A series of α-substituted amides 3 and 7–9 has been synthesized in enantiomerically pure form by diastereoselective alkylation of N-alkyl phenylglycinol amides 2 and 4–6 respectively. A rigid amide enolate has been postulated to explain the observed diastereoselectivity.
The origins of diastereoselectivity in the alkylation of lactams la and Ib and amides 6a and 6b are discussed. A rigid intermediate in which the pyramidalized amide nitrogen chelated the alkoxide lithium cation is invoked. Further experiments conducted with different substrates' are in agreement with the proposed model, Furthermore this model can explain the differences observed previously between ephedrine and pseudoephedrine amide alkylation. Copyright (C) 1996 Elsevier Science Ltd
Enantioselective Synthesis of β-Substituted Primary and Secondary Amines by Alkylation of (R)-Phenylglycinol Amide Enolates
作者:Valérie Jullian
DOI:10.1055/s-1997-1303
日期:1997.9
General and convenient syntheses of optically active β-substituted secondary or primary amines 4 and 8 are described. The method is based on diastereoselective alkylation of amides 1 and 5 derived from R-(-)-phenylglycinol followed by reduction and removal of the chiral appendage. This procedure has also been applied to the preparation of 1,4-amino alcohols 12 and γ-amino esters 14.