diexo-3-Aminonorbornane-2-carboxylic Acid as Highly Applicable Chiral Source for the Enantioselective Synthesis of Heterocycles
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Abstract:
Diastereomers of tetracyclic pyrrolopyrimidine derivatives 2 and 3 were prepared in a three-step domino reaction from diexo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide with levulinic acid or p-toluoylpropionic acid. When subjected to a microwave-mediated retro-Diels-Alder reaction, these tetracycles furnished bicyclic pyrrolo[1,2-a]pyrimidines through the loss of cyclopentadiene. When enantiomeric diexo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide was used, the products were enantiomeric heterocycles with ee >99%, demonstrating that the title compound is an excellent chiral source.Keywords:
Diastereomer
Cyclopentadiene
Enantiomeric excess
Carboxamide
Ene reaction
Controlling chiral recognition and chiral information transfer has major implications in areas ranging from drug design and asymmetric catalysis to supra- and macromolecular chemistry. Especially intriguing are phenomena associated with chiral self-recognition. The design of systems that show self-induced recognition of enantiomers, i.e., involving homochiral versus heterochiral dimers, is particularly challenging. Here, we report the chiral self-recognition of α-ureidophosphonates and its application as both a powerful analytical tool for enantiomeric ratio determination by NMR and as a convenient way to increase their enantiomeric purity by simple achiral column chromatography or fractional precipitation. A combination of NMR, X-ray, and DFT studies indicates that the formation of homo- and heterochiral dimers involving self-complementary intermolecular hydrogen bonds is responsible for their self-resolving properties. It is also shown that these often unnoticed chiral recognition phenomena can facilitate the stereochemical analysis during the development of new asymmetric transformations. As a proof of concept, the enantioselective organocatalytic hydrophosphonylation of alkylidene ureas toward self-resolving α-ureidophosphonates is presented, which also led us to the discovery of the largest family of self-resolving compounds reported to date.
Diastereomer
Molecular Recognition
Enantiomeric excess
Chiral derivatizing agent
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Herein we present a novel route to enantiomerically enriched chiral alpha-substituted carboxylic acids by crystallization-induced dynamic resolution (CIDR) of their diastereomeric salts with chiral amines. Thus, the racemic alpha-bromo acid 3 is converted reliably with (1R,2S)-2-amino-1,2-diphenylethanol in the presence of a catalytic amount of tetrabutylammonium bromide into its R-enantiomer 4 in 90% yield with 88% ee. Similarly, the racemic alpha-thiobenzoyl acid 5 could be resolved to 90% ee in 74% yield. Further enrichment to enantiomeric homogeneity could be achieved in both cases by crystallization. In a telescoped, two-step process, S-alpha-thiobenzoyl acid 6 (>or=99.6% ee) was prepared from the racemic bromide 3 in 63% yield. State-of-the-art parallel experimentation enabled rapid screening for suitable dynamic resolution conditions. Kinetic studies defined the influence of temperature, tetrabutylammonium bromide concentration, molarity, and solvent polarity on the resolution rate, product yield, and enantiomeric excess.
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Abstract Axially chiral 2′-methoxy-1,1′-binaphthyl-2-carboxylic acid (1) was effectively utilized as chiral derivatizing agent for discrimination of enantiomeric alcohols and amines by 1H NMR with the aid of Eu(fod)3. Among a pair of the diastereomeric esters or amides prepared from (aS)-1 and an α-chiral alcohol or amine, the methoxyl protons of the (aS,R)-diastereomer showed the larger lanthanoid-induced downfield shift than those of the (aS,S)-counterpart. Thus, addition of up to 0.5–1.0 equiv amount of Eu(fod)3 caused base-line separation of those protons, allowing determination of the enantiomeric purities and assignment of the absolute configurations of the enantiomeric alcohols and amines. An X-ray crystallographic analysis of the amide ((aS,S)-2) obtained from (aS)-1 and (S)-1-phenylethylamine showed structural resemblance between the amides and esters of 1. Steric models which explain the NMR behavior of the diastereomeric esters and amides are presented based on X-ray analyses. Also reported are two methods to regenerate free acid 1 from amide 2 to afford axially homochiral 1.
Chiral derivatizing agent
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Diastereomers of tetracyclic pyrrolopyrimidine derivatives 2 and 3 were prepared in a three-step domino reaction from diexo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide with levulinic acid or p-toluoylpropionic acid. When subjected to a microwave-mediated retro-Diels-Alder reaction, these tetracycles furnished bicyclic pyrrolo[1,2-a]pyrimidines through the loss of cyclopentadiene. When enantiomeric diexo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide was used, the products were enantiomeric heterocycles with ee >99%, demonstrating that the title compound is an excellent chiral source.
Diastereomer
Cyclopentadiene
Enantiomeric excess
Carboxamide
Ene reaction
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAntidopaminergic effects of the stereoisomers of N-[(1-alkyl-2-pyrrolidinyl)methyl]-5-sulfamoylbenzamides and -2,3-dihydro-benzofuran-7-carboxamidesShu Murakami, Nobuhiro Marubayashi, Takemi Fukuda, Shuzo Takehara, and Tetsuya TaharaCite this: J. Med. Chem. 1991, 34, 1, 261–267Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://pubs.acs.org/doi/10.1021/jm00105a041https://doi.org/10.1021/jm00105a041research-articleACS PublicationsRequest reuse permissionsArticle Views153Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Diastereomer
Absolute Configuration
Moiety
Benzazepines
Pyrrolidine
Benzofuran
Stereospecificity
Carboxamide
Stereoisomerism
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Diastereomer
Enantiomeric excess
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Diastereomer
Chiral derivatizing agent
Carboxamide
Enantiomeric excess
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Diastereomer
Stereospecificity
Enantiomeric excess
Flavour
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Diastereomer
Enantiomeric excess
Chiral derivatizing agent
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A Convenient synthesis of both enantiomeric trans- and cis-2,3-disubstituted 5-norbornenes (bicyclo[2.2.1]heptenes), 2 and 3, has been developed by utilizing the Diels-Alder reaction between cyclopentadiene and chiral dienophiles obtained from a single chiral template, D-mannitol (1).
Cyclopentadiene
D-mannitol
Enantiomeric excess
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