14603-95-3Relevant academic research and scientific papers
Chiral salen-metal complexes as novel catalysts for asymmetric phase transfer alkylations
Belokon, Yuri N.,North, Michael,Kublitski, Vadim S.,Ikonnikov, Nikolai S.,Krasik, Pavel E.,Maleev, Viktor I.
, p. 6105 - 6108 (1999)
Chiral, salen-metal complexes have been tested as catalysts for the C- alkylation of aldimine Schiff's bases of alanine esters with alkyl bromides under phase-transfer conditions (solid sodium hydroxide, toluene, ambient temperature, 1-10% of the catalyst
Benzylic phosphates as electrophiles in the palladium-catalyzed asymmetric benzylation of azlactones
Trost, Barry M.,Czabaniuk, Lara C.
, p. 5778 - 5781 (2012/05/07)
Palladium-catalyzed asymmetric benzylation has been demonstrated with azlactones as prochiral nucleophiles in the presence of chiral bisphosphine ligands. Benzylic electrophiles are utilized under two sets of reaction conditions to construct a new tetrasubstituted stereocenter. Electron density of the phenyl ring dictates the reaction conditions, including the leaving group. The reported methodology represents a novel asymmetric carbon-carbon bond formation in an amino acid precursor.
Diastereoselective functionalisation of Baylis-Hillman adducts: A convenient approach to α-methyl-α-amino acids
Martelli, Gianluca,Orena, Mario,Rinaldi, Samuele,Sabatino, Piera
experimental part, p. 489 - 497 (2010/11/04)
The N-tosyl carbamates 4a-e, easily prepared starting from the Baylis-Hillman adducts 3a-e, underwent cyclization carried out with I 2/NIS in the presence of NaH, to give the corresponding 2-oxo-1,3-oxazolidines 5a-e in good yield and total stereoselection when the substituent at C-5 is Ar. After the removal of tosyl group, followed by the cleavage of the heterocyclic ring, the α-methyl-α-amino acids 8a,b and 10 were obtained in good yield as hydrochlorides. Springer-Verlag 2010.
Asymmetric synthesis of α-amino acids: Preparation and alkylation of monocyclic iminolactones derived from α-methyl trans-cinnamaldehyde
Lu, Ta-Jung,Lin, Cheng-Kun
experimental part, p. 9527 - 9534 (2009/04/07)
(Chemical Equation Presented) Two novel chiral monocyclic iminolactones 14a and 14b have been prepared. The chiral auxiliary 12 was obtained from α-methyl-trans-cinnamaldehyde through reduction, methylation, Sharpless asymmetric dihydroxylation, and oxidation in 87% overall yield. Esterification of compound 12 with the respective protected amino acids followed by deprotection and cyclization provided the corresponding iminolactones, each in 82% overall yield. Alkylation of the iminolactone 14a afforded the α-methyl-α,α-disubstituted products 15 and 16 in good yields (78-99%) and excellent diastereoselectivity (de >98%). Alkylations of the iminolactone 14b furnished the α-benzyl-α,α-disubstituted products 15a, 16b, 17, and 18 in good yields (51-86%) but moderate diastereoselectivities (43-56%). When HMPA or DMPU was used as a cosolvent, the rate of alkylation of the iminolactone 14b was accelerated with improved yields (56-99%) and diastereoselectivities (50-83%). Hydrolysis of the dialkylated iminolactones yielded the α,α-disubstituted α-amino acids in good yields (80-98%) and high enantiomeric excesses (98-99%) with good recovery of compound 12 (83-92%).
A PROCESS FOR RESOLVING RACEMIC MIXTURES AND A DIASTEREOISOMERIC COMPLEX OF A RESOLVING AGENT AND AN ENANTIOMER OF INTEREST
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Page/Page column 31; 79-80, (2008/06/13)
A process for resolving a compound in racemic form comprising the following steps is described: a) reacting a compound in racemic form with a resolving agent, b) forming a diastereoisomeric complex of the resolving agent and an enantiomer of interest, c} separating the enantiomer of interest from the obtained diastereoisomer, wherein such a process is characterized in that said resolving agent is a compound of Formula (I). A diastereoisomeric complex between the resolving agent of Formula (I) and the enantiomer of interest is also described. The process according to the invention allows acid and basic racemic mixtures to be separated.
