Electrogenerated chiral cationic glycine equivalents — Part 2: Chiral 3-methoxy-2,5-morpholinediones from ( S)- α-hydroxy acids and dimethyl aminomalonate

Abstract

Chiral 3-methoxy-2,5-morpholinediones which are cyclic N, O-acetals have proved to be excellent chiral cationic amino acid equivalents, especially if larger nucleophiles are employed. They are easily obtained from dipeptolides formed between chiral α-hydroxy acids and dimethyl amino malonate via regioselective electrochemical methoxylation followed by intramolecular lactonization after decarboxylation. The lactonization can be performed quantitatively from the open-chain peptolide by condenzation under reduced pressure at elevated temperature. The easy separation of the desired amino acid and the α-hydroxy acid being the chiral auxiliary by extraction is valuable.