Stereoselective synthesis of α-hydroxy acids
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N-Acylation of prolinol with α-ketoacid chlorides results in concomitant hemiacetalization of the α-keto amide by the prolinol hydroxyl group. (R) or (S) α-hydroxy acids are obtained with good enantiomeric excess by stereodivergent reduction of these hemiacetals. Reaction with Grignard reagents at ambient temperature furnishes (R) α-alkyl mandelic acids with good stereoselectivity.
- Pansare, Sunil V.,Ravi, R. Gnana
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p. 14549 - 14564
(2007/10/03)
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- Diastereoselective Addition of Allyltriphenylstannane to 3-Sulfinylfurfural Mediated by Titanium(IV) Tetrachloride and Tin(IV) Tetrachloride
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The addition of allyltriphenylstannane to 3-sulfinylfurfural (3) in the presence of titanium(IV) tetrachloride proceeded with high diastereoselectivity to give the furyl alcohol (6), whereas the similar treatment with tin(IV) tetrachloride afforded the other diastereoisomeric alcohol (7), exclusively.
- Arai, Yoshitsugu,Masuda, Tsutomu,Masaki, Yukio,Koizumi, Toru
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p. 1751 - 1756
(2007/10/02)
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- Total Synthesis of Myxovirescins, 1. Strategy and Construction of the "Southeastern" Part
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In this and the following two papers the synthesis of myxovirescins A1, A2 and M2, 28-membered macrocyclic lactam-lactones with antibiotic activity, is described.A retrosynthetic analysis of the myxovirescin family of ca. 30 target molecules leads to a strategy which could be applied to approximately half of them by slight variations of the building blocks used (Schemes 1-3 and following paper).The southeastern part of the molecule, containing the atoms O(1)-C(14) of myxovirescins A and M is described in this first paper (Scheme 3).The assembly is achieved by using the following appropriately protected units: (S)-2-hydroxy-pentanoic acid, (dithian-2-ylmethyl)-amine (Scheme 4), the triflate of (S,R)-2,2-dimethyl-5-vinyl-dioxolan-4-ylmethanol, (E)-3-bromo-2-buten-1-ol, and (E)-2-bromo-2-buten-1,4-diol (Scheme 5), the starting materials for these being malic acid, aminoacetaldehyde, ribose, crotyl alcohol and butyne-1,4-diol.The building blocks are put together by using the following key steps: Kolbe electrolysis, amide formation, lithiodithiane alkylation, and Suzuki coupling (Schemes 6 and 8).The only newly created chirality center is generated stereoselectively by a Li-selectride reduction/Mitsunobu inversion (Table 1, Scheme 7).The termini of the O(1)-C(14) fragment (2 in Scheme 8) carry a (protected) hydroxy acid and an aldehyde group for the Julia coupling and lactonization, respectively, in the final steps of the synthesis.All intermediates are fully characterized.The X-ray crystal structures of two compounds prepared for incorporation as N(4)-C(11) and as C(12)-C(14) of the target molecules are also described (Figures 1 and 2). - Key Words: Myxovirescins / Myxococcus virescens Mx v48 / Suzuki coupling / Macrolides / Lactones / Lactams / 1,3-Dioxolanes / 1,3-Dithianes / Antibiotics
- Seebach, Dieter,Maestro, Miguel A.,Sefkow, Michael,Adam, Geo,Hintermann, Samuel,Neidlein, Axel
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p. 701 - 718
(2007/10/02)
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- Non-peptide Renin Inhibitors Containing 2-(((3-Phenylpropyl)phosphoryl)oxy)alkanoic Acid Moieties as P2-P3 Replacements
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A series of novel renin inhibitors containing 2-(((3-phenylpropyl)phosphoryl)oxy)alkanoic acid moieties as P2-P3 surrogates are presented.The P2-P3 mimetics were obtained from (ω-phenylalkyl)phosphinic acids 1a-c and 2-hydroxyalkanoic acid benzyl esters 2a-f by N,N'-dicyclohexylcarbodiimide-mediated coupling and subsequent oxidation with sodium metaperjodate.Ester cleavage of these derivatives and coupling with P1-P'1 transition-state mimetics I-VII provided highly selective compounds with inhibitory potencies in the lower nanomolar range.Small renin inhibitors, such as analogues 8c and 8h with molecular weights of 539 and 537, respectively, could be prepared.These compounds exhibited IC50 values of about 20 nM against human plasma renin.Compound 7i was examined in vivo for its hypotensive effect.In salt-depleted cynomolgus monkeys, 7i inhibited plasma renin activity almost completely and lowered blood pressure after oral adiministration of a dose of 30 mg/kg.
