Herstellung enantiomerenreiner, α-alkylierter Lysin-, Ornithin- und Tryptophan-Derivate

Synthesis of Enantiomerically Pure, α-Alkylated Lysine, Ornithine, and Tryptophan Derivatives The imidazolidinones 9 and 10 as well as the oxazolidinone 18a were prepared in several steps by known methods from lysine and ornithine with an overall yield of ca. 20%. After double deprotonation with LDA, the corresponding dianionic derivatives could be diastereoselectively alkylated with electrophiles (MeI, C₆H₅CH₂Br, C₆H₅CHO, CH₃CHO). Acid hydrolysis led to the two enantiomeric 2-methyl- and 2-benzyllysines and to the enzyme inhibitor (S)-2-methylornithine. Several α-alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1-(tert-butyloxycarbonyl)-3-(bromomethyl)indole ( 26 ). Alkaline hydrolysis of the five-membered auxiliary ring of 30b followed by treatment with HCl afforded (S)-2-methyltryptophan ( 31 ).