Producción Científica Profesorado

Enantioselective synthesis of ?-amino acids. Part 11: Diastereoselective alkylation of chiral derivatives of ?-aminopropionic acid containing the ?-phenethyl group



Lopez Ruíz, Heraclio

2001

V. M. Gutiérrez-García, Heraclio López-Ruiz, G. Reyes-Rangel y E. Juaristi Enantioselective synthesis of b-amino acids. Part 11: Diastereoselective alkylation of Chiral derivatives of b-aminopropionic acids containing the a-phenethyl group. Tetrahedron, 57, 6487-6496 (2001). DOI: http://dx.doi.org/10.1016/S0040-4020(01)00540-3


Abstract


Several novel, chiral derivatives of ?-aminopropionic acid were studied as potentially useful precursors of enantiopure ?-substituted-?-amino acids. In particular, the diastereoselectivity of alkylation of (R,R)-2-Li enolate showed substantial stereoinduction by the bis[?-phenylethyl]amide auxiliary, leading to 80% ds in the methylation reaction. No appreciable effect upon diastereoselectivity was observed by the presence of additives (LiCl, HMPA, DMPU) in the reaction. On the other hand, stereoinduction by the ?-phenylethylamino group in the methylation of ester enolate (S)-3-Li was lower (65% ds) under standard conditions (THF, ?78C) but improved to 81% ds in the presence of 3 equiv. of HMPA as cosolvent. Matched and mismatched derivatives, (R,R,S)-11 and (R,R,R)-11, respectively, were methylated via their corresponding lithium enolates. Observed diastereoselectivities generally followed the anticipated tendencies based on double stereoinduction. Thus diastereoselectivity reached 89% ds in the methylation of the matched isomer, (R,R,S)-11-Li.



Producto de Investigación




Artículos relacionados

A practical access to acyl radicals from acyl hydrazides

Furocoumarins of three species of the genus Dorstenia

Synthesis and Structures of some Lithium and Sodium (Aminoalcoholato)hydrido Aluminates

Ylidaddukte der Penteltrichloride

An efficient potassium cyanide-promoted synthesis of 2-arylbenzoxazoles from [4.3.0]boron heterobicy...

Preparation of Seven- and Eight-Membered Boron Heterocycles from Different Salen Ligands and Arylbor...

Phenylmethyl 2,3,4-tri-O-acetyl--D-fucopyranoside

Stereoselective addition of allylmagnesium chloride to the CN bond of [4.3.0] boron heterobicycles

Further insight into three center hydrogen bonding. Participation in tautomeric equilibria of hetero...

A flexible access to highly functionalised boronates