A Novel Synthesis of (R)- and (S)-α-Alkylated Aspartic and Glutamic Acids: α-Alkylated Aspartic Succinimides as New Type of β-Turn Type II and II' Mimetics

Article abstract of DOI:10.1016/0040-4020(95)00665-U

A novel and efficient synthesis of optically pure (R)- and (S)-α-methyl glutamic acid (1), (R)-and (S)-α-methyl aspartic acid (2a) and (R)- and (S)-α-isobutyl aspartic acid (2b) using L-phenylalanine cyclohexylamide 4 as chiral auxiliary is described.Crystal structures show that the (R)- and (S)-α-methyl glutamic acid derivatives (S,S)-5 and (R,S)-6 adopt β-turn type I geometries, whereas the corresponding aspartimide derivatives (R,S)-12a,b form a β-turn type II and (S,S)-11a a β-turn type II'.These findings suggest, that the succinimide derivatives of (R)- and (S)-α-alkyl aspartic acids can serve as building blocks to stabilise β-turns of type II (or II') in peptides depending on their absolute configuration.