The Fluorenone Imines of Glycine Esters and Their Phosphonic Acid Analogues

Kobayashi, Shū; Yazaki, Ryo; Seki, Kiyoshi; Yamashita, Yasuhiro

doi:10.1002/anie.200801322

Cited by 86 publications

(19 citation statements)

References 25 publications

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“…Nevertheless, the combination of [CuA C H T U N G T R E N N U N G (CH 3 CN) 4 ]PF 6 /(R)-1 (5 mol %) [14] and Cs 2 CO 3 (20 mol %) was chosen as optimal because a cleaner reaction was observed, leading to a better product yield. [15] The substrate scope and limitations of this method were next examined. As shown in Table 2, a wide range of arylidene malonates with either electron-donating or electronwithdrawing substituents at the ortho-, meta-, or para position of the aromatic ring (substrates 3 a-3 i) reacted with 2 to afford the expected products 4 a-4 i with excellent diastereo-(syn/anti = 92:8-97:3) and enantioselectivities (!…”

mentioning

confidence: 99%

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Hernandez‐Toribio

Arrayás

Carretero

2011

Chemistry A European J

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Peptide-based therapies are emerging at an increasingly rapid pace because peptides offer lower toxicity, show higher specificity, and demonstrate fewer toxicology issues compared with small molecule drugs.[1] Modification of these therapeutics with non-natural amino acids of desired structural complexity is instrumental to identify target-specific peptides. Enantiopure b-branched a-amino acids [2] are highly valuable because the incorporation of the b-substituent generally imposes severe conformational restraints, thus allowing the de novo design of peptidic entities with a predetermined three-dimensional structure.[3] Because glutamic acid is the main excitatory amino acid in the central nervous system, its derivatives have attracted great interest as essential components of peptides, as well as potential signal mediators of neurotransmission. [4] The catalytic asymmetric alkylation of Schiff bases of glycine esters is one of the most reliable and straightforward synthetic routes to optically active a-amino acid derivatives. [5] In particular, the asymmetric conjugate addition of glycinate imines to a,b-unsaturated carbonyl compounds [6] (mainly acrylates) is a highly versatile reaction to afford optically active glutamic acid derivatives. However, in contrast to the number of examples able to provide enantioenriched a-amino acid derivatives, the application of this methodology to the synthesis of b-substituted a-amino acids has proven frustratingly elusive. In addition to the difficulty of controlling both diastereo-and enantioselectivity in the two new contiguous stereogenic centers, a major obstacle is the much lower reactivity of b-substituted a,b-unsaturated carbonyl compounds (e.g., crotonates) compared to simple acrylates. The use of strong bases to overcome this limitation has been reported to be detrimental to enantiocontrol.[6a]In a seminal work, the group of Kobayashi recently described, to our knowledge, the only existing general precedent for the catalytic asymmetric 1,4-addition of glycine derivatives to b-substituted acrylic acid derivatives. [6b, 7] High yields and high levels of diastereo-and enantiocontrol were attained with b-alkyl-substituted substrates by using calcium complexes of chiral deprotonated bisoxazoline (Box) ligands as catalysts. In spite of these excellent results, there is room for innovation, especially with regard to the substrate scope of the electrophile component. For instance, the potential of this reaction has not been applied so far to Michael-type acceptors with aromatic substituents at the b-position (i.e., cinnamates), even though the resulting products would offer unique opportunities for further functionalization.[8] We disclose herein a catalytic enantioselective and diastereoselective method for the synthesis of b-branched a-amino acids (up to 99 % enantiomeric excess (ee) and 99:1 diastereomeric ratio (d.r.)), due to the use of the more reactive gemdiactivated olefins such as alkylidene malonates.On the basis of our previous results, which report highly enanti...

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confidence: 99%

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Hernandez‐Toribio

Arrayás

Carretero

2011

Chemistry A European J

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“…Schiff bases 4 with electron-donating or electron-withdrawing groups on their aromatic rings reacted with 2 b smoothly to afford the desired cycloadducts in high yields with high exo selectivities and enantioselectivities (Table 4, entries 3-7). Moreover, it is worth noting that Schiff bases prepared from a-alkyl-a-aminophosphonates also worked well and that the desired cycloadducts with quaternary carbon centers were obtained in high diastereoand enantioselectivities (Table 4, entries [15][16][17]. The heteroaromatic moiety, 3-pyridyl, also did not affect the results through some extra coordination to the silver atom (Table 4, entry 10).…”

