- Diastereoselective Electrochemical Carboxylation of Chiral α-Bromocarboxylic Acid Derivatives: An Easy Access to Unsymmetrical Alkylmalonic Ester Derivatives
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The diastereoselective electrochemical carboxylation of chiral N-(2-bromoacyl)oxazolidin-2-ones has been studied. This reaction was carried out by cathodic reduction of the C - Br bond, in the presence of carbon dioxide, followed by treatment with diazomethane. The yields and the diastereomeric ratio of the two epimeric alkylmalonic acid derivatives are strongly affected by various factors: solvent-supporting electrolyte system, temperature, electrode material, electrolysis conditions, oxazolidinone moiety. The higher yields (88%) were obtained starting from N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one la, but with poor diastereoselectivity (61:39). The two epimers were easily separated by flash chromatography. The best results were achieved using a different chiral auxiliary: Oppolzer's camphor sultam. Starting from 1j a good yield in carboxylated product was obtained (80%) with excellent diastereoselectivity (98:2). These chiral alkylmalonic acid derivatives are valuable building blocks in the synthesis of molecules with biological activity and of chiral propane-1,3-diols derivatives.
- Feroci, Marta,Orsini, Monica,Palombi, Laura,Sotgiu, Giovanni,Colapietro, Marcello,Inesi, Achille
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Read Online
- Total synthesis of natural (?)- and unnatural (+)-Melearoride A
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This communication details the first total synthesis of the 13-membered macrolide, (?)-Melearoride A, as well as unnatural (+)-Melearoride A. The synthesis features a concise 13 step synthesis (11 steps longest linear sequence) that offers flexible stereo-control and multiple opportunities for unnatural analog synthesis to delve into antifungal SAR. The route features a cuprate addition, an Evans asymmetric alkylation, and a ring-closing metathesis (RCM) to close the 13-membered macrocyclic core.
- Reed, Carson W.,Fulton, Mark G.,Nance, Kellie D.,Lindsley, Craig W.
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supporting information
p. 743 - 745
(2019/02/09)
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- Diastereoselective Electrophilic Trifluoromethylthiolation of Chiral Oxazolidinones: Access to Enantiopure α-SCF3 Alcohols
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Lithium imide enolates featuring Evans’ chiral oxazolidinone auxiliary were involved in diastereoselective α-trifluoromethylthiolation with electrophilic SCF3 donors. Diastereopure products were isolated and converted to enantiopure α-SCF3 alcohols without racemisation. (Figure presented.).
- Chachignon, Hélène,Kondrashov, Evgeniy V.,Cahard, Dominique
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p. 965 - 971
(2018/01/27)
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- AHU - 377 preparation method of the midbody and intermediate and intermediate preparation method
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The invention relates to the field of chemical synthesis of medicines and in particular relates to a preparation method and intermediate of an AHU-377 intermediate and a preparation method of the intermediate. The preparation method of the AHU-377 intermediate shown in a formula (I) in the description comprises the following steps: performing a substitution reaction on a compound shown in a formula (II) in the description and a compound shown in a formula (III) in the description and then carrying out hydrolysis to prepare the AHU-377 intermediate shown in the formula (I), wherein the hydrolysis reaction is carried out in the presence of hydrogen peroxide and lithium hydroxide hydrate. The invention also aims to provide a new compound with a structure shown in the formula (II). In the new route, as a new compound shown in a formula (IV) in the description is prepared through reaction of the compound in the formula (II) and the compound in the formula (III), the selectivity is quite good, and a few diastereoisomers are generated in the reaction process and can be removed only through simple aftertreatment.
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Paragraph 0065; 0066; 0067; 0068
(2017/10/13)
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- PROCESS FOR THE PREPARATION OF (1S,3S,7S,10R,11S,12S,16R)-7,11-DIHYDROXY-8,8,10,12,16-PENTAMETHYL-3-[(1E)-1-METHYL-2-(2-METHYL-4-THIAZOLYL)ETHENYL]-17-OXA-4-AZABICYCLO[14.1.0]HEPTADECANE-5,9-DIONE AND INTERMEDIATES THEREOF
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The present invention relates to an improved process for the preparation of (1S,3S,7S,10R,11S,12S,16R)-7,11-dihydroxy-8,8,10,12,16-pentamethyl-3-[(1E)-1-methyl-2-(2- methyl-4-thiazolyl)ethenyl]- 17-oxa-4-azabicyclo[ 14.1.0]heptadecane-5,9-dione represented by the following structural formula I and intermediates thereof. The present invention also provides novel intermediate compounds useful for the preparation of compound of formula I and its intermediates.
