- A Concise Stereoselective Total Synthesis of Methoxyl Citreochlorols and Their Structural Revisions
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A concise, stereoselective and protecting group free approaches for the total synthesis of (?)-(2S,4R)- and (+)-(2R,4S)-3′-methoxyl citreochlorols and their stereoisomers are demonstrated. All four stereoisomers were synthesized to establish the absolute stereochemistry of the reported structures and the structures were revised accordingly. The approach involves chelation controlled regioselective reduction of a diester, silyl iodide promoted ring-opening iodo esterification of lactones, highly chemo- and regioselective ring-opening of an epoxy ester, dichloromethylation of a carboxyl group, and syn- and anti-selective reduction of the resulted β-hydroxy ketone as key steps.
- Sunnapu, Ranganayakulu,Rajendar, Goreti
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p. 1637 - 1642
(2021/03/15)
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- Stereoselective Synthesis of Coreoside D and Determination of Its Absolute Configuration
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We report the stereoselective synthesis of (3 S)- and (3 R)-coreoside D. The conjugated diyne in the C1-C14 moiety was synthesized through two types of palladium-catalyzed cross-coupling reaction. The introduction of the glucopyranose was achieved by a gl
- Imaizumi, Ryoya,Ogawa, Narihito
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supporting information
p. 1409 - 1412
(2020/11/23)
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- Plant growth regulators and Axl and immune checkpoint inhibitors from the edible mushroom Leucopaxillus giganteus
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A novel compound, (R)-4-ethoxy-2-hydroxy-4-oxobutanoic acid (1), and six known compounds (2–7) were isolated from the fruiting bodies of the wild edible mushroom Leucopaxillus giganteus. The planar structure of 1 was determined by the interpretation of spectroscopic data analysis. The absolute configuration of 1 was determined by comparing specific rotation of the synthetic compounds. In the plant regulatory assay, the isolated compounds (1–7) and the chemically prepared compounds (8–10) were evaluated their biological activity against the lettuce (Lactuca sativa) growth. Compounds 1 and 3–10 showed the significant regulatory activity of lettuce growth. 1 showed the strongest inhibition activity among the all the compounds tested. In the lung cancer assay, all the compounds were assessed the mRNA expression of Axl and immune checkpoints (PD-L1, PD-L2) in the human A549 alveolar epithelial cell line by RT-PCR. Compounds 1–10 showed significant inhibition activity against Axl and/or immune checkpoint.
- Choi, Jae-Hoon,D’Alessandro-Gabazza, Corina N.,Gabazza, Esteban C.,Harada, Etsuko,Hirai, Hirofumi,Kawagishi, Hirokazu,Malya, Irine Yunhafita,Toda, Masaaki,Wu, Jing,Yasuma, Taro
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p. 1332 - 1338
(2020/03/31)
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- A cross-metathesis approach to novel pantothenamide derivatives
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Pantothenamides are known for their in vitro antimicrobial activity. Our group has previously reported a new stereoselective route to access derivatives modified at the geminal dimethyl moiety. This route however fails in the addition of large substituents. Here we report a new synthetic route that exploits the known allyl derivative, allowing for the installation of larger groups via cross-metathesis. The method was applied in the synthesis of a new pantothenamide with improved stability in human blood.
- Guan, Jinming,Hachey, Matthew,Puri, Lekha,Howieson, Vanessa,Saliba, Kevin J.,Auclair, Karine
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supporting information
p. 963 - 968
(2016/07/06)
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- Visible light photoredox-catalyzed deoxygenation of alcohols
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Carbon-oxygen single bonds are ubiquitous in natural products whereas efficient methods for their reductive defunctionalization are rare. In this work an environmentally benign protocol for the activation of carbon-oxygen single bonds of alcohols towards a reductive bond cleavage under visible light photocatalysis was developed. Alcohols were activated as 3,5-bis(trifluoromethyl)-substituted benzoates and irradiation with blue light in the presence of [Ir(ppy)2( dtb-bpy)](PF6 ) as visible light photocatalyst and Hünig's base as sacrificial electron donor in an acetonitrile/water mixture generally gave good to excellent yields of the desired defunctionalized compounds. Functional group tolerance is high but the protocol developed is limited to benzylic, α-carbonyl, and α-cyanoalcohols; with other alcohols a slow partial C-F bond reduction in the 3,5-bis(trifluoromethyl)benzoate moiety occurs.
