Studies on 2-Aziridinecarboxylic Acid. IX. Convenient Synthesis of Optically Active S-Alkylcysteine, threo-S-Alkyl-β-methylcysteine, and Lanthionine Derivatives via the Ring-opening Reaction of Aziridine by Several Thiols

A convenient synthesis of optically active S-alkylcysteine, threo-S-Alkyl-β-methylcysteine, and lanthionine derivatives has been investigated. Benzyl 1-benzyloxycarbonyl-(2S)-2-aziridinecarboxylate and benzyl (2S,3S)-1-benzyloxycarbonyl-3-methyl-2-aziridinecarboxylate, and their enantiomers were treated with several thiols, and the corresponding S-alkylcysteine, threo-S-alkyl-β-methylcysteine, and lanthionine derivatives were prepared via the ring-opening reaction of aziridine in the presence of a catalytic amount of boron trifluoride etherate in good yields.