Synthesis of Methionine-Derived Endocyclic Sulfilimines and Sulfoximines

The asymmetric synthesis of endocyclic methionine sulfilimines and sulfoximines from methionine derivatives was explored. The cyclization was performed by using phenyliodine diacetate (PIDA). In the case of L-methionine, dehydromethionine was obtained, and a deprotonation step by tBuONa was necessary to yield the corresponding sulfilimine. On the other hand, the cyclic sulfilimine of methionine methyl ester, methylthiopropylamine, and L-methioninol were synthesized in a single step by using PIDA. Owing to their instability, the sulfilimines were oxidized to their corresponding sulfoximines in good yields.