203854-56-2Relevant articles and documents
Catalytic Asymmetric Synthesis of Unprotected β2-Amino Acids
Zhu, Chendan,Mandrelli, Francesca,Zhou, Hui,Maji, Rajat,List, Benjamin
, p. 3312 - 3317 (2021/04/07)
We report here a scalable, catalytic one-pot approach to enantiopure and unmodified β2-amino acids. A newly developed confined imidodiphosphorimidate (IDPi) catalyzes a broadly applicable reaction of diverse bis-silyl ketene acetals with a silylated aminomethyl ether, followed by hydrolytic workup, to give free β2-amino acids in high yields, purity, and enantioselectivity. Importantly, both aromatic and aliphatic β2-amino acids can be obtained using this method. Mechanistic studies are consistent with the aminomethylation to proceed via silylium-based asymmetric counteranion-directed catalysis (Si-ACDC) and a transition state to explain the enantioselectivity is suggested on the basis of density functional theory calculation.
Enantioselective synthesis of beta-amino acids using hexahydrobenzoxazolidinones as chiral auxiliaries
Reyes-Rangel, Gloria,Jimenez-Gonzalez, Erika,Olivares-Romero, Jose Luis,Juaristi, Eusebio
experimental part, p. 2839 - 2849 (2009/06/18)
A practical synthetic route for the asymmetric synthesis of β2-amino acids is described. In the first step, the procedure involves the N-acylation of readily available, enantiopure hexahydrobenzoxazolidinone (4R,5R)-1 with 3-methylbutanoyl chloride 2, 4-methylpentanoic acid 3, and 3-(1-tert-butoxycarbonyl)-1H-indol-3-yl)propanoic acid 4 to afford derivatives 5a, 5b, and 5c, respectively, which were alkylated with high diastereoselectivity by means of reaction between their sodium enolates and benzyl bromoacetate. Removal of the chiral auxiliary from the alkylated products followed by hydrogenation and hydrolysis gave β2-amino acids (S)-10a, (S)-10b, and (S)-10c, which were N-protected with Fmoc. Enantiomeric (R)-10a-c were similarly prepared from the isomeric hexahydrobenzoxazolidinone (4S,5S)-1; thus, the route presented here provides access to both enantiomers of valuable highly enantioenriched β2-amino acids.
Efficient synthesis of enantiomerically pure β2-amino acids via chiral isoxazolidinones
Lee, Hee-Seung,Park, Jin-Seong,Kim, Byeong Moon,Gellman, Samuel H.
, p. 1575 - 1578 (2007/10/03)
We report a practical and scalable synthetic route for the preparation of α-substituted β-amino acids (β2-amino acids). Michael addition of a chiral hydroxylamine, derived from α-methylbenzylamine, to an α-alkylacrylate followed by cyclization gives a diastereomeric mixture of α-substituted isoxazolidinones. These diastereomers are separable by column chromatography. Subsequent hydrogenation of the purified isoxazolidinones followed by Fmoc protection affords enantiomerically pure Fmoc-β2-amino acids, which are useful for β-peptide synthesis. This route provides access to both enantiomers of a protected β2-amino acid.
