Enantioselective synthesis of .beta.-amino acids. 2. Preparation of the like stereoisomers of 2-methyl- and 2-benzyl-3-aminobutanoic acid
作者:Eusebio Juaristi、Jaime Escalante、Bernd Lamatsch、Dieter Seebach
DOI:10.1021/jo00034a037
日期:1992.4
An improved procedure for the preparation of (R)- and (S)-3-aminobutanoic acids (2a) through diastereomer separation of the corresponding (1'S)-N-phenethyl derivatives 1 is reported. From 2a, the four possible stereisomeric perhydropyrimidin-4-ones 4 were prepared through the amide 2c and the Schiff base 3. In the cyclization of 3, the cis products 4 predominate ca. 95.5. These heterocycles can be alkylated (LDA, RX), as demonstrated by methylation and benzylation, with formation of a single diastereoisomer (5, 6). Hydrolysis (6 N aqueous HCl) of these 5,6-dialkylperhydropyrimidin-4-ones leads to the free amino acids 7-10.