- Rackl, Daniel,Kais, Viktor,Kreitmeier, Peter,Reiser, Oliver
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supporting information
p. 2157 - 2165
(2015/01/09)
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- Radical-mediated intramolecular C-C bond formation and the deoxygenation of alcohols under solvent-free conditions with tributyl methyl ammonium hypophosphite
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A green, solvent-free protocol was developed for the radical-mediated intramolecular cyclization of haloacetals and the deoxygenation of S-methyl dithiocarbonates and cyclic thionocarbonate. This process uses tributyl methyl ammonium hypophosphite as a H-donor in the presence of triethylborane or t-butyl peroxide. This methodology provides eco-friendly reaction conditions.
- Lee, Eun Hwa,Cho, Dae Hyan,Satyender, Apuri,Jang, Doo Ok
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scheme or table
p. 6927 - 6929
(2012/02/05)
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- Geminal dialkyl derivatives of N-substituted pantothenamides: Synthesis and antibacterial activity
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As a key precursor of coenzyme A (CoA) biosynthesis, pantothenic acid has proven to be a useful backbone to elaborate probes of this biosynthetic pathway, study CoA-utilizing systems, and design molecules with antimicrobial activity. The increasing prevalence of bacterial strains resistant to one or more antibiotics has prompted a renewed interest for molecules with a novel mode of antibacterial action such as N-substituted pantothenamides. Although numerous derivatives have been reported, most are varied at the terminal N-substituent, and fewer at the β-alanine moiety. Modifications at the pantoyl portion are limited to the addition of an ω-methyl group. We report a synthetic route to N-substituted pantothenamides with various alkyl substituents replacing the geminal dimethyl groups. Our methodology is also applicable to the synthesis of pantothenic acid, pantetheine and CoA derivatives. Here a small library of new N-substituted pantothenamides was synthesized. Most of these compounds display antibacterial activity against sensitive and resistant Staphylococcus aureus. Interestingly, replacement of the ProR methyl with an allyl group yielded a new N-substituted pantothenamide which is amongst the most potent reported so far.
- Akinnusi, T. Olukayode,Vong, Kenward,Auclair, Karine
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scheme or table
p. 2696 - 2706
(2011/06/17)
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- Synthesis and biophysical studies on 35-Deoxy amphotericin b methyl ester
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The use of molecular editing in the elucidation of the mechanism of action of amphotericin B is presented. A modular strategy for the synthesis of amphotericin B and its designed analogues is developed, which relies on an efficient gram-scale synthesis of various subunits of amphotericin B. A novel method for the coupling of the mycosa-mine to the aglycone was identified. The implementation of the approach has enabled the preparation of 35-deoxy amphotericin B methyl ester. Investigation of the antifungal activity and efflux-inducing ability of this amphotericin B congener provided new clues to the role of the 35-hydroxy group and is consistent with the involvement of double barrel ion channels in causing electrolyte efflux. 2009 Wiley-VCH Verlag GmbH & Co. KGaA.
- Szpilman, Alex M.,Cereghetti, Damiano M.,Manthorpe, Jeffrey M.,Wurtz, Nicholas R.,Carreira, Erick M.
