An efficient approach to AviCys analogues via regio- and stereoselective hydrosulfuration of ynamides

A novel synthetic strategy for the construction of AviCys analogues via a highly efficient regio- and stereoselective hydrosulfuration of ynamides was reported. It was accomplished via a base-promoted nucleophilic β-addition of thiols to ynamides to furnish a series of (Z)-β-thioenamide derivatives with excellent regio- and stereoselectivities (Z : E > 99 : 1). Notably, peptides containing cysteine (Cys) could also be employed as thiol components, thus providing efficient access to the chemical synthesis of AviCys analogues.