Diastereoselective synthesis of quaternary α-amino acids from diketopiperazine templates
Davies, Stephen G.,Christopher Garner,Ouzman, Jaqueline V. A.,Roberts, Paul M.,Smith, Andrew D.,Snow, Emma J.,Thomson, James E.,Tamayo, Juan A.,Vickers, Richard J.
, p. 2138 - 2147 (2008/03/14)
Sequential enolate alkylations of (S)-N(1)-methyl-5-methoxy-6-isopropyl-3, 6-dihydropyrazin-2-one and (S)-N(1)-p-methoxybenzyl-5-methoxy-6-isopropyl-3,6- dihydropyrazin-2-one proceed with excellent levels of diastereoselectivity (>90% de) affording quaternary α-amino acids in high enantiomeric excess (>98% ee) after deprotection and hydrolysis. This journal is The Royal Society of Chemistry.
Crystallization-induced asymmetric transformations and self-regeneration of stereocenters (SROSC): Enantiospecific synthesis of α-benzylalanine and hydantoin BIRT-377
Napolitano, Elio,Farina, Vittorio
, p. 3231 - 3234 (2007/10/03)
N-Isobutoxycarbonyl protected L-alanine was condensed with 4-phenylbenzaldehyde in a crystallization-controlled process to give the corresponding cis-oxazolidinone derivative as the sole product in high yield; this underwent enolization and benzylation wi
Chiral environment specifically induced by metal ion: Asymmetric α- alkylation of α-amino esters using pyridoxal derivatives having a chiral ionophore function
Miyashita, Kazuyuki,Miyabe, Hideto,Tai, Kuninori,Kurozumi, Chiaki,Iwaki, Hiroshi,Imanishi, Takeshi
, p. 12109 - 12124 (2007/10/03)
Stereoselective alkylation of aldimines, prepared from α-amino esters and pyridoxal models having an ionophoric side-chain composed of a chiral glycerol structure, proceeded in the presence of Li+ or Na+ to afford α,α-dialkyl amino esters after acidic hydrolysis. Both the structure of the side chain and the metal ion were found to be in relation with the stereoselectivity, affording the highest stereoselectivity when the side- chain having a 2-naphthylmethoxy group and a methoxy group at the respective 3'- and 2'-positions was employed in the presence of Na+.
Asymmetric alkylation catalyzed by chiral alkali metal alkoxides of TADDOL. Synthesis of α-methyl amino acids
Belokon',Kochetkov,Churkina,Ikonnikov,Chesnokov,Larionov,Kagan
, p. 917 - 923 (2007/10/03)
It is shown that sodium alkoxides formed from (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-bis(diphenylmethanol) ((R,R)-TADDOL) and some of its derivatives can be used as chiral catalysts for enantioselective alkylation of Schiff's bases derived from alanine with reactive alkyl halides. Acid hydrolysis of the reaction products affords (R)-α-methytphenyl-alanine, (R)-α-allylalanine, and (R)-α-methylnaphthylalanine in 61-93% yields and with ee 69-94%. When (S,S)-TADDOL is used, the (3)-amino acid is formed. A mechanism explaining the observed features of the reaction is proposed.
Enantiomerically enriched (R)- and (S)-α-methylphenylalanine via asymmetric PTC C-alkylation catalysed by NOBIN
Belokon', Yuri N.,Kochetkov, Konstantin A.,Churkina, Tatiana D.,Ikonnikov, Nikolai S.,Vyskocil, Stepan,Kagan, Henri B.
, p. 1723 - 1728 (2007/10/03)
Enantiopure 2-hydroxy-2'-amino-1,1'-binaphthyl (NOBIN) is shown to catalyse C-alkylation of aldimine Schiff's bases of alanine ester under phase-transfer catalysis conditions (solid NaOH or NaH, toluene, ambient temperature, 10% NOBIN). Using (R)-NOBIN, t