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supporting information; experimental part
p. 7117 - 7128
(2010/03/05)
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- Synthesis of 35-deoxy amphotericin B methyl ester: A strategy for molecular editing
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(Chemical Presented) A modular strategy for the assembly of amphotericin B analogues with modifications in the macrolactone ring relies on the efficient gram-scale synthesis of all major and minor motifs of amphotericin B. Proof of concept has been achieved by the preparation of the 35-deoxy aglycone en route to the long-sought-after 35-deoxy analogue of amphotericin B.
- Szpilman, Alex M.,Cereghetti, Damiano M.,Wurtz, Nicholas R.,Manthorpe, Jeffrey M.,Carreira, Erick M.
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supporting information; experimental part
p. 4335 - 4338
(2009/02/08)
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- A one-pot combination of amine and heterocyclic carbene catalysis: direct asymmetric synthesis of β-hydroxy and β-malonate esters from α,β-unsaturated aldehydes
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The one-pot combination of amine and heterocyclic carbene catalysis (AHCC) enabled the synthesis of β-hydroxy, β-malonate and β-amino esters from α,β-unsaturated aldehydes with high enantioselectivity (91-97% ee).
- Zhao, Gui-Ling,Córdova, Armando
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p. 5976 - 5980
(2008/02/10)
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- Total synthesis of (+)-tubelactomicin A. 1. Stereoselective synthesis of the lower-half segment by an intramolecular Diels-Alder approach
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(Chemical Equation Presented) Starting from diethyl (R)-malate, synthesis of the lower-half segment of (+)-tubelactomicin A, a 16-membered macrolide antibiotic, has been achieved. The synthesis involved the highly endo- and π-facial selective intramolecul
- Motozaki, Toru,Sawamura, Kiyoto,Suzuki, Akari,Yoshida, Keigo,Ueki, Tatsuo,Ohara, Aiko,Munakata, Ryosuke,Takao, Ken-Ichi,Tadano, Kin-Ichi
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p. 2261 - 2264
(2007/10/03)
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- Synthesis and in vitro cytotoxicity of novel hydrophilic chiral 2-alkoxy-1,4-butanediamine platinum (II) complexes
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Twenty-six new hydrophilic chiral 2-alkoxy-1,4-butanediamine platinum (II) complexes having a seven-membered ring structure between a bidentate carrier ligand and a platinum atom have been synthesized and most of them were evaluated for their in vitro cyt
- Zhu, Haibin,Cui, Kai,Wang, Lianhong,Gou, Shaohua
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p. 4936 - 4943
(2007/10/03)
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- A method for preparation of unnatural (R)-malic acid derivatives with phenylsilanes
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Enantiomerically pure unnatural (R)-malic acid derivatives were prepared from (R,R)-tartrates via their cyclic thionocarbonate derivatives using phenylsilanes in high isolated yields.
- Cho, Dae Hyan,Song, Seong Ho,Jang, Doo Ok
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p. 515 - 519
(2007/10/03)
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- First total synthesis and determination of the absolute configuration of strictifolione, a new 6-(ω-phenylalkenyl)-5,6-dihydro-α-pyrone, isolated from Cryptocarya strictifolia
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Starting from (S)-malic acid and (S)-glycidol, the first total synthesis of strictifolione, a new 6-(ω-phenylalkenyl)-5,6-dihydro-α-pyrone isolated from Cryptocarya strictifolia, was accomplished, which confirmed its structure including the absolute confi
- Juliawaty, Lia Dewi,Watanabe, Yoshimi,Kitajima, Mariko,Achmad, Sjamsul Arifin,Takayama, Hiromitsu,Aimi, Norio
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p. 8657 - 8660
(2007/10/03)
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- Radical-chain redox rearrangement of cyclic benzylidene acetals to benzoate esters in the presence of thiols
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Cyclic benzylidene acetals derived from 1,2- and 1,3-diols undergo an efficient ring-opening redox rearrangement to give benzoate esters in the presence of a peroxide initiator and a thiol, which acts as a polarity-reversal catalyst to promote the radical-chain reaction.