- Raddatz, Peter,Minck, Klaus-Otto,Rippmann, Friedrich,Schmitges, Claus-Jochen
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p. 486 - 497
(2007/10/02)
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- α-(Arylsulfonamido)borneols as Auxiliaries in Asymmetric Synthesis: An Efficient and Highly Stereoselective Method for the Reduction of α-Keto Esters
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A method for preparation of enantiomerically pure α-hydroxy esters by stereoselective reduction of chiral α-keto esters under convenient conditions (LiAlH(OCEt3)3, THF, 0 deg C) has been developed.The compounds exo,exo-3-(arylsulfonamido)-2-borneol and exo,exo-2-(arylsulfonamido)-3-borneol have been used as novel auxiliaries to achieve highly diastereoselective reductions.The auxiliaries can be removed by mild saponification (LiOH, THF-H2O, rt) without racemization of the reduced products.
- Xiang, Yi Bin,Snow, Ken,Belley, Michel
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p. 993 - 994
(2007/10/02)
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- On the factors controlling the structural specificity and stereospecificity of the L-lactate dehydrogenase from Bacillus stearothermophilus: Effects of Gln102→Arg and Arg171→Trp/Tyr double mutations
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The factors determining the L-stereospecificity of the L-lactate dehydrogenase from Bacillus stearolhermophilus have been probed by introducing Arg171Trp/Tyr and Gln 102Arg mutations. These changes preclude normal 2-keto acid substrate binding via an Arg171-COO- electrostatic interaction and are positioned to induce a reversal of the natural substrate binding mode, thereby leading to D-2-hydroxy acid formation. However, the L-stereospecificities of the mutant enzymes remain unchanged, showing that there are important fail-safe stereospecificity determinants that take over when the key Arg171-COO- binding interaction is removed. The effects of the mutations on structural specificity are approximately additive, resulting in the broad 2-keto acid specificity of the wild-type enzyme being changed to give catalysts highly selective for the dicarboxylic substrate oxalacetate.
- Kallwass, Helmut K.W.,Hogan, James K.,Macfarlane, Emma L.A.,Martichonok, Valeri,Partis, Wendy,Kay, Cyril M.,Gold, Marvin,Bryan Jones
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p. 10704 - 10710
(2007/10/02)
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- Preparation of the diastereomeric mixture 2R,4S-1-[2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole
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The 2R,4S-isomer of formula I and the 2RS,4S-diastereoisomeric mixture of formula Ia of 1-[2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole STR1 and the preparation thereof are described. The compounds of formulae I and Ia have pronounced microbicidal activity without having phytotoxic side-effects. They are used as active ingredients in microbicidal compositions, especially as seed dressings.
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- SYNTHESIS OF MONOCERIN, AN ANTIFUNGAL, INSECTICIDAL AND PHYTOTOXIC HEPTAKETIDE METABOLITE OF EXSEROHILUM MONOCERAS
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Both the naturally occurring enantiomer and the racemate of monocerin were synthesized for the first time.
- Mori, Kenji,Takaishi, Hideo
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p. 1639 - 1646
(2007/10/02)
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- Stereochemical Control on Yeast Reduction of α-Keto Esters. Reduction by Immobilized Bakers' Yeast in Hexane
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Ethyl 2-oxoheptanoate has been reduced by three methods: free bakers' yeast (FBY) in water, immobilized bakers' yeast (IMBY) in water, and IMBY in hexane.It has been found that the stereochemistry of reduction of α-keto esters by bakers' yeast is controlled by appropiate choice of reaction conditions.
- Nakamura, Kaoru,Inoue, Kiyoko,Ushio, Kazutoshi,Oka, Shinzaburo,Ohno, Atsuyoshi
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p. 2589 - 2593
(2007/10/02)
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- A SYNTHON FOR CHIRAL GLYCOLATE ENOLATE (ROC-HCOOR'): A CAMPHOR-BASED OXAZOLINE
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Alkylations of the anion (7a) derived from a camphor-based oxazoline proceed in good yield.Hydrolysis affords the corresponding α-hydroxy acids in high ee.
- Kelly, T. Ross,Arvanitis, Argyrios
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