- Preparation of the optically pure N-methyl amino ester method and product
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The invention belongs to the field of organic synthesis of amino acids and discloses a method for preparing optically pure N-methyl amino-acid ester. The method comprises the following steps of carrying out esterification reaction on amino acid as a starting raw material and aldehyde to form an imine intermediate, carrying out reductive amination in the presence of palladium carbon, and carrying out hydrogenation and debenzylation to finally synthesize optically pure N-methyl amino-acid ester. The method has the advantages of simplicity in method, mild reaction conditions and good adaptability and side chains of D-type or L-type amino acid do not need to be protected.
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Paragraph 0065-0066
(2017/04/13)
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- Facile synthesis of highly functionalized N-methyl amino acid esters without side-chain protection
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(Chemical Equation Presented) The facile, two-pot synthesis of N-methyl amino acid esters by way of reductive amination is presented. Side chain protection schemes are not required, the starting materials are all commercially available, and the synthetic
- White, Kimberly N.,Konopelski, Joseph P.
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p. 4111 - 4112
(2007/10/03)
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- Chiral ligands derived from Abrine 8. An experimental and theoretical study of free ligand conformational preferences and the addition of diethylzinc to benzaldehyde
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(Chemical Equation Presented). Three structurally similar series of 1,2,3,4-tetrahydro-β-carboline ligands, 4a-d, 6a-d and 7a-d, and two series of chiral oxazolidines, 8a-d and 9a-g, were synthesized and used as chiral catalysts in the addition of diethyl
- Zhu,Jiang,Saebo,Pittman Jr.
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p. 261 - 267
(2007/10/03)
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- Chiral ligands derived from abrine. Part 7: Effect of O, S, N in aromatic ring substituents at C-1 on enantioselectivity induced by tetrahydro-β-carboline ligands in diethylzinc addition to aldehydes
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The effect of O, S and N atoms in aromatic ring substituents at C-1 position of tetrahydro-β-carboline ligands on the enantioselectivity of diethylzinc additions to benzaldehyde was studied when esters or tertiary alcohol functions were present at C-3. A mechanism is proposed to explain why the ester ligands 2c and 2d, in which the pyridyl N atom is at C′-2 in 2c and at C′-3 in 2d, catalyzed the addition of diethylzinc to benzaldehyde to form the (R)- and (S)-enantiomers of 1-phenyl-1-propanol, respectively. An explanation was also proposed for the moderate enantioselectivity induced by tert-alcohol 3c versus the very small enantioselectivity induced by 3d, containing a 3-pyridyl function at C-1, during diethylzinc additions. A -CH2-t-Bu substituent at C-1 leads to very high enantioselectivities.
- Zhu,Zhao,Zuo,Pittman Jr.,Dai,Hao
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p. 2613 - 2619
(2007/10/03)
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- Chiral ligands derived from abrine. Part 6: Importance of a bulky N-alkyl group in indole-containing chiral β-tertiary amino alcohols for controlling enantioselectivity in addition of diethylzinc toward aldehydes
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A number of chiral β-amino alcohols possessing a 3-indolylmethyl group have been synthesized from the alkaloid, (S)-abrine and elucidated for potency in the catalytic enantioselective ethylation of PhCHO with Et2Zn. In general, the secondary amines 15a-d bearing a dialkylhydroxymethyl group induced (R)-1-phenyl-1-propanol, whereas 15e-g and 18 bearing a diarylhydroxymethyl group favored the (S)-enantiomer. In contrast, the β-tertiary amino alcohols 20b-d and 21 produced (R)-1-phenyl-1-propanol, regardless of the substituents at the carbon bearing the hydroxy group. Enantiomeric excess of 87.5% was obtained for (R)-1-phenyl-1-propanol using ligand 21 as the promoter. Eleven substituted benzaldehydes and naphthaldehydes were examined for enantioselective ethylation by using 21 and the chiral alcohols were obtained in 93-97% ee, except for o-BrC6H4CHO and p-Me2NC6H4CHO. Excellent enantioselectivity was also observed in the ethylation of cyclohexanecarboxaldehyde (94.8% ee) and 2-thiophenecarboxaldehyde (94.9% ee) by using catalytic 21. The anti 5/4/4-fused tricyclic TS I was proposed to rationalize the asymmetric induction. The diethylhydroxymethyl and N-2-t-butylethyl groups are believed to enforce the preference for the anti-TS(R) I and it results in high enantioselectivity. Copyright (C) 2000 Elsevier Science Ltd.
- Dai, Wei-Min,Zhu, Hua-Jie,Hao, Xiao-Jiang
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p. 2315 - 2337
(2007/10/03)
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