“Alternative method for the resolution of 1-benzoyl-2-tert-butyl-3-methyl-1,3-imidazolidin-4-one”
摘要:
The title heterocycles, which are useful chiral precursors for the asymmetric synthesis of alpha-amino acids, can be prepared in enantiomerically pure form via the separation of diastereomeric derivatives incorporating (S)-alpha-methyl-benzylamine.
“Alternative method for the resolution of 1-benzoyl-2-tert-butyl-3-methyl-1,3-imidazolidin-4-one”
摘要:
The title heterocycles, which are useful chiral precursors for the asymmetric synthesis of alpha-amino acids, can be prepared in enantiomerically pure form via the separation of diastereomeric derivatives incorporating (S)-alpha-methyl-benzylamine.
Highly enantioselective synthesis of (R)- and (S)-2-amino-5-phosphonopentanoic acids [(R)- and (S)-AP5] via modified Seebach imidazolidinones
作者:Oscar García-Barradas、Eusebio Juaristi
DOI:10.1016/0040-4020(95)00091-l
日期:1995.3
isomers, (2R, 1′S)- and (2S, 1′R)-7, afforded the desired phosphorylated products 9 with ≥ 98% diastereoselectivity. Hydrolysis of the alkylated products proceeds under relatively mild conditions to give enantiomerically pure α-substituted α-amino acids. Thus, hydrolysis of (2R,5R,1′S)-9 and (2S,5S,1′R)-9 provided the physiologically important, enantiopure amino phosphonic acids (R)-AP5 and (S)-AP5.
Highly Diastereoselective Alkylation of 1-Benzoyl-2-alkyl-3-(1'-methylbenzyl)imidazolidin-4-ones
作者:Eusebio Juaristi、Jose Luis Anzorena、Alois Boog、Domingo Madrigal、Dieter Seebach、Efren V. Garcia-Baez、Oscar Garcia-Barradas、Barbara Gordillo、A. Kramer
DOI:10.1021/jo00125a029
日期:1995.10
The synthetic utility of 2-alkyl-substituted 1,3-imidazolidinones for the enantioselective preparation of a-amino acids is now well documented in the literature. Incorporation of a N(3)-phenethyl group in these heterocycles leads to substantial enhancements in the diastereoselectivity of alkylation of the corresponding lithium enolates, so that stereoselectivities in the order of 19:1 to 49:1 are observed for 2-isopropyl and 2-tert-butyl derivatives, respectively. X-ray crystallographic analysis on five N(3)-phenethyl-substituted imidazolidinones provided evidence that the long-distance effect of that chiral moiety is the result of conformational changes provoked by steric interactions between the 2-alkyl and the N(3)-phenethyl groups. No additivity of the stereodirecting effects by the stereogenic centers at C(2) and C(1') was noticed, Thus, as it could have been anticipated from basic principles, intramolecular combinations of stereogenic centers do not necessarily lead to ''matched'' and ''mismatched'' joint stereoinducing effects.