Herstellung enantiomerenreiner cis??oder trans??konfigurierter 2??(tert??Butyl)??3??methylimidazolidin??4??one aus den Aminosäuren (S)??Alanin,(S)??Phenylalanin,(R)?? …
In contrast to a-hydroxy and a-mercapto carboxylic acids, simple a-amino acids do not form acetal-type derivatives (2, X= NH) with pivalaldehyde. For the generation of amino-acid- derived chiral, nonracemic enolates (cf 3), and hence, for the a-alkylation of amino acids without racemization and without an external chiral auxiliary, the imidazolidinones 12-14 were prepared diastereoselectively. To this end, the methyl or ethyl esters of amino-acid ...