Section: Asymmetric [3+2] Cycloaddition Of Imines Of A-aminophosphonamentioning

confidence: 98%

Chiral Silver Amides as Effective Catalysts for Enantioselective [3+2] Cycloaddition Reactions

Yamashita

Imaizumi

Guo

et al. 2011

Chemistry An Asian Journal

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Asymmetric [3+2] cycloaddition of α-aminoester Schiff bases with substituted olefins is one of the most efficient methods for the preparation of chiral pyrrolidine derivatives in optically pure form. In spite of its potential utility, applicable substrates for this method have been limited to Schiff bases that bear relatively acidic α-hydrogen atoms. Here we report a chiral silver amide complex for asymmetric [3+2] cycloaddition reactions. A silver complex prepared from silver bis(trimethylsilyl)amide (AgHMDS) and (R)-DTBM-SEGPHOS worked well in asymmetric [3+2] cycloaddition reactions of α-aminoester Schiff bases with several olefins to afford the corresponding pyrrolidine derivatives in high yields with remarkable exo- and enantioselectivities. Furthermore, α-aminophosphonate Schiff bases, which have less acidic α-hydrogen atoms, also reacted with olefins with high exo- and enantioselectivities. The stereoselectivities of the [3+2] cycloadditions with maleate and fumarate suggested that the reaction proceeded by means of a concerted mechanism. An NMR spectroscopic study indicated that complexation of AgHMDS with the bisphosphine ligand was not complete, and that free AgHMDS, which did not show any significant catalytic activity, existed in the catalyst solution. This means that significant ligand acceleration occurred in the current reaction system.

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“…2,3 As we know, the catalytic asymmetric direct Mannich-type reaction of glycinate Schiff bases was one of the most efficient routes to optically active ␣,␤-diamino acids (Scheme 1a). [4][5][6][7][8][9] However, to our knowledge, the glycinate Schiff bases used for Mannich-type reactions were synthesized from glycinates and special ketones [10][11][12] (Scheme 1b). Although the ketimines of glycinate Schiff bases were efficiently applied in the literature, [13][14][15][16][17][18][19][20] the corresponding aldimines of glycinate Schiff bases were difficult to use in the Mannich reactions due to the following reasons: (i) the lower pK a of the ␣ proton and (ii) the competition of the two different types of imines as electrophiles may cause a dirty reaction.…”

Section: Introductionmentioning

confidence: 99%

First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines

et al. 2016

Can. J. Chem.

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Abstract:The catalytic enantioselective Mannich-type reaction between glycinate Schiff base and imines has been one of the most efficient routes for accessing ␣,␤-diamino acids. However, the glycinate Schiff bases used in the references were almost ketimines. Only several examples of aldimines were used in the presence of metal catalyst. We developed the first example of an asymmetric direct Mannich reaction using aldimines of glycinates instead of ketimines of glycinates. The reaction was well catalyzed by chiral guanidine with high yield (up to 92%) and moderate stereoselectivity (up to 65%).Key words: organocatalyst, aldimine, glycinates, sulphonyl imine, chiral guanidine.Résumé : La réaction catalytique énantiosélective de type Mannich entre des glycinates, utilisés comme base de Schiff, et des imines se révèle être l'une des voies les plus efficaces pour accéder à des acides ␣,␤-diaminés. Cependant, dans les articles de référence, les glycinates utilisés comme base de Schiff sont presque toujours des cétimines. Il n'existe que peu d'exemples où des aldimines ont été utilisées en présence d'un catalyseur métallique. Nous avons mis au point le premier exemple d'une réaction de Mannich asymétrique directe où des aldimines de glycinates sont utilisés à la place de cétimines de glycinates. La catalyse de cette réaction, dont le rendement était élevé (jusqu'à 92 %), était convenablement assurée par une guanidine chirale, et ce, avec une stéréosélectivité modérée (jusqu'à 65 %). [Traduit par la Rédaction]

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The Fluorenone Imines of Glycine Esters and Their Phosphonic Acid Analogues

Cited by 86 publications

References 25 publications

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Chiral Silver Amides as Effective Catalysts for Enantioselective [3+2] Cycloaddition Reactions

First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines

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The Fluorenone Imines of Glycine Esters and Their Phosphonic Acid Analogues

Cited by 86 publications

References 25 publications

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using CuI‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using CuI‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Chiral Silver Amides as Effective Catalysts for Enantioselective [3+2] Cycloaddition Reactions

First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines

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Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins

Enantiocontrolled Synthesis of β‐Branched α‐Amino Acids by Using Cu^I‐Catalyzed 1,4‐Addition of Glycine Imines to β‐Substituted gem‐Diactivated Olefins