New Stereoconservative Syntheses of β,β,β- and γ,γ,γ-Trifluoro-α-amino, α-Hydroxy, and α-Mercapto Acids and Their Incorporation into a Peptide and Depsipeptide Fragment

Syntheses of β,β,β- and γ,γ,γ-trifluoro-α-amino, α-hydroxy and α-mercapto acids using hexafluoroacetone as protecting and activating reagent are described. The key step of the syntheses is the transformation of an ω-carboxy group into a trifluoromethyl group on treatment with sulfur tetrafluoride. The carboxy activated species obtained are suitable for direct incorporation into peptide and depsipeptide fragments. RP-HPLC experiments and Mosher's TMPA method (¹H and ¹⁹F) demonstrate that the reaction sequence occurs without racemization.

amino acids - heterocycles - hexafluoroacetone - lactones - peptides - sulfur tetrafluoride