- Roberts, Brian P.,Smits, Teika M.
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p. 137 - 140
(2007/10/03)
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- Facile synthesis of enantiopure (R)-malates
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(R)-Malates were synthesized from cyclic thionocarbonates of (R,R)- tartrates by reacting with hypophosphorous acid in high isolated yields.
- Jang, Doo Ok,Song, Seong Ho
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p. 247 - 249
(2007/10/03)
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- Synthesis of the C1-C28 Portion of Spongistatin 1 (Altohyrtin A)
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A synthetic approach was developed to the C1-C28 subunit of spongistatin 1 (altohyrtin A, 65). The key step was the coupling of the AB and CD spiroketal moieties via an anti-aldol reaction of aldehyde 62 and ethyl ketone 57. The development of a method for the construction of the AB spiroketal fragment is described and included the desymmetrization of C2-symmetric diketone 10 and the differentiation of the two primary alcohols of 16. Further elaboration of this advanced intermediate to the desired aldehyde 62 included an Evans' syn-aldol reaction and Tebbe olefination. The synthesis of the CD spiroketal fragment 56 involved the ketalization of a triol-dione, generated in situ by deprotection of 45, to provide a favorable ratio (6-7:1) of spiroketal isomers 46 and 47, respectively. The overall protecting group strategy, involving many selective manipulations of silyl protecting groups, was successfully developed to provide the desired C1-C28 subunit of spongistatin 1 (altohyrtin A) (65).
- Claffey, Michelle M.,Hayes, Christopher J.,Heathcock, Clayton H.
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p. 8267 - 8274
(2007/10/03)
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- Synthesis of unnatural (R)-malates from L-tartrates
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The cyclic thionocarbonates of L-tartrates were cleanly converted to (R)-malates by treating with magnesium iodide or magnesium and iodine.
- Rho, Ho-Sik
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p. 843 - 847
(2007/10/03)
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- Synthesis of (+)-2,8-dihydroxyethyl-1,4,7,10-tetraoxaspiro[5.5]undecane from (R)-4-hydroxymethyl-2,2-dimethyl-1,3-dioxane
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Selective transformations of diethyl (R)-malate afforded (R)-4-hydroxymethyl 2,2-dimethyl-1,3-dioxane 7 in reasonable yield. Subsequent synthesis of (2S,6R,8S)-2,8-di hydroxyethyl-1,4,7,10-tetraoxaspiro[5.5]undecane 11 was achieved using precursor 7.
- Sauret-Cladiere, Sandrine,Jeminet, Georges
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p. 417 - 423
(2007/10/03)
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- Highly Regioselective Nucleophilic Substitution of Cyclic Carbonates of threo-2,3-Dihydroxy Esters: Synthesis of Optically Pure β-Hydroxy Esters
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The nucleophilic ring opening of the cyclic carbonates of optically active threo-2,3-dihydroxy esters 1 afforded the α-substituted β-hydroxy esters 2 with highly regio- and stereo-selectivity under mild conditions.The α-sulfanyl or α-iodo β-hydroxy esters 2 thus obtained were transformed to the β-hydroxy esters 3, which are useful chiral synthons for natural product synthesis.
