Sulfur-mediated synthesis and antimicrobial activity of 4-thioisosteres of flavanoids

Each step of the synthetic sequence inverse electron-demand hetero-Diels–Alder reaction of o-thioquinones with styrenes, oxidation at sulfur, and Pummerer rearrangement allowed the preparation of 4-thioisosteres of flavanoids, namely thiaflavans, thiaflavanones and thiaflavanols. A preliminary screening indicates a clear, though moderate, antimicrobial activity of such compounds that depends upon the substitution pattern and the oxidation state at sulfur.