Organocatalytic Asymmetric Michael/Dieckmann Cyclization Reaction of Alkynones To Construct Spirocyclopentene Oxindoles
27
Citation
65
Reference
10
Related Paper
Citation Trend
Abstract:
A highly enantioselective conjugate addition/Dieckmann cyclization of 3-carboxymethyl substituted oxindoles with electron-deficient internal alkynes was achieved under the catalysis of a chiral guanidine catalyst and NaH. This protocol provides access to a wide range of synthetically useful optically active spirocyclopentenone oxindoles and their derivatives under mild reaction conditions.Keywords:
Conjugate
Guanidine
Michael reaction
Abstract Methylation of the phosphinothioates (I) gives the S‐methyl compounds (III) which are sulfurized to produce the optically active phosphinodithioates (IV).
Active compound
Cite
Citations (0)
The guanidine group is one of the most important pharmacophoric groups in medicinal chemistry. The only amino acid carrying a guanidine group is arginine. In this article, an easy method for the modification of the guanidine group in peptidic ligands is provided, with an example of RGD-binding integrin ligands. It was recently demonstrated that the distinct modification of the guanidine group in these ligands allows for the selective modulation of the subtype (e.g., between the subtypes αv and α5). Moreover, a formerly unknown strategy for the functionalization via the guanidine group was demonstrated, and the synthetic approach is reviewed in this document. The modifications described here involve terminally (Nω) alkylated and acetylated guanidine groups. For the synthesis, tailor-made precursor molecules are synthesized, which are then subjected to a reaction with an orthogonally deprotected amine to transfer the pre-modified guanidine group. For the synthesis of alkylated guanidines, precursors based on N,N′-Di-Boc-1H-pyrazole-1-carboxamidine are used to synthesize acylated compounds, the precursor of choice being a correspondingly acylated derivative of N-Boc-S-methylisothiourea, which can be obtained in one- and two-step reactions.
Guanidine
Surface Modification
Functional group
Protecting group
Pyrazole
Amidine
Cite
Citations (0)
Guanidine D,L-pantoate was synthesized from D,L-pantolactone,guanidine carbonate and calcium hydroxide in a yield of 91.6%.Guanidine D-pantoate and Guanidine L-pantoate were separated from guanidine D,L-pantoate in methanol.Guanidine D-pantoate was hydrolyzed with sulfuric acid to D-pantolactone with a yield of 92.3%.D-Panthenol was synthesized from D-pantolactone and 3-aminopropanol with a yield of close to 100%.Guanidine L-pantoate was racemised to D,L-pantolactone with a yield of 86.5%.The resolution agent of guanidine can be reused.The structure of the product was identified by IR and elementary analysis.
Guanidine
Cite
Citations (0)
Abstract Phospha—Michael addition of P(O—Et) 3 to benzylidenemalononitriles (I) in the presence of a proline‐based organocatalyst represents one of the most straightforward routes for the synthesis of optically active β‐malonophosphonates (III) (13 examples).
Michael reaction
Cite
Citations (0)
The guanidine group is one of the most important pharmacophoric groups in medicinal chemistry. The only amino acid carrying a guanidine group is arginine. In this article, an easy method for the modification of the guanidine group in peptidic ligands is provided, with an example of RGD-binding integrin ligands. It was recently demonstrated that the distinct modification of the guanidine group in these ligands allows for the selective modulation of the subtype (e.g., between the subtypes αv and α5). Moreover, a formerly unknown strategy for the functionalization via the guanidine group was demonstrated, and the synthetic approach is reviewed in this document. The modifications described here involve terminally (Nω) alkylated and acetylated guanidine groups. For the synthesis, tailor-made precursor molecules are synthesized, which are then subjected to a reaction with an orthogonally deprotected amine to transfer the pre-modified guanidine group. For the synthesis of alkylated guanidines, precursors based on N,N′-Di-Boc-1H-pyrazole-1-carboxamidine are used to synthesize acylated compounds, the precursor of choice being a correspondingly acylated derivative of N-Boc-S-methylisothiourea, which can be obtained in one- and two-step reactions.
