Synthesis of α-Amino Acids and Derivatives
Diethyl N-Boc-iminomalonate, prepared on multi-gram scale, served as a stable and highly reactive electrophilic glycine equivalent which reacted with organomagnesium compounds affording substituted aryl N-Boc-aminomalonates. Subsequent hydrolysis produced arylglycines.
P. Cali, M. Begtrup, Synthesis, 2002, 63-64.
The use of catalytic loadings of picolinaldehyde and Ni(II) salts in catalytic α-allylation of unprotected amino acid esters induces preferential reactivity at the enolizable α-carbon over the free nitrogen with electrophilic palladium π-allyl complexes to produce α-quaternary α-allyl amino acid esters. Additionally, the use of chiral ligands to access enantioenriched α-quaternary amino acid esters from racemic precursors is demonstrated.
P. Fang, M. R. Chaulagian, Z. D. Aron, Org. Lett., 2012, 14, 2130-2133.
Using a cinchonine-derived alkaloid catalyst, enantioselective alkylations of N-(diphenylmethylene) glycine tert-butyl ester were efficiently carried out with various alkyl halides to give products in high enantiomeric excess.
W. He, Q. Wang, Q. Wang, B. Zhang, X. Sun, S. Zhang, Synlett, 2009, 1311-1314.
Phase-transfer-catalyzed alkylation of glycinate Schiff base with racemic secondary alkyl halides proceeded with excellent levels of syn- and enantioselectivities under the influence of a chiral quaternary ammonium bromide and 18-crown-6. The alkylation product can be selectively converted to the corresponding anti isomer, allowing the preparation of all the stereoisomers of β-alkyl-α-amino acid derivatives.
T. Ooi, D. Kato, K. Inamura, K. Ohmatsu, K. Maruoka, Org. Lett., 2007, 9, 3945-3948.
A new method for the Rh(I)-catalyzed addition of arylboronic acids to chiral N-tert-butanesulfinyl imino esters allows the asymmetric synthesis of arylglycine derivatives in high yields and diastereoselectivities for various functionalized arylboronic acids.
M. A. Beenen, D. J. Weix, J. A. Ellman, J. Am. Chem. Soc., 2006, 128, 6304-6305.
A cationic palladium-complex catalyzes the addition of arylboronic acids to N-tert-butanesulfinyl iminoacetates to yield optically active arylglycine derivatives with good yield and high diastereoselectivity. This reaction provides a convenient and efficient method for the synthesis of arylglycine derivatives.
H. Dai, X. Lu, Org. Lett., 2007, 9, 3077-3080.
An efficient method for the asymmetric synthesis of anti-β-hydroxy-α-amino acid derivatives is based on highly enantio- and diastereoselective aldol reactions of the silicon enolate derived from N-trifluoroacetylglycinate with aldehydes using a chiral zirconium catalyst.
J. Kobayashi, M. Nakamura, Y. Mori, Y. Yamashita, S. Kobayashi, J. Am. Chem. Soc., 2004, 126, 9192-9193.
A highly efficient direct asymmetric aldol reaction of a glycinate Schiff base with aldehydes has been achieved under mild biphasic conditions with excellent stereochemical control, using a chiral quaternary ammonium salt as a phase-transfer catalyst.
T. Ooi, M. Kameda, M. Taniguchi, K. Maruoka, J. Am. Chem. Soc., 2004, 126, 9685-9694.
A straightforward three-component reaction of preformed aromatic or in situ generated benzylic organozinc reagents with amines and ethyl glyoxylate allows the synthesis of a range of α-amino esters in very good yields. The procedure, which is characterized by its simplicity, allows the concise synthesis of esters bearing a phenylglycine or a phenylalanine scaffold.
C. Haurena, E. Le Gall, S. Sengmany, T. Martens, M. Troupel, J. Org. Chem., 2010, 75, 2645-2650.
A copper(I)-catalyzed direct three-component coupling of ethyl glyoxylate, p-anisidine, and terminal alkynes provides β,γ-alkynyl α-amino acid derivatives in good yields.
Z. Shao, A. S. C. Chan, Synthesis, 2008, 2868-2870.
The regioselective opening of Bn2N-α-methylserine-β-lactone with organocuprates gave enantiopure α-methyl amino acids in excellent yields.
N. D. Smith, A. M. Wohlrab, M. Goodman, Org. Lett., 2005, 7, 255-258.
The Hf(OTf)4-catalyzed Mannich-type reaction of an enol silyl ether or a ketene silyl acetal with an N,O-acetal allows the preparation of amino acid derivatives. In particular, use of the N,O-acetal having a bis(trimethylsilyl)amino group directly produced N-unprotected aspartic acid derivatives after a standard aqueous workup.
N. Sakai, A. Sato, T. Konakahara, Synlett, 2009, 1449-1452.
An efficient α-arylation of imino amides with arylboronic acids provides an alternative approach for the synthesis of α-functionalized glycine derivatives. Different substrates were examined for this arylation reaction.
