- Enantioselective protonation of catalytically generated chiral enolates as an approach to the synthesis of α-chloroesters
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Treatment of α,α-dichloroaldehydes with various phenols in the presence of chiral triazolium salt catalysts and excess base results in the synthesis of α-chloro aryl esters in good yield and enantioselectivity. The reaction is tolerant of various function
- Reynolds, Nathan T.,Rovis, Tomislav
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- Glycerol conversion to high-value chemicals: The implication of unnatural α-amino acid syntheses using natural resources
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Glycerol derivatives are an important class of compounds, which have great applications as basic structural building blocks in organic synthesis. O-Benzylglycerol was oxidised to produce a high-value compound in high yield using a NaOtBu-O2 system. Furthermore, the synthetic utility of the resulting product was demonstrated by its transformation into unnatural α-amino acids, thus showing the valorisation of glycerol biomass.
- Park, Yun Ji,Yang, Jung Woon
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p. 2615 - 2620
(2019/06/03)
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- Triazolopeptides: chirospecific synthesis and cis/trans prolyl ratios of structural isomers
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As cis/trans prolyl isomerization plays a crucial role in various biological processes, peptide mimics capable of modifying the cis/trans Xaa-Pro ratio are of particular interest. A practical approach toward proline derived triazolopeptides employing [3+2] azide-alkyne cycloadditions as the key reaction step and the analysis of their cis/trans prolyl ratios are reported. Structural investigations indicated the adjustability of both the cis-percentage and the conformational stability toward intramolecular H-bonding effects.
- Paul, Andreas,Bittermann, Holger,Gmeiner, Peter
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p. 8919 - 8927
(2007/10/03)
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- A novel application of a [3+2] cycloaddition reaction for the synthesis of the piperazinone rings of pseudotheonamides A1 and A2
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A novel approach to synthesize the piperazinone ring system of pseudotheonamide A1 and A2 is described. The key step is the intramolecular [3+2] cycloaddition reaction of a suitably orientated azide and an α,β-unsaturated ester.
- Gurjar, Mukund K,Karmakar, Sukhen,Mohapatra, Debendra K,Phalgune, Usha D
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p. 1897 - 1900
(2007/10/03)
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- Preparation of (R)-2-azidoesters from 2-((p-nitrobenzene)sulfonyl)oxy esters and their use as protected amino acid equivalents for the synthesis of di- and tripeptides containing D-amino acid constituents
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(R)-2-Azidoesters and their derived (R)-2-azido acids are readily prepared from common amino acids by an inversion methodology that employs (S)-2-nosyloxyesters as key intermediates. The (R)-2-azidoesters can be used as protected amino acid equivalents in peptide synthesis. Basic hydrolysis frees the carboxyl group. Triphenylphosphine/water is used to free the amine group. By these reactions a variety of L-D and D-L dipeptides, L-D-L tripeptides, and depsipeptides can be prepared easily in good yields, and without detectable epimerization.
- Hoffman,Kim
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p. 3007 - 3020
(2007/10/02)
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- Nucleophilic Substitution Reactions of Alkyl Halides By Using New Polymer-Supported Reagents Containing Hemin
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A new polymer reagent consisting of hemin, divinylbenzene, and 2-methyl-5-vinylpyridine was synthesized by suspension copolymerization.Substitution reactions of primary, secondary, and tertiary alkyl halides with the hemin copolymer combined with cyanide, azide, and thiocyanate ions were given satisfactory yields.This reaction mechanism was revealed to be a SNi type on the basis of stereochemical study.The hemin copolymer was not only a polymer-supported reagent with functional capabilities, but also served to separate the product from the reaction mixture.
- Saito, Kiyoshi,Harada, Kaoru
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p. 2562 - 2566
(2007/10/02)
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