Mannich-Type Reaction of α-Sulfanyl --Butanesulfinylimidates: Diastereoselective Access to α-Mercapto-β-amino Acid Derivatives.

A series of α-mercapto-β-amino acid derivatives were synthesized diastereoselectively in good yields through the aza-enolization of α-sulfanyl --butanesulfinylimidates, followed by their nucleophilic addition to -tosyl imines via a Mannich-type reaction. The resulting derivatives bearing a β-sulfonylamino sulfide moiety participated in further inter- and intramolecular transformations involving episulfonium ion intermediates generated through neighboring-group participation.