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anti ‐Selective Aldol Reactions of Amino Acid Ester Enolates. Application to the Synthesis of α‐Alkylated β‐Hydroxy Amino Acids
Author(s) -
Grandel Roland,
Kazmaier Uli,
Nuber Bernhard
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960713
Subject(s) - chemistry , aldol reaction , alkylation , deprotonation , amino acid , steric effects , organic chemistry , valine , chelation , alanine , metal , catalysis , biochemistry , ion
Deprotonation of N ‐protected esters of the amino acids alanine 1 , ethylglycin 6 , valine 7 , and phenylalanine 8 with LDA and subsequent addition of various metal salts result in the formation of a probably chelated metal enolate. Aldol reactions of these enolates with aldehydes afford the anti isomers of α‐alkylated α‐amino‐β‐hydroxy acids in a highly diastereoselective fashion. Best results are obtained with titanium enolates, bulky aliphatic aldehydes, and sterically demanding amino acids.