Guanidine
Surface Modification
Functional group
Protecting group
Amidine
Pyrazole
Cite
Citations (1)
1,1-Diaminoazines can act as effective organocatalysts for the formation of phosphorus-carbon bonds between biphenylphosphine oxide and an activated alkene (Michael acceptor). These catalysts provide the P-C adducts at a faster rate and with relatively better yields in comparison to the organocatalysts employed earlier. The notable advantage is that 1,1-diaminoazines catalyse the reaction even in an aqueous medium with very good yields. Organocatalysis using 1,1-diaminoazines was also successfully carried out between dimethylphosphite and benzylidenemalononitrile under multicomponent conditions.
Michael reaction
Alkene
Acceptor
Addition reaction
Carbon fibers
Cite
Citations (11)
Abstract Review: ca. 80 refs.
Guanidine
Cite
Citations (0)
Here we describe our studies on solvent-dependent enantiodivergent Mannich-type reactions utilizing conformationally flexible guanidine/bisthiourea organocatalyst (S,S)-1. Our mechanistic investigations revealed that the stereo-determining steps in both the (R)- and (S)-selective Mannich-type reactions are governed by the cooperative effect of guanidine and thiourea in the inherently monomeric structure of (S,S)-1. Based on the mechanistic similarity between the (R)- and (S)-selective Mannich-type reactions, we discovered that (S,S)-1-catalyzed reactions show unique reversibility in mixed solvent systems. We highlight the development of sequential enantiodivergent organocatalysis using (S,S)-1, which allows enantio-switching with single-flask operation and high in situ tunability.
Guanidine
Mannich reaction
Cite
Citations (34)
The Michael addition reaction represents one of the most powerful methods for the formation of carbon–carbon bonds in organic synthesis. Thanks to the rapid development of asymmetric organocatalysis, significant progress has been made during the past years in achieving organocatalytic asymmetric Michael reactions with a diverse combination of Michael donors and acceptors. Many new substrates have been accordingly applied in this reaction, together with the new approaches developed for the purpose of target- and diversity-oriented asymmetric synthesis. This review surveys the advances in target- and diversity-oriented asymmetric organocatalytic Michael reactions developed between 2009 and early 2011.
Michael reaction
Organic Synthesis
Cite
Citations (255)
The conformational changes of creatine kinase during denaturation by different concentrations of guanidine hydrochloride have been studied by fluorescence and ultraviolet difference spectroscopic methods. At low concentrations of guanidine, less than 1 M, the denatured minus native difference spectra showed two negative peaks at 281 and 287 nm, whereas the fluorescence emission increased markedly with its maximum red-shifted from 337 to 345 nm. Control experiments showed that guanidine also increased the emission of ionized tyrosine at 345 nm. With the increase of concentrations of guanidine, both negative peaks at 281 and 287 nm increased in magnitude to reach maximal values at 3 M guanidine and at this time a small peak appeared at 292 nm. The fluorescence maximum was further red-shifted to 355 nm, whereas the emission intensity of the main peak decreased and a small shoulder appeared at 310 nm when the guanidine concentration increased from 1 to 3 M. Further increase in guanidine concentration produced little further change either in UV absorption or in fluorescence. From the above results, it seems that, in the native enzyme. Trp residues are partly buried and partly exposed and some of the Tyr residues are in ionized state. Guanidine below 1 M does not expose the buried Trp residues nor affects significantly the microenvironments of the ionized Tyr residues. At 3 M guanidine, Trp residues are exposed and the ionization state of Tyr residues is also affected. At this concentration, the peptide chain seems to be fully unfolded as evidenced by the fact that 5 M guanidine produces little further change in both UV absorption and fluorescence.
Guanidine
Hydrochloride
Denaturation (fissile materials)
Cite
Citations (24)