- Asymmetric synthesis of the cis- And trans-stereoisomers of 4-aminopyrrolidine-3-carboxylic acid and 4-aminotetrahydrofuran-3-carboxylic acid
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The diastereoselective conjugate addition of lithium (S)-N-benzyl-N- α-methylbenzylamide has been successfully applied to the first asymmetric syntheses of cis-(3S,4R)- and fraBs-(3R,4R)-4-arninotetrahydrofuran-3-carboxylic acids (26% and 25% overall yield respectively, >98% d.e. and >97% e.e. in each case). Furthermore, the most efficient asymmetric synthesis to date of cis-(3R,4R)- and trans-(3R,4S)-4-aminopyrrolidine carboxylic acids is delineated: for cis-(3R,4R), four steps, >98% d.e., 52% overall yield; for trans-(3R,4S), five steps, >98% d.e., 50% overall yield.
- Bunnage, Mark E.,Davies, Stephen G.,Roberts, Paul M.,Smith, Andrew D.,Withey, Jonathan M.
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p. 2763 - 2776
(2007/10/03)
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- The use of enantiomerically pure ketene dithioacetal bis(sulfoxides) in highly diastereoselective intramolecular nitrone cycloadditions. Application in the total synthesis of the beta-amino acid (-)-cispentacin and the first asymmetric synthesis of cis-(3R,4R)-4-amino-pyrrolidine-3-carboxylic acid.
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Intramolecular 1,3-dipolar nitrone cycloaddition onto an enantiomerically pure ketene dithioacetal dioxide using a three-carbon tether gave the corresponding 5,5-disubstituted isoxazolidine as a single diastereomer in good yield. This reaction has been used as the key step in an asymmetric synthesis of the naturally occurring antibiotic, (-)-cispentacin. An asymmetric synthesis of 4-amino-pyrrolidine-3-carboxylic acid has also been carried out using the intramolecular nitrone cycloaddition as the stereocontrolling step.
- Aggarwal, Varinder K,Roseblade, Stephen,Alexander, Rikki
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p. 684 - 691
(2007/10/03)
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- Radical cyclization in heterocycle synthesis. Part 13: Sulfanyl radical addition-cyclization of oxime ethers and hydrazones connected with alkenes for synthesis of cyclic β-amino acids
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A combination of sulfanyl radical addition-cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.
- Miyata, Okiko,Muroya, Kanami,Kobayashi, Tomoko,Yamanaka, Rina,Kajisa, Seiko,Koide, Junko,Naito, Takeaki
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p. 4459 - 4479
(2007/10/03)
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