470-51-9Relevant articles and documents
Sequential ruthenium catalysis for olefin isomerization and oxidation: Application to the synthesis of unusual amino acids
Liniger, Marc,Liu, Yiyang,Stoltz, Brian M.
supporting information, p. 13944 - 13949 (2017/11/06)
How can you use a ruthenium isomerization catalyst twice? A ruthenium-catalyzed sequence for the formal two-carbon scission of allyl groups to carboxylic acids has been developed. The reaction includes an initial isomerization step using commercially available ruthenium catalysts followed by in situ transformation of the complex to a metal-oxo species, which is capable of catalyzing subsequent oxidation reactions. The method enables enantioselective syntheses of challenging α-tri- and tetrasubstituted α-amino acids including an expedient total synthesis of the antiepileptic drug levetiracetam.
Microbial enantioselective removal of the N-benzyloxycarbonyl amino protecting group
Maurs, Michele,Acher, Francine,Azerad, Robert
, p. 22 - 26 (2012/10/29)
In order to deprotect N-carbobenzoxy-l-aminoacids (Cbz-AA) and related compounds, a series of microorganisms was selected from soil by enrichment cultures with Cbz-l-Glu as sole nitrogen source. A lyophilized whole-cell preparation of two Arthrobacter sp. strains grown on Cbz-Glu or Cbz-Gly exhibited a high cleavage activity. The conditions of hydrolysis have been optimized and a quantitative enantioselective deprotection of several Cbz-dl-amino acids was obtained, as well as the deprotection of N-carbamoylester derivatives of several synthetic amino compounds. The preparation of Cbz-d-allylglycine and l-allylglycine in high yield and high optical purity is described as an application of this method.
Synthesis of optically active, unnatural α-substituted glutamic acid derivatives by a chiral calcium-catalyzed 1,4-addition reaction
Tsubogo, Tetsu,Kano, Yuichiro,Ikemoto, Koki,Yamashita, Yasuhiro,Kobayashi, Sh
experimental part, p. 1221 - 1225 (2010/10/20)
The first catalytic asymmetric 1,4-addition reactions of azlactones with acrylic esters have been developed. A chiral coordinative calcium catalyst was found to be effective for these reactions, and the desired 1,4-adducts were obtained in good yields and enantioselectivities. The product was converted to the corresponding α-alkylated glutamic acid by acid hydrolysis.
Asymmetric Strecker reaction of γ-keto acids. Facile entry to α-substituted and α,γ-disubstituted glutamic acids
Tang, Guozhi,Tian, Hongqi,Ma, Dawei
, p. 10547 - 10552 (2007/10/03)
The Strecker reaction of γ-keto acid derived sodium salts with (S)-phenylglycinol followed by treatment of the resultant α-amino nitriles with methanolic HCl and heating at 200°C give bicyclic lactones 11 and 12. Hydrolysis and subsequent debenzylation of
Asymmetric synthesis of α-Methyl α-Amino Acids through diastereoselective alkylation under mild reaction conditions of an iminic alanine template with a 1,2,3,6-Tetrahydro-2-Pyrazinone structure
Najera, Carmen,Abellan, Tomas,Sansano, Jose M.
, p. 2809 - 2820 (2007/10/03)
(6R)-6-Isopropyl-3-methyl-5-phenyl-1,2,3,6-tetrahydro-2-pyrazinone, obtained from (R)-valine and (S)-alanine, is highly diastereoselectively alkylated at room temperature by: a) activated alkyl halides under solid-liquid PTC conditions, b) non-activated alkyl halides with organic bases, c) electrophilic olefins employing both solid-liquid PTC conditions and organic bases, and d) allylic carbonates by means of palladium catalysis under neutral conditions. Enantiomerically pure (S)-α-methyl α-amino acids 8 are obtained by hydrolysis of the alkylated pyrazinones.
Chiral 3,6-dihydro-2H-1,4-oxazin-2-ones as alanine equivalents for the asymmetric synthesis of α-methyl α-amino acids (AMAAs) under mild reaction conditions
Chinchilla, Rafael,Galindo, Nuria,Nájera, Carmen
, p. 704 - 717 (2007/10/03)
3,6-Dihydro-2H-1,4-oxazin-2-ones 1 act as very reactive chiral cyclic alanine equivalents and can be diastereoselectively alkylated or allylated using mild reaction conditions: potassium carbonate under phase-transfer catalysis (PTC) conditions when using activated alkyl halides, organic bases such as tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2- diazaphosphorine (BEMP) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) when using unactivated alkyl halides, and neutral Pd(0)-catalysis when allylic carbonates are used. In most cases, the diastereoselectivity under all these different reaction conditions is excellent although the reactions are always carried out at room temperature. Hydrolysis of the obtained alkylated or allylated oxazinones allows the preparation of enantiomerically enriched (S)- α-methyl α-amino acids (S)-AMAAs. The PTC and organic base methodologies have also been applied to the synthesis of (R)-α-methyl α-amino acids starting from (R)-alanine. When dihalides are used as electrophiles under PTC or BEMP conditions, a spontaneous N-alkylation also takes place giving bicyclic oxazinones, which can be hydrolyzed to enantiomerically pure cyclic (S)-AMAAs.