- Kang, Suk-Ku,Park, Dong-Chui,Rho, Ho-Sik,Yoon, Seung-Hyun,Shin, Joon-Seob
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p. 3513 - 3514
(2007/10/02)
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- Stereoselective Additions of Chiral, Functionalized Organozinc Reagents to Achiral and Chiral Aldehydes: a Matched-Mismatched Case in Organozinc Chemistry
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The additions of the enantiomerically pure organozinc reagents 17 and 33 to the THF-aldehyde 1 in the presence of the monodentate Lewis acid boron trifluoride-ether give the nonchelation-controlled addition products 7 and 36, respectively (stereoselectivity 95:5, 86:14).These results provide a route to oligo(tetrahydrofuran)s with the relative stereochemistry trans-syn-cis.A stereodirecting effect of the chiral center in the organozinc reagent 17 is found, leading to simple diastereoselectivies in the reaction with achiral aldehydes and to a matched-mismatched case in the reaction with the chiral aldehyde 1. - Key Words: Addition, stereoselective, nonchelation-controlled / Reagent, organozinc / Stereodifferentiation, double / Oligo(tetrahydrofuran)
- Koert, Ulrich,Wagner, Holger,Pidun, Ulrich
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p. 1447 - 1458
(2007/10/02)
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- A Biocatalytic Approach to the Enantioselective Synthesis of (R)- and (S)-Malic Acid
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(S)-Diethyl malate 1a was prepared (70-80percent yield; >98percent optical purity) by an enantioselective reduction of sodium diethyl oxalacetate 2 by fermenting baker's yeast (Saccharomyces cerevisiae).Other microorganisms were tested for their capability of reducing 2.Most of them afforded (S)-1a with ee from 8 to 94percent and only Candida utilis, Aspergillus niger and Lactobacillus fermentum ILC G18D preferentially reduced compound 2 to (R)-1a. (R)-Dimethyl malate 1b was obtained from (R,S)-malate 1b by hydrolysis with pig liver esterase (PLE), the highest ee (93percent) being realized at 0 deg C in 20percent aqueous methanol.Enzymatic hydrolyses of protected malates 1d and 1e did not lead to improvement of the ee.
- Santaniello, Enzo,Ferraboschi, Patrizia,Grisenti, Paride,Aragozzini, Fabrizio,Maconi, Elisabetta
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p. 601 - 605
(2007/10/02)
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- A practical synthesis of D-malate esters from L-tartrate esters
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D-malate esters were synthesized in one-pot from L-tartrate esters in 70-80% overall yields via the corresponding tartrate cyclic sulfites.
- Gao,Zepp
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p. 3155 - 3158
(2007/10/02)
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- A HIGHLY EFFICIENT DEOXYDATION OF α-OXYGENATED ESTERS VIA SmI2-INDUCED ELECTRON TRANSFER PROCESS
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A variety of α-oxygenated esters, such as α-acetoxy, α-methoxy-, α-OTPH, and α-hydroxy esters were easily reduced at room temperature to give the corresponding saturated esters in good to excellent yields with the aid of an efficient electron transfer system, SmI2-THF-HMPA.The method was succesfully applied to the direct conversion of (R,R)-tartrates to (R)-malates.
- Kusuda, Kazuhiro,Junji, Inanaga,Yamaguchi, Masaru
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p. 2945 - 2948
(2007/10/02)
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- Enantiomerically Pure Synthetic Building Blocks with Four C-Atoms and Two or Three Functional Groups from β-Hydroxy-butanoic, Malic, and Tartaric Acid
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The pool of chiral, non-racemic electrophilic building blocks, which are available from simple natural products in both enantiomeric forms is enlarged by the epoxides 3, 5, and 10, by the tosylate 12a, and by the aldehydes 18 (cf. symbols A-D, 14, and Scheme 1).Key steps of the conversions leading from hydroxyacids to the building blocks are: epoxide-opening by triethylborohydride (1 --> 2a) and tosylate reduction (12a --> 12b); the Mitsunobu inversion (2a --> 4a); the reduction of (R,R)-tartaric ester to (R)-malic ester by NBS (N-bromosuccinimide) opening of the benzaldehyde acetal 8 and tin hydride reduction (6c -->7c); the enantiomer enrichment of optically active ethyl β-hydroxy-butanoate through the crystalline dinitrobenzoate 21b.Detailed procedures are given for large scale preparations of the key intermediates.The enantiomeric purities of the building blocks are secured by correlations.
- Hungerbuehler, Ernst von,Seebach, Dieter,Wasmuth, Daniel
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p. 1467 - 1487
(2007/10/02)
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