L. Zhao, X. Liao, C.-J. Li, Synlett, 2009, 2953-2956.
In the presence of a catalytic amount of Cu(OTf)2 and a chiral diamine ligand, various N-acylimino esters reacted smoothly with silyl enol ethers and alkyl vinyl ethers to afford the corresponding Mannich-type adducts in high yields with high diastereo- and enantioselectivities. The reaction mechanism is discussed.
S. Kobayashi, R. Matsubara, Y. Nakamura, H. Kitagawa, M. Sugiura, J. Am. Chem. Soc., 2003, 125, 2507-2515.
Both (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid and (R)-3-pyrrolidinecarboxylic acid efficiently catalyzed the Mannich-type reactions of aldehydes with α-imino esters under mild conditions and afforded anti-Mannich products with high diastereo- and enantioselectivities.
H. Zhang, S. Mitsumori, N. Utsumi, M. Imia, N. Garcia-Delgado, M. Mifsud, K. Albertshofer, P. H.-Y. Cheong, K. N. Houk, F. Tanaka, C. F. Barbas, III, J. Am. Chem. Soc., 2008, 130, 875-886.
Direct catalytic, enantioselective, anti-selective Mannich-type reactions between unmodified ketones and α-imino esters using 5-10 mol % of (R)-3-pyrrolidinecarboxylic or (R)-β-proline as catalyst in 2-PrOH at room temperature gave products in good yields with high diastereo- and enantioselectivities.
H. Zhang, M. Mifsud, F. Tanaka, C. F. Barbas, III, J. Am. Chem. Soc., 2006, 128, 9630-9631.
Proline-catalyzed Mannich-type reactions of N-PMP-protected α-imino ethyl glyoxylate with a variety of unmodified ketones provided functionalized α-amino acids in high yields with excellent regio-, diastereo-, and enantioselectivities. In reactions involving ketone donors where diastereoisomeric products could be formed, two adjacent stereogenic centers were created simultaneously upon carbon-carbon bond formation with complete syn-stereocontrol.
A. Cordova, W. Notz, G. Zhong, J. M. Betancort, C. F. Barbas, J. Am. Chem. Soc., 2002, 124, 1842-1843.
Proline-catalyzed Mannich-type reactions of N-PMP-protected α-imino ethyl glyoxylate with a variety of unmodified aliphatic aldehydes provided functionalized α-amino acids in high yields with excellent enantioselectivities. The diastereoselectivity of the reaction increased with the bulkiness of the substituents of the aldehyde donor.
A. Cordova, W. Notz, G. Zhong, J. M. Betancort, C. F. Barbas, J. Am. Chem. Soc., 2002, 124, 1866-1867.
A direct highly anti-selective and enantioselective asymmetric Mannich reaction using a novel axially chiral amino trifluoromethanesulfonamide has been developed. Reactions between aldehydes and N-PMP-protected α-imino ethyl glyoxylate proceed smoothly to give β-amino aldehydes with high anti/syn ratio and enantioselectivity.
T. Kano, Y. Yamaguchi, O. Tokuda, K. Maruoka, J. Am. Chem. Soc., 2005, 127, 16408-16409.
(3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid as catalyst for Mannich-type reactions afforded anti-products in good yields with excellent diastereo- and enantioselectivities under mild conditions and low catalyst loadings.
S. Mitsumori, H. Zhang, P. H.-Y. Cheong, K. N. Houk, F. Tanaka, C. F. Barbas, III, J. Am. Chem. Soc., 2006, 128, 1040-1041.
Chelated amino acid ester enolates are excellent nucleophiles for allylic alkylations. With these enolates, even terminal π-allyl palladium complexes react without significant isomerization.
K. Krämer, U. Kazmaier, J. Org. Chem., 2006, 71, 8950-8953.
A Lewis acid-catalyzed three-component, mild, highly atom econocial, direct-type Mannich reaction of simple aromatic and enolizable aliphatic aldehydes, secondary amines, and glycine derivatives affords various synthetically important anti-α,β-diamino ester derivatives in high yields with high diastereoselectivities.
M. M. Salter, J. Kobayashi, Y. Shimizu, S. Kobayashi, Org. Lett., 2006, 8, 3533-3536.
Chiral complexes of calcium promote asymmetric 1,4-addition reactions and [3+2] cycloaddition reactions of α-amino acid derivatives with α,β-unsaturated carbonyl compounds. The reactions proceeded smoothly in the presence of 5-10 mol % of the chiral calcium catalyst to afford the desired adducts in high yields with high diastereo- and enantioselectivities.
S. Saito, T. Tsubogo, S. Kobayashi, J. Am. Chem. Soc., 2007, 129, 5364-5365.
Homoallylic α-amino esters and amines were prepared via a Pd(II)-catalyzed coupling of 1,2-nonadiene and boronic acids with ethyl iminoacetate or aliphatic, aromatic, and heteroaromatic imines.
C. D. Hopkins, H. C. Malinakova, Org. Lett., 2006, 8, 5971-5974.
Chiral diaminodioxaphosphonium salts can be used in catalytic amounts in a highly enantioselective protonation of α-amino acid-derived ketene disilyl acetals in the presence of 2,6-dimethylphenol as stoichiometric proton source.
D. Uraguchi, N. Kinoshita, T. Ooi, J. Am. Chem. Soc., 2010, 132, 12240-12242.