New chiral alanine template with a 1,2,3,6-tetrahydro-2-pyrazinone structure for the asymmetric synthesis of α-methyl α-amino acids
Abellan, Tomas,Najera, Carmen,Sansano, Jose M.
, p. 2211 - 2214 (2007/10/03)
(R)-6-Isopropyl-5-phenyl- 1,2,3,6-tetrahydro-2-pyrazinone, prepared from (R)-valine and (S)-alanine, reacts With activated alkyl halides and electrophilic olefins under solid-liquid PTC conditions: with K2CO3 as base, at room temperature and with high diastereoselectivity (>94%). The palladium-catalyzed allylation reaction of this alanine derivative under neutral conditions at room temperature also takes place with a de>96%. Final hydrolysis of alkylated pyrazinones affords enantiomerically pure α-methyl α-amino acids.
Asymmetric synthesis of α-methyl α-amino acids by diastereoselective alkylation of optically active 6-isopropyl-3-methyl-2,3-dihydro-6H-1,4-oxazin-2-ones
Chinchilla,Falvello,Galindo,Najera
, p. 995 - 997 (2007/10/03)
At room temperature already highly diastereoselective alkylation of the new, cyclic, chiral alanine ester derivatives (6R)-1 can be achieved with either K2CO3 as base under solid liquid phase-transfer catalysis or Pd catalysis under neutral conditions. The products (3S,6R)-2 can be easily hydrolyzed to form (S)-α-methyl α-amino acids.
Enantioselective allylation of nitro group-stabilized carbanions catalyzed by chiral crown ether phosphine-palladium complexes
Sawamura, Masaya,Nakayama, Yuki,Tang, Wen-Ming,Ito, Yoshihiko
, p. 9090 - 9096 (2007/10/03)
Enantioselective allylations of α-nitro ketones (3) and α-nitro esters (15) with allyl acetate were carried out in the presence of 2 equiv of alkali metal fluorides (KF, RbF, CsF) and 1 mol % of palladium catalysts prepared in situ from Pd2(dba)3·CHCl3 and chiral phosphine ligands. Moderate enantioselectivities were observed in the reaction of nitro ketones 3, giving products 4 (4a, 49% ee; 4b, 58% ee; 4c, 44% ee) when rubidium fluoride and ferrocenylphosphine ligands bearing monoaza-15-crown-5 (1b) or monoaza-18-crown-6 (1c) moieties were used as a base and a chiral ligand, respectively. Optically active allylation product 4a was converted into 1-methyl-1-azaspiro[4.5]-decan-10-amine (13), a precursor to opioid receptor binding agents. Enantioselectivity in the reaction of nitro esters 15 increased in accord with increasing steric demand of the ester alkyl group (Me 4 (1 equiv). The pronounced effect of the crown ether moiety for both enantioselection and rate acceleration can be explained by assuming the formation of a ternary complex involving the crown ether, rubidium cation, and enolate anion at the stereodifferentiating transition state. Optically active nitro ester (R)-16c was converted into (R)-α-methylglutamic acid (20).
A Novel Synthesis of (R)- and (S)-α-Alkylated Aspartic and Glutamic Acids: α-Alkylated Aspartic Succinimides as New Type of β-Turn Type II and II' Mimetics
Obrecht, Daniel,Bohdal, Udo,Daly, John,Lehmann, Christian,Schoenholzer, Peter,Mueller, Klaus
, p. 10883 - 10900 (2007/10/02)
A novel and efficient synthesis of optically pure (R)- and (S)-α-methyl glutamic acid (1), (R)-and (S)-α-methyl aspartic acid (2a) and (R)- and (S)-α-isobutyl aspartic acid (2b) using L-phenylalanine cyclohexylamide 4 as chiral auxiliary is described.Crystal structures show that the (R)- and (S)-α-methyl glutamic acid derivatives (S,S)-5 and (R,S)-6 adopt β-turn type I geometries, whereas the corresponding aspartimide derivatives (R,S)-12a,b form a β-turn type II and (S,S)-11a a β-turn type II'.These findings suggest, that the succinimide derivatives of (R)- and (S)-α-alkyl aspartic acids can serve as building blocks to stabilise β-turns of type II (or II') in peptides depending on their absolute configuration.