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Page/Page column 48-49
(2015/06/25)
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- Absolute configuration of lactams and oxazolidinones using kinetic resolution catalysts
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A simple method for determining the absolute configuration of oxazolidinones, lactams, and their derivatives using kinetic resolution catalysts is described. The optically pure substrates were acylated using the (S)-HBTM and the (R)-HBTM catalyst, and the faster reaction was determined. An empirical mnemonic was developed for the assignment of the absolute configuration based on the fast-reacting catalyst.
- Perry, Matthew A.,Trinidad, Jonathan V.,Rychnovsky, Scott D.
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supporting information
p. 472 - 475
(2013/04/11)
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- Synthesis of α-CF3-substituted carbonyl compounds with relative and absolute stereocontrol using electrophilic CF3-transfer reagents
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Evans-type chiral lithium imide enolates undergo diastereoselective α-trifluoromethylation with a hypervalent iodine-CF3 reagent with up to 91% combined isolated yield and 97:3 dr. The resulting isolated diastereopure products can be further transformed into valuable products without racemization.
- Matousek, Vaclav,Togni, Antonio,Bizet, Vincent,Cahard, Dominique
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supporting information; experimental part
p. 5762 - 5765
(2012/01/06)
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- Kinetic resolution of 2-oxazolidinones via catalytic, enantioselective N-acylation
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Kinetic resolution of racemic 2-oxazolidinones via catalytic, enantioselective N-acylation has been achieved for the first time and with outstanding selectivities. Copyright
- Birman, Vladimir B.,Jiang, Hui,Li, Ximin,Guo, Lei,Uffman, Eric W.
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p. 6536 - 6537
(2007/10/03)
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- Development of a scalable process for 1-β-methyl azetidinone: A carbapenem key intermediate
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An optimized process for the stereoselective synthesis of 1-β-methyl carbapenem key intermediate (3S,4S)-[(R)-1′-((tert-butyldimethylsilyl)oxy) ethyl]-4-[(R)-1-carboxyethyl]-2-azetidinone (1) and (3R,4R)-4-acetoxy-3-[(R)- 1′-((tert-butyldimethylsilyl)oxy)ethyl]-2-azetidinone has been developed employing commercially available chiral 4-phenyl-2-oxazolidinone. This method provides an efficient and cost-effective process with improved selectivity and higher yield.
- Tewari, Neera,Nizar, Hashim,Rai, Bishwa Prakash,Mane, Avinash,Prasad, Mohan
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p. 827 - 829
(2012/12/26)
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- Electrochemical carboxylation of N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one: An efficient route to unsymmetrical methylmalonic ester derivatives
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(Matrix presented) Electrochemical carboxylation of N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one aimed at the synthesis and chiral resolution of unsymmetrical methylmalonic ester derivatives is described. The presence of the Evans' chiral auxiliary perm
- Feroci, Marta,Inesi, Achille,Orsini, Monica,Palombi, Laura
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p. 2617 - 2620
(2007/10/03)
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- An Activated Germanium Metal-Promoted, Highly Diastereoselective Reformatsky Reaction
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Activated germanium metal, prepared by the reduction of germanium(II) iodide with potassium metal, was found to promote the Reformatsky reaction effectively under mild conditions. In the presence of activated germanium metal, the reactions of α-bromo ketones 2a and 2b and α-bromo imides 2e and 2f with benzaldehyde (1a) proceeded smoothly to give the corresponding β-hydroxy carbonyl compounds 3a, 3b, 3e and 3f, respectively, in good yields and with good syn diastereo- selectivity. The activated germanium metal-promoted, asymmetric Reformatsky reaction of enantiomerically pure-oxazolidinone derivatives 2g-j with various aldehydes 1a-d was also examined; the highest diastereoselectivity was achieved when (1S,2R)-2-amino-1,2-diphenylethanol- derived 2j was used as the Reformatsky donor. The excellent diastereoselectivity could be explained in terms of the formation of a chairlike, six-membered transition state between the aldehyde and enolate as in the Zimmerman-Traxler model. A single recrystallization of the Reformatsky adducts, followed by hydrolysis and subsequent esterification, led to enantiomerically pure methyl 3-hydroxy- 2-methylalkanoates 10j-m, with almost quantitative recovery of the enantiomerically pure 2-oxazolidinone 14.
- Kagoshima, Hirotaka,Hashimoto, Yukihiko,Oguro, Dai,Saigo, Kazuhiko
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p. 691 - 697
(2007/10/03)
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- One Pot Synthesis of N-Derivatized 2-Oxazolidinones from Amino Alcohol Carbamates
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A one pot protocol for the synthesis of N-derivatized 2-oxazolidinones from amino alcohol carbamates is described.The method is exceptionally useful if the parent amino acids are prepared in their enantiopure forms via enzymatic resolution of the racemic carbamate esters.
- Huwe, Christoph M.,Blechert, Siegfried
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p. 9533 - 9536
(2007/10/02)
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